Refrigeration & Air Conditioning Mechanic Red Seal · Question
A rooftop HVAC unit is operating with high head pressure and low subcooling. The discharge line is very hot. What could be the cause?
Reversed condenser fan rotation significantly reduces airflow over the condenser, leading to poor heat rejection, high head pressure, and a very hot discharge l
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Question: A rooftop HVAC unit is operating with high head pressure and low subcooling. The discharge line is very hot. What could be the cause?
Answer options:
- Evaporator coil is deeply frosted ✅ Condenser fan motor has reversed rotation
- Liquid line solenoid valve is stuck closed
- Expansion valve is open too wide
Correct answer: Condenser fan motor has reversed rotation
Explanation: Reversed condenser fan rotation significantly reduces airflow over the condenser, leading to poor heat rejection, high head pressure, and a very hot discharge line. Low subcooling would also be observed due to inefficient condensation.
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Question explanations
- Which of the following refrigerants is a hydrofluorocarbon (HFC) and has a high ozone depletion potential (ODP
- Which component is responsible for compressing the refrigerant vapour to a high pressure and temperature?
- According to the Canadian Electrical Code (CEC), what is the minimum required working clearance in front of el
- What is the main operating characteristic difference between a fixed orifice (capillary tube) and a Thermostat
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