Air Compressor Pressure Switch Cut-In / Cut-Out Calculator

Formula

Differential = Cut-out − Cut-in · Starts/hr = 60 ÷ (Run + Off)

What do you want to calculate?

Cut-out (motor stops)

psi

Differential

psi

Cut-in

100psi

Cut-out

125psi

Differential

25psi

Cut-in ratio

80%

of cut-out

Verify: motor starts per hour

Tank MAWP

psi

Tank size

gal

Pump output

cfm

Avg demand

cfm

Motor duty class (max starts/hr)

Run time

2.6min

Off time

2.3min

Starts / hour

12.3

Duty cycle

53%

Too many starts (12.3/hr > 10)

Widen the differential, add a larger receiver, or fit an auto-drain and constant-speed unloader. See the receiver sizing calculator.

Field procedure

Disconnect power and lock out. Bleed tank to 0 psi.
Remove switch cover. Identify the large range spring and small differential spring.
Restore power. Let compressor pump up. Note actual cut-out on gauge.
Bleed slowly through an outlet. Note actual cut-in.
Range screw CW = raise both settings. Differential screw CW = widen the gap.
Re-test one full cycle. Confirm relief valve does not pop at cut-out.
Time one full cycle with a stopwatch and compare to the "starts / hour" result above.
Replace cover.