RMO Test Prep Information
Two types of flooded Evaporators (distinguished by refrigerant in the shell or in a coil)
"Coil type" flooded evaporator (does not need to be studied for exam) AND "Shell and tube" type evaporator
Water circulated through the condenser is referred to as (2 things)
"Condenser water" or "Cooling water" *Do not confuse with CHILLED water which is at the evaporator*
Engineers use what to calculate the total head loss in a piping system?
"Friction loss table" *indicates pressure drop per 100 feet*
Forces needed to actuate the TEV are often expressed in terms of
"degrees of superheat"
Some solenoids not only close when the compressor stops, but also depending on what? by using..
"load conditions" by use of a thermometer *Temperature is satisfied, sends signal to Low Pressure cutoff, circuit is opened, no electricity flows closing solenoid*
The more methods of capacity control used the more "__________________" you will have
"steps of capacity" Ex: System with unloaders or bypass valves will have more "steps of capacity" than a system without bc the compressors will have individual steps of capacity available
The strong liquor is pumped by the *"strong liquor pump"* from the absorber into the ______________.
(Analyzer) *generator- best answer*
0 psig = __________ psia = _________ "Hg = ______"Hg Ab
*0 psig = 14.7 psia = 0 "Hg = 29.92 "Hg Ab*
1 psi = _______ pascal = ___________ kPa
*1 psi = 6890 pascal = 6.890 kPa*
Aqua-ammonia is used in absorption systems, and is composed of _____% ____________, and ___% ______________.
*78% water, 22% ammonia*
In an absorption system the solution is made stronger in the ...
*Absorber*
Dye Method (Indirect Systems- Brines) Bromothymol Blue, Nesslers solution added to brines Red litmus paper dipped into brines
*Bromothymol blue* turns yellow c02 present *Nesslers solution turns yellow if Ammonia is present* *Red litmus paper turns blue if ammonia is present*
Automatic expansion valve (AEX, AXV) is for small to midsize refrigeration systems with what?
*Constant load*
An decrease in temperature of the evaporator, decreases the pressure on the low side, which _________ the bellows, _________ the circuit, and turning the compressor __________.
*Decrease Load* contracts the bellows, opening the circuit, turning the compressor off *Closes solenoid valve*
If you flood the evaporator the super heat will ________________.
*Decrease*
Mufflers are installed ..? What is their function?
*Discharge line- As close to the compressor as possible* Smooth out pulsations (using baffles) to *attenuate noise and limit vibrations* REMEMBER: MUFFLERS ARE CLOSE TO CARS- MUFFLERS ARE CLOSE TO COMPRESSOR
Oil trap (oil separator) are installed...? What is their function
*Discharge line- As far from the compressor as possible* *prevent compressor lubricating oils from circulating through the entire cycle* *limits possibility of trapping oil in system AKA oil not returning* REMEMBER SEPARATOR- SEPARATE OIL TRAP AND COMPRESSOR- FAR AWAY
Two things to remember about scroll compressors: Do not have _________ Vapor occupying are at ____________________________.
*Do not have discharge* *Vapor occupying are at different stages of compression*
(HOT WORK OPERATIONS) A _____________ shall be maintained and ______________ provided in accordance with Fire Code. This shall be maintained during ALL hot work operations.
*Fire watch* shall be maintained and *Fire Guards Provided*
Certain fixtures in buildings can cause water pressures to drop when being used. If this occurs you can look into (first... if not suitable...)
*First* Installing a cooling tower *If not suitable* get a newer, larger water meter installed
(EMERGENCY ACTION PLANS) Office buildings required to prepare EAP are those that are: 1. or 2.
*Greater than 6 stories in height* or *Greater than 75 feet (22 860 mm) in height*
(FLAME RESISTANT DECORATIONS) Group __,___, __ and __ occupancies, Common areas in group ____,____, and __ occupancies, and any building or structure used as a place for _____________, curtains, drapes, hangings and decorations are required to be made of a flame resistant material. *This does not apply to decorations being displayed solely for sale in any building or as a work of art in any museum or gallery; to guest rooms in hotels and motels, private offices in commercial buildings; or to houses of worship,*
*Group A, E, I, and M occupancies* *Common area in group R-1, R-2, and B occupancies* and any building/structure used as a place for *public gathering*
An increase in temperature of the evaporator (meaning the evaporator is absorbing heat), increases the pressure on the low side, which _________ the bellows, _________ the circuit, and turning the compressor __________.
*Increase load* expands the bellows, closing the circuit, turning the compressor on *Opens solenoid valve*
If you starve the evaporator the super heat will _______________.
*Increase*
The thermostatic expansion valve does what to volume, which decreases pressure
*Increases volume* and *decreases pressure*
The purpose of a *shaft seal* is to do what?
*Keep refrigerant and oil from escaping*
What is short cycling? What causes it?
*Leaky valves allow high side pressure to leak through to the low side during off cycle*. This *raises the pressure*, *expanding bellows*, *turning on the compressor*. *It pumps out the high pressure vapor, shuts off do to decrease in load*, and *continues* in this manor. Leaky compressor valves cause it.
Todays more popular absorption systems use what as the refrigerant and what as the absorbent?
*Lithium Bromide as the absorbent* *Water as refrigerant* REMEMBER Ammonia systems use *Anhydrous Ammonia as the refrigerant*
what type of seal is likely to be used in a midsize reciprocating compressor?
*Mechanical*
If the heat exchanger is removed from an absorption system, how and where will it affect the system?
*More steam* will be required in the generator
Dry expansion chiller (Water in shell, Refrigerant in coil) are used in ______________________________________.
*Multiple refrigeration circuits* -share the same evaporator. Circuits pick up heat from object, then flow through the evaporator, where the evaporator absorbs heat.
(PORTABLE FUELED EQUIPMENT) including snowblowers, portable generators, power washers, weed trimmers and lawn mowers, must not be used indoors. Portable fueled equipment must be stored ____________ unless stored in an ______________________ storage area.
*Must be stored outdoors* *Unless stored in an FDNY indoor storage area*
What describes the compressors shaft seal relative to the position of the bearings? The shaft seal is _______ of the bearings
*Out-board*
What two things affect the Capacity (ability to do work) of the condenser?
*Quantity and temperature of the* 1. *refrigerant* and 2. *air or water cooling the refrigerant*
Shell and tube type flooded evaporator has refrigerant in the ________________, and water in the __________.
*Refrigerant in Shell* *Water in the tube*
Horizontal shell and tube can be cleaned by what? Shell and coil can be cleaned by what? Where is the refrigerant? Where is the water
*Refrigerant in shell, Water in tube/coil* Shell and tube- Punching tubes Shell and coil- Acid
In a multiple temperature system, which evaporator restarts the compressor?
*Rising suction pressure* in either evaporator may restart
By-pass valves are used to do what? It brings them to their _______________, WITHOUT having to overcome discharge pressure.
*Start compressors* Brings them to their *rated rpm*, WITHOUT having to overcome discharge pressure (puts less strain on the motor, by preventing pressure build up) *Cylinder is bypassed, pressure doesn't rise, discharge doesn't open*
Rupture disks are located on the ....? and blow at?
*Top of the evaporator (centrifugals)* 15 psi
What distinguishes a water pump motor from compressor motor? (Think thin tube)
*Venturi line*
What creates vertical movement on an engine indicator? What creates horizontal movement?
*Vertical* - Change in pressure within the compressor's cylinders *Horizontal* - Rotating of card holder (which mimics the piston movement, and is interpreted as the location of the piston in its travel)
Water cooled condensers use ________ in the tubes, and ___________ in the shell.
*Water in tubes* *Refrigerant in shell* Heat is transferred from refrigerant to water
The sight glass turns what color when moisture is present? What color it is regularly?
*Yellow* for moisture Turns from green (regular) to yellow (moisture present)
Direct drive compressor is connected ...
*directly* to the prime mover (electric motor)
The _____________ the compression ratio the harder it is for the compressor to move the vapor
*greater* GREATER COMP RATIO = HARDER TO MOVE
Taking the *discharge of the compressor* and comparing it to the PT chart will give you the *saturation temperature*. If you *subtract the measured temperature from this saturation temperature* it will give you the ...
*heat of compression* Includes the additional BTUs added by compressors moving parts
Increased distance between Atmospheric pressure line and bottom of an indicator diagram suggest...
*high suction pressure*
(NON WATER FIRE EXTINGUISHING SYSTEMS) *Carbon Dioxide fire extinguishing systems* must have a licensed master _________________________ properly trained and having knowledge of the installation, operation, and maintenance of the system to inspect, test, service, and otherwise maintain such system in accordance with this section and the manufacturers specifications and servicing manuals at least on a ______________ basis.
*licensed master fire suppression piping contractor* At least on a *semi-annual* basis
refrigerating effect is
*liquid temp leaving condenser* from heat content of *vapor entering compressor*
As fluid vaporizes, bubbles form at the pump suction and travel through the impeller. Pressure increases at the outer circumference cause the bubbles to collapse. This rumbling sound within the pump, that can cause potential damage to the impeller is known as what? and not be confused with what?
*pump cavitation* not to be confused with a pump simply being "air bound"
A multi-zone standpipe system must be *continuously* under the supervision of an _______ certificate of fitness holder
*s-14*
(COMMERCIAL COOKING SYSTEMS) A sign clearly and concisely summarizing the operation, maintenance, and cleaning requirements for commercial cooking systems regulated by the ________, together with a __________________ depicting the origin, run and terminus of the exhaust system MUST BE POSTED.
*sign regulated by the code* together with a *schematic drawing*
Valve plate is suction on the _____________, discharge on the ____________.
*suction on the bottom* *discharge on the top*
Couplings require proper alignment to the __________________________ by use of what?
*thousandths of an inch* Dial Indicator
All methods of capacity control are summarized by their ability to move ...
*varying* amounts of vapor
Functions of a compressor (4)
- Provide differential pressure to move refrigerant - separate high/low side - Coupled with control system, maintain desired evaporator pressure - Increase pressure of refrigerant to *condensing pressure*
Freon-12 (R-12) has a boiling point of
-21.4ºF
One foot column of water = _________ psi
.433 psi
R-717 is ______ lbs/min/ton based on 200 btu/min and its boiling point is _______
.5 lb/min/ton Boiling point -28ºF
Adding 10 Btu to 10 lbs of water will increase the temperature by how many degrees?
1 Btu = 1 lb of water 1º
For every 2 orifice plates, there will be _______________________ return line.
1 Flash gas return line
Water exerts pressure Water to Psi 1 inch = 1 ft = 2.31 ft =
1 inch of water = .0361 psi 1 foot of water = .433 psi 2.31 feet of water = 1 Psi On the reverse side, 1 Psi added by a pump to a volume of water, would displace the water 2.31 feet
Causes of crystallization: (3)
1. *Air* leaking into the machine 2. *Low temperature condenser water* 3. *Power failures*
What is the function of the Heat exchanger in an absorption system? (2)
1. *Cool the weak* liquor leaving generator 2. *Preheat the strong* liquor leaving absorber
Causes of condenser High head pressure: (3 main)
1. Over-charge of refrigerant 2. Not enough condenser water 3. Condenser water temp to high
Causes of frost on the liquid line: (1)
1. Partial blockage of refrigerant flow
What can cause to much oil to remain in the evaporator? (3 things)
1. Poor piping arrangement * 2. Low suction pressure 3. Oil overcharge
Methods used by compressors (2)
1. Positive displacement 2. Non-positive displacement (Variable displacement, dynamic compressors)
List the 2 types of centrifugal capacity control and how they work
1. Pre-rotation guide vanes- Control amount of vapor entering the eye of the impeller 2. Variable speed compressors- Change operating speed which changes amount of vapor moved by the compressor
Sight glass/ Moisture Indicator signifies what two things?
1. Presence of Moisture (non-condensables) or 2. Insufficient Refrigerant Charge
Oil pressure controls have what two purposes? (hint- protects compressor and machine)
1. Prevent compressor start up until oil pressure is developed 2. prevent continued operation should the oil pressure fall below design limits
Vapor charging allows greatest control for precise adding, and is used .. (2 ways)
1. Prior to liquid charging empty water chiller (to raise pressure) 2. To top of system (after majority is added as liquid)
Parallel *pumping* (pumps in parallel) is used for:
1. Provide *full redundancy for critical load applications* where systems are expected to provide cooling capacity on an uninterrupted basis 2. Provide means of *capacity control* (*each pump delivers equal percentage* of desired flow rate at design head)
Pressure testing (Machines below Atmospheric Pressure)
1. Raise pressure to Atmospheric and use halide torch or electronic detector 2. Empty systems/isolated components can be pressurized with nitrogen and a small trace of R-22 then use halide torch or electronic detector
TD may be increased by doing what? (3)
1. Raising the condensing pressure 2. lowering the temperature of entering water 3. Increasing quantity of water (maintains lower average water temp)
Condenser water supply must be what 4 things?
1. Reasonably cool 2. Abundant 3. At sufficient pressure 4. must not excessively foul or scale water passages
Main components of an evaporator
1. Refrigerant/ Chilled water ; In and out 2. Water boxes- usually at both ends of the evaporator, direct flow of water, often segmented with *baffles* to increase passes + heat transfer 3. Tube sheet- separate water box from inner shell *tubes are flared (water tight connection) into openings in the tube sheet* 4. Shell (rated pressure vessel) 5. Tube bundle- Copper tube (3/8" to 5/8") * 6. Moisture eliminators- *top of evaporator* Prevent droplets of moisture from entering suction side of compressor 7. Insulation- covers entire shell, prevents condensate on cold metal surface
Causes of incorrect rotation w/ ELECTRIC MOTOR: (1)
1. Reverse any two of the motor's power leads
2 types of filter driers: (think of the dessicant- One is ________, the other is __________)
1. Sealed type (must be changed) 2. Replaceable core (can change just desiccant)
Shells are rated pressure vessels complying with what two things?
1. Section VIII of the ASTM- establishing rules of safety limiting rupture or explosion 2. Section 9 of ANSI/ASHRAE Standard 15 - describing requirements for pressure relief protection (RELIEF DEVICES)
Causes of TEV- Flooded Evaporator: (1)
1. Sensing bulb disconnected from coil (false load)
Centrifugal compressors consist of:
1. Shell and Tube type evaporator (refrigerant in shell) 2. Suction line 3. Impeller 4. Diffuser 5. Volute 6. Discharge line 7. Shell and Tube Condenser 8. Liquid line 9. Metering device (orifice plate{s}) 10. Control Panel
Qualities desired of a refrigerant (13 things)
1. Should produce maximum refrigeration per cubic foot of vapor pumped 2. Suitable condensing pressure for the compressor used 3. Suitable evaporating pressure for the compressor used 4. Should be stable (not breakdown) 5. No effect on metal 6. No effect on oil 7. Critical temperature should be well above the condensing temperature 8. Should be non-poisonous and non-toxic 9. non- flammable 10. Available at "reasonable" prices 11. Should be easy to find leaks 12. A minimum of power should be able to compress it 13. Freezing point should be well below the evaporator
Driers in liquid line should be installed upstream, meaning before, what three things?
