RSES Condenser Systems 5 — Questions and Answers
Question 1: A technician measures 15°F of subcooling at a water-cooled condenser operating at design conditions. This indicates:
- The system is overcharged
- Normal operation with adequate liquid seal at the metering device (Correct answer)
- Non-condensables present in the condenser
- Insufficient condenser water flow
Correct answer: Normal operation with adequate liquid seal at the metering device
15°F of subcooling is within the normal range and confirms the metering device receives a full column of liquid refrigerant without flash gas.
Question 2: What causes 'refrigerant migration' to the condenser during an off cycle?
- High ambient temperature driving refrigerant toward the cold condenser
- Low ambient temperature making the condenser the coldest part of the system (Correct answer)
- Compressor oil absorbing refrigerant vapor
- Expansion valve closing and trapping refrigerant in the condenser
Correct answer: Low ambient temperature making the condenser the coldest part of the system
During the off cycle in cold weather, the condenser becomes the coldest point and refrigerant vapor migrates to it, condensing and accumulating there.
Question 3: An air-cooled condenser with recirculated hot discharge air will show which symptom?
- Low suction pressure
- Abnormally high condensing pressure despite normal ambient temperature (Correct answer)
- Excessive subcooling
- Low discharge superheat
Correct answer: Abnormally high condensing pressure despite normal ambient temperature
Recirculated hot air raises the effective entering air temperature at the condenser, elevating condensing pressure above what the true ambient would cause.
Question 4: In a parallel condenser configuration with multiple refrigerant circuits, what is the main balancing concern?
- Keeping all circuits at identical subcooling levels
- Ensuring equal refrigerant distribution to prevent liquid pooling in one circuit (Correct answer)
- Matching fan motor amp draw across all circuits
- Keeping all condensing pressures above 400 psig
Correct answer: Ensuring equal refrigerant distribution to prevent liquid pooling in one circuit
Unequal distribution causes liquid to pool in one circuit while another starves, reducing overall heat rejection and causing operational problems.
Question 5: Which ASHRAE standard provides guidelines for cooling tower and evaporative condenser water treatment to prevent Legionella?
- ASHRAE 15
- ASHRAE 188 (Correct answer)
- ASHRAE 90.1
- ASHRAE 34
Correct answer: ASHRAE 188
ASHRAE Standard 188 establishes minimum risk management requirements for water management programs in building water systems, including cooling towers and evaporative condensers.
Question 6: A condenser with an excessive temperature difference between refrigerant condensing temperature and leaving water temperature (large approach) indicates:
- The system is properly charged
- Fouled tubes, low water flow, or non-condensable gases (Correct answer)
- Too much subcooling
- An oversized condenser for the load
Correct answer: Fouled tubes, low water flow, or non-condensable gases
A large condenser approach temperature means heat transfer is impeded, most commonly by fouled tubes, restricted water flow, or non-condensable gases blanketing the surface.
Question 7: When replacing condenser fan blades on a rooftop unit, a technician must verify:
- The blade pitch angle matches the original design specification (Correct answer)
- The motor has been replaced with a higher horsepower unit
- The refrigerant charge is reduced before proceeding
- The liquid line solenoid valve is closed
Correct answer: The blade pitch angle matches the original design specification
Blade pitch angle directly determines airflow volume and static pressure capability; incorrect pitch can cause inadequate airflow or motor overload.
RSES Condenser Systems 5
A technician measures 15°F of subcooling at a water-cooled condenser operating at design conditions.
This indicates: