Pressure Control - KP Series

The KP series is the general-purpose pressure switch for refrigeration and air-conditioning plant: a single-pole double-throw contact, a bellows sensing element and a setting that is adjusted with a screwdriver on site.

Five families cover the usual duties. KP1 and KP35 are low pressure controls, used to cut the compressor out on low suction and to restart it on rise - the standard pump-down and low-pressure protection arrangement. KP5 and KP38 are high pressure controls, cutting out on rising discharge pressure. KP15 is the dual version, with both functions in one body, which is what most small condensing units actually use.

The pressure range runs from -0.9 bar to 32 bar, with differentials from 0.7 to 4 bar depending on model; the KP38A offers a wider 1.8 to 6.0 bar differential for high pressure duty. Reset is automatic or manual depending on the variant - manual reset is normally chosen for high pressure cut-outs, so that the fault has to be acknowledged rather than the compressor restarting into the same condition.

Contact arrangements include SPDT and SPDT with a low-pressure signal or with both low and high signal outputs, for plant that needs to report state to a controller as well as switch the compressor.

Connection is 1/4 inch NPT or 1/4 inch G, with specials on request, and the allowable fluid temperature is -10 C to +110 C.

Setting notes: set the cut-out below the normal operating point by a margin that reflects the ambient swing, not by a fixed number, and check the differential against the compressor's minimum run time - too narrow a differential short-cycles the machine.