MCQUAY DEFROST CONTROL PARTS

McQuay Defrost Controls are used to provide time/temperature initiation and ending of the defrost cycle. There are different types of defrost controls. The time initiated and time terminated type is used where the two parameters - the time needed for ing and the time between s - need to be very accurately predicated. The other type is the time initiated and temperature terminated, which starts the according to the set time. Any rise in temperature will stop the and start the refrigeration . The time initiated and pressure terminated type also starts s according to time set but only when the coils do not have any frost. A sensor detects when the coils are frost free and the refrigeration is started again.

Different types of ing methods are typically used. For coils operating in room temperatures of -18ºC and higher, water spray type is used. The fans are stopped and the coils are sprayed with water. If required the water might need to be heated. The water flow will then need to be handled via drain pipes, etc. If hot gas is used to , vapor from the compressor applies the heat to the evaporator. In the case of electric , the heat is applied externally to the evaporator against internal applications in the other methods which takes a bit longer.

Operation- Control

When operating, the power to the circuit board is controlled by a temperature sensor that is clamped to a return bend on the outdoor coil. Timing periods of 30, 60, or 90 minutes may be selected by connecting the circuit board jumper wire to 30, 60 or 90 respectively. Accumulation of time for the selected timing period begins when the sensor closes (approximately 28°F) and when the wall thermostat is calling for heat. At the end of the timing period, a will be initiated, provided the sensor remains closed. When the sensor opens (approximately 65°F), the is terminated. If the is not terminated due to the sensor temperature, a 10 minute override interrupts the period.

When the heat pump is on the heating , it is necessary to redirect the refrigerant flow through the refrigerant circuit external to the compressor. This is accomplished with a reversing valve. Thus, the hot discharge vapor from the compressor is directed to the inside coil (evaporator on the cooling ) where the heat is removed, and the vapor condenses into liquid. It then goes through a capillary tube, or expansion valve, to the outside coil (condenser on the cooling ) where the liquid is evaporated, and vapor goes to the compressor.

At HVACPLUS you can find all types of controls as well as many other HVAC replacement spares. We have components from heating, ventilators, air conditioning and refrigeration systems from manufacturers like Trane, AAF, Carrier, Barber Coleman, York, Honeywell, Herman Nelson and many more. We are your one stop online parts supply store.