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1. When performing indoor air balancing tests, the thermostat should be set to: o A. Lowest fan speed o B. Cooling mode only o ✅ C. Bring on the indoor fan on mid-high speed o D. Heating mode Rationale: A mid-high fan speed allows for accurate air volume measurements during balancing. 2. Most manufacturers recommend the thermostat wire should be: o A. 12 AWG o B. 14 AWG o ✅ C. 18 AWG o D. 20 AWG Rationale: 18 AWG is typically the smallest allowable size that meets voltage drop and safety standards. 3. Voltage input to a compressor should be checked at the: o A. Thermostat o B. Line side of the contactor o ✅ C. Load side of the contactor o D. Breaker panel Rationale: Measuring at the load side confirms power is reaching the compressor. 4. If 1st and 2nd stage are calling, the compressor runs, but not the electric heater in a heat pump: o A. Heater is defective o ✅ B. Second stage is open o C. Thermostat is in cool mode o D. Compressor is off Rationale: A break
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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... - ANSWER Which could mean the main power element of the indoor expansion valve has lost its charge Conditions that can cause a reduction from design capacity in a heat pump are an... - ANSWER Undersized vapor line A symptom that a technician would expect on a heat pump system in the cooling mode if the check valve is leaking internally is... - ANSWER Flooding of the indoor coil A voltage reading across a closed contact in a 24V control circuit indicates... - ANSWER Pitted or dirty contacts The first two checks typically made on an electronic check are... - ANSWER Presence of proper input signals and proper output signals In a low voltage circuit, a corroded wire-to-terminal connection acts in the circuit like... - ANSWER An additional resistor The continuity of a fuse should be tested by... - ANSWER Checking resistance with the power off The first check made for most electrical troubleshooting is... - ANSWER Voltage check of the supply line To properly check an energized compressor circuit... - ANSWER The technician should use a VOM set for volts The following conditions exist in a circuit that supplies power to three parallel loads
The three things that happen when a heat pump is cycled into the defrost mode are... - ANSWER Reversing valve switches to cooling mode, Outdoor fan turns off, and Auxiliary heat is energized An extended plenum duct system is a... - ANSWER Single trunk extending in one or two directions with many branch ducts The effect on supply airflow when static pressure on the return is reduced is... - ANSWER Airflow will be increased The voltage most often used to power the outdoor unit in a residential system is... - ANSWER 240V single phase Residential control or low voltage wiring normally is... - ANSWER Shredded wired If you increased suction pressure on a reciprocating compressor... - ANSWER The capacity would increase The refrigerants typically used in residential and light commercial pumps... - ANSWER Have a storage life of an indefinite length of time A restricted drier can cause... - ANSWER A lower than normal suction pressure The blower motor type generally used on air handling equipment with capacities of 4000cfm or greater is... - ANSWER A belt driven 3 phase Electronic air cleaners can operate with internal voltages as high as... - ANSWER 5000V A "cross-break" made on all flat sides of any rectangular section of metal duct will... - ANSWER Increase rigidity and reduce vibration
The terms grille and register are often used interchangeably. There is a difference between these components. The primary difference between a grille and a register is... - ANSWER A register is equipped with an air volume control device, while a grille is not Thermostatic expansion valves meter refrigerant flow to a coil to... - ANSWER Maintain superheated refrigerant leaving the coil Some electromechanical type thermostats require connections to Both the hot side and Common side Of the low voltage transformer... - ANSWER Because the display lights must be powered using both sides of the line Disc type temperature limit controls, used to protect auxiliary heat elements from overheating are... - ANSWER Always auto reset by temperature 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... - ANSWER The system is less likely to shut down as a result of a small leak The sensor of an outdoor ambient thermostat for a heat pump system is typically installed in the... - ANSWER Entering airstream to the outdoor coil A high pressure limit control, used to shut down a compressor if condensing pressure becomes excessive is... - ANSWER Typically installed to sense compressor discharge line pressure Low pressure limit controls are often placed in the suction line of a heat pump for two purposes. They are to... - ANSWER Protect the compressor if suction pressure drops, and to detect a loss of charge
