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An air-to-air heat pump has many of the same components as an air conditioning system. The major difference is that a heat pump also has an ๐ธ๐ธ๐ธ : Reversing valve What is the difference between "demand defrost" and "timed defrost"? ๐ธ๐ธ๐ธ : Demand defrost happens only when needed and timed defrost is based on time/temperature. The thermostat that controls the auxiliary electric heat according to the outdoor temperature is called the; ๐ธ๐ธ๐ธ : Outdoor ambient thermostat The outdoor temperature at which the heat pump provides the same amount of heat as the heat loss of the conditioned space without an auxiliary heat is known as the; ๐ธ๐ธ๐ธ : Initial balance point At what temperature is an outdoor ambient thermostat normally set? ๐ธ๐ธ๐ธ : Slightly above the initial balance point.
The outdoor coil is frozen solid on a "no heat" service call. The most likely reason is; ๐ธ๐ธ๐ธ : The outdoor fan is inoperative. In order to determine a heat pumps' balance point, you must first calculate; ๐ธ๐ธ๐ธ : The building's heat load. When a heat pump is used for heating and cooling, the system is sized by the; ๐ธ๐ธ๐ธ : Cooling load. A high efficiency heat pump system designed to function from high to low ambient conditions below 10*F, may have? ๐ธ๐ธ๐ธ : Two outdoor coils with each one incorporating a dual stage compressor. Room thermostats for heat pumps should be installed; ๐ธ๐ธ๐ธ : As near to the main return air grill as possible. When the heat pump compressor has malfunctioned, the customer has the option to switch the system into; ๐ธ๐ธ๐ธ : Emergency heat mode. Start up with a night set back digital thermostat requires the technician to always;
๐ธ๐ธ๐ธ : The system will not properly remove the humidity from the conditioned space. The most preferred method of charging any system in the field is; ๐ธ๐ธ๐ธ : By weight. What is the industry standard for deep vacuum? ๐ธ๐ธ๐ธ : Maintain 500 microns for 15 minutes. Good service practice for installation of a reversing valve includes; ๐ธ๐ธ๐ธ : Use heat paste and wet rags while brazing in the new valve. Off-cycle crankcase heat is provide by; ๐ธ๐ธ๐ธ : A small amount of current is passed through the start capacitor to start the heat winding. You are checking for proper airflow in CFM on a three ton heat pump system. The system has one return grill measuring 24"X24", which has a net free area of 3.4 square feet. You measure air velocity and calculate an average of 400 FPM. From this information you can conclude that; ๐ธ๐ธ๐ธ : Airflow in CFM is below normal range. What control operates the 1st stage of secondary heat?
๐ธ๐ธ๐ธ : The second heating stage of the indoor thermostat. What is the industry standard for maximum duration for defrost? ๐ธ๐ธ๐ธ : A maximum of 10 minutes. What is the recommended CFM across the evaporator cool of a heat pump? ๐ธ๐ธ๐ธ : 400 to 450 CFM If manufacturer specifications are not available, a good way to calculate cubic feet per minute through a coil is to; ๐ธ๐ธ๐ธ : Use temperature rise on emergency heat mode. What type of defrost is employed on this heat pump? ๐ธ๐ธ๐ธ : Time or temperature initiation, time and temperature termination. Which component is responsible for energizing auxiliary heat during the defrost cycle? ๐ธ๐ธ๐ธ : The defrost relay. When this unit switches to the heat mode, select the sequence of events which will take place. ๐ธ๐ธ๐ธ : The RVR coil is energized through TH-1. The CR coil is energized through the RVR contacts.
An R410A heat pump operating in the heating mode has a suction pressure 50 PSIG and head pressure of 285 PSIG has a compression ratio of; ๐ธ๐ธ๐ธ : 4.6: Which type of heat pump does not require a defrost cycle? ๐ธ๐ธ๐ธ : Water source. An R-410A heat pump operating in the cooling mode has a suction pressure of 131 PSIG. Adding 2 PSIG for pressure drop in the coil, the true outlet pressure is 131 PSIG. The temperature of the suction line at the outlet of the evaporator is 57ยฐ F. What is the superheat? ๐ธ๐ธ๐ธ : 12 Degrees On a time initiation/temperature termination defrost, the defrost time clock has one N.O. And N.C. switch. When do the positions of these switches change? ๐ธ๐ธ๐ธ : Every 30 or 90 minutes, depending on the cam installed in the timer. What would be the result of closing registers in rooms that are uninhabited while operating in the heating mode? ๐ธ๐ธ๐ธ : The discharge pressure and temperature will rise decreasing the life span of the unit.
What is the most common complaint from a customer changing from gas heat to a heat pump? ๐ธ๐ธ๐ธ : Cold air at high velocities coming out of the registers. When a heat pump is operating in the heat mode, the suction line at the compressor; ๐ธ๐ธ๐ธ : Cold and sweaty The use of a scroll type compressor on a heat pump can eliminate the need for a; ๐ธ๐ธ๐ธ : Suction line accumulator. A heat pump operates satisfactorily in the cooling mode, but not in the heat mode. This could be caused by; ๐ธ๐ธ๐ธ : A stuck check valve or clogged TXV screen. It is not always a good idea to immediately connect a standard gauge manifold set and hoses to a heat pump when a problem is suspected because; ๐ธ๐ธ๐ธ : The charge is critical, sometimes to 1/2 oz. refrigerant. Which component is responsible for changing the direction of the flow of refrigerant? ๐ธ๐ธ๐ธ : Reversing valve. Some heat pump systems use a ______________ as a metering device.
