Selecting an unloader valve


I have an older Champion compressor that is running strong after 30 years! I would like to update the control systems for this compressor.

The unloader:

I would like to get specific recommendations of what kind of unloader valve to get (and if its 110v or 12v), where to get it and also the same for the tank drain.

The wiring and the rest of this looks easy.

I recently put in a new magnetic starter switch. This is a 5HP single phase 220v motor and its on a 40amp breaker, do you recommend upgrading to an SSR? If so please provide specific product information for that as well.

Thank you.




Hi Geon,
A good place to install the unloader valve is to the unloader tube coming into the centrifugal unloader.

Disconnect the unloader tube connection nut and genly pry away the unloader tube and connect the tube and nut to the NO unloader valve (a fitting to mate the two may be required), it can be mounted similarly to the air compressor as:

Here is an example part number for a normally open unloader valve that could work in your setup:
Unloader Valve: 110VAC NO (Normally Open) 1/8 NPT electric solenoid (Grainger Item # 39P476)

this unloader valve is 110V and can be connected just like in the sample connection diagrams, available under the installation tab at:

Dont forget to as well install and drill the unloader valve plug:

Unloader Valve Plug: (Grainger Item # 6AYZ7 ) and a 1/16″ orifice drilled out (to satisfy a 5 second air purge time)

A bit more information on unloader vales and plugs can be found here:

A good rule of thumb is to use a SSR that the one second maximum overcurrent is rated at x10 amp output of the motor. Check out this article in comparing SSR to magnetic relays: