Air compressor switch

[gnxtc2]

I have a 20 gallon belt driven air compressor in my trailer. The generator (Honda EU7000) mounted in the trailer has difficulty starting the air compressor when there is air in the compressor. If the air compressor is empty from sitting or is low, it has no problem starting. I tried switching the air compressor to 220v and it made no difference. The air compressor has no problem starting when on utility power.

I was thinking on changing the pressure switch/unloader valve to a delayed type so the motor can get up to speed before closing the switch. Have the switch close at 20 psi instead of instantly closing when the pressure drops. I'm having difficulty in locating a delayed type air switch.

If the delayed air switch doesn't work, then I'll probably need to wire in a soft starter.

Thanks

Billy T.
[email protected]

 

[johnre]

Most of the pressure switch / unloader valve assemblies that I've seen have direct mechanical linkages between the moving contacts and the unloader - meaning what you are proposing may not be something you'll find.

But you could put in a tee in on the unloader line and add on your own waste valve that is normally closed, and opens immediately and then closes again on a delay timer for only a few seconds after the compressor motor starts.

Or, you could upsize the generator to be able to handle the motor. What's it rated for starting?

 

[gungatim]

Your check valve is bad or stuck open. Easy fix.

 

[gnxtc2]

Your check valve is bad or stuck open. Easy fix.

I took the line between the check valve and compressor head off and there was no pressure.
Correct me if I'm wrong, I think the pressure switch/unloader valve closes instantly and doesn't allow the motor to get up to speed. With a delayed type unloader valve, the motor will start and the loader valve will bleed the pressure until its set pressure makes it close.

Billy T.
[email protected]

 

[MacMcMacmac]

If everything is working well, you could try to plumb in a section of pipe between the compressor and the tank so that there is an empty surge vessel the compressor must fill before the check valve, which should give it a bit of extra time to get up to speed before there is pressure to work against. Right now all it has to fill is the skinny aluminum tube, which gets up to pressure pretty fast. If it doesn't work, there is minimal sunk cost. A length of pipe fastened along the saddle with compression fittings on either end, and some copper tubing. It will blow down a little longer after shut down to drain the pipe fully.

 

[firebirdparts]

That is a great idea ^^^ I inadvertently did this when I added a cooler directly after the compressor outlet. It certainly works and that unloader will blow air for a really long time.

 

[niget2002]

This is going to sound completely off the wall, but maybe plumb in an electric compression release like on a high-compression motorcycle. Put some type of timer/delay on it so it stays open for a few seconds when the compressor kicks on.