A Stuck Valve in an HVAC Compressor

HVAC Compressor

• An HVAC compressor unit moves heat from the indoors to the outdoors via a series of components that use liquid refrigerants as the heat carrier. The components inside an HVAC system include a compressor unit, a condenser, a cooling coil, an evaporator coil and refrigerant liquid. The system houses one set of components on the outside and another set on the inside. The compressor component sits on the outside since its job is to deliver heat gases into the outside air. The compressor contains a motor that’s designed to squeeze heat gases out of the refrigerant liquid. Heat gases then evaporate into the outside air.

Thermostatic Expansion Valve

• The thermostatic expansion valve (TEV) runs into the low pressure side of an HVAC compressor unit. The low pressure side describes the side of the system where liquid refrigerant carries heat gases to the compressor. The high pressure side consists of cooled refrigerant liquids once heat gases have evaporated into the outside air. The thermostatic expansion valve regulates the flow of refrigerant liquids into the compressor unit. The valve feeds the liquid into the compressor in portioned amounts, which allows the compressor to squeeze heat gases out of incoming refrigerant liquids.

Frozen Valve

• The rate in which a TEV releases refrigerant into a compressor enables the unit to compress or pressurize the refrigerant liquid. This high pressure state forces heat gases out of the liquid. A frozen TEV will cause the valve to stick. When this happens no refrigerant material enters the compressor unit. In many cases, a piece of ice that’s formed on top of the TEV will cause the valve to stick. If this is the case, warming up the TEV device will loosen or unstick the valve.

Clogged Tube

• The TEV uses a tube to deliver refrigerant materials into an HVAC compressor unit. If the tube becomes clogged or a piece of debris gets trapped inside it, refrigerant materials cannot enter the compressor in the needed amounts. In effect, a clog will cause the valve to stick and become inoperable. Unclogging the TEV involves taking it apart and cleaning it. The refrigerant line also includes a filter that should prevent debris from entering the TEV. In cases where debris makes it way to the TEV, a worn out filter may require replacement.