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137 Cards in this Set
- Front
- Back
R-22 vapor line diameters and lengths are typically specified for a:
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Vapor pressure drop that does not exceed 6 – 7 psi or 6°F
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The primary purpose of using flux when soldering copper or brass parts is to:
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Prevent oxidation.
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The water that results from a defrost cycle of an air to air heat pump (runoff) must:
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Drain off and away from the outdoor coil to prevent excessive ice can build up on the bottom of the coil and reduce capacity.
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The component used to reduce sound transmission and prevent water leaks of a packaged heat pump installed on a roof is:
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The curb gasket.
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On some installations, a heat pump indoor coil can be installed on an existing, operable, fossil fuel furnace.When this type of installation is done you need to add a control so that:
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~The furnace and heat pump do not operate at the same time in normal heating.
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When under a deep vacuum, a hermetic refrigeration compressor’s motor windings could be:
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Damaged if energized.
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In order for an evacuation to be considered complete:
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A heat pump refrigerant circuit should be evacuated to a vacuum pressure of 500 microns or below.
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A system is supplied from the factory with charge for a:
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15 foot line set.
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The data plate shows the required system charge to be 5 pounds 10 ounces.The line set uses a liquid line and is
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3/8 inch. And 25 feet long.
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The manufacturer’s instruction sheet specifies ________________ of refrigerant to be added for each added foot of refrigerant line length
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0.6 Ounces
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A system is supplied from the factory with charge for a: 15 foot line set.The data plate shows the required system charge to be 5 pounds 10 ounces.The line set uses a 3/8 inch liquid line and is 25 feet long.The manufacturer’s instruction sheet specifies 0.6 ounces of refrigerant to be added for each added foot of refrigerant line length so:
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~The total refrigerant charge for the system would be6 pounds.
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Drive slips are typically installed on the:
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Shorter sides of rectangular duct.
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To properly set a heat anticipator it is necessary to:
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Check the heating control circuit amperage draw.
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A heat pump operating in normal ice free conditions maintains a certain temperature difference between the outdoor coil temperature and the surrounding outdoor ambient:
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This temperature difference is referred to as coil TD.
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The smallest refrigerant leak that an electronic leak detector should be capable of sensing is:
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0.05 oz. per year.
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When checking the pressures in an operating system with a manifold gauge set:
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Refrigerant oil in a hose will have no effect on the gauge reading.
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At sea level, a gauge pressure of 35 psigis equal to an:
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Absolute pressure of 49.7 psia
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A technician measures the return air temperature of a 100,000 Btu output furnace to be 65°F and the supply side air temperature is 135°F:
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The CFM would be 1323.
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A residential supply diffuser that is noisy because of a loose vane is best serviced by:
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Replacing the diffuser.
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When performing preventive maintenance on a heat pump the technician should check the outdoor fan to be certain that the:
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Fan runs freely with no binding
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What is the effect of 170 volts supplied to a 208/230 volt compressor:
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Would cause a current increase and the motor may trip on overload.
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On a service call for a cooling problem with a heat pump, your inspections find a liquid line that has condensation on it:
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The most likely cause would be the liquid line is restricted.
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A reason for cool air complaints when a heat pump is operating in the heating cycle:
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Excessive supply air velocities.
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The following measurements are recorded on an operating heat pump system. The heat pump is operating with the compressor only with no auxiliary heat
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~Heat pump only supply air temperature 92°F~Heat pump only return air temperature 70°F~Outdoor temperature 54°F~Supply air temp. /auxiliary heat ON 115°F~Return air temp. /auxiliary heat ON 70°F~CFM 1228~The heating capacity of the unit in Btu/h would be 29,177 Btu/h
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A dirty or clogged air filter in an operating heat pump system can cause by:
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Inadequate heating
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To minimize noise problems in residential duct systems, what is the range (recommended to maximum) of design air velocity in the rectangular main supply trunk is:
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700 to 900 fpm.
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Proper ductwork connections and sealing is critical to good system performance.Conditions are:
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Return side air leak of 15% in a ventilated attic~2½ ton system rated at 1,000 CFM.~Attic Air 95°F
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A technician has the following conditions while checking a packaged heat pump in cooling.
