313A System Troubleshooting & Safety

Question 1

A refrigeration system shows high discharge pressure, high suction pressure, and low superheat. What is the most likely cause?

Accepted Answer

Refrigerant overcharge

Answer

Refrigerant undercharge

Answer

Restricted liquid line filter-drier

Answer

Faulty compressor discharge valves

Question 2

A system has low suction pressure, low discharge pressure, normal subcooling, and high superheat. What is the most likely diagnosis?

Accepted Answer

Refrigerant undercharge

Answer

Refrigerant overcharge

Answer

Faulty compressor discharge valves

Answer

Dirty condenser coil

Question 3

What instrument is used to measure refrigerant pressure at service valves on a refrigeration system?

Accepted Answer

A digital manifold gauge set

Answer

A clamp-on ammeter

Answer

A megohmmeter

Answer

A psychrometric chart

Question 4

What does a bubbling sight glass indicate when the system is at steady-state operation?

Accepted Answer

Refrigerant shortage, moisture contamination, or a restriction causing partial vaporization of the liquid upstream of the sight glass

Answer

Normal operation with a full liquid line

Answer

The TXV is functioning correctly and modulating flow

Answer

The condenser fan is operating at reduced speed

Question 5

A compressor is running but suction pressure is very high and the system is not cooling. The discharge line is not hot. What is the most likely cause?

Accepted Answer

Failed compressor discharge or suction valves, causing the compressor to pump poorly

Answer

Refrigerant overcharge causing high suction pressure

Answer

Dirty condenser coil blocking heat rejection

Answer

A failed TXV stuck in the open position

Question 6

What personal protective equipment (PPE) is mandatory when handling refrigerants under Canadian safety regulations?

Accepted Answer

Safety glasses or goggles and insulated gloves as a minimum; a face shield, chemical-resistant apron, and respiratory protection depending on the refrigerant and quantity

Answer

Hard hat and steel-toed boots only

Answer

Flame-resistant clothing only, required for all refrigerants

Answer

Hearing protection and fall arrest harness only