RSES Installation, Maintenance & Repair Procedures 2 — Questions and Answers
Question 1: When installing a condensing unit outdoors, what minimum clearance is typically required from walls and obstructions for proper airflow?
- 6 inches on all sides
- 12 inches on all sides
- 24 inches on the discharge side, 12 inches on others (Correct answer)
- 48 inches on all sides
Correct answer: 24 inches on the discharge side, 12 inches on others
Condensing units require greater clearance on the discharge side (typically 24 inches) and at least 12 inches on intake sides to prevent recirculation of hot discharge air.
Question 2: During a compressor replacement, you discover the old compressor failed due to a flooded start. What maintenance step should be added going forward?
- Install a suction line accumulator (Correct answer)
- Replace the metering device with a larger orifice
- Add a hot gas bypass valve
- Install a desuperheater
Correct answer: Install a suction line accumulator
A suction line accumulator prevents liquid refrigerant from entering the compressor during startup, protecting against flooded starts.
Question 3: What is the correct procedure when brazing a copper-to-brass fitting joint in a refrigeration system?
- Use soft solder (50/50 tin-lead) for maximum flow
- Use BCuP filler metal without flux
- Use silver alloy filler with appropriate flux on the brass side (Correct answer)
- Heat the brass fitting exclusively to avoid copper oxidation
Correct answer: Use silver alloy filler with appropriate flux on the brass side
When brazing copper-to-brass, silver alloy filler (phos-copper works on copper but requires flux on brass) with appropriate flux on the brass side is required to prevent oxidation and ensure proper bonding.
Question 4: A technician is retrofitting an R-22 system to R-407C. Which oil change is required?
- Alkylbenzene (AB) oil must be added
- Mineral oil can remain if system is clean
- Polyol ester (POE) oil must replace mineral oil (Correct answer)
- Polyalkylene glycol (PAG) oil must replace mineral oil
Correct answer: Polyol ester (POE) oil must replace mineral oil
R-407C is an HFC refrigerant that requires POE oil because it is miscible with HFCs, whereas mineral oil is not compatible and must be removed.
Question 5: When performing an oil change on a hermetic compressor, how is oil typically added to the system?
- Through the high-side service valve only
- Through the compressor oil fill port
- Through the suction service valve using an oil injector or pre-charged compressor (Correct answer)
- By draining the crankcase and refilling with new oil
Correct answer: Through the suction service valve using an oil injector or pre-charged compressor
Hermetic compressors lack an external oil fill port, so oil is introduced through the suction service valve using an oil injector while the system is under vacuum.
Question 6: What is the purpose of performing a triple evacuation during system commissioning?
- To remove all refrigerant charge before servicing
- To progressively remove moisture and non-condensables by alternating vacuum and dry nitrogen breaks (Correct answer)
- To test the system for leaks at elevated pressure
- To flush contaminants out with refrigerant vapor
Correct answer: To progressively remove moisture and non-condensables by alternating vacuum and dry nitrogen breaks
Triple evacuation uses alternating deep vacuum pulls and dry nitrogen breaks to progressively dilute and remove moisture and non-condensables more effectively than a single evacuation.
Question 7: A scroll compressor is running but producing no cooling. Suction and discharge pressures are nearly equal. What is the most likely cause?
- Low refrigerant charge
- Scroll compressor running in reverse rotation (Correct answer)
- Plugged liquid line filter-drier
- High superheat at the evaporator
Correct answer: Scroll compressor running in reverse rotation
Scroll compressors rotating in the wrong direction (reverse rotation) will run but fail to build pressure differential, resulting in near-equal suction and discharge pressures.
RSES Installation, Maintenance & Repair Procedures 2
When installing a condensing unit outdoors, what minimum clearance is typically required from walls and obstructions for proper airflow?