Installation, Maintenance & Repair Procedures Flashcards

When performing a standing pressure test on a newly installed refrigeration system, what is the recommended holding time before declaring the system leak-free?

Answer: 24 hours minimum at test pressure

A minimum 24-hour standing pressure test is recommended to allow temperature stabilization and confirm that pressure remains constant, indicating a leak-free system.

During installation of a parallel compressor rack, why are unloaders or capacity steps typically required on individual compressors?

Answer: To allow staged capacity matching to varying load conditions and prevent short cycling

Capacity control via unloaders or staging allows the rack to match refrigeration output to varying load, preventing short cycling and improving efficiency across different operating conditions.

A technician finds that a newly commissioned system has high discharge superheat (greater than 75°F above condensing temperature). What is the most likely cause?

Answer: Low refrigerant charge or refrigerant restriction

Excessively high discharge superheat typically indicates low refrigerant charge or a restriction starving the compressor of suction vapor, causing gas to superheat more than normal.

What is the proper technique for straightening bent condenser or evaporator fins during maintenance?

Answer: Use a fin comb sized to match the fins-per-inch rating of the coil

A fin comb matched to the coil's fins-per-inch count is designed to straighten multiple fins simultaneously without further damage to the delicate coil surface.

When installing a refrigeration system in a machinery room, which code requirement governs the minimum ventilation rate?

Answer: ASHRAE Standard 15 specifies ventilation based on refrigerant quantity and room volume

ASHRAE Standard 15 (Safety Standard for Refrigeration Systems) provides the formula and requirements for machinery room ventilation rates based on refrigerant type and quantity.

A technician needs to braze a refrigerant line while it is still pressurized with nitrogen. What is the correct procedure?

Answer: Maintain 2–3 PSIG nitrogen flow through the line while brazing to prevent oxidation scaling

Industry best practice is to flow dry nitrogen at 2–3 PSIG through the line while brazing to prevent internal oxidation (black scale) that can contaminate the refrigeration system.

After completing repairs on a commercial refrigeration system, what is the correct sequence for returning the system to service?

Answer: Pressure test with nitrogen, evacuate, charge refrigerant, verify operation, document

The correct return-to-service sequence is: leak test with nitrogen, pull deep vacuum, charge with correct refrigerant amount, verify system operation, then document all work performed.