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~The unit has a piston type metering device on both the indoor and outdoor coils.~Outdoor temperature 75°F~Superheat 55°F
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The effect of adding a charge to sub cooling is it:
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Increases it (sub cooling).
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When a capillary tube is overcharged you would get a:
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Low superheat and high sub cooling
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The effect of a low charge on the switchover operations of a reversing valve is the:
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Reversing valves are less likely to transfer if charge is low.
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A technician is working on a heat pump with a capacitor start-capacitor run compressor. On initial startup, the compressor hums momentarily and the shuts down on internal overload:
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The problem is too great a pressure difference on the compressor.
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A step down transformer has a rating of 40 VA. Its primary voltage is 120V with a secondary voltage of 24V. This transformer must not be connected to a load above a maximum current draw of:
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1.7 amps
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A bright red or orange glow from the resistance element in a duct heater:
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Indicates that the flow of air is insufficient.
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The outdoor fan on a heat pump stops during
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Defrost to minimize defrost time
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A capacitor start-capacitor run (CSCR) motor has an open run capacitor so it may start:
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But it draws a higher than normal running current.
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Bent vanes on a direct drive blower wheel in an air handler can cause:
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~Loss in airflow~Excessive motor wear~Increased noise
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A split system heat pump is using thermostatic expansion valves. The system performs properly in heating but in cooling the compressor pumps down:
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Which could mean the power element of the indoor expansion valve has lost its charge.
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Conditions that can cause a reduction from design capacity in a heat pump are an:
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Undersized vapor line
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Flash gas in the liquid line of any heat pump must be avoided.Liquid line flash gas can be caused by:
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Excessive liquid line length or lift.
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A symptom that a technician would expect on a heat pump system in the cooling mode if the check valve is leaking internally is a:
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Flooding of the indoor coil.
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A voltage reading across a closed contact in a 24V control circuit indicates:
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Pitted or dirty contacts.
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The first two checks typically made on an electronic control are:
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Presence of proper input signals.~Proper output voltages.
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In a low voltage circuit, a corroded wire-to-terminal connection acts in the circuit like:
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An additional resistor.
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The continuity of a fuse should be tested by
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Checking resistance with power off
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The first check made for most electrical troubleshooting is a:
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Voltage check of the supply line.
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To properly check an energized compressor circuit:
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The technician should use a VOM set for volts.
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The following conditions exist in a circuit that supplies power to three parallel loads:
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One load is resistive.
~One load is capacitive. ~One load is inductive. |
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The technician is using an analog multimeter to check a run capacitor. With the meter set to ohms the needle swings toward zero and then slowly rises toward infinity:
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This tells the technician that the capacitor charges and discharges.
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If the technician believes that a hermetic compressor has a permanently open internal overload protector:
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The technician should test the compressor while it is cool.
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A control string is defined as two or more switch contacts connected in a circuit, or set of circuits, to control a load.In order to troubleshoot a load controlled by a control string:
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The technician must first check for proper voltage applied across the load.
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The technician suspects that an outdoor thermostat used to bring on auxiliary heat may be out of calibration. The thermostat is a close-on-fall type that is adjustable.One method for checking the thermostat calibration is to:
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Manually rotate the shaft until the thermostat closes and compare the dial setting to an accurate outdoor temperature reading plus 10°F.
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When changing out an evaporator coil the installer must be certain to:
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Plumb the cabinet so its sides are vertical.
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The recommended maximum external static pressure used for heating and cooling equipment with blowers for 5 ton of cooling or less is:
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~ 0.1 in W.C.~
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When a balancing check of a newly installed duct system the:
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Dampers should be open completely in all rooms.
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Operating sound is a consideration in the location of a condensing unit because:
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Excessive noise could be disruptive to the customer.
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A technician has determined a supply in a flexible duct system is leaking:
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All connections including inner and outer layers should be checked.
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Sensible heat ratio is:
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Sensible removed ÷ total heat removed.
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Service site conditions are:
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House feels “drafty” in cooling.~3½ ton split system.~High supply face velocities.~Ductwork is properly sized.~Total CFM 1400.
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A wet bulb reading that is very close to the dry bulb reading from the same instrument indicates:
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The relative humidity is very high.
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The following measurements would be needed to properly evaluate a complaint of “drafty” operation with a heating system are:
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System TD drop.~Static pressure.
