A reversing valve is a type of valve and is a component in a

heat pump A heat pump is a device that can heat a building (or part of a building) by transferring thermal energy from the outside using a refrigeration cycle. Many heat pumps can also operate in the opposite direction, cooling the building by removing h ...

, that changes the direction of

refrigerant A refrigerant is a working fluid used in the heat pump and refrigeration cycle, refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Ref ...

flow. By reversing the flow of refrigerant, the heat pump

refrigeration cycle Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. A heat pump is a mechanical system that allows for the transmission of heat from one locat ...

is changed from

cooling Cooling is removal of heat, usually resulting in a lower temperature and/or phase change. Temperature lowering achieved by any other means may also be called cooling.ASHRAE Terminology, https://www.ashrae.org/technical-resources/free-resources/as ...

heating A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning (short: HVAC) systems, which can both cool and warm interior spaces. ...

or vice versa. This allows a residence or facility to be heated and cooled by a single piece of equipment, by the same means, and with the same hardware.What is a Reversing Valve
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Operation

The reversing valve has two states, relaxed (unactivated) versus energized. The energized state is typically achieved by applying 24 volts AC, which is commonly used in

HVAC Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HV ...

equipment. The heat pump can be designed by the manufacturer to produce either cooling or heating with the reversing valve in the relaxed state. When the reversing valve is energized, it will produce the opposite transfer of heat from its relaxed state. For example, a reversing valve installed in such a way as to produce cooling when relaxed will produce heating when energized. Likewise, a reversing valve installed to produce heating when relaxed will produce cooling when energized.

Control

Depending on the construction and use of the heat pump, the reversing valve may be driven by the heat pump through the use of a

defrost control Defrosting or defroster may refer to: *Defrosting (refrigeration) * Frozen food#Defrosting * De-icing * Defogger A defogger, demister, or defroster is a system to clear condensation and thaw frost from the windshield, backglass, or side windows ...

board, or it may be driven directly by a

thermostat A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint. Thermostats are used in any device or system tha ...

(typically from the "O" terminal of the thermostat).

Replacement

Reversing valves are built into the heat pump by the manufacturer, and must be replaced by an HVAC technician if they fail. Since the valve is an integral part of the sealed refrigerant circuit, proper procedures for recovering and then later refilling the refrigerant must be followed, to prevent its loss into the atmosphere.

References

{{HVAC , state=collapsed Heat pumps Valves

Operation

Control

Replacement

See also

References