1. Solenoid valve 2. Sensing bulb 3. Metering device
Internal Lubrication includes: 1. ____________ system 2. __________ feed
1. Splash system 2. Force Feed
The building shall be evacuated or a fire watch maintained if any of what 3 things occur?
1. Standpipe system is out of service 2. Sprinkler system is out of service 3. Fire alarm system is out of service
Defrosting evaporator coils is effected by what? (3 things)
1. Temperature of the coil 2. Humidity of the ambient air 3. Moisture of product being cooled
Filter driers (liquid line) have 4 functions:
1. Absorb moisture (prevent acid formation, or evaporator freeze up) 2. Remove acids (limit corrosion) 3. Act as strainer (separate particulate) 4. Remove sludge (formed by lubricants/oils)
2 types of condensers
1. Air cooled or 2. Water cooled
Service valves do 3 things
1. Allow gauge connection 2. Allow isolation of system for servicing/repair 3. Allow refrigerant to be added/removed
Causes of AXV- Starved evaporator at high load, flooded evaporator at low load: (1)
1. Automatic Expansion used in a variable load system (does not adjust)
Causes of Premature bearing wear/ high running amps (FLA) w/ MECHANICAL MOTOR: (3)
1. Belt tension too high 2. Pulley out of alignment 3. Coupling out of alignment
Causes of High side float- *Starved evaporator*: (1)
1. Broken/ punctured float assembly
Causes of Low side float- *suction pressure rising*: (1)
1. Broken/ punctured float assembly
Centrifugal pumps consist of an impeller on a rotating shaft, enclosed in a (1) , with inlet and outlet connections. The shaft is connected to a (2) which supplies the energy to spin the (3) . As the impeller swirls the water, (4) force builds enough pressure to force the water through the discharge. The energy transferred to the water is limited by (5) , (6), (7). FILL IN BLANKS
1. Casing (volute) 2. motor 3. impeller 4. centrifugal 5. Type and size of impeller 6. Motor speed 7. Total head of the System
Place in correct order for start up procedure: - Make sure crankcase heater is operating - Start Chilled and condenser water pumps - Start machine - Check oil level - Check cooling tower
1. Check oil level 2. Make sure crankcase heater is operating 3. Check cooling tower 4. Start Chilled and condenser water pumps 5. Start machine
Causes of High suction pressure, low discharge pressure w/ a reciprocating compressor: (1)
1. Compressor valves not seating properly NO PRESSURE BUILD
Causes of condenser Low head pressure: (2)
1. Condensing water temperature too low 2. Under-charge of refrigerant
Components of a Engine Indicator: (4)
1. Connecting tube with valve (fed from compressor) 2. Plunger/spring 3. Linkage assembly and pen 4. Spring loaded card holder
Purpose of metering devices?
1. Control the flow of low pressure liquid to the evaporator 2. Separate high/low side 3. Reduce pressure of refrigerant entering valve
Water treatment programs address what 5 issues?
1. Corrosion Control 2. Scale control 3. Biological growth 4. suspended solids 5. Deposition control
Causes of Oil foaming in crankcase w/ a reciprocating compressor: (2 things)
1. Crankcase heater not operating properly 2. Sudden drop in crankcase pressure (from startup)
Factors that determine Volumetric efficiency of a compressor: (4 things)
1. Cylinder heating 2. Compressor valve leakage 3. Clearance volume 4. Compression ratio
Centrifugal pumps are: (4 things)
1. Dependable 2. Low maintenance 3. Made of variety of materials 4. Move high volume of water efficiently
Causes of Low evaporator pressure: (6)
1. Dirty coil 2. Dirty evaporator filter 3. Supply air short cycling 4. Oil logged 5. Low refrigerant charge 6. Paraffin based refrigerant oil
Causes of centrifugal water pump not delivering rated GPM: (6)
1. Discharge/ suction valves partially closed 2. Pump air bound 3. Pump cavitating 4. Plugged strainer 5. Piping configuration altered 6. Check valve in a parallel pump not seating properly
Air inside the pump casing will cause: (3)
1. Drastically lower flow rates 2. Promote corrosion 3. Noisy operation
(EMERGENCY POWER SYSTEMS) NFPA Standard 110 refers to testing of what two things and how often?
1. Emergency generators- Monthly 2. Transfer switches- Semi Annually
2 methods to lubricate compressors
1. External Lubrication Systems 2. Internal Lubrication
Causes of TEV- Starved Evaporator: (3)
1. External equalizer line blockage 2. Broken sensing bulb 3. Internally equalized TEV used on a coil with a PD greater than or equal to 2.5 psi
TEV consists of 6 parts:
1. Feeler bulb 2. Powerhead 3. Superheat spring (adjusting spring) 4. Stem cap (removable cap) 5. Needle point 6. Orifice
Low evaporator superheat can result in what 3 things?
1. Flood-back 2. Suction line + compressor suction frost 3. Presence of LPL
External lubrication systems include: (2) 1. ____________ feed 2. ____________ feed
1. Gravity feed systems at atmospheric pressure (such as horizontal double acting compressors) 2. Force Feed
High operating temperatures w/ ELECTRIC MOTOR: (1)
1. High current (FLA)
Causes of compressor surging on a centrifugal compressor: (1)
1. High head pressure
Causes of short circuit to ground w/ ELECTRICAL MOTOR: (1)
1. High resistance reading; Use ohmmeter (set: R x 10,000Ω) or megaohmmeter
Air can find its way into a pump casing because of what two things?
1. Improper venting of piping system or pump casing 2. Loss of water level in cooling tower basin (more often when pump and basin are equal elevation)
In order to increase capacity of an absorption plant, the operator should do what two things?
1. Increase Steam 2. Reset expansion valve
Causes of bubbles in liquid line sight glass: (1 Main)
1. Loss of liquid seal (shortage of refrigerant)
Causes of liquid line *warmer* than normal: (1)
1. Loss of liquid seal (shortage of refrigerant)
Causes of Low evaporator superheat: (5)
1. Low load 2. Dirty Coil 3. Dirty Evaporator filter 4. Overcharge refrigerant 5. TEV sensing bulb disconnected from coil
2 Classifications for oils used for lubricating equipment (Hint- 1 is internal and the other is external)
1. Lube Oil- external, not in contact with refrigerant 2. Refrigerant oil- internal, light mineral oil
Causes of High evaporator superheat: (4)
1. Manual expansion valve needs re-adjusting 2. Partially blocked expansion valve 3. Insufficient condensing pressure 4. TEV sensing bulb incorrectly located
Oil temperature is maintained at approximately what temperature within the sump? What controls it? And why?
15ºF by Thermostatically controlled electric heater to prevent refrigerant from condensing in the sump and diluting the oil
Fusible can be installed ____________________ the liquid level of the vessel being protected
Above or Below
-460ºF is
Absolute zero *all substances at this temperature contain some quantity of heat*
Ammonia is vaporized in the evaporator by the temperature of the chilled water or brine, and the vapor is attracted to the solution in the ______________.
Absorber
What major component, in an absorption system, removes the vapor from the evaporator?
Absorber
Non Positive (centrifugal) relies on what process
Acceleration than rapid deceleration of vapor
What function does the oil lantern perform inside of a stuffing box type seal?
Act as a spacer to hold oil
The range of a low pressure cut out may be adjusted by changing the pressure of the _____________. However this will not change the _____________.
Adjustable spring *Does not change differential*
Intercoolers remove refrigerant heat *without* doing what two things before sending it to the primary compressor? why?
Affecting pressure or changing state Only removes sensible heat, not latent heat.
*Suction* driers are installed when? Remember this is not a LIQUID line drier
After a motor burnout *removes water, acid, dirt (sludge)*
Petcock valve is used to bleed what from the pump?
Air
Because they are installed outdoors, they can be used as what during the colder months. what does this do?
Air cooled condenser Save the expense of having to replace the water lost to evaporation and saves the cost of running the water circulating pump
Which would not cause a pump to become *air bound* - Air entering through the pump seal - improper piping system venting - Malfunctioning cooling tower make-up assemble - insufficient quantity of water
Air entering the pump seal
What can occur if operating a pump with the suction valve closed (and will result in reduced capacity) ?
Air leaks
Ultrasonic leak detector (Shell and tube type heat exchangers)
Allows you to hear minute sounds of leaks
R-717 is
Ammonia
When using a manual purger what substance is used to separate ammonia from the non-condensables?
Ammonia
Group 2 NYC Code Refrigerants (toxic, irritant) (6)
Ammonia, Sulfur Dioxide, Dichloroethylene, Methyl Chloride, Ethyl Chloride, Methyl Formate
Electric controls and control valves control the ...
Amount of cooling provided by a refrigeration machine
Specific Gravity of a brine is based on the ______________
Amount of salt in the solution Compares density of solution to density of water Increase salt = Increase specific gravity
(REFRIGERATING SYSTEMS - Supervision) "RSOE present in the building" is a critical requirement while in operation. On the flip side, when the machine is not in operation _______________________________"
An RSOE is not required to be in the building
To prevent the metering device or evaporator from freezing, in an absorption system, vapor leaving the generator passes through the _______________.
Analyzer
What is the refrigerant in an absorption system?
Anhydrous Ammonia (pure ammonia)
Salt in a brine acts as what? how?
Antifreeze by lowering freezing point
Suction service valve is a ___________ valve also referred to as...
3 way valve "stop valve" "block valve" "3 way valve"
3 way valves, connected to 2 PRV's, differ because...
3 way valves allow repair of blown valve, without shutting down system or recovering refrigerant
R-12 is ______ lbs/min/ton based on 200 btu/min
3.9 lb/min/ton
Oil should be where, in regards to the sightglass, when the system is not operating?
3/4 Full
Minimum operating temperature used in a steam jet system is..
33º *Absolute minimum- recommended is 38º*
Many centrifugals are *direct connected* to a _______ RPM motor
3450 (remember 3-4-5 are numbers that are *directly connected*)
In comfort cooling the saturation temperature in the evaporator is _______ºF
35ºF
Measured in degrees of rotation, how far does the crankshaft turn in the time it takes one of the compressors pistons to go through a suction and discharge stroke?
360º
(FIRE ALARM SYSTEMS - Fire guard) For the initial ____________(time period) of an unplanned and planned out of service condition when the affected area does not exceed _____________ Sq Ft.
4 hours not exceeding 50,000 sq ft.
Heat pumps use what kind of valve to reverse flow in a system.
4-way
Which of the following is not a form of compressor valve? 1. Ring plate 2. Poppet 3. Reed type 4. Disc type
4. Disc type
Which of the following is not a function that can be performed by a compressor's service valves? 1. Charge vapor refrigerant 2. Evacuate the refrigeration system 3. Install pressure gauges 4. Regulate refrigerant flow
4. Regulate refrigerant flow
R-22 (Freon-22) has a boiling point of
41.4ºF
Silica gel can be dehydrated by being heated to __________ºF
450ºF
Each stage (centrifugal) builds a compression ratio of:
4:1
A (centrifugal) machine running refrigerant such as ammonia (High pressure refrigerant) would require *at least* how many stages?
5
Range of overall centrifugal tonnage that can be used?
50 T capacity up to 3000 T capacity
A vacuum must be held at how many microns for 30 minutes, by a vacuum gauge, to create an air tight seal?
500 Microns
If 100 BTUs are removed from 10 pounds of 60ºF water, what will the new temperature be?
50ºF 1 BTU= 1 LB 100 BTU/ 10 LB = 10º 60-10= 50ºF Formula: Weight x Temp Diff x Specific Heat = BTU
What is the *maximum operation pressure* of a vapor *or* vapor cross charged* TEV?
55 psi
TEV, with vapor charge, will have MOP of
55 psig
If there are 5 baffles, how many passes would there be? "I'm *baffled* that I *passed one more* exam
6 *always one more pass*
What temperature is a hydrometer most accurate at?
60ºF
(ELEVATORS-IN-READINESS) Building code and Fire code require every building ___ feet or more in height to be kept ready for immediate use by the Fire department ________ (time period)
75 feet or more 24/7 including holidays and weekends
According to *NYC code* refrigerant containers cannot be filled more than _____% EPA is ____%
75% *EPA regulations 80%*
Under standard tons condtions refrigerant entering the expansion valve should be?
77ºF Standard ton says 86º at condenser, and 9º sub cooling 86-9 = 76º
Weight = gpm x ?
8.33 lbs/gallon
A freon system, using a properly designed evaporative condenser, will conserve how much water? (percentage)
85-90%
Under standard ton conditions refrigerant leaving the compressor should be?
86º
Critical temperature of R-44 is
87.8 ºF
Factory setting adjustment of superheat spring will produce an operating superheat of _____________
8º - 12º when installed on an air conditioning system.
Typical subcooling is _______º
9-10º (8-12 factory)
The maximum setting that a pressure limiting device may be adjusted to may not exceed..
90% of the setting of the pressure relief device
The bulb of a thermostatic expansion valve should be installed ____________.
90º from the top of the line
BTUs required: Liquid to Vapor
970 BTU's
Condenser water systems, often used in commercial environments like NYC, recirculate water from ....
A cooling tower Allowing it to give off heat to atmosphere, return, absorb heat, and repeat
Dx evaporator with pressure drop grater than 5 psi is not equipped with an equalizing line, which component is likely to be included?
A distributor
When there is a need for more refrigerant in the evaporator high pressure LIQUID will travel from the receiver to where?
A metering device (TEV)
(REFRIGERATING SYSTEMS - Supervision) Persons responsible to provide personal supervision of a refrigeration system must understand what that means. FC606.1.1 states "...personal supervision shall mean that such person is present in the building __________________________ and that the operation of such systems is under his/her ______________..."
AT ALL TIMES when the system is IN OPERATION and operation is under his/her PERSONAL DIRECTION AND CONTROL *FC606.1.1*
If a few swirls become clogged on a VERTICAL shell and tube condenser, what could be the result?
A need to increase water flow to the remaining spray heads to prevent head pressure from rising If less water is sprayed, water temp will increase, create high head pressure.
Flow rate of aqua-ammonia (refrigerant) pump, must be equal to what flow rate?
Aqua-ammonia at weak liquor regulating valve
If city water is used for cooling water, the service connection should be ...
As close to the condenser as practical and not ran through any hot rooms or near heating equipment
Benefit to a Dry Expansion Chiller
As cooling load increases, additional circuits can be brought on line to transfer more heat to the evaporator.