Because of the possibility of liquid flood-back, a heat pump that uses a reciprocating compressor should be equipped with a; ๐ธ๐ธ๐ธ : Suction Accumulator. A scroll type compressor; ๐ธ๐ธ๐ธ : is less susceptible to damage from liquid flood-back. On a split system heat pump. A "no heat/no cooling" service call, you turn the thermostat to the fan on/ cont position and the indoor fan operates. This action verifies that; ๐ธ๐ธ๐ธ : The transformer is functioning. On most air-to-air heat pumps; ๐ธ๐ธ๐ธ : The indoor and outdoor coils are the same size and physical capacity. A heat pump system, operating at 45ยฐF ambient, may be _______ efficient than electric resistance heat ๐ธ๐ธ๐ธ : 3 to 4 times more. Since electric resistance heat produces 1 watt of usable heat for each watt of energy purchased, electric resistance heat has a COP of; ๐ธ๐ธ๐ธ : 1:
As outdoor ambient air temperature decreases, a heat pump's COP; ๐ธ๐ธ๐ธ : Decreases. During the defrost cycle, the system switches to the ___________ Mode. ๐ธ๐ธ๐ธ : Cooling. During the heating mode, the refrigerant in the indoor coil is under; ๐ธ๐ธ๐ธ : High pressure. What three things happen in most air-to-air heat pump during defrost? ๐ธ๐ธ๐ธ : The reversing valve must switch to cooling mode, the outdoor fan shuts off and auxiliary heat is energized. High suction pressure and low discharge pressure on a heat pump system operating in either the heating or cooling mode can be an indication of; ๐ธ๐ธ๐ธ : Compressor inefficiency. The preferred method to preform adjustments to the refirgerant charge in a heat pump system is in the ________ more. ๐ธ๐ธ๐ธ : Cooling. You answer a service call for insufficient heat. You find the suction pressure is higher and discharge pressure is lower than normal. Using a digital thermometer, you measure
๐ธ๐ธ๐ธ : Time and temperature. The defrost cycle can be terminated by; ๐ธ๐ธ๐ธ : Time/temperature Movement of the piston in the reversing valve is accomplished by; ๐ธ๐ธ๐ธ : Bleeding pressure from one side of the piston to the suction side of the compressor. Some close coupled (package unit) heat pumps use an electronic expansion valve is; ๐ธ๐ธ๐ธ : Electronic expansion valves can meter refrigerant in either direction. Liquid line filter-driers that are used on heat pump system; ๐ธ๐ธ๐ธ : Must be a bi-flow design if used without check valves. When installing the heat pump outdoor unit, care should be taken to provide for drainage during the ________ cycle. ๐ธ๐ธ๐ธ : Defrost. The indoor coil is usually mounted in the air stream _______ the auxiliary electric heat strips. ๐ธ๐ธ๐ธ : Before.
On Dual Fuel Systems, the indoor coil must be located; ๐ธ๐ธ๐ธ : After the heat exchanger. Air-to-air heat pumps are most practical to operate in areas where the lowest winter temperature does not go below ______ *F ๐ธ๐ธ๐ธ : + 10 Air-to-air heat pumps, operating without auxiliary heat, provide air to the registers that is approximately _______ *F or less. ๐ธ๐ธ๐ธ : 100 The most common method of defrosting the outdoor coil on an air source heat pump is; ๐ธ๐ธ๐ธ : Reverse cycle defrost. COP is the abbreviation for; ๐ธ๐ธ๐ธ : Coefficient of performance. At temperatures above 45 degrees *F, the heat pump refrigeration cycle permits the; ๐ธ๐ธ๐ธ : Condenser to release 3 to 4 times more heat than it takes in electrical energy to drive the compressor.
A heat pump has a thermostatic expansion valve (TEV) and a check valve at each coil. When the modes are reversed; ๐ธ๐ธ๐ธ : Refrigerant will bypass the TEV on the coil serving as the condenser. Mechanically troubleshooting a reversing valve can be done by; ๐ธ๐ธ๐ธ : By checking the temperature differential between the connection serving the low side. Compressors designed for heat pumps differ from compressors designed for A/C in that; ๐ธ๐ธ๐ธ : It is designed to operate at high compression ratios. One of the most important devices to insure the longevity of a heat pump's reciprocating compressor is the; ๐ธ๐ธ๐ธ : Crankcase heater. A heat pump can be difficult to charge properly because; ๐ธ๐ธ๐ธ : Heat pumps can only be charged in the cooling mode. High efficient heat pump systems charged with R-410A refrigerant normally use a; ๐ธ๐ธ๐ธ : Fixed orifice metering device for the heating cycle and a TXV for the cooling cycle.
When a heat pump is operating in the cooling mode, the; ๐ธ๐ธ๐ธ : Indoor metering device is metering refrigerant and the outdoor check valve is open. When in the cooling mode, the low pressure refrigerant vapor leaves the reversing valve and tracked to the; ๐ธ๐ธ๐ธ : Accumulator and then to the compressor.
