Unit 40 Typical Operating Conditions
30, Saturation, High side
30 Over Rule: Ambient Air Temperature (Condenser) + _______ degrees F Convert Temperature to ________________ Pressure _________________ = 30 over Saturation Pressure
B
A compressor that is operating at design or above-design conditions will A. overheat B. operate at close to full-load amperage C. operate over its RLA D. operate at its service factor amperage
B
A four-pole motor typically runs at A. 960 rpm B. 1800 rpm C. 3600 rpm D. 4200 rpm
False
A high temperature in the conditioned space is the only thing that will cause the pressures and capacity of a system to vary True or False
Nominal Ratings
A rounded-off stated size. The nominal size is the closest rounded-off size
C
A standard efficiency condenser will condense refrigerant at a temperature of about ___________ degrees F higher than the ambient temperature A. 35-40 B. 15-20 C. 30-35 D. 20-25
C
A two-pole motor typically runs at A. 960 rpm B. 1800 rpm C. 3600 rpm D. 4200 rpm
B
A typical analysis of a system's major power-consuming devices would include the A. thermostat, contactor, and the capacitor B. indoor fan motor, outdoor fan motor, and the compressor C. compressor, transformer, and the contactor D. thermostat, compressor, contactor, and the outdoor fan motor
B
A typical temperature relationship between a high-efficiency condenser and the ambient temperature is A. 10 degrees F B. 20 degrees F C. 30 degrees F D. 40 degrees F
A
An equipment rating system that includes the start-up and shut-down cycles as well as the steady-state operation is A. SEER B. EER C. AHRI D. HSPF
A
As the outdoor ambient temperature rises, the system capacity will A. decrease B. increase C. remain constant D. fluctuate
larger, maximum
Compressors Operating at Full Load Current Compressor motor may be ______________ than needed most of the operating time May not reach its rated horsepower until it gets to the _______________ design rating for the system
RLA, current
Compressors Operating at Full Load Current Rare for a compressor motor to operate at its ____________ rating Usually other conditions keep the compressor from drawing too much ______________
nominal ratings, rarely
Determining the Compressor Running Amperage Ratings that are not completely accurate are known as ___________________________ Compressor _______________ operates at full load amperage
Current, run load amperage (RLA), replacing
Determining the Compressor Running Amperage _____________ draw may not be easy to determine Manufacturers do not all stamp the compressor ___________________________ rating on the nameplate Term rated-load amperage is ____________________ run-load amperage
publish
Documentation with the Unit Furnished with unit in the start-up manual Manufacturer may also ___________ a bulletin
Load on the outdoor coil, Sensible-heat load on the indoor coil, Latent-heat load on the indoor coil
Documentation with the Unit Three things must be considered: 1. ________________________________ 2. ________________________________ 3. ________________________________
evaporators, condensers
Electrically commutated motors (ECMs) for __________________ and ___________________ will also usually accompany high-efficiency equipment
Btu/hr (output)/ wattage (input), efficient
Equipment Efficiency Ratings Energy Efficiency Ratio (EER) EER= _______________________________________ The larger the EER rating the more _____________________ the equipment
lower, total cooling produced in BTU/HR/Watt-hours of energy
Equipment Efficiency Ratings Seasonal Energy Efficiency Ratio (SEER) Has a higher first cost, so _____________ efficiency equipment is still popular SEER = ____________________________________________________ consumed to produce the cooling
+/- 10%
Equipment manufacturers require that operating voltages of____________ of the rated voltage of the equipment be maintained
larger, lower, standard, thermostatic expansion, fixed-bore, larger
