solenoid valve is installed
A solenoid VALVE installed in the liquid line as close to the evaporator as possible, in conjunction with a narrow differential thermostat, is an excellent temperature control. By mounting the thermostat bulb in the supply or discharge air across the evaporator, the temperature swing is limited only by the differential of the thermostat.
This type of temperature control can be used on a single or multiple evaporator system and is particularly useful on multiplexed systems with evaporators at different temperatures.
Defrost Pump Down
In situations where the condensing unit is installed in a low ambient, such as on a rooftop in northern climates, and the evaporator is operating at a temperature above the ambient, a pump down solenoid valve should be used. This allows the pressure control to be set at a cut out of 1 to 2 psi and the cut in to be set at a pressure below the pressure corresponding to the ambient temperature. This will ensure that the condensing unit will start after cooling down during the defrost.
When
a system has a defrost pump down solenoid valve, a thermostat should be used in
series with the defrost time
clock to control the temperature of the space or fixture. An alternative to the
thermostat would be an evaporator pressure regulator.
Note: System diagrams
are for illustrative purposes and are intended to show application of solenoid VALVES only.
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