Installation, Maintenance & Repair Procedures Flashcards

A walk-in cooler compressor short-cycles on the high-pressure cutout. Condenser coil is clean and airflow is adequate. What should the technician check next?

Answer: Refrigerant overcharge

If the condenser is clean and airflow is adequate but high pressure is still tripping, refrigerant overcharge is the next likely cause, as excess refrigerant raises condensing pressure.

When installing a liquid line solenoid valve, what is the correct orientation requirement?

Answer: The body must be installed with the flow direction arrow matching refrigerant flow

Solenoid valves have a directional flow arrow on the body that must align with the direction of refrigerant flow; incorrect orientation prevents proper valve seating and operation.

What is the primary reason nitrogen is used to pressurize a refrigeration system during a leak test rather than oxygen?

Answer: Oxygen can react violently with refrigerant oil creating a combustion risk

Oxygen can react with compressor oil at high pressure to create a potentially explosive mixture, making it extremely dangerous to use in refrigeration systems.

A technician installs a new evaporator coil and finds that the refrigerant distributor tubes are different lengths to various coil circuits. Why?

Answer: Different tube lengths compensate for unequal pressure drops to balance refrigerant distribution

Unequal distributor tube lengths are intentional engineering to create equal pressure drops across all coil circuits, ensuring balanced refrigerant distribution and uniform coil performance.

During a preventive maintenance visit on a large commercial refrigeration system, what is the correct procedure for checking compressor valve performance?

Answer: Perform a pump-down test and measure the rate of pressure rise on the low side after shutdown

A pump-down test followed by monitoring the low-side pressure rise rate after compressor shutdown reveals leaking suction or discharge valves without disassembly.

When sizing a suction line riser for a refrigeration system with capacity control, what additional design consideration is required?

Answer: A double riser or P-trap may be needed to ensure oil return at reduced load conditions

Capacity-controlled systems may have insufficient refrigerant velocity at reduced loads to carry oil up a suction riser, requiring a double riser or P-trap arrangement to maintain oil return.

A technician is replacing a burned-out compressor motor in a semi-hermetic compressor. What additional service step is mandatory due to the burn contamination?

Answer: Install a suction filter, replace the liquid line filter-drier, and perform an acid test after initial operation

A burned compressor leaves acid and carbon contaminants in the system; a suction filter and liquid line drier must be installed and the system acid-tested after initial run to verify cleanup.