Establishing a Reference Point on Unknown Equipment High-efficiency equipment: Is usually __________ Operates with ____________ head pressures Has lower amperage rating than _________________ efficiency system Often uses a _____________________ valve rather than a _______________________ metering device May have a _____________ evaporator than normal
rarely
Evaporator Operating Conditions Actual field conditions are ____________ ideal
troubleshooting
Evaporator Operating Conditions Common conditions are used for _____________________ purposes
40 degrees F, 75, 50%, 10 degrees F
Evaporator Operating Conditions Normal operating temperature ____________ ___________ inside air temperature ___________ humidity Approximate evaporator superheat is __________
Fixed-bore, thermostatic expansion valve, superheat
Evaporator Operating Conditions: Efficient State, figure 40.2 ______________________ metering device will not vary the amount of refrigerant feeding the evaporator as much as the _____________________________. It is operating at an efficient state of 10 degrees _________________
up
Evaporator Operating Conditions: Temperature and Humidity Up, figure 40.5 This system has been off, long enough that the temperature and the humidity have gone _______ inside the conditioned space. Notice the excess moisture forming on the coil and going down the drain
motor, fan motor, actual load
Finding a Point of Reference for an Unknown Motor Rating Nameplate data may not be correct if the ___________ was replaced Condensing unit will have a nameplate for the condenser________________ Should be sized close to ____________________
Compare
Finding a Point of Reference for an Unknown Motor Rating __________________ the system in question to a known unit
Electrical ratings
Finding a Point of Reference for an Unknown Motor Rating ________________________ can be estimated by estimating system capacity
Wet Bulb, Dry Bulb
Fog 100% Relative Humidity _________________ and _____________ are the same
standard, high, materials, appearance, High
Grades of Equipment Economy, __________ - efficiency, and ________-efficiency Economy and standard efficiencies are similar, but differ in _______________ and _________________ __________-efficiency equipment may be much more efficient and will not have the same operating characteristics
30 degrees F, 35 degrees F
Grades of Equipment Refrigerant condenses at a temperature about _______ to _________ higher than ambient
efficient, Liquid, evaporator, freeze
High Evaporator Load and a Cool Condenser If the temperature is warm and the outside temperature is cooler than normal: The condenser will become too ___________ ___________ refrigerant will accumulate in the condenser The ____________________ will starve and lose system capacity, and the coil may ____________
speed fan, two-speed
High Evaporator Load and a Cool Condenser Some modern systems reduce the chances of this with a variable-_____________ or _____________ operation for the condenser fan
decrease
High Evaporator Load and a Cool Condenser: Cooler Ambient Air, figure 40.6 A system operating when the outside ambient air is cooler than the inside space temperature air. As the return air cools down, the suction pressure and boiling temperature will ______________
D
High efficiency condensers may condense refrigerant at a temperature as low as ___________ degrees F over the ambient temperature A. 35 B. 5 C. 30 D. 20
Compression ratio =
High side/ Low side = answer: 1 ratio
larger, modern, 20 degrees F
High-Efficiency Systems Have __________ condenser coils or use more _____________ alloys with more extended surfaces or fins Refrigerant condenses at a temperature as low as ________ higher than the outdoor ambient temperature
TXV
High-Efficiency Systems Incorporate ___________ metering devices
lower
High-Efficiency Systems Operate with ____________ head pressures
head pressure
High-Efficiency Systems Require means of _____________________ control
lower, condenser, 20, 25
High-efficiency equipment has a ___________ operating head pressure than standard-efficiency equipment partly because the _______________ is larger. It has a different relationship to the outside ambient temperature, normally _______ degrees F to ______ degrees F.
