REF UNIT 43 Flashcards
(43.1) What is responsible for the heat pump’s ability to reverse the direction of refrigerant flow?
the four-way reversing valve
(43.2) what does a water-to-air heat pump mean?
it uses water to heat air.
(43.3) what does it mean when a heat pump “fails in heating?”
when the solenoid is de-energized, the refrigerant will flow from the compressor into the indoor unit.
(43.3) what is a direct-acting four-way reversing valve and where are they used?
a reversing valve that moves by direct force from the solenoid. They’re found in small heat pumps.
(43.3) where are pilot-operated reversing valves found?
in larger heat pumps.
(43.5) what are the names of the 2 lines in a heat pump?
gas line and liquid line
(43.6) in a heat pump, two metering devices are used. what stops the refrigerant for going through the unintended metering device?
a check valve
(43.6) what kind of TXVs are used in heat pumps?
vapor charged TXVs
(43.6) what are the TXV’s with built in check valves called?
bidirectional thermostatic expansion valves
(43.6) T or F: in old cap tube heat pumps, two cap tubes are used, one for heating and one for cooling.
true
(43.6) T or F: heat pumps that use an EEV only need one
true
(T or F) heat pumps that use a piston metering device only need one.
false
(43.6) why would a heat pump system use a cap tube in the indoor coil and a TXV in the outdoor?
the cap tube is used in summer as the conditions are somewhat constant, and the TXV is used in winter where the conditions vary.
(43.8) what are the three possible sources of auxiliary heat that a heat pump could have?
electric, gas, or oil.
(43.8) define balance point in heatpumps
the lowest ambient temperature that a heat pump will pump the exact same amount of heat that the structure is leaking.
(43.9) why is COP so high in heat pumps?
because the total effect isn’t the NRE, but the THOR, which is more that NRE.
(43.10) in a furnace with a coil, why Is the coil placed before the auxiliary heating in the airstream?
so that the auxiliary heat doesn’t heat the coil too much and cause damage.
(43.10) what is a cold wall?
the wall close to outside. So when a ducted system is heating, the wall it’s closest too will be warm, and the walls closest away will feel cold as a result.
(43.12) what are heat anticipators?
devices used in space thermostats to reduce temperature swing.
(43.12) T or F: there are two anticipators in a space thermostat with 2nd stage heating, and only one in single stage heating.
true
(43.13) define time and temperature initiated defrost?
exactly what it sounds like. it uses a temperature sensor or air pressure switch on the coil
(43.13) what is the normal defrost termination temperature on a heat pump?
50°F
(44.2) define open-loop and closed-loop geothermal heat pumps.
open-loops are water source, closed-loop are earth-coupled.
