CFC Compressor & Component Diagnostics 2

Question 1

A scroll compressor exhibits abnormal noise during startup but runs quietly at full speed. What is the most likely cause?

Accepted Answer

Refrigerant slugging due to liquid floodback

Answer

Liquid refrigerant entering a scroll compressor during startup causes slugging noise as the incompressible fluid damages scroll wraps.

Question 2

When diagnosing a reciprocating compressor with low suction pressure and low discharge pressure, which condition is most likely?

Accepted Answer

Worn or broken valve reeds

Answer

Broken or worn valve reeds cause low compression efficiency, resulting in both low suction and low discharge pressure simultaneously.

Question 3

A technician measures a compressor's amp draw at 85% of the rated full-load amps with normal pressures. This indicates:

Accepted Answer

Normal operation within acceptable tolerance

Answer

Amp draw at 85% of rated FLA with normal pressures indicates the compressor is operating normally within standard tolerance bands.

Question 4

What does a high superheat reading at the compressor suction combined with normal subcooling at the condenser outlet most likely indicate?

Accepted Answer

TXV or metering device starving the evaporator

Answer

High superheat with normal subcooling indicates insufficient refrigerant flow through the metering device, starving the evaporator of refrigerant.

Question 5

A compressor trips on its internal overload repeatedly on hot days but resets overnight. The most probable diagnosis is:

Accepted Answer

High ambient temperature causing high head pressure overloading the motor

Answer

High ambient temperatures elevate condensing pressure, increasing compressor motor load and amp draw until the overload trips.

(CFC) Chlorofluorocarbon Certification Practice Test