TXV
High-efficiency equipment will also incorporate ___________ metering devices to keep the evaporator active under all heat load conditions
more, metal, alloy
High-efficiency will have __________ surface area and may be made of a different ___________ or __________ with more extended surfaces or fins
True
If the outside temperature increases from 95 degrees F to 100 degrees F, the air-conditioning equipment will experience a drop in capacity. True or False
A
In some cases, the electrical data for the indoor blower motor may be difficult to obtain because A. the motor may be mounted inside the blower wheel, making it hard to see the nameplate B. smaller motors are not required to list electrical data on the motor nameplate C. the nameplate on the furnace or air handler is not accurate D. the information is only printed in the manufacturer's literature which may have been lost
10%, minimum, maximum
Matching the Unit to the Correct Power Supply Operating voltages should be withing ______ of rated voltage 208/230-V motor: 208 x 0.90 = 187.2 V _______________ operating voltage 230 x 1.10 - 253 V ______________ operating voltage
Technician
Matching the Unit to the Correct Power Supply ________________ must use some judgement when conditions are beyond the rated conditions
95 degrees F, 80 degrees F, 50%
Mechanical Operating Conditions Design conditions for air conditioning: ___________ outside air temperature ___________ inside air temperature ___________ humidity
125 degrees F
Mechanical Operating Conditions Standard efficiency systems condense refrigerant at about ___________ at design conditions
Systems
Mechanical Operating Conditions ______________ are rated at the above conditions
B
Most manufacturers specify that the supply voltage to the equipment should be within _________% of the name-plate voltage A. 5 B. 10 C. 15 D. 20
41%
Now __________ Relative Humidity Dry bulb- 100 degrees F, 70 degrees F, 32 degrees F Wet bulb- 100 degrees F, 56 degrees F, 32 degrees F
D
On a high-efficiency system, if the condensing temperature is more than __________ degrees F above the ambient temperature, the system should be checked for problems A. 5 B. 10 C. 20 D. 30
D
On a standard-efficiency system that is operating with an indoor temperature that is higher than normal A. the suction pressure will be lower than normal B. the discharge pressure will be lower than normal C. the suction and discharge pressure will both be lower than normal D. the suction and discharge pressure will both be higher than normal
either C or D
On a system equipped with a two-speed condenser fan, the temperature at which the motor switches from low to high speed is usually _________ degrees F A. 95 B. 80 C. 85 D. 90
C
One way manufacturers gain a higher efficiency is by A. designing the unit to run with a higher head pressure B. equipping the system with a fixed-bore metering device C. using a two-speed or variable speed compressor D. using a lower evaporator saturation temperature
C
One way manufacturers gain a higher efficiency is by A. designing the unit to run with a higher head pressure B. equipping the system with a fixed-bore metering device C. using a larger condenser surface area D. using a lower evaporator saturation temperature
20%
Phoenix, AZ __________ Relative Humidity Dry bulb- 100 degrees F, 70 degrees F, 32 degrees F Wet bulb- 100 degrees F, 50 degrees F, 32 degrees F
True
Ratings that are not completely accurate are known as nominal ratings True or False
B
Ratings that are not completely accurate or that are rounded to the next closest rating are known as A. EER ratings B. nominal ratings C. SEER ratings D. AHRI ratings
45
Refrigerant in a high-efficiency unit will boil at a temperature of about ______ degrees under typical operating conditions
Higher head pressure, Reduced system capacity, system capacity
Relationships of System Component under Load Changes Increases in outside temperature result in: _______________________________ and ______________________________ Space temperature and humidity also affect _________________________________
Changes
Relationships of System Component under Load Changes _________________ in relationship among various components in the system
humidity, Pressures, temperatures
Relative Humidity and the Load Equipment capacity varies with changes in __________________ ___________________ and __________________ will also change
Relative Humidity
Relative Humidity and the Load _______________________ increases the load on the system
14, 32, 8
SEER (Seasonal Energy Efficiency Ratio) Baseline, and it can go up to _______ and down to ________
two-speed motors, variable-speed motors
Some manufacturers are not using ___________________________ and _______________________ for variable capacity
B
Some things that should be considered along with the manufacturer's published list of typical operating conditions are the ______________________. A. latent load on the outdoor coil and the sensible load on the indoor coil B. load on the outdoor coil and the sensible and latent load on the indoor coil C. latent load on the conditioned space and the latent load on the outdoor coil D. load on the conditioned space and the sensible load on the indoor coil
voltage, blower wheel
Start the Equipment with the Correct Data The ______________ must be printed on the motor so that they will not come off May not be visible depending on mounting May be inside the ____________________
nameplate
Start the Equipment with the Correct Data The motor electrical characteristics can be obtained from the ________________________