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The kind of energy that the condenser removes from the refrigerant is:
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Sensible and latent heat.
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In a simple refrigerant system:
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The refrigerant boils in the evaporator.
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The common suction line on a heat pump is:
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Connected between the indoor coil and the compressor.
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There are two generally used methods for changing capacity on demand in a heat pump:
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One is to use a two speed compressor.~The other method is using a two stage thermostat.
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The three things that happen when a heat pump is cycled into the defrost mode are:
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The reversing valve switches to the cooling mode.~The outdoor fan is shut off and the auxiliary heat is energized.
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An extended plenum duct system is a:
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Single trunk extending in one or two directions with many branch ducts.
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The effect on supply airflow when static pressure on the return is reduced is:
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Airflow will be increased.
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The voltage most often used to power the outdoor unit in a residential system is:
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240V single phase.~
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Residential control or low voltage wiring normally is:
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~Shielded wired.
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If you increased suction pressure on a reciprocating compressor:
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The capacity would decrease.
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The refrigerants typically used in residential and light commercial pumps:
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Have a storage life of an indefinite length of time.
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A restricted drier can cause:
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A lower than normal suction pressure
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The blower motor type generally used on air handling equipment with capacities of 4,000 cfm or greater is:
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A belt driven with three phase.
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Electronic air cleaners can operate with internal voltages:
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As high as 5000 volts.
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A “cross break” made on all flat sides of any rectangular section of metal duct will:
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Increase rigidity and reduce vibration.
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The terms grille and register are often used interchangeably.There is a difference between these two components.The primary difference between a grille and a register is that:
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A register is equipped with an air volume control device.~A grille is not.
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Thermostatic expansion valves meter refrigerant flow to a coil to:
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Maintain superheated refrigerant leaving the coil.
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Some electromechanical type thermostats require connections to:
Of the low voltage transformer: |
Both the hot sideandCommon side
Because the display lights must be powered using both sides of the line. |
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Disc type temperature limit controls, used to protect auxiliary heat elements from overheating are:
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Always auto reset by temperature.
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A disc-type, close-on –rise pressure control is being used as a loss-of-charge limit control on the liquid line of a heat pump. The control must sense a specified pressure within 15 seconds of a compressor start for the compressor to continue operation.If the cut-in setting of the control drifts lower:
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~The system is less likely to shut down as a result of a small leak.
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The sensor of an outdoor ambient thermostat for a heat pump system typically installed in the:
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Entering airstream to the outdoor coil.
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A high pressure limit control, used to shut down a compressor if condensing pressure becomes excessive is:
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Typically installed to sense compressor discharge line pressure
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Low pressure limit controls are often placed in the suction line of a heat pump for two purposes.They are to:
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Protect the compressor if suction pressure drops too low.&~To detect a loss of a charge.
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The function of a reversing valve is to:
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Provide heating and/or cooling.
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The relationship between inrush current and holding current of a relay coil is:
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Inrush current is always greater than Holding current.
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The timing specification of sequencers is often marked on the device using a code similar to H1-24 C45-75. The specification for this particular sequencer marked with this code is:
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Contacts close 1 to 24 seconds after coil is energized.~Contacts open 45 to 75 seconds after coil is de-energized.
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A seven day programmable thermostat can program a different daily schedule which is:
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Used for the next seven days only.
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The capability of electronic programmable room thermostat to reset the set point early so that the space temperature reaches a set temperature at a specific time is called:
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Computed recovery.
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An important reason for using electronic controls is:
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They can make decisions based on many inputs.
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One method used with electronic defrost controls to determine the need for defrost is
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To use two temperature sensors.
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One of the sensors measures coil temperature.The other measures outdoor air temperature.The two temperatures used by the control to determine if a defrost is needed because:
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The lower temperature, the faster the outdoor coil builds up frost.
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When using a double (dual) element time-delay fuse with a 20 amp motor:
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The maximum fuse size should be 25 amps.
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According to fire protection codes, fire dampers should be used in:
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Any air duct that passes through all walls.or~Partitions of a light commercial installation.
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When the capacity of a heat pump in heating, measured in Btu’s, is the same at the heat loss of a structure:
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The system is said to have reached its balance point.
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Electronic air cleaners:
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Do not remove odors. |
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A packaged heat pump must be:
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Mounted on a slab if its location is at grade level.
