HVAC Refrigeration 4

Question 1

What is the purpose of a hot gas bypass valve in a refrigeration system?

Accepted Answer

Maintain minimum evaporator load by diverting hot gas to the evaporator inlet

Answer

A hot gas bypass valve diverts discharge gas to the evaporator inlet to maintain minimum system load and prevent evaporator freeze-up during low-load conditions.

Question 2

Which refrigerant is classified as A2L and is being adopted as an R-410A replacement?

Accepted Answer

R-454B

Answer

R-454B (sold as Puron Advance) is an A2L refrigerant with a GWP of 466 being adopted as the primary R-410A replacement in residential systems.

Question 3

In a refrigeration cycle, what happens to the refrigerant in the condenser?

Accepted Answer

It rejects heat and condenses from vapor to liquid

Answer

In the condenser, high-pressure refrigerant vapor rejects heat to the outdoor air or water and condenses into a liquid.

Question 4

What is the purpose of crankcase heaters on a refrigeration compressor?

Accepted Answer

Prevent refrigerant from migrating to and mixing with the compressor oil during off cycles

Answer

Crankcase heaters keep the compressor oil warm during off cycles to prevent refrigerant from migrating into and diluting the oil, which can cause compressor damage on startup.

Question 5

What is 'coefficient of performance' (COP) in refrigeration?

Accepted Answer

The ratio of refrigerating effect to compressor work input

Answer

COP is the ratio of the useful refrigerating effect (heat removed from the space) to the work input to the compressor, measuring the efficiency of a refrigeration system.

HVAC Practice Test

HVAC Practice Test

HVAC Refrigeration 4