What is a Reversing Valve?

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  • Written By: B. Turner
  • Edited By: W. Everett
  • Last Modified Date: 06 November 2019
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A reversing valve is an important element within a heat pump system. It is located along the tubes or pipes that connect the major operating components of the heat pump, and helps direct the flow of refrigerant through these pipes. This valve allows the heat pump to act as both an air conditioner and a heating system. Heat pump reversing valves eliminate the need for separate heating and cooling systems, which typically results in lower costs, less maintenance, and improved efficiency.

To understand how the reversing valve works, it's important to first understand how air conditioning works. Most air conditioning systems consist of an indoor evaporator unit and an outdoor condenser. A series of tubes connects these two units, and allows refrigerant to pass between them. As the refrigerant passes through the evaporator, it collects heat energy, which makes the inside of the home feel cooler. The refrigerant then passes out of the condenser, which exhausts the heat energy to the outdoors.


With a reversing valve, it is possible to reverse this process to add heat to a room instead of removing it. When the reversing valve is set to heat mode, the condenser and evaporator automatically switch roles, so that the evaporator is now outdoors while the condenser is inside. As refrigerant passes outdoors, it collects heat energy and transports it back into the home. The condenser exhausts the heat energy into the home, then passes the cooled refrigerant back outdoors to complete the cycle.

Depending on the type of heat pump in use, the reversing valve may be operated using a thermostat or control panel. If a thermostat is used, the reversing valve automatically switches on and off as needed to maintain the desired temperature level. Valves connected to a control panel require manual activation by the homeowner as the weather changes each season. Some very basic systems may have a simple reversal switch on the casing of the heat pump itself.

Reversing valves are built into the heat pump system by the manufacturer, and are very difficult to access or replace. Failure of the reversing valve is a common problem over the life of the heat pump, and is often confused with condenser failure. While it is possible to replace a failed reversing valve, homeowners should not attempt this repair on their own. A trained professional should be hired to replace the valve without damaging the heat pump or related piping.


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Post 2

@ElizaBennett - Just call an HVAC person. You can take some time first to observe the system and see if it seems to be running more often than usual, not blowing as cold, etc., but really only a pro can tell you what's wrong.

I've had this problem, the high AC bill, and it's been totally different problems. One time, our condenser was running constantly instead of shutting down when not in use. (Probably should have noticed that sooner. Oops!)

Another time, the heat was sort of stuck on and it was blowing at the same time as the AC. Not sure how that could work with the reversing valve in place, but somehow it was.

Unless you yourself have special training, you pretty much always need to call a pro for your heat pump, but reading articles like this one can at least help you fine-tune your BS detector for evaluating what the person tells you!

Post 1

Is there any reversing valve troubleshooting I can do? My AC bill has gone through the roof and I'm wondering if it could be a problem with the reversing valve.

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