RSES Installation, Maintenance & Repair Procedures 3 — Questions and Answers
Question 1: When installing refrigerant piping, what is the maximum recommended horizontal suction line pitch to ensure proper oil return to the compressor?
- 1/8 inch per foot downward toward compressor
- 1/2 inch per foot upward toward compressor
- 1/4 inch per foot downward in direction of flow (Correct answer)
- Level within 1/16 inch per foot
Correct answer: 1/4 inch per foot downward in direction of flow
Horizontal suction lines should slope 1/4 inch per foot downward in the direction of refrigerant flow to assist oil return to the compressor via gravity.
Question 2: During maintenance of a cooling tower, a technician finds biological growth (Legionella risk). What is the immediate required action?
- Increase condenser water flow rate
- Perform shock chlorination and notify the facility manager (Correct answer)
- Reduce system operating hours
- Replace the cooling tower fill material
Correct answer: Perform shock chlorination and notify the facility manager
Biological growth in cooling towers poses a Legionella health hazard requiring immediate shock chlorination treatment and notification of facility management per safety protocols.
Question 3: A technician notices that a newly installed evaporator coil has frost forming only on the lower half of the coil. What is the most likely cause?
- Overcharge of refrigerant
- Incorrect refrigerant type
- Low airflow across the evaporator (Correct answer)
- Liquid line restriction
Correct answer: Low airflow across the evaporator
Frost forming on only part of the coil indicates insufficient airflow, preventing the upper portion from absorbing enough heat to keep that section above freezing.
Question 4: When replacing a TXV on a refrigeration system, what critical adjustment step is required after installation?
- Set the valve superheat to match system design specifications using bulb placement and stem adjustment (Correct answer)
- Pre-set the valve to fully open before charging refrigerant
- Bypass the valve during initial startup to verify compressor operation
- Replace the bulb charge with nitrogen before installing
Correct answer: Set the valve superheat to match system design specifications using bulb placement and stem adjustment
After TXV replacement, superheat must be measured and the valve adjusted (by turning the stem) so system superheat matches design specifications, typically 8–12°F for comfort cooling.
Question 5: What is the required procedure when connecting a manifold gauge set to an operating system for pressure readings?
- Connect hoses with both hand valves open to equalize quickly
- Purge the hoses with refrigerant before connecting to service ports
- Connect hoses with manifold hand valves closed, then open service port valves slowly (Correct answer)
- Crack open the high-side valve first to pressurize the hose before connecting the low side
Correct answer: Connect hoses with manifold hand valves closed, then open service port valves slowly
Manifold hand valves should be closed before connecting to prevent refrigerant release, then service port valves are opened slowly to take readings safely.
Question 6: A refrigeration system with an electronic expansion valve (EEV) is hunting (oscillating superheat). What is the best corrective action?
- Replace the EEV motor
- Adjust the EEV controller's proportional-integral (PI) gain settings (Correct answer)
- Install a larger capacity EEV
- Add refrigerant charge to stabilize suction pressure
Correct answer: Adjust the EEV controller's proportional-integral (PI) gain settings
EEV hunting is typically caused by improper PI gain settings in the controller; adjusting these parameters stabilizes valve response and eliminates oscillation.
Question 7: When decommissioning a system with a refrigerant blend, which recovery method is preferred to minimize fractionation?
- Vapor-only recovery through the high side
- Liquid recovery followed by vapor recovery (Correct answer)
- Vapor recovery through both high and low sides simultaneously
- Push-pull recovery method using two cylinders
Correct answer: Liquid recovery followed by vapor recovery
Liquid recovery first (followed by vapor recovery) minimizes fractionation of blended refrigerants by keeping the components together rather than allowing lighter components to boil off preferentially.
RSES Installation, Maintenance & Repair Procedures 3
When installing refrigerant piping, what is the maximum recommended horizontal suction line pitch to ensure proper oil return to the compressor?