System Troubleshooting & Safety Flashcards

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

Answer: Refrigerant overcharge

High discharge pressure, high suction pressure, and low superheat together indicate refrigerant overcharge — excess refrigerant floods the evaporator (low superheat) and overwhelms the condenser (high discharge pressure).

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

Answer: Refrigerant undercharge

Low suction pressure combined with high superheat and low discharge pressure indicates insufficient refrigerant in the system — the evaporator is starved of liquid, causing high superheat, and the compressor is moving less vapour mass, lowering both pressures.

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

Answer: A digital manifold gauge set

A manifold gauge set (or digital manifold) connects to the high- and low-side service valves to measure suction and discharge pressures, allowing the technician to diagnose system performance and charge level.

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

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

A bubbling or foamy sight glass at steady state indicates the liquid line contains vapour bubbles, which can be caused by low refrigerant charge, excessive pressure drop, or a restriction in the liquid line producing flash gas.

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?

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

If the compressor is running but the discharge line is not hot and suction pressure is very high, the compressor valves have likely failed — the compressor is spinning but not effectively compressing the refrigerant, so it is not moving refrigerant through the system.

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

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

Canadian OHS regulations and manufacturer SDSs require at minimum safety glasses/goggles and chemical-resistant gloves when handling refrigerants; additional PPE such as face shields and respirators are required for larger quantities or toxic refrigerants like ammonia.