CARO Refrigeration System Troubleshooting and Diagnosis 2

Question 1

A compressor is short-cycling (turning on and off rapidly). What is the most common cause?

Accepted Answer

Incorrect pressure control setpoint differential or refrigerant undercharge

Answer

Short-cycling is often caused by a pressure control with too narrow a differential (cut-in too close to cut-out) or low refrigerant charge causing rapid pressure swings.

Question 2

What does an abnormally high compressor amp draw combined with low suction pressure indicate?

Accepted Answer

Possible liquid slugging or mechanical issue within the compressor

Answer

High amp draw with low suction pressure can indicate liquid slugging, worn compressor internals, or tight bearings, all of which cause the motor to work harder than normal.

Question 3

Moisture contamination in a refrigeration system most commonly causes what problem in the expansion device?

Accepted Answer

Ice formation that blocks or partially freezes the expansion valve orifice

Answer

Moisture in the refrigerant freezes at the expansion device orifice where temperature and pressure drop sharply, causing intermittent or permanent blockage and starving the evaporator.

Question 4

When troubleshooting an ammonia system that is not reaching its design suction temperature, what should be checked first?

Accepted Answer

Refrigerant charge level and expansion device operation

Answer

Insufficient refrigerant charge or a malfunctioning expansion device are the most common reasons a system cannot reach its design suction temperature, making these the first things to check.

Question 5

What does a continuously running compressor that never shuts off, combined with a warm refrigerated space, most likely indicate?

Accepted Answer

Insufficient refrigeration capacity — possible refrigerant loss, dirty coils, or excessive load

Answer

A compressor that runs continuously without achieving the setpoint indicates the system lacks sufficient capacity, which may be due to refrigerant loss, fouled heat exchangers, or an unusually high heat load.

CARO - Certified Assistant Refrigeration Operator Practice Test

CARO - Certified Assistant Refrigeration Operator Practice Test

CARO Refrigeration System Troubleshooting and Diagnosis 2