Liquid seals are established where? why?
At the condenser or receiver Prevent high pressure vapor from entering liquid line
The powerhead of a TEV is located where? The powerhead is used to enclose the valve's ________________________.
At the top of the Valve body Used to enclose the valve's flexible diaphragm
The metric unit of Barometric pressure expressed in millimeters of mercury is "mmHg" What is atmospheric pressure in mmHg?
Atmospheric Pressure is 760 mmHg
What line on the engine indicator diagram is created by running it without connecting the compressor's cylinder?
Atmospheric Reference line
(HOT WORK OPERATIONS) A hot work authorization bearing the signature of the responsible person shall be obtained for any project conducted on premises involving hot work operations by the person in charge of such hot work operations. The authorization shall be available for inspection by any representative of the department at what times?
Authorization must be available *During work and 48 hours after the work is completed*
Unlike fusible plugs, relief valves _________________ to prevent a complete loss of refrigerant charge
Automatically reset
(BATTERY SYSTEMS - Periodic Inspection and testing requirements) All such visual inspections should be conducted by a _________ C of F holder to provide general supervision. This holder should do "quick" visual inspection at least _____________.
B-29 C of F Holder "quick" visual inspection *at least once per day*
Which of the following do not express a perfect vacuum? A. 0 psia B. 0 psig C. 29.9 inches of vacuum D. 0 "Hg Ab (barometric)
B. 0 psig *0 psig= 14.7 psia*
Specific heat x temp diff x weight = ?
BTU
The quantity of heat entering a system are measured in ...
BTU's
How does a gravity coil work
Baffle directs air movement. Air leaving the dx coil is cooler air, the cooler air goes along the baffle to the far end of the refrigerator, where it can drop down, forcing warmer air up into the dx coil on the opposite side. This air is pushed through the dx coil and the cycle repeats
If the line between the king valve and expansion valve starts to sweat, it may be due to _____________.
A partially clogged line (possible clogged filter drier)
What is flash gas?
A portion of refrigerant absorbs heat energy, and boils to vapor (accounts for 10%)
In some systems, usually air cooled, condensers cannot hold the systems full refrigerant charge. This would require what?
A reciever
Operating pressure inside a steam jet flash tank is above or below atmospheric pressure?
Below atmospheric
A low pressure controller has adjustments for a "cut in value" and "differential" At what pressure does the compressor cycle off? Above cut in Below cut in Equal to cut in
Below cut in *temperature is satisfied*
What is the function of the Generator in an absorption system?
Boil refrigerant out of solution "compress it"
Steam condensate that forms downstream of a steam jet's ejectors should be piped to which component?
Boiler feed water system
What is the function of the Evaporator in an absorption system?
Boils liquid for refrigeration (cooling) *same as always*
Portable Fire extinguisher Types Include Class ___, ___, ___, ___, and ___. What is each type for?
A- (abstract) wood, cloth, paper, rubber B- (barrels) flammable liquids, combustable *liquids*, greases, tars, oils C- (circuit) electrical equipment D- (dangerous metals) combustable *metals* magnesium, titanium, zirconium K- (Kitchen) Cooking appliances combustable *cooking media/oils*
Causes of "not enough condenser water" which leads to high head pressure: (4)
A. Blocked strainer B. Faulty make-up water assembly C. Air bound condenser water pump D. Air bound condenser water piping (improper venting)
Causes of "Condenser water temperature too high" which leads to high head pressure: (8) *Think of water tower, increase temperature means water is not cooling (or evaporating) properly*
A. Tower fan not operating properly B. Tower dampers not open C. Blocked tower eliminators D. Blocked spray nozzles E. Damaged tower fill F. Dirty condenser tubes G. Non-condensables in refrigeration circuit H. Improper water treatment (REMEMBER this is not the primary purpose of the water treatment program)
(REFRIGERATING SYSTEMS - Permits) Fire code requires a permit to maintain a refrigeration system that uses a Group __________________________ refrigerants or refrigerant ____________________
A1,A2,A3,B1,B2, B3 refrigerants or refrigerant that is mounted on or suspended from a roof or ceiling
A synchronous motor uses both AC and DC current but started ___________.
AC only
If the Evaporator Pressure Regulator is stuck in the open position...
Both evaporators would operate at the temp of the coldest coil.
Cold storage rooms (meats or dairy) use ______________ to deal with inevitable frost. What degree can its freezing point go down to?
Brine spray Freezing point as low as -59º recirculated and relatively cheap
If the cylinder of a compressor is running hot and at a decreased capacity, what is most likely the problem?
Broken or leaking piston rings
All bronze pumps will have a volute, impeller and sleeves made of ___________.
Bronze
Centrifugal pumps are *generally* manufactured as "_______________" or "________________" (types of metal used)
Bronze fitted or All bronze
Condensers with sufficient surface or water flow, prevent what for a reasonable amount of time w/o effecting system?
Build up of impurities
(ELEVATORS-IN-READINESS) What codes (2) require every building 75 feet or more in height to be kept ready for immediate use by the Fire department during all hours of the night and day including holidays and weekends.
Building code and Fire code
(BATTERY SYSTEMS - Multi-tenant buildings) The ____________________ is responsible to know the location of all UPS battery systems in their building, and know who is responsible for each one.
Building manager
Emergency over-speed trip valve is known as a _____________________.
Butterfly Valve
Amount of vapor moved by compressor is measures in
CFM
What unit expresses the capacity of the compressor (amount of vapor it is capable of moving)?
CFM Cubic feet per minute
In an absorption system, the rectifier designed like a ....
CLOSED type heat exchanger
(MEANS OF EGRESS) Furnishings, decorations, or other objects must not be placed so as to obstruct __________, ___________ thereto_, ___________ therefrom, or ______________ thereof.
Cannot obstruct *exits*, *access* thereto_, *egress* therefrom, or *visibility* thereof
If the vanes (pre-rotation guide vane) rotate towards the closed position on a centrifugal compressor, what happens to the capacity?
Capacity is reduced Closed vanes = less vapor = less compression/discharged vapor
What connects the TEV to a sensing bulb?
Capillary tube
R-744 is
Carbon Dioxide
Absorption systems have which type of heat exchangers?
Closed type heat exchangers *not open to atmosphere*
Freon 11 Code #: Color Code: Toxicity/ Flammability: Color/odor: Detection Method: Materials it cannot be used with:
Code #: *R-11* Color Code: *Orange* Toxicity/ Flammability: *Non tox, non flam* Color/odor: *Colorless, odorless* Detection Method: *Halide Torch* Materials it cannot be used with: *Magnesium*
Freon 12 Code #: Color Code: Toxicity/ Flammability: Color/odor: Detection Method: Materials it cannot be used with:
Code #: *R-12* Color Code: *White* Toxicity/ Flammability: *Non tox, non flam* Color/odor: *colorless, odorless* Detection Method: *Halide torch* Materials it cannot be used with: *Magnesium*
Freon 22 Code #: Color Code: Toxicity/ Flammability: Color/odor: Detection Method: Materials it cannot be used with:
Code #: *R-22* Color Code: *Green* Toxicity/ Flammability: *non tox, non flam* Color/odor: *colorless, odorless* Detection Method: *Halide torch* Materials it cannot be used with: *Magnesium*
Methyl Chloride Code #: Color Code: Toxicity/ Flammability: Color/odor: Detection Method: Materials it cannot be used with:
Code #: *R-40* Color Code: *Red* Toxicity/ Flammability: *slightly tox, slightly flam* Color/odor: *odorless, near colorless* Detection Method: *Soapy water, Halide torch* Materials it cannot be used with: *Aluminum, Zinc, Magnesium*
Ammonia Code #: Color Code: Toxicity/ Flammability: Color/odor: Detection Method: Materials it cannot be used with:
Code #: *R-717* Color Code: *Silver/Aluminum* Toxicity/ Flammability: *Toxic, Non-flam* Color/odor: *Sharp odor* Detection Method: *Nesslers Solution, Red litmus paper* Materials it cannot be used with: *Copper or copper alloys, muntz metal, admiralty brass*
Carbon Dioxide Code #: Color Code: Toxicity/ Flammability: Color/odor: Detection Method: Materials it cannot be used with:
Code #: *R-744* Color Code: *Silver* Toxicity/ Flammability: *non tox, non flam* Color/odor: *colorless, odorless* Detection Method: *Soapy water, Bromothymol blue* Materials it cannot be used with:
What term relates to the "index of performance"
Coefficient of performance
A partially frosted evaporator coil can indicate that the ...
Coil is being starved (refrigerant supply to coil is insufficient)
Evaporators use what as heat exchangers?
Coils or tubes
Crystallization is most frequently caused by what?
Cold condenser water temperature
In addition to identifying text how would an RMO know which refrigerant a particular valve was used with?
Color Code
What regulates water in a hot well? (2 parts)
Combined operation of a recirculating valve and overboard valve
(NON WATER FIRE EXTINGUISHING SYSTEMS) *Wet chemical fire extinguishing systems* are commonly used with commercial ___________________. How often must an inspection be done by trained and knowledgable person to asses the system is in working order?
Commercial cooking systems Inspection- At least once a month
Vacuum testing (extremely time consuming)
Components isolated, placed in vacuum state, if vacuum cannot be held air is being drawn into system
Schematic diagrams depict the ....
Compression refrigeration cycle *To understand: look for 4 major components, then seek that they are in correct order*
Name the stroke below: Piston compresses vapor, discharge opens, discharge valve closes when pressures equalize
Compression stroke
Which component creates suction to draw the vapor from a Shell and tube type evaporator?
Compressor
If a valve plate of a reciprocating compressor is to be replaced, what else should be replaced at the same time?
Compressor valves
Water cooled condensers can do what compared to air cooled condensers? why?
Condense a far greater amount of refrigerant B/c of increased heat transfer
What is the function of the condenser in an absorption system?
Condense vapor into liquid which can be used to COOL THE EVAPORATOR
Once inside the absorber, the ammonia vapor is _____________, which allows it to mix with what solution?
Condensed *Mixes with aqua-ammonia solution*
Subcooling is an indication of which components performance?
Condenser
"High side pressure" "Discharge pressure" are both...
Condenser pressure
Condensing ton has a value of ________ BTUs, while a ton of cooling (evaporator) is measured to be ____________ BTUs. Therefor, heat of compression contributes roughly _____ BTUs to the overall condenser load.
Condensing ton- 250 BTUs Ton of cooling- 200 BTUs *therefor* "heat of compression" adds 50 BTUs to the load
Liquid in compressor poses risk of: (3 things)
1. broken or bent piston rods 2. damaged compressor valves 3. Blown gaskets or bearing washouts
Purpose of capacity control? (2 things)
1. makes it possible to remove *varying* quantities of heat (systems subject to change in loads) 2. Affects movement of how much vapor is taken from evaporator to condenser
Which form of heat transfer requires physical contact?
Conduction
The differential is changed inside the ____________, and limited to access of service men.
Control
Gravity coils use what kind of current?
Convective current *move air and heat energy without the aid of a fan*
Which of the following expresses the greatest value of pressure? A. 15 "Hg Vac B. 30.0 "Hg Ab C. 0 Psig D. 5 Psig
Convert all to Psia
Gravity coil relies on the fact that
Cooled air is heavier and *hot air rises*
Energy Efficiency Ratio (EER)
Cooling power (BTU/hour) / electric input (watts) = EER
What type of coil is located inside the absorber?
Cooling water
Spray ponds spray water through a nozzle, some evaporates which does what to the remaining water? *think of the fountains outside of buildings, some are actually spray ponds*
Cools the remaining water which is being pumped back into the condenser.
Modern compressors use what type of material for their shaft seals?
Copper and packing
Coils or tubes of evaporator are made of what? and why?
Copper or aluminum Durable, affordable, transfer maximum quantity of heat
Finned coils
Copper tubing serpentines (twists) through lightweight metal fins, positioned perpendicular (90º angle) to the tubing
Double pipe condenser is a _______________ heat exchanger. It has one pipe inside another. Where is the refrigerant? ..The water?
Counter flow *refrigerant in outer pipe* *water in inner pipe*
In the analyzer of an ammonia absorption system, the flow of ammonia vapor in relation to strong liquor can be described as ....
Counter flow Baffles *counter* the natural flow
Maximum specific gravity of a salt solution?
1.33
What are used to join the pumps shaft with the shaft of the motor?
Couplings
Force Feed systems use a _____________ mounted pumped to deliver oil to the system through drilled passageway in the shaft.
Crankshaft
Designed difference between suction and discharge pressure on Centrifugal Machines is ______-_____ psi
15 to 20 psi
Primary compressor raises pressure from 15 psi to
155 psi
Oil foaming in crankcase of a compressor is caused by
Sudden drop in crankcase pressure
R-764 is
Sulphur Dioxide
Operating superheat
Sum of Static and opening superheat. *bulb pressure's opening force exerted on diaphragm*
Measured temperature- Saturation temperature=
Superheat
The TEV attempts to maintain what operation conditions?
Superheat
For a TEV... Bulb pressure (opening force) =_____________+_____________ (combined closing force)
Superheat spring pressure + evaporator pressure (sum creates closing force)
Vertical shell and tube condensers use _________ to circulate the water in a circular motion so the water comes into contact with as much of the tubes as possible. (Carbon steel shell and carbon steel heads, brass tubes)
Swirls
Where is the refrigerant located in the evaporator of a multiple circuit chiller? (AKA Shell and Coil Evaporator- multiple refrigeration circuits ran into *the same* evaporator)
In the coil Shell and coil- Dry expansion (Water in shell) Shell and tube *think tubing, tubes are wet* (water in tubes)
Oil seperator should installed
In the discharge line as far from the compressor as possible
The unit of vacuum on a compound gauge is
Inches of mercury
Air circulating fans and moisture eliminators, which capture evaporating water when defrosting pipes, help ______________.
Increase efficiency
Fins on finned coil serve what purpose?
Increase heat transfer
At a constant suction pressure, any increase in head or condensing pressure will require an increase in what? why?
Increase in power input B/c additional work is required to compress gas to higher pressure
If the load increases (facing a high load) for a absorption system, what will have to be increased to maintain operation?
Increase in steam *More steam= More tons of refrigeration*
What is the primary reason for allowing high pressure liquid to be cooled by suction vapor?
Increase refrigeration effect (Subcooling)
Evaporator coils may be arranged in multiple rows to ...
Increase surface area that can be fit into a machine
Brines are secondary refrigerants typically used with what kind of system?
Indirect *low temperature refrigeration applications*
Rupture *guards* are installed where? and do what?