indoor fan motor, outdoor fan motor, compressor, current
Start the Equipment with the Correct Data The three motors- _____________________, ___________________, and the ___________________ - can be checked for correct ______________ draw
modulating, superheat
TXV (___________________)- subcooling, maintains _________________
D
The amperage for a typical 1/3-hp permanent split-capacitor motor operating at 230 V is about A. 9.4 A B. 8.5 A C. 10 A D. 3.6 A
A
The evaporator will normally operate at a _________ degrees F boiling temperature when the indoor temperature is 75 degrees F with a 50% humidity condition A. 40 B. 50 C. 60 D. 70
operating voltage
The first thing that the technician need to know for electrical troubleshooting is what the ______________________ for the unit is supposed to be
C
The higher the EER rating is A. the smaller the equipment is B. the higher the system capacity is C. the more efficient the equipment is D. the lower the system efficiency is
space temperature, humidity
The indoor conditions that vary the load on the system are the __________________ and __________________
B
The latent-heat load on the indoor coil is influenced by A. the outdoor temperature and the evaporator heat load B. the wet-bulb temperature of the indoor air C. the indoor dry-bulb temperature D. the location of the outdoor coil
C
The load on the outdoor coil is influenced by A. the indoor dry-bulb temperature B. the wet-bulb temperature of the indoor air C. the outdoor temperature and the evaporator heat load D. the location of the indoor coil
A
The most noticeable aspect of an increase in humidity is __________________. A. an increase in the condensate in the drain system B. a rise in suction pressure on the gauge manifold C. a rise in temperature recorded by the thermostat D. a drop in the sensible heat measured in the conditioned space
D
The sensible-heat load on the indoor coil is influenced by A. the location of the outdoor coil B. the outdoor temperature and the evaporator heat load C. the wet-bulb temperature of the indoor air D. the indoor dry-bulb temperature
D
The standard design conditions for air-conditioning system's established by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) are A. 95 degrees F outside, 70 degrees F inside, 40% relative humidity B. 100 degrees F outside, 75 degrees F inside, 50% relative humidity C. 90 degrees F outside, 80 degrees F inside, 30% relative humidity D. 95 degrees F outside, 80 degrees F inside, 50% relative humidity
B
The system output in Btu/h divided by the watts of power used to produce the output is called A. SEER B. EER C. AHRI D. HSPF
A
The typical operating voltages for any air-conditioning system must be within the manufacturer's specifications, typically +/- ___________% of the rated voltage A. 10 B. 5 C. 20 D. 15
C
The typical temperature relationship between a standard-efficiency air-cooled condenser and the ambient temperature is A. 50 degrees F B. 40 degrees F C. 30 degrees F D. 20 degrees F
RLA, exceed
The unit nameplate may have the compressor's _________ printed on it. It should not be ______________
C
The voltage being supplied to a 208/230-V motor should be between A. 187 and 229 volts B. 207 and 253 volts C. 187 and 253 volts D. 207 and 229 volts
high seasonal efficiencies, two, four, 1800, 3600
Two-Speed and Variable Speed Compressors Two-Speed Compressor are sometimes used to achieve ________________________________ Can operate as ________-or ________-pole motors Four-pole motor runs at ________ RPM Two-pole motor runs at _______ RPM
electronic circuits, efficiency, more
Two-Speed and Variable Speed Compressors Variable speed may be obtained with _____________________ Improves _________________, but __________ factors for establishing typical running conditions under other-than-design conditions
voltage
Typical Electrical Operating Conditions Know what the system supply ___________________ is supposed to be
amp
Typical Electrical Operating Conditions Measured with a DMM with an _______ clamp
Indoor fan motor, Outdoor fan motor, Compressor
Typical Electrical Operating Conditions Three major power-consuming devices to be analyzed: 1. __________________ 2._________________ 3. _____________________
A
Under high evaporator heat loads, the temperature difference between the condenser and the ambient will be A. much higher B. much lower C. about the same D. unpredictable
B
When a technician has no literature on the equipment and cannot obtain any, what should be done? A. Reference a temperature/pressure chart for refrigerant information B. Establish some known condition as a reference point C. Calculate the system superheat and subcooling D. Test the refrigerant oil for the presence of acid
A
When the air passing over the condenser is cooler than the air passing over the evaporator A. the capacity of the condenser will greatly increase B. the condenser will begin to frost up or freeze C. the capacity of the condenser will be reduced D. the refrigerant in the evaporator will begin to condense
D
When the air temperature passing over the evaporator is higher than the air temperature passing over the condenser, __________________. A. the system may short cycle until the load B. liquid refrigerant may return to the compressor through the suction line C. the head pressure may rise to a dangerous level D. the condenser becomes so efficient that it may slightly starve the evaporator
decreases
When the discharge pressure rises, the system capacity ____________
High-efficiency systems
____________________________ often use larger or oversized evaporators
