313D Fundamentals of Air Conditioning Systems 4

Question 1

When charging an R-410A system, the refrigerant cylinder must be kept upright or inverted so that:

Accepted Answer

Liquid is drawn from the cylinder because R-410A is a near-azeotrope blend

Answer

R-410A is a near-azeotropic blend that must be charged as a liquid to maintain the correct refrigerant composition ratio.

Question 2

What is the typical temperature differential (TD) across a properly functioning residential evaporator coil?

Accepted Answer

16–22°F

Answer

A properly charged residential system typically produces a 16–22°F temperature drop across the evaporator coil from return to supply air.

Question 3

Which component prevents liquid refrigerant from entering the compressor during startup?

Accepted Answer

Accumulator

Answer

An accumulator is installed on the suction line to trap and hold any liquid refrigerant before it reaches the compressor, preventing liquid slugging.

Question 4

A technician finds that both high and low side pressures are lower than normal but the system is cooling adequately. This most likely indicates:

Accepted Answer

Low outdoor ambient temperature reducing load

Answer

Lower ambient temperatures reduce the heat load, causing both suction and discharge pressures to drop while the system continues to operate normally.

Question 5

What is the purpose of the crankcase heater on a compressor?

Accepted Answer

To prevent refrigerant migration and oil dilution in the crankcase during off cycles

Answer

The crankcase heater keeps the oil warm so refrigerant does not migrate into and dilute the compressor oil during the off cycle, protecting bearings on startup.

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

313D Fundamentals of Air Conditioning Systems 4