Installed on the top of the rupture disk, and prevent complete loss of charge after rupture disk breaks
(ANNUAL SERVICE RECORD - Portable fire extinguishers) Record keeping for the annual servicing and recharging of portable fire extinguishers be maintained on a ______ or _________ attached to the extinguisher. What should this include? (3)
Tag or label Tag should include: 1. *Name and C of F number of person who serviced* 2. *Month and year it was serviced* 3. *Name, street address, and telephone # of servicing company* ,if any, servicing the portable fire extinguisher
Semi-hermetic reciprocating compressors where the compressor and motor share the same body, would use which type of oil lubrication?
Internal
TEV can be either _______________ or ________________.
Internally equalized or externally
Because the pressure is the same at the first orifice plate (of a 2 stage compressor) as that of the pressure leaving the first stage, the flash gas return line is piped?
Into the suction of stage 2 Suction of stage 2 = orifice plate 1
Refrigerant strainers are made of _______ when used with ammonia, and ________ when used with non-corrosives
Iron- Ammonia Copper- Non-corrosives (smaller in size)
Pumps must be installed to allow... how is this accomplished?
Isolation Accomplished by using suction+discharge isolation valves
Kilowatt to BTU
Kw x 3415 = BTU's
ASHREA-15 establishes ___________
Machine room safety standards
Fusible plugs release refrigerant into ...
Machine rooms or out to the atmosphere
(MEANS OF EGRESS) What must not be placed on exit doors, or in or adjacent to any exit in such a manner as to confuse the direction of exit?
Mirros
Refrigeration removes hot air but also removes
Moisture
Removing a heat exchanger in an ammonia system will require what?
More steam at the generator (Strong liquor is not preheated, more steam required to increase pressure/temperature)
Where would you find the inlet to the exhaust duct in a machine room with an R-123 unit?
Near the floor, next to the compressor
Booster system or two stage system are necessary to refrigerate brine below ____ºF
Necessary to refrigerate brine below 0ºF Booster compressor discharge into intercooler, which discharge into primary compressor, which compresses vapor and send its to condenser
Why do cascade systems use multiple compressors?
Negate effects of high compression ratio
PH of 7 is considered what?
Neutral - Neither acidic nor alkaline
Heat of compression has what kind of affect on the system? What is required because of "heat of compression"
No affect on the system. It will however *require rejection of a slightly greater quantity of heat from the condenser*, than that absorbed by the evaporator In other words.. Condenser would reject heat from evaporator, but if you add in heat of compression, the condenser must reject evaporator and "heat of compression" heat.
Portable fire extinguishers having a gross weight not exceeding 40 lbs shall be installed so that the top of the extinguisher is not more than ___ feet above the floor, and clearance space between the bottom of the extinguisher and floor shall not be less than ____ inches.
No more than 5 feet above the floor No less than 4 inches from the floor (no fire extinguishers on the floor) *40lbs or less = 4 inches minimum up to 5 feet maximum*
Once a brine is saturated with refrigerant due to leak can it be treated?
No. The brine must be dumped and a new batch must be made.
Non Positive displacement Vs. Positive displacement
Non-positive displacement: *Moves large volume* (increase velocity, followed by sudden decrease) to increase pressure Positive displacement: *Decreases volume* to increase pressure
Cast Iron piping may only be used in refrigeration systems with what?
Non-volatile brines
(SMOKE CONTROL SYSTEMS - Periodic Inspection and testing requirements) All systems must be tested under both __________ power and ____________ power.
Normal and emergency power
Cryogenics
Obtaining and observing materials at very low tempuratures
A Rotating Vane type Rotary compressor has a rotor mounted ...
Off-center of the compressor housing
Which instrument tests a motor for grounded or shorted winding?
Ohmmeter
Refrigerant oil is pumped into where? and what should be done with left over oil?
Oil charging port, left over oil should be discarded
Splash feed oil systems use an ______________ which splashes oil on internal working parts every time the compressor crank rotates.
Oil slinger
Low side float metering device are found on what type of evaporator? How do they work?
On the *side of horizontal shell and tube type evaporators* Refrigerant boils and evaporates in shell, water level is mimicked in float. When float level drops valve is opened, allowing liquid to replenish. *Liquid leaves, float drops, opens valve, liquid replenishes* *Valve assembly contains orifice responsible for pressure drop* REMEMBER LOW SIDE FLOAT DROPS TO OPEN
*Water regulating valve* is found where? What does it do?
On the *water inlet line* to condenser *Controls flow of water to the condenser*
In a low temperature refrigeration system where is the booster compressor located? On the leaving side of the evaporator OR At the mid point between the evaporator and condenser
On the leaving side of the evaporator
(EMERGENCY POWER SYSTEMS - Individuals authorized to perform tasks) Fire code requires that the inspection, testing and other maintenance of *emergency power systems* be conducted under the supervision of a person having one of the following qualifications: 1. A person holding ______ C of Q 2. A person holding C of F as a _____________ 3. An __________ licensed by Department of buildings. 4. An electrician holding a ______________ issued by Department of buildings. 5. A person holding a _________________ license, or __________________ operating engineer license, issued by Department of buildings 6. A _____________________ professional
One of the following qualifications: 1. A person holding *Q-01 C of Q* 2. A person holding C of F as a *Fire safety director* 3. An *electrician* licensed by Department of buildings. 4. An electrician holding a *special license* issued by Department of buildings. 5. A person holding a *stationary engineer* license, or *High pressure boiler* operating engineer license, issued by Department of buildings 6. A *registered design professional*
Halide torch w/ snifter tube (Chlorinated Refrigerants) (Inexpensive, fast, reliable) LIST COLORS AND WHAT THEY STAND FOR
Pale Blue- No leak Green- small leak yellow- restriction in snifter tube dark blue, purple, violet- large leak
What is most likely the cause of an increase in the superheat temperature of refrigerant entering a reciprocating compressor?
Partially blocked valve orifice.
(COMMERCIAL COOKING SYSTEMS) A _________ is required to maintain and operate commercial cooking systems.
Permit
What determines the amount of clearance space?
Physical space between top of piston and bottom of valve plate
What kind of valves precisely control flow rates through evaporators, chilled water coils, and condensers?
Plug Valves (Balancing Valves)
Which type of compressor valves need the most clearance space?
Poppet valves (think POP UP)
A lithium bromide water absorption systems is used to produce chilled water. What is the lowest POSSIBLE water temperature leaving the evaporator of this system? What is the RECOMMENDED?
Possible- 33ºF Recommended practice- 38ºF
In a spray pond condenser, what can be used to kill algea?
Potassium per-man-ga-nate
(REFRIGERATING SYSTEMS - Operator logbook) Fire code requires a logbook for refrigeration systems whose operation requires supervision by a _____ C of Q holder
Q-01
Tip speed is based on what two things?
Diameter of the Impeller and RPM's
In a centrifugal compressor, which type of pressure moves vapor from the evaporator to the compressor?
Differential Pressure
Low pressure control set to "cut out" at 25 psig, and "cut in" at 45 psig. What is the differential? What is the range
Differential is 20 psig Range is 35 psig
What actuates reed type compressor valves?
Differential pressure
Types of evaporators
Direct Refrigeration systems/ Indirect refrigeration system Dry expansion/Flooded Type
Heat rejected from the "indoor coil" during heating mode, can be used as a _____________ or ___________ heating medium
Direct or indirect
Open piping systems (open to atmosphere) expose water and tend to pick up
Dirt and particulate
Rotor compressors only have which valves?
Discharge
Compression ratio formula
Discharge "Head" pressure (Psia) / Suction pressure (Psia) = Compression Ratio
What type of condenser consists of two tubes, where the refrigerant is condensed in the space between the tubes?
Double pipe condenser
A product of the friction produced as water flows through a system is
Dynamic head
(REFRIGERATING SYSTEMS - Operator logbook) Who is required to make entries in the logbook? What must the entries include?
Q-01 C of Q holder *Entry must include:* 1. Any operating problems or deficiencies 2. Required periodic tests conducted
A single stage wheel (centrifugal) can use which refrigerant?
R-11
Group 1 NYC Code Refrigerants (non-toxic and non flammable) (5)
R-744, R-11, R-12, R-21, R-22
(REFRIGERATING SYSTEMS - Supervision) An _________ must be PRESENT IN THE BUILDING where the system is installed when the system is IN OPERATION.
RSOE
A condenser is a _______________ vessel
Rated pressure vessel (designed to operate a maximum pressure)
What effectively reduces the amount of suction vapor that will be drawn into a cylinder? Hint- think of clearance space/ clearance vapor
Re-expansion
Lead seal on a spring loaded relief valve prevents
Readjustment of the valve setting
When do you use INTERNALLY equalized TEV
Single row evaporators w/ pressure drop less than 2.5 psi *Refrigerant from evaporators inlet is applied to the underside of TEV diaphragm through passages in the valve body*
Sensing bulb should be installed at the
End of the evaporator coil to detect superheat.
The COP of a heat pump expresses ...
Energy efficiency
What was used originally to confirm the operation of compression engines?
Engine Indicators
What make it possible to replace dirty grease without over-packing the bearing?
Relief Plugs
Hold over capacity allows for what?
Engineers to do work during off-peak (nighttime in commercial buildings) while still cooling the building by circulated water
What makes it possible to access evaporators water boxes without permanently damaging insulation?
Removable heads
What is the function of the Absorber in an absorption system?
Removes vapor from evaporator
What is used to eliminate scraping frost off the coils? They are operated by a __________ What kind of appliances use these?
Resistors - send an electric current through circuit generating heat. *usually operated by a timer* small appliances
What is the function of the Weak liquor regulating valve in an absorption system?
Return weak liquor from generator to absorber to maintain differential pressure and continue refrigerant movement
Two types of rotary compressors:
Rolling piston and Fixed Vane
Refrigerant pressure increases (Rolling piston Rotary Compressor) as volume between what reduces?
Rotor and Compressor housing
When the differential of a thermostat is not wide enough, what will occur?
Shutdown on low pressure cutout. (Low temperature is obtained to quickly, telling LP cutout to open circuit & shut off compressor)
Modern refrigeration systems are more likely to use what (2 things) for freeze protection?
Ethylene or Propylene Glycol
(SMOKE CONTROL SYSTEMS) Smoke control systems are intended to provide a tenable environment for the ____________ or ____________ of building occupants under fire conditions
Evacuation or relocation
Sub-cooling liquid refrigerant increases the refrigerating effect in the _________.
Evaporator
In an ammonia system, the scale trap is located after the ___________________________. What material is it made out of?
Evaporator *to filter sediment* *made of iron*
Centrifugal compressors (because of large volume, low pressures) cannot have refrigerant lines running around the plant like HP systems. Therefor the compressor is coupled into a packaged unit with its ______________
Evaporator and condenser
Sensing bulb should be attached to the end of the _______________.
Evaporator coil
In an absorption system, the strength of the strong liquor (in the absorber) decreases as the ....
Evaporator load decreases
The strength of the strong liquor in an absorption system decreases as the ....
Evaporator load decreases (less refrigerant required to be pulled into absorber)
Externally equalized TEV use the __________________ pressure Prevents loss of ________ associated with high superheat
Evaporator outlet pressure through capillary line to push up on diaphram as closing force *Prevent loss of capacity associated with high superheat*
"Low-Side pressure" "Back pressure" "suction pressure" are all ...
Evaporator pressure
During normal operation the crankcase pressure is closest to what other pressure?
Evaporator pressure
What specific pressure causes the suction compressor valve to open? (not asking for differential)
Evaporator pressure
The oil sump is equalized at what pressure to induce a gravity return of oil?
Evaporator pressure *Some systems use high pressure condenser gas to induce flow of oil from evaporator to sump*
Freezing point of brine solution should be lower than what? why?
Evaporator saturation temperature - prevent freeze up
When the sensing bulb is clamped to the middle of the evaporator, how will it effect the coil operation?
Excessive superheating
Disadvantage of low head pressure
Expansion valve will not feed the evaporator properly
____________ actuated solenoid valve opens to provide defrosting and closes automatically
Externally actuated
Pressure drop of refrigerant distributors must be accounted for, therefor you must use what type of TEV?
Externally equalized
(FIRE ALARM SYSTEMS - Fire Guard) If a fire guard has been on watch for 4 hours, in a building not exceeding 50,000 sq ft, who must patrol after the out of service condition exceeds 4 hours?
F-01 C of F
(REFRIGERATING SYSTEMS - Monthly testing) ______________ requires refrigerating equipment and systems having a refrigerant circuit containing more than 200 lbs of Group A1 or 30lbs of any other group refrigerant to be subject to monthly testing
F606.6
The S-97/S-98 C of F holder could work citywide but must be employed by an FDNY _________________ or FDNY _________________.
FDNY *certified central Station company* or FDNY *certified smoke detector company*
A system is cycling excessively; -Crankcase temperature is high - Discharge pressure is low - suction pressure is high What is a possible explanation?
Faulty compressor valves
Unit of measure to express head pressure is what?
Feet of water
Types of Dry expansion Evaporators (HINT- end in coil)
Finned coil Plate coil Gravity coil
Fire extinguishers are to be "quick checked" ___________. "quick check" should check if: 1. 2. 3. 4.
Fire extinguishers are to be "quick checked" *monthly* "quick check" should check if: 1. *it is fully charged* 2. *It is in its designated place* 3. *It has not been actuated or tampered* 4. *no physical damage or condition to prevent operation*
When there is an overcharge of refrigerant, using a high side float, what will occur?
Flow is unchecked (continues flowing with valve open), can flood the evaporator
Receiver (liquid line) are designed to hold entire charge of system, composed of both:
HPL and HPV
What is clearance vapor?
HPV remaining in cylinder at the end of the compression stroke
Oil should be where, in regards to the sightglass, when the system is operating?
Half way
If a system has 3 compressors, which can operate at 50% or 100% capacity, how many different capacities can this system operate at?
Six (3 compressors x 2 capacities)
How is each bearing lubricated? (sleeve and ball)
Sleeve bearings are lubricated by means of *oil ring or suitable wicking material* Pumps with ball bearings are equipped with *grease fittings*
Pumps either use ____________ or _________ bearings. Which is use generally on larger pumps?
Sleeve or ball bearings *Ball bearings for larger pumps*
Brine solutions and condenser water systems should be as near neutral as possible. For optimal protection these systems should be what?
Slightly Alkaline (7.8 PH level)
When a new compressor is installed, how much oil should be charged into the system?
Slightly more than normal
Higher condensing pressure, requires what?
Smaller quantities of condenser water
If a paraffin based oil was to foul an evaporator, how would you remove the wax?
Heating up the coil, and pumping it out
A heat exchanger in an absorption system heats the ________________________, and cools the ___________________________. THINK OF IT AS A PREHEATER
Heats the cold "strong liquor" leaving the absorber (which is pumped into the generator) Cools the hot "weak liquor" leaving the generator (returning into the absorber)
Screw compressors are expensive to manufacture because of the _______________________, however they are ___________.
