CNST 2321
Absolute humidity
The amount of water in the air (measured in grains or pounds of water per pound of dry air):
Net positive suction head (NPSH) is which of the following?
The inlet pressure required to prevent cavitation
Which heat recovery system (ERU) will result in the highest cooling savings?
Enthalpy wheel
To prevent a destructive event of a short circuit, protective devices ( fuses or circuit breakers) must have an interrupting capacity conforming to which of the following?
Equal to or greater than the calculated short circuit current
What fluid is used in the vapor compression cycle?
Refrigerant
Match
- Air pressure in a duct - in.w.c (inches of water column) - Water pressure in a pipe -ft of head or psi - Air velocity in a duct - ft/min - Water velocity in a pipe - ft/sec
What piping materials might be used for a fire protection automatic sprinkler system?
- Black steel with welded fittings - Copper
Which of the following is NOT a type of compressor used in a chilled water system?
A) TURBINE b) Reciprocating c) Scroll d) Centrifugal e) Screw
According to the (NEC), which of the following is a "bathroom" ?
An area with a toilet and sink
What are normal materials of construction for coils?
Copper tubes and aluminum fins
Which is the normal flow in a heating coil?
Counter flow, which is water in on the leaving air side
Most telecommunications systems operate on DC circuitry. Why?
DC devices are more sensitive than AC
A "domestic water system" includes the water distribution system, the fire protection system, and the industrial processing water system
False
A branch circuit is the portion of the wiring that connects the feeder to distribution center
False
A feeder schedule is the most important schedule of power system design
False
Dew point is the temperature at which moisture begins to condense and when the relative humidity reaches 80%
False
Fire tube boilers are so named because the water travels through the inside of steel tubes
False
In HVAC, load is the amount of people or equipment allowed in a given room
False
In an alternating current (AC) system, current flow is always in one direction flow from negative to positive
False
Pipe hangers support the pipes from above to protect from vibration and shock
False
The tendency of an assembly to conduct heat (U-factor) or heat transfer is directly proportional to R and inversely proportional to U
False
Refrigerants transfer heat (cooling) by changing phase from solid to vapor
False (Liquid to vapor)
Dew point is when the humidity level reaches 75% at a given temperature
False (100%)
What type of valve would be a good choice for isolation or shut off service?
Gate valve
What is the primary purpose of a plumbing trap?
To prevent sewer gas from entering the building
Heating and cooling the ventilation air (outside air) requires considerable energy, which is wasted unless the energy is recovered from indoor exhaust air
True
If refrigerant is used in the air conditioning coil (evaporator), refrigerant to air exchange, the system is generally termed direct expansion (DX)
True
In HVAC terminology, a zone is an area where temperature is controlled by a single thermostat
True
Installation of fire safety equipment must be in compliance with code requirements from Chapter 9 of International Building Code and the fire marshal must be consulted
True
Which HVAC System is used extensively in commercial buildings despite potential "stuffiness" during light load conditions and is least flexible for adding r changing zones after instalation?
Multiple zone VAV
The actuated assembly is _____ _____ if flow is prevented when the control pressure (or other signal) is absent
Normally closed
"The ampacity of an individual feeder shall not be required to be larger then the ampacity for the entire building" is an example of NEC ______ rules:
Permissive
What is the major difference between shell and tube vs plate and frame heat exchangers?
Plate and frame can achieve small temperature difference between liquids
What is the unit of measure for water pressure in a pipe?
Psi
Which statement is true about refrigerant cooling coils?
Refrigerant changes from liquid to vapor in the coil
The primary objective of a fire protection system is to
Save lives and protect property
_____ is the primary sense of fire-related deaths
Smoke
A recirculating system using a pump is a method to keep hot water available quickly at a remote plumbing fixture
True
According to the NEC all connections or splices of wires and cables must be made within code-approved boxes that are accessible for inspection and service
True
Conduction also depends on the insulating quality of the wall or envelope, which is measured by resistance to heat transfer: the R-value
True
Control dampers are used to control the flow of air and can be direct-acting or reverse-acting
True
Drainage in buildings consists of three major components: sanitary waste, storm water, specialty waste (toxic, radioactive, chemical (acid), etc, ).
