Refrigeration & Air Conditioning Mechanic Red Seal · Question
A two-stage heat pump system is experiencing nuisance trips of the auxiliary heat strips as soon as the outdoor temperature drops below 5°C, even though the thermostat is set to 'auto' with a 2°C temperature swing. The balance point for the heat pump is -5°C. What is a likely cause for the auxiliary heat engaging prematurely?
If the outdoor temperature sensor is sending an incorrect, much lower reading to the control board, the system will incorrectly assume it's operating below its
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Question: A two-stage heat pump system is experiencing nuisance trips of the auxiliary heat strips as soon as the outdoor temperature drops below 5°C, even though the thermostat is set to 'auto' with a 2°C temperature swing. The balance point for the heat pump is -5°C. What is a likely cause for the auxiliary heat engaging prematurely?
Answer options: ✅ The outdoor temperature sensor is reading incorrectly or is out of calibration.
- The indoor fan motor is oversized, causing excessive airflow and demand.
- The reversing valve is intermittently sticking in the defrost position.
- The compressor is short-cycling due to low refrigerant charge.
Correct answer: The outdoor temperature sensor is reading incorrectly or is out of calibration.
Explanation: If the outdoor temperature sensor is sending an incorrect, much lower reading to the control board, the system will incorrectly assume it's operating below its balance point prematurely, thus engaging the auxiliary heat when it's not actually required. This is a common cause for premature auxiliary heat engagement.
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