If an electric heat pump won't turn on despite the thermostat and power to the house/unit being operational, there could be several potential problems. Here are some common issues to consider:
Tripped Circuit Breaker or Blown Fuse: Check the circuit breaker panel or fuse box to see if the circuit for the heat pump has tripped or if a fuse has blown. If you find a tripped breaker or blown fuse, reset the breaker or replace the fuse and try turning on the heat pump again. If the breaker trips again immediately, there may be an electrical issue or a problem with the heat pump's components.
Faulty Thermostat Wiring: Even if the thermostat appears to be working, there may be an issue with the wiring that prevents it from communicating with the heat pump. Check the thermostat wiring to ensure it is connected properly and securely. If you're not familiar with thermostat wiring, it's best to seek help from a qualified HVAC technician.
Defective Capacitor: The heat pump's capacitor plays a crucial role in providing a jolt of electricity to start the compressor and motors. If the capacitor is faulty, the heat pump may not start. A trained technician can test the capacitor and replace it if necessary.
Faulty Contactor: The contactor is a relay switch that controls the flow of electricity to the heat pump's compressor and fan motors. If the contactor is faulty, it may prevent the heat pump from turning on. A technician can inspect and replace the contactor if needed.
Low Refrigerant Charge: Heat pumps require a precise amount of refrigerant to operate correctly. If the refrigerant charge is too low due to a leak, the heat pump may not start or function efficiently. A professional HVAC technician can diagnose and fix refrigerant-related issues.
Faulty Compressor or Motor: If the heat pump's compressor or fan motors are malfunctioning, the unit may not turn on. A technician can diagnose these components and determine if they need repair or replacement.
High-Pressure Switch Tripped: Heat pumps have safety switches that monitor system pressure. If the pressure becomes too high, such as in the case of a blocked air filter or a refrigerant issue, the high-pressure switch may trip and shut down the heat pump as a safety measure.
Defective Thermostat: Even though the thermostat may seem operational, it's possible that it's faulty or not sending the correct signals to the heat pump. Try replacing the thermostat batteries or consider having the thermostat checked and replaced by a professional.
Issues with the Defrost Cycle: If the heat pump is in heating mode, issues with the defrost cycle, such as a malfunctioning defrost control board, can prevent the heat pump from turning on.
Since heat pump systems can be complex, it's best to have a qualified HVAC technician diagnose and address the problem. They have the expertise and tools to identify the specific issue and ensure proper repairs are made.