Refrigeration & Air Conditioning Mechanic Red Seal · Question
A technician is dispatched to a walk-in cooler that is consistently running warm. Upon arrival, they observe the evaporator coil is heavily iced over, and the liquid line is colder than usual. The system uses an R134a thermostatic expansion valve (TXV). What is the most likely cause?
If a TXV sensing bulb loses its charge, it defaults to a more closed position, starving the evaporator. This causes low suction pressure, reduced refrigerant fl
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Question: A technician is dispatched to a walk-in cooler that is consistently running warm. Upon arrival, they observe the evaporator coil is heavily iced over, and the liquid line is colder than usual. The system uses an R134a thermostatic expansion valve (TXV). What is the most likely cause?
Answer options:
- Overcharge of refrigerant. ✅ TXV sensing bulb has lost its charge.
- Condenser fan motor failure.
- Restriction in the liquid line filter drier.
Correct answer: TXV sensing bulb has lost its charge.
Explanation: If a TXV sensing bulb loses its charge, it defaults to a more closed position, starving the evaporator. This causes low suction pressure, reduced refrigerant flow, excessive superheat at the bulb but low superheat after the TXV, and eventual evaporator ice-up due to coil starvation.
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- 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?
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- What is the main operating characteristic difference between a fixed orifice (capillary tube) and a Thermostat
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