Johnson Controls Pressure Switch Fan Cycling In 250PSI

The Johnson Controls P100AP-4C is a fan cycling pressure switch with an approximate 250 PSI setting.

Fan cycling controls exist to solve the low ambient problem on air cooled equipment, and understanding what they are actually protecting explains why the setpoint matters.

The metering device, whether a thermostatic expansion valve or a fixed orifice, is driven by the pressure difference between the high and low sides. In cold weather the condenser rejects heat too readily, head pressure falls, and that pressure difference collapses. The evaporator is then starved of refrigerant regardless of how much the system contains, and the symptoms are poor cooling, low suction pressure, and on refrigeration a fixture that will not pull down.

Cycling the condenser fan off raises head pressure back to a workable level, restoring the differential.

The 250 PSI figure describes the pressure range the control operates within, which must suit the refrigerant in the system. What matters is the condensing temperature that pressure represents, and because every refrigerant has its own pressure-temperature relationship, a control appropriate for one may be entirely wrong for another.

Applications include commercial refrigeration and air conditioning with air cooled condensers exposed to variable ambient conditions.

Brand

Johnson Controls

SKU

P100AP-4C

Category

Pressure Switches

Weight

0.2 lbs

Dimensions

4.20" x 1.50" x 1.20"

Price

$44.00

Availability

In stock

Rating

0 / 5.0