Helical Rotors (lobes) Cheaper to operate
How is a safety head held in place?
Helical spring
Low temperatures result in _________ compression ratios
High
Centrifugals are characterized by what volume and what pressure? (High or Low)
High Volume, Low Pressure
Dual pressure controls monitor both ______________ pressure.
High and Low
Which of the following will not affect a systems compression ratio? Evaporator Operating temperature High head pressure Dirty evaporator filter High atmospheric humidity
High atmospheric humidity
Inadequate condenser water not only lessens the amount of heat removed from a load, but inadequate water flow rate will also limits the heat absorbed from the condenser resulting in...
High head pressure
Restricted tube connecting water regulating valve to the refrigeration system will cause
High head pressure *Think water. Less chilled water =instant High HP*
If the refrigerant temp is too high a TEV will send ___________ refrigerant. If the refrigerant temp is too low...
High refrigerant temp = Send more Low refrigerant temp = Send less
Single compressor operates two evaporators 1 at 40º and 1 at 20º. Where would the two temperature valve be placed in this system?
Higher temp suction line (either evaporator can turn on the compressor) *LP controller adjusted to the coldest coil to turn off compressor*
If there are 3 evaporators in a system with different temperatures, the *evaporator pressure relief valve* would be placed in-between the two ____________ temperature evaporators. On what line?
Highest *on suction line*
What is the function of the receiver in an absorption system?
Hold refrigerant charge *same as always*
Rotary compressors are often used in
Household refrigerators and small a/c units
(ELEVATORS-IN-READINESS) Phase 1 emergency recall operation generally requires that elevator landings and elevator machine rooms be provided with _________________ that, when activated, will recall the elevator to a safe location as required by building code. Such recall is also required for ___________________ alarms.
Smoke detectors also required for sprinkler water flow alarms
Two salts traditionally used in salt brines are?
Sodium Chloride (NaCl) or Calcium Chloride (CaCl)
Sodium Dichromate is added in lbs per 1000 cu/ft of brine. How much Sodium Dichromate is added to CaCl? to NaCl?
Sodium Dichromate added to CaCl: 100 lbs NaCl: 200 lbs
in the "pump-down" cycle the thermostat should be wired in series with which device?
Solenoid valve
When the compressor stops running, what usually closes? why?
Solenoid valve prevents HPL from trying to stabilize (flow) to the low side of the system
Sodium Chloride (Eutectic Point) Spec. Gravity: % by weight: Freezing point:
Spec. Gravity: *1.178* % by weight: *23.31* Freezing point: *-6ºF*
Calcium Chloride (Eutectic Point) Spec. Gravity: *higher than NaCl* % by weight: *higher than NaCl* Freezing point: *lower than NaCl*
Spec. Gravity: *1.29* % by weight: *29.6* Freezing point: *-59.8ºF*
All mufflers are made of
Hydrogen copper brazed steel
What device measures specific gravity?
Hydrometer
What testing occurs to leak test Evaporator tubes? What is it?
Hydrostatic testing- exerts water pressure 150% operating pressures and any loss of pressure indicates a leak
In freon compression system, a practical way to check for oil carry-over into the refrigerant circuit is to Spray refrigerant from ____________________ onto a piece of ___________________, and inspect paper for oil stain
Spray refrigerant from *bottom of receiver* onto a piece of *bond paper*, and inspect paper for oil stain
A Rotating Vane type Rotary compressor has _______________________ fixed to the rotor, which trap refrigerant in the compression chambers as the rotor turns.
Spring loaded *vanes*
What pressure keeps a "single vane" on a Rolling piston (Rotary Compressors) in constant contact with the rotor?
Spring pressure
AXV opening and closing forces (2)
Spring pressure (opening force) Evaporator pressure (closing force)
What device bends copper tubing?
Spring type tube bender
Packing gland on a service valve, allows cap to be tightened which does what?
Squeezed packing material together, after a period of time, preventing leaks and tightening seal
A two stage wheel (centrifugal) is common for what?
Standard ton conditions
Compressor by-pass valves (capacity control method) are used to ________________.
Starting the compressor (without having to overcome discharge pressure)
Booster compressors take very low pressure refrigerant and compress them to avoid what?
Starving the compressor
The pressure needed to lift water through vertical distances is
Static Head
Operating superheat (forces acting on TEV) is the combination of what two types of superheat?
Static superheat + Opening superheat
Which of the following could be the prime mover in an absorption system? - Aqua-ammonia pump - Generator - Evaporator spray heads - Steam coil
Steam Coil
Gland seal systems prevent
Steam leaking out AND Air leaking in
The EPR maintains evaporator coil temperature, but can also act as what kind of valve?
Stop Valve
Receivers (horizontal or vertical) are ...
Storage tanks for the liquid *in* a refrigeration system *meaning refrigerant storage not water*
_____________ are installed on the inlet side of the pump to prevent particles from damaging the impeller, while ______________ are installed on the discharge to prevent back flow.
Strainers - inlet Check Valves - outlet
When the absorber condenses the ammonia vapor, it raises the concentration of the ammonia solution to 28% (ammonia). This 28% ammonia, 72% water solution is referred to as _____________.
Strong liquor
Name the stroke below: Re-expansion of HPV, suction valve opens, draws vapor into cylinder
Suction Stroke
Suction drier location vs. Filter drier location
Suction drier- SUCTION LINE Filter drier- LIQUID LINE
Liquid line heat exchangers increase refrigeration effect by crossing liquid line to evaporator with what?
Suction line to compressor LPV drawn out of evaporator, absorbs heat from HPV in liquid line *enclosed pipe carrying HPL refrigerant enters Heat exchanger (open pipe) filled with suction line LPV*
Head loss can further be distinguished as ______________ or ___________________
Suction loss or Discharge loss
The compression stroke starts at an elevation that corresponds to what pressure? (when using an engine indicator diagram) Compression stroke elevation = _________________ guage
Suction pressure gauge
What service valve is located at the motor end of the compressor?
Suction service valve
Bypass valves allow low pressure vapor to be circulated back to where?
Suction side of the compressor
Cylinder unloaders control capacity of a reciprocating compressor by holding what valve(s) in the open position?
Suction valve(s)
What is used to cool motor windings in a hermetic compressor?
Suction vapor
(FIRE ALARM SYSTEMS - Fire guard) In other words, the impairment coordinator or a trained and knowledgable person designated by the building owner should ______________ begin conducting a fire watch in the area where the fire protection services are out of service. After 4 hours of an out of service condition, such patrols should only be conducted by fire guards holding the ________ C of F
IMMEDIATELY After 4 Hours requires F-01 C of F
Prior to installing a rooftop unit it must be decided _______________________.
If the building will support the weight
Similiar to sprinkler system the building owner is required to designate an ____________________ who must take specific action when a system goes out of service
Impairment coordinator
*Capacity* in a centrifugal machine is determined by what?
Impeller vane size
A clearance pocket creates an additional area in which high pressure vapor can collect. Explain how this creates capacity control?
The clearance pocket holds *more high pressure vapor, meaning a greater quantity of refrigerant must re-expand*, which further reduces the amount of vapor entering the compressor.. thus lower the amount discharged
While the evaporator, metering device, and condenser are functionally the same, absorption systems used other major (and auxiliary) components to replace ______________.
The compressor
When the compressor is not in operation, what is energized to separate refrigerant that has migrated into the oil?
The crankcase heater
An adjustment screw allows the user to preset what on an AEX?
The desired evaporator pressure/temperature
Multiple compressors piped in parallel (NOT IN SERIES) allow operation of all or some combination of compressors without elevating ____________ pressure
The discharge pressure
Shell and Coil *condenser* is a ______________ condenser
Water-cooled *Refrigerant in shell* *Water in coil*
In an absorption system, for the system to be continuous, what must be returned back to the absorber? What performs this task?
Weak Liquor *Weak liquor regulating valve* returns weak liquor from generator, PASSES THROUGH HEAT EXCHANGER, to the absorber
To ensure overcharging doesn't take place, "__________________" is used to make sure the correct amount is added
Weighing the cylinder
5 Lbs of water at 50ºF requires how many BTUs to freeze?
Weight x Temp Diff x Specific Heat = BTU's (sensible heat) Weight x 144= BTU's latent heat *144 for liquid to solid, but 970 for vapor to liquid* (sensible heat) + (latent heat) = Total BTU's required
Low head pressure will lack what pressure? What will occur?
Will lack differential pressure, and starve the evaporator
Where are eliminators located? What is their function?
Within an evaporative condenser Prevents moisture carry over
Which motor is the *only* multi-speed motor?
Wound rotor induction motor
Operating temperatures for brines *can be at* but must not exceed what?
The eutectic point (Freezing point)
The water pump pumps into _________
The evaporator *the water leaves the evaporator and enters air handler system*
If specific gravity exceeds the Eutectic point of a brine solution what will occur?
The freezing point (temperature) will increase rather than continue to descend
In a multiple temperature system, which evaporator shuts down the compressor?
The lowest temperature evaporator
The tubes which extend from the top of a water pump to the housing on the pump shaft are used to cool what?
The mechanical seals
In a 2 stage (centrifugal) system, as the refrigerant passes through the first orifice plate, its pressure will be equal to that of what pressure?
The pressure leaving stage 1 P1 = pressure into stage 1 P2= pressure exiting stage 1 P3= pressure exiting stage 2
Centrifugal machines must be designed based on what two things? HINT- these two things play a factor in size of machine, and metals used.
The refrigerant used and temperature (operating) conditions
(HOT WORK OPERATIONS) The responsible person shall inspect the hot work site prior to issuing a hot work ______________________ and periodically monitor the work as it is being performed to ensure there are no ________________. *Hot work operations shall be conducted under the general supervision of the responsible person.* This person is also responsible to maintain "_______________" reports.
The responsible person shall inspect the hot work site prior to issuing a hot work *program authorization* and periodically monitor the work as it is being performed to ensure there are *no fire safety hazards*. *Hot work operations shall be conducted under the general supervision of the responsible person.* This person is also responsible to maintain *"Pre-work check" reports*.
As pressure pushes up on the diaphragm of a TEV...
The spring pushes up the needle, because the diaphragm is not pushing down.. thus stopping flow. *once the sensing bulb pressure overcomes, it pushed down on the diaphragm, pushing down the needle, allowing refrigerant to flow
Hold over capacity is determined by what two things?
The temperature of the water when the system was shut down AND The amount of cooling that will be required
Flash gas return line is piped from ... (centrifugal)
The top of the economizer, to the suction *of the equal pressure stage* in the compressor
A systems compressor may lose oil if ______________. Theres air in the system The velocity of refrigerant in the riser is too low There are medium pressure drops in the evaporator There are small load variations in the system
The velocity of refrigerant in the riser is too low. Refrigerant carries oil to compressor, and decrease in velocity equals decrease in oil
A vertical shell and tube is different than a horizontal because what?
The water only makes one pass through the tubes.
Primary function of heat exchanger in an absorption system is to let....
The weak liquor HEAT the strong liquor vice verse The strong liquor COOL the weak liquor
TEV are usually rated by ..
Tons of refrigeration
(MEANS OF EGRESS) To provide a path of travel that is clear, unobstructed, well-marked, and illuminated and in which all components are under control of the user without requiring any ________, ________, or _______________.
Tools Keys Special Knowledge or effort
Bellows of a water regulating valve should be connected where?
Top of the condenser shell
Clearance pockets are a small amount of space between the top of the ______________ and the bottom of the ________________.
Top of the piston and the bottom of the valve plate
Water, oil and refrigerant would settle in a contain in what order? (top to bottom)
Top- Oil Middle- Water Bottom- Refrigerant
The total of all the plumbing and equipment head for the entire system is
Total Dynamic Head
In terms of the motor required for parallel pumping, each pump must develop the horsepower needed to over come what? without risking _________.
Total system head (design head) without risking motor burnout
Powerhead of a TEV has labeling which indicated what?
Type of refrigerant for that valve
(BATTERY SYSTEMS - Multi-tenant buildings) The building manager is responsible to know the location of all _______________________ in their building, and know who is responsible for each one.
UPS battery systems
How does a cylinder *unloader* work? What does it do?
Unloaders allow refrigerant vapor to be sucked in during the suction stroke, and then *hold the suction valve open during the compressor stroke*, which does *not allow pressure to build*, thus never compressing the refrigerant, and *never opening the discharge valve* REDUCES TORQUE ON THE MOTOR WHICH DRIVES THE PISTON
Soap and bubbles (simplest way, High pressure only)
Used when approximate area is known
Cross charged TEV Uses refrigerant that expands at a faster rate, causing __________________ *prevent _______________ on loss of load* *prevent __________________ as superheat temp increases* Referred to as "Vapor or liquid cross charges"
Uses refrigerant that expands at a faster rate, causing quicker response *prevent flood back on loss of load* *prevent loss of capacity as superheat temp increases* Referred to as "Vapor or liquid cross charges"
Indirect Refrigeration system
Uses secondary refrigerant (chilled water or brine) Centrifugal pump will deliver water to wherever cooling capacity is needed.
V Compressor vs. W Compressor _____ cylinders, ____ pistons
V compressor *4 cylinders, 4 pistons* W compressor *6 cylinders, 6 pistons*
Centrifugal compressors move large quantities of vapor (heat) and maintain what kind of pressures?
Vacuum Pressures
If an engine indicator diagram pointer is "hunting" (wide and relatively slow back and forth movement), it would most likely indicate that the compressor?
Valve is acting sluggish
Scale trap protects : (4 components)
Valves Metering devices Capillary tubes Compressors
Stem cap on TEV is used to protect what?
Valves superheat adjustment screw
Which sensing bulb uses a refrigerant other than that in the system and maintain a maximum operating pressure? liquid charge vapor cross charge liquid cross charge all of the above
Vapor Cross charge *think MOP* only vapor cross charge has MOP (55 psig)
A TEV can be rated in terms of _________________________ entering the valve
Vapor free saturated liquid
Low suction pressure at the *pump* will cause some types of fluids (especially those at high temperatures) to approach their ...
Vapor pressure (boiling point) *Generally not a problem with environmental heating and cooling systems*
Centrifugal compressors use what type of displacement?
Variable
TEV are used on small to midsize refrigeration applications with _______________.
Variable loads
Thermostatic charges ________ with the application and operating conditions.
Vary
Steam jet systems spray steam through a _____________, which creates a vacuum in a chamber where the chilled water is circulated.
Venturi
Fumigation and insecticidal fogging operations shall be conducted by or under the personal supervision of a person holding a _________ C of F, employed by and _____________________ fumigation and insecticidal fogging operation company
W-97 C of F Employed by *FDNY Certified fumigation and insecticidal fogging operation company*
R-718 is
Water
Steam jet systems use what as their refrigerant?
