How does a screw compressor work?

A screw compressor can run loaded ('pumping air') or unloaded ('idle'). The inlet/loading valve opens and closes according to air demand. The inlet valve is controlled by a solenoid valve that supplies control air to the inlet/loading valve. Check solenoid valve coil and solenoid valve operation.

How does a compressor switch work?

The air pressure deflects a membrane inside of the switch. A mechanical spring acts on the other side of the membrane. If the membrane deflects far enough, an electrical switch is operated that switches the compressor pump on or off. By adjusting the pre-tension of the springs, the switch point can be altered.

What should I do if my air compressor is too low?

If the capacity of the air compressor is really too low, check the following: Check differential pressure over oil separator. Replace separator when necessary. Check and replace compressed air filters (if installed). Compressor does not unload. Check if pressure switch is correctly set and working.

How do you set a pressure switch?

The hysteresis (difference between the cut-out and cut-in pressure) can often be set by a second smaller adjustment spring. The switch can thus be easily set with 2 set screws. The graph below shows a typical pressure switch diagram. The horizontal axis shows the cut-out pressure and the vertical axis the cut-in pressure.

How do I know if my air compressor is working?

If you have a compressed air dryer, check the dewpoint. Check the current draw with a current clamp meter. If the motor draws exeessive current: Try to turn the compressor by hand. It should be possible to turn it around. It should turn around smoothly, without any 'hickups' (be sure to completely shut down the air compressor!).

How do you adjust spring pressure?

By turning the nut on the rod end, the spring pressure can be adjusted. The small spring (see Figure below) is used to adjust the differential pressure (hysteresis). The large springs are used to adjust the cut-out and cut-in pressure simultaneously and proportionally.