True
Good indoor environmental quality results in real economic benefit from productivity. These benefits should be included in life-cycle cost analysis.
True
Ground Fault Circuit Interrupter (GFCI) will trip or cut out the circuit if an imbalance of current flow is detected.
True
HVAC systems use fluids to transport heat and cold to satisfy loads and maintain comfort. Such fluids include air, water, steam, and refrigerant
True
Heating and cooling loads represent how much heat is lost or gained and must be made up or removed by the system
True
Heating and cooling the ventilation (outside) air requires considerable energy, which is wasted unless the energy is recovered from the exhaust air
True
Single-zone reheat is a constant-volume system used for air-conditioning when humidity control is especially important
True
A ______ circuit is the portion of the wiring that connects the utility service to the panel board
feeder
What is "connected load"?
sum of all electrical loads connected to the system, on or off
What is the primary purpose of a plumbing vent line?
To equalize pressure across traps
Methods of producing indoor cooling include the following
- Dessicant cooling - Evaporative cooling - Absorptin cooling - Vapor compression cooling?
Variable frequency drives often take the place of motor starters, and can provide which of the following functions?
- On-off control - Energy savings - Soft start
Refrigerants with their properties
- Was a replacement for R-22 - R-134A - Banned by Montreal Protocol due to high ODP - R-12 - On its way out due t high GWP - R-410A - Environmentally friendly, but flammable and toxic - R-717
What are functions of an uninterruptible power system (UPS)?
-Allow time for a generator to start when there is a power outage - Provide high quality power interns of voltage and frequency -Keep critical equipment running in the event of a utility power outage - Allow time to shut down in an orderly fashion
Multi Zone VAV systems are
1 used extensively in commercial buildings 2 have pot 3 least f
Match the ASHRAE Standard numbers with their topics
1) Energy conservation is covered in Std - 90.1 2) Ventilation is covered in Std - 62.1 3) Thermal comfort is covered in Std - 55 4) Measures filter performance - 52.1
Magnitude of energy consumption for a typical office building in midwest USA. (1 highest)
1) HVAC 2) Lighting 3) Appliances 4) Hot water
List the four components of the vapor compression cycle in order
1) compressor 2) condenser 3) expansion valve 4) evaporator
What are the three circuits in a chilled water system?
1) refrigerant 2) chilled water circuit 3) condenser circuit
Which of the following statements are true regarding DX systems?
1) they include roof top units and PTAC units 2) they can have condensers remote from the fan coil unit 3) refrigerant is used in the air conditioning coil (evaporator)
Positive pressure is needed in a domestic water system to:
1. Establish a flow in the distribution system and through the plumbing fixtures or equipment 2. Prevents water from being contaminated by external sources 3. Sufficient to overcome any pressure loss due to friction and elevation
What is the unit of measure for water velocity in a pipe?
1. Gpm 2. Ft/sec
Outside weather conditions affect heating and air conditioning loads from introduction of outside air for:
1. Infiltration 2. Ventilation 3. Conduction
What are the three conditions that affect heating and air conditioning loads from introduction of outside air?
1. Infiltration 2. Ventilation 3. Conduction
Comfort for building occupants is affected by a number of environmental variables, including the following:
1. Temperature 2. Airflow 3. Humidity 4. Radiation
All HVAC systems require some form of control to accomplish their task of controlling one or more of the following properties
1. Temperature 2. Pressure 3. Flow rate 4. Humidity 5. Speed (fixed or variable) 6. Time
What are the methods of control for air systems
1. Varying the temperature of the air supplied while holding the flow constant 2. Varying the flow of warm or cold air supplied while holding the temperature constant 3.varying both the temperature and the flow of air supplied or turning the system on or off
What nominal single phase system voltage is used in residential?