Water
What type of condensers often double as a receiver?
Water cooled condensers
High pressure cutouts are recommended for systems with what type of condensers? OR air cooled condensing units containing over _____ lbs of refrigerant
Water cooled condensers or Air cooled w/ charge over 20 lbs
Vertical shell and tube condensers are used when floor space is minimal, but also when ...
Water has high potential for tube fouling
If the discharge valve is closed on a centrifugal pump, the pressure will not increase and may cause damage to the system. This is because the centrifugal pump will not exceed ...
a maximum pressure
The net effect of a lower TD created by sub cooling is refrigerant that will be able to .. HINT Lower temp diff means the numerical value for temperature difference is lower..not that the distance between the temperatures has lowered. (mean has increased)
absorb more heat from the load
Tracing out a system is more __________ than schematic diagrams and allow one to "fill in the gaps" of the systems components
accurate
Change in evaporator on a manual metering device system requires an ...
adjustment of the valve (metering device)
Chilled water can be distributed to: (3 things)
air handlers fan coils terminal units designed to remove heat from air
Suction pressure decreases, capacity will ..
also decrease
High steam condenser pressure will cause the ________________ valve to open
atmospheric
Fusible plugs cannot...
be reset
Oil pressure controls monitor oil by sensing the pressure across the what?
bearings
Low Pressure control (controlling pressure/temp) is connected by a flexible _____________
bellows on low pressure side of system
The pressure on the seal in an R-11 system is _____________? (above or below atm.)
below atmospheric pressure
Larger systems redirect high temperature vapor discharged from the compressor, through a "__________________" into the evaporator
by-pass line Raises temp of coil.
Because of the vapor pressure in the generator, the vapor is "____________" the same as in a non-absorbsion system
compressed
The oil sump stores the oil required for the
compressor
"head pressure" is...
compressor discharge pressure
The High pressure ammonia vapor travels from the generator into the ______________.
condenser
Spring loaded release valves are located on top of the ...
condenser, receiver or evaporator
Multiple impellers (multi-stage compression) can be used when a single stage cannot lift the refrigerant to the required ....
condensing pressure
Bringing an additional pump on line, will increase the flow rate while maintaining a ....
constant head
A water regulating valve connected to the top of a condenser is used to maintain
constant refrigerant pressure
How should the seat of a service valve be positioned *when a permanent pressure gauge has been installed*?
cracked off the back seat
Oil pressure differential switch measures difference between ____________ and _________
crankcase and oil pump
For a multi-cylinder compressor, capacity is a function of the number of _____________ being bypassed.
cylinders
Engine indicators are used to check the mechanical operation of a __________________ compressor.
reciprocating compressor
When a sufficient quantity of refrigerant has become vaporized the temperature of the the product being cooled can be effectively __________
reduced
The LP cutout can be placed right at the compressor _____________ lines.
refrigerant
Capacity of condenser increases as TD of what increases?
refrigerant gas and water/air (cooling refrigerant)
Thermostatic charge is the ..
refrigerant used to exert an opening force on diaphragm.
Superheating and sub cooling enhance and/or protect the
refrigeration cycle
Pressurized oil is fed to centrifugal compressors through bearings. The bearing oil pressures are controlled by a ____________________ in the oil pump discharge
regulating valve
Any time a relief discharges, it must be ______________, since the spring may have lost its tension or the valve may not seat properly
replaced with a new one
Rupture disks are like fusible plugs because they do not...
reset
(HOT WORK OPERATIONS) Whenever hot work is performed the owner shall ensure that such work is performed in accordance with the Fire Code and shall designate a ________________ to ensure compliance.
responsible person
The vacuum created by a steam jet lowers the _______________ of water, but operating temperatures must remain above 32ºF to prevent freezing.
saturation point
In a single screw compressor refrigerant vapor moves through the
screw and gate rotor
cascade systems are 3 _____________ systems.
separate
In an ammonia absorption system the generator receives the ...
strong liquor
Pumps in parallel are all fed by the same ...
suction header *discharge header receives pump discharge*
Systems with a suction pressure lower than ____ psi or a compression ratio grater than _______ are generally booster systems
suction pressure lower than 5 psi compression ratio greater than 9.5 : 1
Spinner tubes
supplies atomized oil to motor bearings
If the external equalizer line breaks...
system refrigerant charge will be lost
Evaporator pressure regulators are installed to maintain different... (remember- multiple evaporators)
temperatures in the evaporators *Limits flow of Evap 2, increasing pressure and temp*
(SPRINKLER SYSTEMS) Master fire suppression piping contractor holding s-12 is authorized to _____________, ______________, and ___________/_____________ all sprinkler systems components
test, maintain and repair/replace
Flashpoint of refrigerant oil should take place at a temperature higher than
the compressor discharge temperature
Liquid line service valve (KING VALVE) is located after...
the condenser or reciever
If gauge reading between rupture disk and rupture guard is above or below 0 psig, it is an indication that ...
the disk has ruptured
Solenoid valve does not regulate flow of refrigerant to ....
the evaporator
The larger the size of the evaporator...
the more heat it can move
(HOT WORK OPERATIONS) Hot work must not be performed in areas where ....
the sprinkler protection is impaired
When the pressure inside the crankcase overcomes the pressure holding the suction valve closed
the suction valve will open and allow refrigerant vapor to flow
The operating temperature of the evaporator should be well below ...
the temperature of the object being cooled AND well below the prevailing dew point
When the crankcase heater boils out refrigerant, where does the vapor become trapped?
the top of the crankcase
On an increase in load, an AEV will respond by ___________________, using less of the evaporators heat transfer surface.
throttling back
As resistance to flow increases, the flow rate will ...
decrease
Excessive superheating can cause _____________________ in the evaporator.
decreased capacity
Centrifugal water pumps provide...
design flow rate (provided by system)
Setpoint determines when the electrical contact inside of a _______________ closes
determines when the electrical contact inside of a *thermostat* closes.
Cascade systems has 2 or 3 different refrigeration systems with ____________ refrigerants.
different
What is the function of the Analyzer in an absorption system?
dry hydrous ammonia leaving generator
Electric controls turn off system or components by ...
electric means
modern refrigeration compressors operate at such high speeds (RPMS) that _________________ cannot effectively monitor their operation
engine indicators
Auxilary components are designed to __________ or ___________ the system.
enhance or protect the system
The building shall be __________ or a _________________ maintained when a standpipe system, sprinkler system, or fire alarm system is out of service.
evacuated or fire watch maintained
Cooling towers rely on the ______________ of small amounts of condenser water to ultimately remove heat.
evaporation
Heat rejected at condenser is the same heat (BTU) absorbed in the ...
evaporator
sub cooling increases cooling capacity at the ____________ and also reduces what?
evaporator reduces TD between high and low side
When a reciprocating compressor is operating the crankcase pressure is closest to the
evaporator pressure
What allows screw compressors to have low operating costs?
excellent "part load performance" (Kw/ton)
As the temperature at the evaporator coil increases, the thermostatic charge will ...
expand *increasing opening force*
Pressure drop greater than 2.5 psi in a system *requires* an
externally equalized TEV
Superheat spring (adjustment spring) on a TEV is _________________ adjusted to maintain superheat
factory
Scale trap (refrigerant strainer) is used to ...
filter sediment
Air cooled condensers use circulated air across a ...
finned or bare coil
refrigerant entering the evaporator is a mixture of liquid and vapor. The vaporized portion is referred to as ______________.
flash-gas
Removing external equalizer line from TEV will ...
flood the evaporator
Frost on the compressor and suction line indicate a ...
flooded evaporator (low superheat)
AEX will adjust its ____________ in an effort to maintain a constant evaporator pressure.
flow rate
Direct Expansion Evaporator (DX Coil)
heat is transferred from object *directly* to refrigerant Refrigerators, water coolers, cold storage facilities
the generator contains a continuous ____________________ (such as a steam coil)
heat source
*Temperature difference* between refrigerant and product being cooled make ...
heat transfer possible
Screw compressors are characterized by
helically grooved rotors
Receivers can hold refrigerant when the machine is pumped down. Along with this they can do what, which will prevent the need to remove refrigerant from the system.
hold the refrigerant charge during service
Subcooling prevents inadvertent vaporization aka
increased flashing *subcooling prevents high flash gas*
As suction pressure (temperature) increases, capacity of compressor ___________
increases *increased density of gas, pumps greater amount with each piston stroke*
Desiccant is the material inside the _______________. Can include (3 materials)
inside the filter drier *Can include* Silica gel Activated Alumina Molecular sieve
The primary compressor is called the primary because...
it must be started first to allow the booster compressor to discharge. If the booster compressor is started first, there will be a pressure build, and possible damage to the system.
Water passing through a condenser can come from what natural sources? why?
lakes, streams, wells, rivers or ponds They are convenient and can *sometimes be* continuous
Liquid charging is the fastest method to add refrigerant, and is used for __________ amounts
large
Decrease in capacity of a reciprocating compressor may be due to?
leaking compressor valves
Multiple circuits (ACME system) use separate circuits and a shared evaporator. Bringing an additional circuit on line will make it possible to maintain what temperature as the load varies? HINT- think of the big picture. what would want to be maintained by the system? What is its purpose?
leaving water discharge temperature (keeps object being cooled the same temp that is being required)
Capillary tube metering devices (small refrigeration systems; Window a/c units or compact refrigerators) consist of a ________________ that is responsible for pressure drop
length of tubing
Lower TD, in turn, creates _____________ flash gas
less flash gas at metering devices
High pressure cutouts are pressure _____________ devices used to cut out at set pressure on high side of system.
limiting
Solenoid valve is a __________ line stop valve
liquid
Superheating provides a measure of safety assuring there will be no _____________ present in the suction vapor.
liquid
Control valves control the ____________ flow in some parts of the system
liquid *such as a metering device* *keeps proper amount of liquid in the evaporator*
Abrupt change in load, dirty filter driers, or malfunctioning metering devices can be responsible for
liquid leaving the evaporator (liquid in suction line)
Liquifying of refrigerant that takes place at the condenser is a __________ heat process, however the continued removal of heat is a ____________ heat process.
liquifying is latent continued removal is sensible (sub cooling)
Lithium bromide systems use a solution of
lithium bromide salt and water
A crack in the bellows of a LP cutout, can result in ...
loss of entire refrigerant charge
Scroll compressors are often associated with low what? (two things) Low _____________ and low _____________
low noise level and low vibration levels
"pump down" moves refrigerant from
low side to high side (into receiver) *cannot pass solenoid valve bc it is shut*
Booster compressor always has a _______________ suction pressure, compared to the primary compressor
lower
A very cold coil will cause dew/frost to freeze. This insulates the coil preventing proper heat transfer. Less refrigerant boiling in the evaporator results in a _______________, which does what?
lower suction pressure, reducing capacity
Vapor charged TEV
maximum force exerted is limited by the quantity of liquid refrigerant in the bulb. When all liquid boils off, maximum operating pressure is being exerted, allowing refrigerant to flow
Water cooled condensers will only operate at their designed capacity when the ___________________________ is obtained (between the water and refrigerant)
maximum temperature difference
An abnormal engine diagram indicates a ______________ problem in the compressor
mechanical problem
After leaving the condenser, in an absorption system, the liquid passes through the ______________, and back to the evaporator
metering device
Support sheets in the evaporator are designed for tube bundles and minimize ______________ of the tubes, limiting possibility of _______________
minimize *deflection* of the tubes, limiting possibility of *leakage*
There is always one _________ pass than baffles
more *2 baffles = 3 passes* *1 baffle connects 2 passes*
High head pressure will risk system safety shutdown or ___________________.
motor burnout
Warm water supplies should
not be used, because warmer water will require greater power (less efficient)
Thermostatic charges are contained in the TEV, meaning they are ...
not part of the refrigeration cycle.
A coil with no frost on the bottom indicated that the coil may be ....
oil logged Coil is insulated and preventing proper heat transfer
indirect systems allow the refrigeration cycle to be confined to ________________
one room
Water passes through the condenser, provides cooling, and returns...
to its source
The crankcase breather vents from the top of the crankcase to the
top of the suction valve on the valve plate under the compressor head.
Screw compressors move refrigerant vapor through the space created by
twin screws
Solenoid valve is a ___-way valve
two
How many lubricating oils are used in a horizontal double acting compressor?
two 1. internal 2. external
remember frost is *inevitable* when operating a DX evaporator coil below 32ºF Evaporator operating efficiently near full capacity should have ______________ frost across the coil. When it is not, what is this a sign of?
uniform If frost is not uniform, some parts of the coil are absorbing more BTUs then others
Hold over capacity (INDIRECT SYSTEMS)
unlike normal operation where refrigerant must be cycled to maintain chilled water temp... "hold over capacity" allows *adequate cooling by simply circulating water through fans and terminals during off-peak*
To check the efficiency of reciprocating compressor valves you can ...
use an indicator card diagram
Absorption systems are ____________ compression refrigeration systems, which are installed where heat or steam is available at a *lower* cost then electricity needed to run the motor of a compressor.
vapor
Centrifugal pumps increase pressure by converting ...
velocity energy into pressure *same as centrifugal compressor* increase velocity,travel through volute(casing), reduce velocity, creating an increase in pressure
Compressor design is characterized by an impeller which is housed within a ...
volute
The hand purge on a condenser connects the ____________________________ to the top of the condenser
water regulating valve
The absorber, in an absorption system, contains a substance which has a strong attraction for the vapor produced in the evaporator. This substance is called _______________.
weak liquor
When charging a system, the quantity of refrigerant to be added is determined by
weighing the cylinder (prevent overcharging)
Moisture laden air can only be leaked into a system which operates...
with pressures below atmospheric pressures (Vacuum pressures)
sum of the pressure loss through _______, ____________, __________, and __________ will give you the overall system head loss
pipes, fittings, valves, and coils
Dynamic compression exists when there is no ....
positive displacement
Subcooling lowers refrigerant below its saturation temperature, without affecting what?
pressure
Superheating increases temperature without affecting its ...
pressure
Force exerted by evaporator pressure may be affected by the amount of refrigerant _______________ across the evaporator
pressure drop
If bubbles are not caused by lack of refrigerant charge, although the most common reason, they may be caused by
pressure drop in the liquid line *REMEMBER- always assume it is from lack of charge, not pressure drop*
pressure *limiting* device stops the operation of the ___________________ device
pressure imposing
As the rotors turn (Screw compressors) the space is continually reduced, eventually causing ...
pressure increase of refrigerant to condensing pressure
Electric controls and control valves can be actuated by
pressure/temperature inside the machine
Oil piston rings
prevent high pressure vapor from passing piston during compression
Kingsbury Thrust counteracts the forces acting parallel to the compressors shaft. In other words it ...
prevents axel displacement
Oil strainer
prevents particles from entering pump
Pressure relief devices are used to ...
protect system in the event that the pressure exceeds a certain limit
Couplings should be enclosed by a _________________.
protective guard
Formula Psi to "Hg
psi / .491
Total force in pounds exerted by a 4" diameter piston with a given pressure of 90 PSI is ?