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Whenever possible, the slab should be:
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Located away from the structure to minimize noise
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A suction line accumulator should be used in a residential heat pump only when recommended by the manufacturer:
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If long refrigerant lines increase system charge over recommended maximum charge
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The measurement of a heat pumps efficiency is often stated using its:
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Coefficient of Performance” or COP.
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The COP of a heat pump is the:
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Heat pumps heat output in wattsdivided by~Total electrical input in watts
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A benefit in using electronic air cleaner is:
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Indoor air quality (IAQ) is improved.
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The purpose of calculating the heat loss at an outside design temperature is to:
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Select the appropriate equipment based on Btu output.
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The thermal balance point of a dual fuel heat pump is:
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The outdoor conditions at which the capacity of auxiliary heat alone matches the heating load
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The minimum circuit amp listed on a units’ data plate is used to:
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~Determine the max fuse or circuit breaker size.
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Heat pumps are particularly sized based on:
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The cooling load.
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The effective method of reducing sound when AHU is located in a closet is to:
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Use vibration isolators.
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When wiring a 20 amp FLA motor, the minimum amp fuse or circuit breaker:
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Should be 25.
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The typical staging of a two stage HP system uses the:
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Deviation of the t-stat setting to determine when to engage each stage.
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The purpose of a sequencer in a HP with an AUX 20 kW electric heater is to:
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Energize one or two elements and the blower then energize the other elements in timed intervals.
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In a HP circuit, an open check valve is used to:
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By-pass refrigerant flow around the metering device.
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The forward curve centrifugal fan is the:
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Most commonly used type in residential systems.
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In A reversing valve:
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The single pipe is connected to the compressor discharge.
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The airflow path of with an outdoor unit pull through coil is:
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Air moves from the outside to the inside.
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Economizer systems close the outdoor air vent to a:
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Preset minimum when outdoor air enthalpy exceeds the set point.
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Condensation on vapor lines is a:
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Concern when the lines are routed inside a wall.
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Refrigerant sub-cooling is measured:
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Between~Refrigerant Condensing Temp&~Liquid line temp
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In a single zone system; if a customer complains of feeling damp or sticky the cause could be:
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Unconditioned air being pulled into the duct work through holes in the duct.
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When performing indoor air balancing tests the t-stat should be set to:
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Bring on the indoor fan on mid-high speed.
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Most manufacturers recommend the:
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Smallest allowable t-stat wire at~ 18 AWG.~
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Checking voltage input to a compressor should take place at the:
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Load side of the contactor.
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HP unit; 1st and 2nd stage appear to be calling, compressor runs but not electric heater:
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This is due to second stage being open.
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After compressor burn out:
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Test the oil for acidity levels.
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Manufacturers recommend that the most acceptable method of attaching line sets to the AHU is:
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Utilizing brazing alloy.
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There are more circuits in a HP outdoor coil than in an A/C outdoor coil to:
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Minimize refrigerant pressure drop.
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Inefficient voltage or current to a solenoid will result in:
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Vibration or chatter of the solenoid.
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A compressor that is suspected to be grounded to its’ housing should be checked for:
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Continuity from the terminal windings to ground.
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The coil of a potential relay is connected to:
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The common and start terminals of a compressor.
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When the load on a HP in cooling mode decreases:
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Suction pressure increases.&~Discharge pressure decreases.
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The measurements needed to find suction superheat are:
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~Suction pressure&~Suction line temperature.
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The purpose of an auto change over switch on a t-stat is to:
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Allow automatic change over between heating and cooling.
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Undersized duct work will often cause:
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High noise levels~High air quantity~High static pressures.
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Determining voltage drop at the outdoor unit requires:
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Checking voltage feed with the outdoor unit not running&~Then with the outdoor unit running.
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A manometer is used to:
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Measure static duct pressure.
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A system that has been evacuated to 500 microns:
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Rises immediately and at a constant rate after the vacuum pump has been shut off~Due to a leak in the system.
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To obtain an accurate refrigerant temperature on a horizontal suction line that is 1 1/8” or larger:
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The TXV sensing bulb should be located at4 or 8 o’clock on the pipe.
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The primary consideration when bending soft copper to any radius is the:
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Cross sectional area must not be significantly reduced.
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