Mars Low Pressure Switch 20/45 OP M43345

The Mars M43345 is a low pressure switch with settings of approximately 20 and 45 PSI.

Pump-down control is worth describing in full because it is a common application for low pressure controls and it changes how their operation should be interpreted.

In a pump-down system, the temperature control does not directly stop the compressor. Instead it closes a solenoid valve in the liquid line. The compressor continues running, drawing refrigerant out of the evaporator and suction line into the receiver, and as it does so suction pressure falls. When it reaches the low pressure control's cut-out, the compressor stops.

The purpose is to prevent refrigerant migrating to the compressor crankcase during the off cycle. Refrigerant condensing in the crankcase dilutes the oil, and on the next start the sudden pressure drop causes violent foaming that can wash bearings and cause liquid slugging.

The operational consequence is that the low pressure control cycles routinely by design. Its operation is normal rather than a fault, and interpreting it as a fault leads to unnecessary diagnosis.

Recognising whether a system pumps down is therefore the first question when a low pressure control is found operating.

Applications include commercial refrigeration and refrigeration racks.

Brand

Mars

SKU

M43345

Category

Pressure Switches

Weight

0.2 lbs

Dimensions

3.50" x 2.00" x 1.50"

Price

$137.00

Availability

In stock

Rating

0 / 5.0