(2x2x3.14) x 90 psi = 1,130.4
Refrigerant oil characteristics (7)
1. Miscible with refrigerant 2. Low pour point 3. high viscosity 4. No moisture 5. No wax 6. High flash point 7. neutral, non-corrosive
Methods of capacity control: (7 things)
1. Multiple compressors (in parallel) 2. Multiple refrigeration circuits (shared evaporator) 3. By-pass valves 4. Clearance pockets 5. Pre-rotation guide vanes (Centrifugal) 6. Variable speed compressors (Centrifugal) 7. Unloaders
Booster compressor must be what when compared to the primary compressor? (2 options) Why?
1. Operating at a higher Speed 2. Larger, with greater bore and stroke Because the booster compressor operates anywhere from 5lbs suction pressure, down to 15 inches of vacuum; while the primary operates at 5 to 20 lbs of suction
Causes of open winding w/ ELECTRICAL MOTOR: (1)
1. Ohmmeter reads ∞ (infinity)
Causes of Banging sound on startup w/ a *reciprocating compressor*: (1) Hint- not water
1. Oil overcharge SLUGGED
Reciprocating compressors (small to medium size ac or refrigeration appliances) movement
1. Top dead center (Both valves closed, still has a clearance pocket) 2. Suction Stroke (Piston moves down, creates suction greater than evaporator, opens suction valve, LP vapor fills cylinder) 3. bottom dead center (both valves closed) *cylinder pressure= suction pressure= discharge pressure* 4. (Discharge) Compression stroke (Pressure builds as piston moves up, opens discharge, releases HP vapor, returns to Top dead center)
Causes of shorted motor windings w/ ELECTRICAL MOTOR: (2)
1. Winding resistance less than the motor's published value 2. Less resistance causes temperature rise, motor overload device opens circuit
Causes of noisy operation w/ MECHANICAL MOTOR: (1)
1. Worn bearings
percentage of oil traveling through system during operation
10%
Scroll compressors are approximately _____-______% more energy efficient than similarly sized reciprocating compressors. Why?
10-15% B/c of *continuous flow* and *no re-expansion of HP vapor*
DX cooling coil is equipped with TEV. If load variations are wide and subject to change, the superheat setting should be 1-3º 3-5º 5-7º 10-15º
10-15º allowing for varying load. 5º compared to the rest which are 2º
Oil pump discharge pressure should be:
10-30 Psi above the compressors suction pressure
The discharge pressure of R-744 (*carbon dioxide*) at 86ºF is _________
1031 psig
If an air conditioning system is set for 10º superheat, the gas passing the remote bulb (sensing bulb) should be .... Why?
10º Above the temperature of the evaporating refrigerant If temp of refrigerant in evaporator is 35º, you add 10º superheat, and refrigerant leaving is 45º
The crankcase heater heats oil to about
115ºF
BTUs required: Solid (ice) to liquid
144 BTU's
How many times is the high side and low side separated in an absorption system?
3 Metering device Weak liquor regulating valve Strong liquor pump
How the cascade works
1st system- (highest temp) could be R-12, single (water cooled) compressor plant, except the evaporator would be similar to construction of shell and coil condenser. The evaporator would cool the second condenser. 2nd system- possibly R-22, normal system, except condenser would be refrigerant cooled condenser. Evaporator of system 2 would cool third system's condenser. 3rd system- Possibly Kulene 131, both discharge and suction side would be lower, can produce temperatures of -135º below zero. *Condensing at low temperatures allows the metering device to reduce temperatures extremely low* *Note- Other refrigerants can be used, these are just examples* *separate systems, intertwined, where each evaporator cools the next condenser*
One psi = _________ feet of water
2.31 ft of water
____ lbs of steam = 1 ton of refrigeration
20
1 T of cooling equals how much steam?
20 Lbs used in the generator
1 Ton of Refrigeration equals how much ice?
2000 lbs
Which voltage is often used in control systems?
24 Volt
29"Hg is equal to how many microns?
25,400 Microns
Speed increasing gears or steam drive turbines are used to drive others up to what RPM?
2500
One Ton of Refrigeration is ____________ Btu's per day, per hour, per minute
288,000 btu/day 12,000 btu/hour 200 btu/min
Bronze fitted pumps have a ____________ body, with the impeller and seal assembly being made of ___________.
Cast Iron body Brass
When a single compressor machine is needed with a capacity over 300 T which machine is used?
Centrifugal (usually)
(REFRIGERATING SYSTEMS - Operation inspection after repairs) After ANY repairs are made to a refrigeration system, the operation of which requires supervision by a _________________ holder. This holder must check the ____________ together with the functioning of all _______________ and the positioning of all _______________.
Certificate of qualification holder. Must check the *repairs together with* the *functioning of all control devices* and the *positioning of all valves*.
In a 3 wire, 3 phase motor, the direction of rotation may be changed by doing what?
Changing any two power leads (reverse polarity)
Which procedure is used when charging a 60 T refrigeration unit?
Charge into low side of system (liquid charge)
What law states relationship between Temperature, Pressure and Volume
Charles Law As Volume increases, Pressure and Temperature decrease And Vice Versa
The strength of an absorber's solution increases as it passes through the absorber. Which of the following best describes the process that makes it possible to transfer low pressure vapor from the evaporator to the absorber?
Chemical Attraction Weak liquor *attracts* the vapor from the evaporator
Evaporators can also be called (2)
Chillers or Brine coolers
Refrigerant distributor is commonly used with ...
DX cooling coils
Fire safety inspection should be part of an engineers ______________ inspection
Daily
Which law states "the total combined mixture of gases is the sum of the pressure of each of the constituent gases"
Daltons Law
In what way does an unloader affect a compressor?
Decrease capacity
Because ammonia has a far lower boiling than water, the concentration of ammonia in the "strong liquor" is _____________ in the generator.
Decreased
Higher elevations lead to ________________ barometric pressure readings,
Decreased Higher altitude, less pressure force pushing down
A clearance pocket should be OPENED as the load on the system _________________.
Decreases *Load decreases, open clearance pocket, less vapor pulled from evaporator*
In order to use water as a refrigerant, a ___________________________ must be maintained.
Deep vacuum in the evaporator (prevent freezing)
The purpose of the visual inspection of fire alarm devices is to detect _________________________ or ____________.
Defective components or abnormalities
Rolling piston (Rotary Compressors) have the rotor mounted on an __________________.
Eccentric shaft
Vessel that contains the orifice plates
Economizer
In a steam jet system which component makes it possible to adjust the system capacity?
Ejector
Solenoids are _____________ valves that are used to do what?
Electric valves used to *control flow of refrigerant-NOT REGULATE THE AMOUNT*
What device measures a deep vacuum (29.25"Hg - 29.92"Hg)
Electronic Deep Vacuum Gauge *Measures in Microns*
Newer reciprocating compressors operate (rotate) at extremely high speeds, and require which lubrication system?
Force Feed
Centrifugal Compressors use what kind of oil system?
Force feed
Static superheat
Force needed to overcome the closing force of TEV *any additional superheat will cause valve to open*
Opening superheat is the _________________ needed to push TEV needle point from the valve seat.
Force needed to push TEV needle point away from valve seat after superheat spring and evaporator pressures have been overcome. *the additional force*
What advantage does a forced draft cooling tower have over a natural draft tower?
Forced draft are *smaller* and *not affected by prevailing winds*
What is a measure of the buildup of impurities on the water side of the condenser tubes reducing heat transfer
Fouling factor
What consists of two-position sliding valve controlled by a piloted actuated solenoid?
Four way check valve
What benefit is gained from circulating a brine through an indirect system?
Freeze protection
Crystallizing is what?
Freezing up of lithium bromide Solution becomes so concentrated that crystals form and plug the machine.
A bellows type shaft seal *most commonly made of copper* is found on which type of systems?
Freon Systems
Would would an RMO notice if there was liquid refrigerant at the compressor suction?
Frost forming on suction line
How should the seat of a service valve be positioned *in order to isolate the compressor from the refrigeration circuit*?
Fully front seated
The oil service valve is in what position during normal operation?
Fully front seated
What is the function of the rectifier in an absorption system?
Further dry hydrous ammonia prior to entering condenser
Latent heat of fusion vs latent heat of vaporization
Fusion- water to ice, ice to water Vaporization- water to vapor, vapor to water
What kind of duct work provides conditioned air to the occupied areas of a facility?
Galvanized sheet-metal
What kind of piping would you not choose for an ammonia or aqua-ammonia solution? - Black steel - Stainless steel - Galvanized steel - Wrought Iron
Galvanized steel
Scroll Compressors orbit mounted shaft around the fixed shaft, creating ______________. What do these do?
Gas pockets Move vapor towards center, reducing volume, and increasing pressure
Preheating the (cold) strong liquor in the heat exchanger means that less heat will be required in the ___________ to boil out ___________.
Generator to boil out the ammonia
Which *valve* is a throttling device and *allows operator to minimize the pressure drop* in a system? Globe Valve or Gate Valve
Globe valve- throttling device gate valve will create largest pressure drop
(COMMERCIAL COOKING SYSTEMS) Systems that include commercial cooking equipment, exhaust hoods, filters, exhaust duct systems, fire extinguisher system and other components designed to capture _______________ vapors and exhaust them safely outdoors.
Grease-laden vapors
What valves should not be used to regulate flow in/out of a pump? ________________ valves (especially gate valves)
Hand actuated valves (especially gate valves)
What does the analyzer have and do?
Has a series of *baffles*, which *collects moisture and returns it to the generator*
Liquid charged TEV Change in temperature will correspond with change at the __________. Used for _______________.
Have some liquid refrigerant present at all times, any change in temperature will correspond with change in pressure at bulb "The bulb always controls the valve" Used for substantial change (cross-ambient conditions)
What is the purpose of the auxiliary oil pump? (additional oil pump)
Lubricates during startup and shutdown
Concerning the ratio of a refrigerating reciprocating compressor, which is most nearly correct concerning the compression ratio? It varies according to the conditions under which the compressor operates OR Is determined by the ratio of the gauge suction pressure to the discharge
It varies according to the conditions under which the compressor operates.
Reciprocating refrigeration compressor unloaders usually unload a compressor by ________________.
Keeping SUCTION valve open
What must be provided on pumps to prevent excessive wear of the moving parts?
Lubrication
Types of Controls Include: (9) (For controls.. think valves, cutouts, switches, devices)
LP Cutout HP Cutout Dual Cutout Water regulating valves Solenoid valves Pressure relief devices Flow switch Check Valve Oil pressure differential switch
Accumulator allows what two things to pass into compressor suction?
LPV and Oil
Large capacity units piping connections are usually connected how? While smaller units provide what type of connections?
Large capacity units piping connections are usually *Flanged or welded/soldered* While smaller units provide *threaded connections*
What is needed to change the state of a substance?
Latent heat
Gaskets in ammonia systems are made of ? (think fishing)
Lead
Fusible plugs have a _______ (type of metal) core and melt at what temperature?
Lead core Melt at 275ºF
Other than malfunctioning compressor valves, what else can affect the relative shape of engine indicator diagrams?
Leaking pistons
Hydrostatic testing is commonly used to test
Leaks in evaporator tubes
When there is a shortage of refrigerant, using a high side float, what will occur?
Less refrigerant will condense, float will not rise, evaporator will be starved
Condensers funtion (2)
Liquefy refrigerant and Reject heat from refrigeration cycle (give off to outside air)
Which of the following plants is most likely to incorporate a purger? - Ammonia Absorption - Lithium bromide Absorption - Ammonia reciprocating compression - Ammonia centrifugal compression
Lithium bromide Absorption
Fusible Plugs are used to release refrigerant in the event of a machine room fire, preventing the vessel from rupturing. Where is it located?
Located on the top of the condenser or receiver
Bubbles in sight glass indicate what?
Loss of liquid seal (lack of refrigerant charge)
In a compression refrigeration system, how would the evaporator be effected if it becomes oil logged?
Loss of refrigeration effect (less refrigerant boiled = less heat absorbed)
The absorber helps maintain what in the evaporator?
Low pressure and Low temperature
What condition could cause high superheat?
Low refrigerant charge
Charging vapor (Valve seat) Low, High, King
Low side valve- back seated (open) high side valve- front seated (closed) king valve- cracked off the backseat *allows vapor to be "sucked" into the compressor from the evaporator and charging cylinder*
Charging liquid (Valve seat position) Low side- High side- King valve-
Low side valve- front seated (closed) high side valve- back seated (open) King valve- front seated (closed) *provides pressure differential for liquid to be "sucked" into system from charging cylinder*
Gravity coil evaporators make it possible to deliver conditioned air in what two ways? ________ velocity AND _________ relative humidity
Low velocity AND High relative humidity *ideal to prevent stored products from drying out*
What is the lowest possible chilled water temperature for lithium bromide absorption system? What is the lowest operating temperature
Lowest POSSIBLE *chilled water* temperature 33º (32º will freeze) Lowest OPERATING temperature 38º
Of the following types of refrigerant distributors, which does not require an external equalizer valve? Manifold type Centrifugal type Venturi type Pressure drop type
Manifold type
Scroll Compressors *Involute Spiral attached to base plate* have a pair of _______________. One is what? while the other is...
Matched scrolls *One fixed, one mounted on motor shaft*
When using a parallel pumping arrangement, operating all pumps simultaneously would make available the ...
Maximum design flow rate
A thermometer at the end of the evaporator coil, attached to the sensing bulb will yield what temperature? (not specific temperature.. what is this temperature called)
Measured Temperature
Calculated superheat =
Measured temperature - saturation temperature
Superheat formula
Measured temperature at the end of the evaporator coil - saturation temperature of refrigerant = superheat
Electronic leak detector (quickest way to find leaks)
Measures resistance of vapors Should not be used near flammable vapor due to high temperature of internal sensor
What type of seal is likely used on a small compressor?
Mechanical
To ensure the casings are air tight, pumps include a ________ seal or ___________ seal at the point where the shaft enters the casing
Mechanical Seal or Packing Seal
Types of pump seals: (2)
Mechanical seal- Closed seal, Uses *graphite seal ring for water tight connection, rubber bellows around shaft* Packing type seal- *Packing gland* (Seen as bolts around impeller housing) *compress stuffing box* (box can be full of graphite impregnated coil, molded lead foil, or other resilient material) *creates force that should allow steady drip of water across the seal.