120/240 (120/208 for three phase)
which of the following conductors has the largest diameter?
2/0 (smaller number, bigger diameter. 14, 8, 2/0, 16)
A three-phase circuit has a line-to-neutral voltage of 120 volts. What is the line-to-line voltage?
208 volts
The slope of the horizontal drainage pipe shall not be less than ______ for a 24 ft section of 4" drain pipe
3"
In general, the overall cross-sectional area of all conductors shall not exceed __________ percent of the cross-sectioned area of the conduit when there are three or move conductors in the conduit
40%
How much power is dissipated by passing 10 amps through a 5-ohm resistor?
500 watts
Energy codes recommend a maximum winter indoor design temperature of ____ and a minimum summer indoor design temperature of ____.
72°F / 75°F
According ASHRAE, boilers and furnaces which condense flue gas in second heat exchangers generally have annual fuel utilization efficiency (AFUE) in what range?
92% to 98.5%
To avoid frequent start-up of the fire pump, a small pressure maintenance pump is installed in parallel with the fire pump. What is this device called?
A "jockey" pump
_____ humidity, also known as the humidity ratio (W), is the amount of water in the air and is measured in grains or pounds of water per pound of dry air
Absolute
What kind of pumps are most used in HVAC applications (e.g. chilled water)?
Centrifugal
What type of valve would be used to prevent backflow?
Check valve
Which of the following installations is NOT covered by the NEC?
Electric utility power lines within city limits
What type of cooling towers uses a fan to blow air through the tower?
Forced-drafted counterflow
Reverse osmosis is used for water purification and is the name for which of these phenomena?
Forcing water from strong solution to weak solution through a membrane by pressure
which of the following valves is used for throttling or regulating?
Globe valve
The device in a PV system which allows the solar power to run AC appliances is which of the following?
Inverter
Which of the following lamp types is generally the most energy efficient?
LED
The __________ diagram is also called an elementary diagram, which is the simplest way to illustrate the operating principle of on electrical circuit
Ladder
Extra low voltage systems are defined as which of the following?
Less than or equal to 50 volts
Light sources can be grouped into four major classes. Which of the following is not one of those classes?
Low intensity discharge
Filters are rated based on which of the following systems?
MERV rating value
The management level hardware of a distributed control system is generally which of the following?
Mainframe computer
The secondary objective of a five protection is to
Minimize interruptions of service
Which of the following cable types is commonly used in residential construction?
NM
The National Electrical code is published by __________.
National Fire Protection Association (NFPA)
Heat, fuel, and _____ make up the three sides of the fire triangle
Oxygen
Which HVAC system must be placed on an outside wall?
PTAC
A ______ schedule is the most important schedule of power system design
Panel
Two basic properties of air-water mixtures are:
Temperature and humidity
The "normal" position of an actuated value or damper is which of the following?
The position (open or closed) that the device assumes with no signal
Kirchhoff's first law states which of the following?
The sum of the currents at a junction is zero
The "connected load" sum of all electrical loads connected to the system, on or off
True
The common methods of joining piping and velves include flanges , welded, glued, threaded, grooved, and clamped.
True
The primary purpose of piping and valves in the commercial building is to move fluid
True
The purpose of the National Electrical Code (NEC) is the practical safeguarding of persons and property from electrical hazard
True
When air is the most common medium used to deliver a heating or cooling effect to a space, the delivery system is called an air-handling system consisting of an air-handling unit, ductwork, and air devices
True
contactors and relays are remote- control power transmitting devices
True
Which of following fans would be appropriate for kitchen grease exhaust?
Upblast roof ventilator
The electromotive force (EMF) or potential difference that causes an electric current to flow is called
Voltage
The electromotive force (EMF) or potential difference that senses on electric current to flow is called:
Voltage
Ohm's Law states which of the following?
Voltage is proportional to current and resistance
Low Voltage Systems according to the NEC are:
nominally below 600V
