CARO Refrigeration System Troubleshooting and Diagnosis

Question 1

A refrigeration system has high suction pressure and high discharge pressure. What is the most likely cause?

Accepted Answer

Dirty or fouled condenser reducing heat rejection

Answer

A dirty condenser restricts heat rejection, causing both condensing pressure (discharge) and suction pressure to rise as the system struggles to remove heat from the refrigerant.

Question 2

Low suction pressure and low discharge pressure on an ammonia system most likely indicates what condition?

Accepted Answer

Undercharge of refrigerant or low refrigerant level

Answer

A low refrigerant charge causes both suction and discharge pressures to drop because there is insufficient refrigerant mass circulating through the system.

Question 3

A technician notices frost forming on the suction line all the way back to the compressor. What does this indicate?

Accepted Answer

Liquid refrigerant is flooding back to the compressor (liquid slugging risk)

Answer

Frost or ice on the suction line back toward the compressor indicates liquid refrigerant is not fully vaporizing in the evaporator and flooding back, which can cause severe compressor damage.

Question 4

High discharge temperature with normal suction pressure on an ammonia compressor most likely indicates what problem?

Accepted Answer

High suction superheat or discharge valve inefficiency

Answer

High discharge temperature with normal suction pressure often points to excessive suction superheat, leaking discharge valves, or high compression ratio, all of which cause the discharge gas to overheat.

Question 5

What symptom would indicate that a thermostatic expansion valve (TXV) is stuck closed?

Accepted Answer

Low suction pressure, warm suction line, and starved evaporator

Answer

A TXV stuck closed starves the evaporator of refrigerant, resulting in low suction pressure, a warm suction line, and reduced cooling capacity.

CARO - Certified Assistant Refrigeration Operator Practice Test

CARO - Certified Assistant Refrigeration Operator Practice Test

CARO Refrigeration System Troubleshooting and Diagnosis