Heat pumps have become a popular alternative to traditional heating, ventilation and cooling (HVAC) systems. Rather than purchasing an air conditioning system and a furnace, many homeowners in warm regions like the Southeast purchase a heat pump. It’s a dual-purpose system that can heat and cool indoor spaces. Whether you currently own or are thinking about purchasing a heat pump, however, you may hear some noises when it runs.
Heat pumps often make a clicking sound during startup. This clicking sound is typically caused by a relay switch. Also known as control relays, relay switches are electrical switches that control a circuit. They allow heat pumps to turn on and off by completing or disrupting the flow of electricity. When your heat pump initially turns on, you may hear a clicking sound as the relay completes the flow of electricity.
You may hear your heat pump make a humming noise as it enters defrost mode. Defrost mode, as the name suggests, is designed to defrost the heat pump. Heat pumps feature an outdoor coil and an indoor coil. During the winter, the outdoor coil may freeze over. Fortunately, most heat pumps have a defrost mode that will melt ice off the outdoor coil, which typically sounds like a humming noise.
While some heat pump noises are normal, others are a sign of an underlying problem. If your heat pump has a bad compressor, for instance, you may hear a grinding noise. A grinding noise indicates the compressor’s internal parts are worn out.
Heat pumps have a compressor just like air conditioning systems have a compressor. The compressor raises the pressure of the system’s refrigerant. When the bearings or other components in the compressor wear out, it may manifest in the form of grinding noise.
A loose belt can make an unusual noise. Many heat pumps feature a belt-driven fan. Over time, this belt can become loose. It won’t have the proper tension, so it will make a squealing or whistling noise. If you hear sounds such as these coming from the ductwork entrance near the indoor coil, you may be dealing with a loose belt.
Heat pumps can experience refrigerant leaks. Like air conditioning systems, they consist of a closed system with lines and coils. Refrigerant will travel through this system while absorbing and releasing heat. If your heat pump has a refrigerant leak, you may hear a hissing noise. A hissing noise indicates that refrigerant is leaking out of a line or coil.