Question

When this unit switches to the heat mode, select the sequence of events which will take place.

a) Expansion valve opens, compressor reverses, outdoor coil becomes evaporator, indoor coil becomes condenser.
b) Compressor stops, expansion valve closes, outdoor coil becomes condenser, indoor coil becomes evaporator.
c) Expansion valve opens, compressor continues in the same direction, outdoor coil remains condenser, indoor coil remains evaporator.
d) Compressor continues running in the same direction, expansion valve closes, no change in coil functions.

Answer 1

The correct sequence when a unit switches to heat mode is: expansion valve opens, compressor reverses, outdoor coil becomes evaporator, indoor coil becomes condenser.

Step-by-step explanation:

When the unit switches to the heat mode, the sequence of events that will take place correspond to the operation of a heat pump. The correct sequence is: expansion valve opens, compressor continues in the same direction, outdoor coil becomes evaporator, indoor coil becomes condenser. So, the right answer is a) Expansion valve opens, compressor reverses, outdoor coil becomes evaporator, indoor coil becomes condenser.

In the heating mode of a heat pump, the outdoor coil, which acts as the evaporator, absorbs heat from the outside air (heat transfer Qc). The compressor then increases the pressure and temperature of the refrigerant gas, and pumps it to the indoor coil that acts as the condenser. Here the gas releases heat, warming the indoor space as it condenses into a liquid. The refrigerant then returns to the outdoor coils through the expansion valve, where it cools and expands before starting the cycle over.