According to fire protection codes, fire dampers should be used in Any air duct the passes through walls or... - ANSWER Partitions of a light commercial installation When the capacity of a heat pump in heating, measured in Btu's, is the same at the heat loss of a structure... - ANSWER The system is sad to have reached its balance point Electronic air cleaners... - ANSWER DO NOT remove odors A packaged heat pump must be... - ANSWER Mounted on a slab if its location is at grade level Whenever possible, the slab should be... - ANSWER Located away from the structure to minimize noise A suction line accumulator should be used in a residential heat pump only when recommended by the manufacturer... - ANSWER If long refrigerant lines increase system charge over recommended maximum charge The measurement of a heat pumps efficiency is often stated using its 'Coefficient of Performance' or COP. The COP of a heat pump is the... - ANSWER Heat pumps heat output in watts/ Total electrical input in watts A benefit in using electronic air cleaner is... - ANSWER Indoor air quality(IAQ) is improved The purpose of calculating the heat loss at a outside design temperature is to... - ANSWER Select appropriate equipment based on Btu output The thermal balance point of a dual fuel heat pump is... - ANSWER The outdoor conditions at which the capacity of auxiliary heat alone matches the heating load
The minimum circuit amp listed on a units' data plate is used to... - ANSWER Determine the max fuse or circuit breaker size heat pumps are particularly sized based on... - ANSWER The cooling load The effective method of reducing sound when AHU is located in a closet is to... - ANSWER Use vibration isolators When wiring a 20 amp FLA motor, the minimum amp fuse or circuit breaker... - ANSWER Should be 25 The typical staging of a two stage heat pump system uses the... - ANSWER Deviation of the t-stat setting to determine when to engage each stage The purpose of a sequencer in a heat pump with an AUX 20 kW electric heater is to... - ANSWER Energize one or two elements and the blower then energize the other elements in timed intervals In a heat pump circuit, an open check valve is used to... - ANSWER By-pass refrigerant flow around the metering device The forward curve centrifugal fan is the... - ANSWER Most commonly used type in residential systems In a reversing valve... - ANSWER The single pipe is connected to the compressor discharge What is the purpose of the reversing valve on an air-to-air heat pump: - Ans - It changes the flow of the refrigerant, making the indoor coil the condenser during the winter months On a reversing-valve solenoid, what is connected to the top tube: - Ans - the compressor discharge line
What position must the reversing valve be in during the defrost cycle: - Ans - the cooling mode When a heat pump switches into the defrost cycle, it must: - Ans - remain in defrost until the outdoor coil has reached a predetermined temperature A defrost termination thermostat is commonly located: - Ans - on the outdoor coil, and opens at 55° F What type of system uses a temperature and a pressure sensor to control the defrost cycle: - Ans - a pressure-initiation-temperature-termination defrost system A pressure switch, used on the defrost cycle of a heat pump, commonly closes at a preset pressure difference of: - Ans - .5" to .65" WC Temperature split refers to: - Ans - the temperature difference between the air entering a coil and the temperature of the coil The outdoor ambient thermostat is commonly used to: - Ans - energize the auxiliary strip heaters during the second stage of heating A hold-back thermostat is used to: - Ans - keep the system energized during a defrost cycle, when the room thermostat is satisfied A discharge temperature thermostat is used: - Ans - on air-to-air heat pump systems that use fossil fuel When sizing a heat pump, it must initially be sized for: - Ans - the cooling load
When sizing for the auxiliary heat for a heat pump system, the auxiliary heat must: - Ans - be capable of handling the entire heat load of the structure Auxiliary strip heaters are: - Ans - located at the indoor unit downstream from the indoor coil What controls the auxiliary strip heaters in a heat pump system: - Ans - the second stage of a two-stage thermostat What is the purpose of the de-ice coil on an air-to-air heat pump: - Ans - It prevents the formation of ice on the lower section of the outdoor coil The coefficient of performance (COP) is: - Ans - a heat pump's rating in the heating cycle, comparing the heat output by the electrical input When installing a heat pump system, the unit should always be located as close to the indoor unit as possible because: - Ans - during the heating cycle a longer vapor line will cause the system to operate less efficiently When installing an outdoor coil, it must: - Ans - never be placed under the overhang of the building What are common supply-air static pressures for a heat pump duct system: - Ans - .15" WC What is a common temperature rise over the indoor coil of a heat pump during the heating cycle: - Ans - 35° F When installing an indoor unit, a clearance that is commonly required for service accessibility is: