Refrigeration System Troubleshooting and Diagnosis Flashcards

An ammonia detector alarm activates in the machine room. What is the FIRST action the operator should take?

Answer: Don appropriate respiratory protection and evacuate personnel before investigating

The first priority when an ammonia alarm activates is protecting personnel — don SCBA or supplied-air respirator and evacuate non-essential personnel before attempting to locate or address the leak.

A refrigeration system shows normal discharge pressure but abnormally low suction pressure with high suction superheat. The TXV bulb is properly clamped. What is likely wrong?

Answer: Plugged liquid line filter-drier or partially closed liquid line valve starving the TXV

A plugged filter-drier or closed liquid line valve restricts liquid refrigerant flow to the TXV, starving the evaporator and causing low suction pressure with high superheat even though the TXV is functioning correctly.

What does liquid slugging in an ammonia compressor sound like and what damage can it cause?

Answer: A loud knocking or hammering sound; can break valve reeds, connecting rods, or cause catastrophic compressor failure

Liquid slugging sounds like heavy knocking or hammering because liquid is incompressible; it can shatter valve plates, bend or break connecting rods, and cause catastrophic compressor failure.

After completing maintenance on an ammonia system, how should the technician confirm there are no refrigerant leaks before restarting?

Answer: Use electronic ammonia leak detector or sulfur stick test, and check all joints at operating pressure

Electronic leak detectors or sulfur sticks (which produce white smoke with ammonia) should be used to check all opened connections at operating pressure, as visual inspection alone cannot detect small leaks.

A pressure relief valve on an ammonia vessel has been found to have a small weeping/dripping of refrigerant. What should the operator do?

Answer: Tag the valve out of service, install a second relief valve if required by code, and arrange for immediate replacement of the leaking valve

A weeping relief valve should be replaced promptly — it may not reseat properly and could fail to protect at the correct pressure; follow your jurisdiction's code requirements for maintaining pressure relief protection during valve replacement.

What is the purpose of a log book or equipment log in a refrigeration machine room?

Answer: To record operating conditions, maintenance performed, refrigerant added, and alarms — providing a baseline for troubleshooting and regulatory compliance

Equipment logs record operating data, maintenance history, refrigerant additions, and incidents, creating a baseline that helps operators identify trends, diagnose problems, and demonstrate regulatory compliance.