Oil Gauge

An oil pressure gauge on a compressor shows the difference between oil pressure and suction pressure, which is the number that actually protects the machine. Two gauges, or one differential gauge, tell you whether the oil pump is developing enough pressure to keep the bearings fed - a compressor running with low oil pressure will fail in hours, not months.

The range covers four pressure spans: 0 to 1.8 MPa, 0 to 3.8 MPa, 0 to 3.5 MPa and 0 to 5.5 MPa. The 1.8 and 3.8 MPa versions are intended for R22, R134a, R404A and R407C systems; the 3.5 and 5.5 MPa versions are for R410A, whose higher working pressure needs a gauge that does not sit at full scale in normal operation.

Two filling media are offered. Glycerol filling damps the needle against compressor vibration and is the general-purpose choice, rated from -25 C to +70 C. Silicone filling stays fluid down to -40 C, so it is the version for freezer plant and outdoor installations where a glycerine gauge would become sluggish in winter.

The connection is 1/4 inch SAE, the standard gauge port size on commercial compressors, and the case is shock resistant.

Selection is by refrigerant first, then by the pressure range that puts normal operation in the middle third of the scale - a gauge that reads near full scale all the time is both less accurate and harder to read at a glance. Fit a snubber or a capillary restrictor on the gauge line where the compressor is small and the pulsation is severe; without it the needle flickers and the movement wears out.