If vapor leaving the generator has moisture (water) as it enters the condenser it may freeze in the __________________ or the ____________.
Metering device or evaporator
R-40 is
Methyl Chloride
R-30 is
Methylene Chloride
(REFRIGERATING SYSTEMS - Monthly testing) F606.6 requires refrigerating equipment and systems having a refrigerant circuit containing more than __________ of Group A1 or ______ of any other group refrigerant to be subject to monthly testing as follows: - Fans and associated equipment intended to operate __________________ - _____________ and ________ Systems
More than 200 lbs of Group A1 or 30 lbs of any other group refrigerant Monthly Testing: - *Fans and associated equipment intended to operate emergency ventilation systems* - *Detection and alarm systems*
(FIRE ALARM SYSTEMS - Notification to Department) when the sprinkler system or fire alarm system will be out of service on _______________________.
More than one floor of a building
Suction service valve is located off the _____________ of a reciprocating compressor
Motor end (AKA suction end)
Check valve (oil pump) Allows oil to drain from______________, while preventing oil from escaping
Motor side
High side float metering devices are found where? How do they work?
Mounted on condensers or receivers (high side) Rely on condensing of high pressure liquid to feed refrigerant to evaporator *Proper function based on precise amounts of refrigerant charge* vapor condenses (bottom), the float rises, opens valve, passing refrigerant on to evaporator. REMEMBER HIGH SIDE FLOAT RISES TO OPEN
Multiple temperature systems (2 temperature systems) use one compressor, one condenser, and serve ________ evaporators.
Multiple
Oil equalizer line is used on systems with what? why?
Multiple compressors in parallel to ensure oil level is equal in each compressor
(COMMERCIAL COOKING SYSTEMS) Commercial cooking exhaust systems must be inspected and cleaned at least once every ______________, by a person holding a ___________. The exception is vertical portions of interior and exterior vertical ducts in excess of ___ stories in height may be cleaned every _____________ by a person holding a _________.
Must be *cleaned once every 3 months by a C of F holder* except: *Vertical portions* of interior and exterior vertical ducts in *excess of 3 stories in height* may be *cleaned every 6 months by a C of F holder*
Electricity will do what to a NC solenoid? N/O solenoid?
NC- open with electromagnetic electricity N/O- close with electromagnetic electricity
What refers to the amount of pressure a fluid exerts on the *suction* side of a pump? Includes all factors effecting fluid pressure *except the reduction in pressure created at the inlet to the pump's impeller*
NET POSITIVE SUCTION HEAD (NPSH)
(EMERGENCY POWER SYSTEMS- Periodic inspection and testing requirements) NFPA Standard 110- Chapter 8 - Emergency generator must be tested ______________ for a minimum of _____ minutes under operating temperature conditions and at not less than _____% of the emergency power system nameplate kilowatt rating, or under loading that maintains the minimum __________________ temperatures as recommended by the manufacturer. Instructions must be provided for safe manual transfer in the event ____________ transfer switches malfunction. - Transfer switches must be tested ________________ and consists of electrically operating the transfer switch from the _________ position to the _________ position and returning it back to the ____________ position.
NFPA Standard 110- Chapter 8 - *Emergency generator* must be *tested monthly* for a *minimum of 30 minutes under operating temperature conditions and at not less than 30% of the emergency power system nameplate kilowatt rating*, or under loading that *maintains the minimum exhaust gas temperatures as recommended by the manufacturer*. Instructions must be provided for *safe manual transfer in the event automatic transfer switches malfunction.* - *Transfer switches* must be tested *Semi-annually* and consists of electrically *operating the transfer switch from the standard position to the alternate position and returning it back to the standard position.*
A NC solenoid valve will ______ when energized. *A normally open will do the opposite*
Open
The outlet to the compressor on a service valve is always what? (regardless of being front seated or back seated)
Open
Direct drive compressor and gear drive compressors are what type? Open or closed?
Open compressors - shaft of compressor is coupled to the shaft of the motor or drive
External lubrication systems are used on systems with
Open compressors and motor arrangements
Condenser water systems, unlike chilled water systems (evaporator), are usually ______________ systems. Meaning...
Open piping systems meaning they come in contact with outside air
A multiple stage compression cycle (centrifugal) requires multiple _________________.
Orifice plates *2 stage chiller requires 2 orifice plates*
(HOT WORK OPERATIONS) Pre-Hot work check (once per day + while authorization is in effect) to ensure safety includes: 1. ________________ personnel, where required, are assigned 2. Approved precautionary measures must be taken to avoid accidental operation of automatic fire detection systems during hot work operations. For example, smoke detectors may need to be taken out of service during work to avoid unwarranted alarms. The ______________ the alarm was taken offline, the ___________ for such action, the __________ and ________________ of the person notified at the central station (or other evidence of notification satisfactory to the department), and the _______________ the system was restored to service, must be entered in the _________________ in each such circumstance.
Pre-Hot work check: 1. *Fire watch personnel*, where required, are assigned 2. Approved precautionary measures must be taken to avoid accidental operation of automatic fire detection systems during hot work operations. For example, *smoke detectors may need to be taken out of service during work* to avoid unwarranted alarms. The *date and time* the alarm was taken offline, the *reason* for such action, the *name* and *operator number* of the person notified at the central station (or other evidence of notification satisfactory to the department), and the *date and time* the system was restored to service, must be entered in the *alarm log book* in each such circumstance.
Cryonics
Preserving humans and animals at very low temperatures with intention of future revival
What causes fluid to flow through an operating system?
Pressure differential
On an decrease in load, an AEV will open the valve because of
Pressure from the adjustment spring
On the top of the condenser shell is a what?
Pressure relief device
In centrifugals the size of the compressor is more dependent on what? The Capacity or Pressure required
Pressure required
What benefit does a safety head provide?
Prevent compressor damage *caused by liquid*
What is the purpose of baffles at the top of a cooler?
Prevent liquid from entering suction line
Group 3 NYC Code Refrigerants (Explosive Hydro Carbons) (5)
Propane, butane, isobutane, ethane, ethylene
The crankcase of compressors running in parallel are interconnected to allow what?
Proper maintenance of operating oil level
Separating the refrigeration process from the building does what?
Protects the occupants of hazards caused by fire or leaks.
Psig to Psia
Psia = psig + 14.7
What are the two absolute pressures?
Psia and "Hg Ab
"Hg absolute (Barometric) to Psia
Psia= "hg Ab x .491
Vacuum Pressure ("Hg) to Psia
Psia= (30/"Hg) / 2
Performance of Centrifugal pumps are expressed by pump "_________________" curves
Pump *"Head-capacity"* curves *relates gpm to total head in feet on graph* *where system curve and pump curve intersect, the numbers can be drawn.*
What is the function of the Strong liquor pump in an absorption system? Why is this necessary?
Pump strong liquor to generator Differential pressure will not allow fluid to flow
*Refrigerant distributors* (Brass consisting of Housing, removable nozzle, and retainer ring) (Equal lengths of tubing) Receive low pressure refrigerant from ____________________ and equally distribute to individual circuits of a ____________________ ________________. This increases coil ____________. Creates ______________ to insure effective use of each circuit.
Receive low pressure refrigerant from *metering device* and equally distribute to individual circuits of *multi-circuted* evaporator. increases coil *capacity* create *flash gas* to insure effective use of each circuit
Positive displacement compressors (4)
Reciprocating Scroll Screw Rotary
NC solenoids are most often used in the liquid line of what kind of systems?
Reciprocating refrigeration systems
Tachometer
Records speed of the turbines shaft
After the analyzer the ammonia vapor passes through a _______________. What does this have and what does it do?
Rectifier, which contains a *cooling coil*, that *condenses any remaining moisture in the vapor*
How does reduced head pressure affect the operation of a water regulating valve? reduced head pressure = reduced ___________________
Reduced cooling water flow
What is the function of the metering device in an absorption system?
Reduces pressure and temperature of liquid leaving condenser *same as always*
If two water pumps are running in parallel, throttling down on the discharge valve of one of the pumps would result in a ...
Reduction in water flow *and* pressure
ASHREA-34 establishes __________
Refrigerant classifications/safeties
Dry Expansion Evaporator
Refrigerant enters, picking up heat, vaporizing, and refrigerant leaving is 100% vapor *package type air conditioning units and domestic refrigerants*
Manual metering devices require the machine operator to keep an eye on the...
Refrigerant thermometer and/or pressure gauge
Crankcase breather is an internal or external passage that allows the crankcase to vent
Refrigerant vapor that has boiled out of the oil in the sump
Ammonia System Refrigerant: Absorbent: Pressure range:
Refrigerant: Ammonia (Anhydrous- no water) Absorbent: Aqua Ammonia Pressure range: Above Atmospheric
Lithium Bromide Refrigerant: Absorbent: Pressure range:
Refrigerant: Water Absorbent: Lithium Bromide Pressure range: Below Atmospheric
What is Sodium Dichromate
Rust inhibitor used to prevent deterioration on pipes by neutralizing NaCl and CaCl
It is highly recommended that *fire alarm devices be visually inspected* for any evidence of abnormal conditions by an _______/_______/______ C of F holder *at the beginning of each day*
S-95/F-58/F-25
*Program, service, clean, test or repair of any fire alarm systems* may be performed only by an ____________/____________ C of F holder
S-97/S-98
Causes of High evaporator pressure: (1)
SYSTEM AT MAXIMUM LOAD (Expansion valve open, assuming system can handle designed load)
High pressure cutouts are strictly a ______________ device, and cannot restart the compressor
Safety
What *filter is the industry standard for compressors* to prevent build up of particulate from condenser water systems? How do you prevent excess pressure drop in the filter? Regular ___________ and replacement of ____________
Sand filter Regular *backwashing* and *replacement of sand* prevent excessive pressure drop across the filter
Any brine solution with a specific gravity past 1.33 is said to be what?
Saturated - meaning additional salt will not dissolve
Guages allow monitoring of high and low side pressures. These pressures determine the evaporator and condenser ...
Saturation points
A pressure gauge at end of end of evaporator, cross referenced with a PT chart will give you the ...
Saturation temperature
In relation to water and power, you can ...
Save power at the expense of water or save water at the expense of power
Which of the following is used to erect brine piping systems?
Schedule 40 Black Steel
Which compressor compresses suction gas between rotating gears (helical lobes) after entering sliding vane type capacity control valve?
Screw compressor
value of head loss in which water will no longer flow is
Shut off head
Inhibited hydrochloric acid can be used to clean what?
Shell and coil condenser
Which of the following would cause a refrigeration circuit to short cycle? Shortage of refrigerant System overcharge Restriction in liquid line Short circuit at the motor windings
Shortage of refrigerant
Temperature control is identical to pressure control, except the pressure of the bellows vary with _________.
Temperature *not system pressure* Changes in room/evaporator temp cause refrigerant to expand increasing pressure of bellows.
How do you identify a centrifugal compressor that has a packing gland (GLAND FOLLOWER)
There would be bolts on the plate around the shaft, to tighten the packing
What device is used to prevent motor burnout?
Thermal protector
Which device measures sensible heat?
Thermometer
Absorption systems and compression systems have the same _______________, but _____________.
They have the same expansion valves but They do not have similar compressors, because the absorption system does not have a compressor.
Which cycle will have higher operating pressures when an ammonia COMPRESSION refrigeration cycle is compared to an ammonia ABSORPTION cycle of like tonnage?
They will be similar *key words- "like tonnage"*
There are more ____________ per inch on a metering device's valve stem than on a conventional valve. What does this do?
Threads Limits the valves vertical movement as the wheel is rotated *allows for more precise control*
*Pressure build* in a centrifugal depends on the
Tip Speed
Which of the following explains why compressors are installed in series arrangement?
To obtain sufficiently low evaporator temperatures
Belt driven compressor is connected..
To the prime mover by one (or a series) of *belts*
Gear driven compressor is connected...
To the prime mover through a series of *gears*
How many bearings are needed at the shaft of a reciprocating compressor?
Two
In a "v" or "w" compressor how many cylinders are under each head?
Two
(FUMIGATION AND INSECTICIDAL FOGGING OPERATIONS) These operations are hazardous because they are __________ to most forms of life, including humans.
Toxic
When there are no documents to describe or delineate the system, what method may be the only means of obtaining useful information?
Tracing out the system
Shell and Tube (most common in comfort cooling industry)
Transfers heat from secondary refrigerant (chilled water or brine) to the refrigerant *Evaporator absorbs heat* Vaporized refrigerant will occupy the *upper* region of the shell
*Actual* displacement
cfm = cylinder volume x # of cylinders x rpm (divided by volumetric efficiency as decimal)
Compressor displacement formula
cfm= cylinder volume x # of cylinder x rpm
TEV will adjust *itself* to any
change in load
Rotary compressors have rotors that move in a ... (think ROTATION)
circular motion
Plate coil evaporator
coils formed into metal plates. Can be aligned vertically or horizontally (and double as a shelf in a commercial refrigerator)
The formation of what is a particular concern after a compressor burnout?
formation of acids
Heat of compression is a product of _____________. Describe what it is.
friction Heat of compression is *heat transfer* from working parts of the compressor (cylinder walls/ working parts) *to the refrigerant.*
A pump must be delivering water at a pressure high enough to overcome all of the _____________ losses.
friction losses (head losses)
PH Scale from 7 towards 0: at 7: from 7 towards 10:
from 7 towards 0: *Towards 0 becomes more acidic* at 7: *Neutral* from 7 towards 10: *Towards 10 becomes more alkaline* BY FACTORS OF 10 Ex: 7 to 9 is 100x more alkaline (10 x 10 = 100)
While the vapor that exits the evaporator is capable of absorbing sensible heat, it is a far lesser amount of BTUs, which is why it will not result in ...
frost on the coil
Solenoid valves are either ____________________ or ___________________, therefor they cannot regulate flow like a metering device.
fully open or fully closed
Generally the pressure drop through valves and pipe fittings is _________________ that of a linear foot of pipe of the same diameter
greater than
Viscosity refers to an oils
internal friction
If carbonate deposits form from brine solution, the best way to control it would be to Reduce the brine to ___________________ for a period of time
slightly under 7
Accumulators prevent liquid refrigerant from __________ the compressor, *without trapping oil*
slugging (entering)
The diameter of the valve seat orifice is much ____________ than the line-size of the valve
smaller
Eutectic Point is the max _________________ of a brine to aid in frost prevention
specific gravity
a ______________________ system is piping installed in a building that serves to transfer water to hose connections located within the building for firefighting purposes.
standpipe
Low condenser pressure will do what to the evaporator?
starve the evaporator (not feed it properly)
