air compressor surges when run off a generator?

[The motor guy]

Ok so I have a Honda 6500 watt generator that I run my craftsman air compressor off of. It's a 33 gallon and it's 2hp I think and I know it pulls 15amps. Anyways, I noticed that when I power it from my generator and I turn it on the compressor kind of surges up and down slightly in rpm for about 8 seconds before it levels out. Why is that? I know the compressor probably has a pretty good power surge at startup so is it because the generator is putting out a bunch of wattage all of a sudden and then dropping down shortly after?

 

[Chris142]

The compressor pulls about 6000w on start up. Pretty close to the max rating on your generator and it hits all at once. Your generator can't rev up as fast as the compressor is trying to start.

So it surges until it catches up which makes the compressor surge.

 

[eljefino]

When your compressor motor is below speed it draws more current and above, the inverse. The governor of the generator is trying to fight this. If your generator has auto voltage control this tightens the demand on its governor as well.

If you can reach into the carb/ governor area of the gen you can stick your finger in and rev it up a little until everything stabilizes.

 

[The motor guy]

I would have thought it would be in the 4000 watt range. My generator isn't the kind that revs up when a load is placed on it. It runs at a set rpm. Is the air compressor the one tool that has the most startup load like compared to a miter saw or table saw?

 

[Joel_MD]

Any capacitor-start motor always has a big current draw when it's first started. I don't think it would be 50 amps (6,000 watts / 120 volts) like Chis142 says, but it might be around 30 amps for a second or so until the RPM gets up to operating speed. I know circuit breakers are designed to allow big momentary loads without breaking the circuit to allow for a motor like that.

 

[Clevy]

Turn off the idle switch and have it run full blast. That will fix the surge.
I run electric compressors of generators daily. I shut the idle off all of them. Ya it's harder on gas but easier on the equipment so pick your poison.

 

[eljefino]

Originally Posted By: motor_oil_madman
I would have thought it would be in the 4000 watt range. My generator isn't the kind that revs up when a load is placed on it. It runs at a set rpm. Is the air compressor the one tool that has the most startup load like compared to a miter saw or table saw?


I'm sure it runs at a larger throttle to make 3600 RPM with a load vs unladen. The inrush current temporarily bogs it down. The good news vs an inverter gen is you have some flywheel effect helping make a temporary boost in power to get your compressor going.

I suspect an air compressor has more mass to get going than a table saw.

If you listen closely when you cram wood into your saw "too fast" your generator will load up a little.

 

[The motor guy]

Originally Posted By: Clevy
Turn off the idle switch and have it run full blast. That will fix the surge.
I run electric compressors of generators daily. I shut the idle off all of them. Ya it's harder on gas but easier on the equipment so pick your poison.


That's what I'm saying. This generator runs at 3600rpm or whatever it is all the time, which is why I'm surprised the compressor surges.

 

[Clevy]

Originally Posted By: motor_oil_madman
Originally Posted By: Clevy
Turn off the idle switch and have it run full blast. That will fix the surge.
I run electric compressors of generators daily. I shut the idle off all of them. Ya it's harder on gas but easier on the equipment so pick your poison.


That's what I'm saying. This generator runs at 3600rpm or whatever it is all the time, which is why I'm surprised the compressor surges.


Ohhhhh. Alright. So even at full blast in the generator the pump still surges.
Interesting.
And you've got one of the best generators money can buy. I don't know that you can get around this problem.
The compressor will pull 20 amps at start up and as it warms requires less power. So I'm not sure if there's anything you can do to avoid it.

 

[zzyzzx]

Don't expect utility grade electrical voltage and frequency from a home generator.

 

[The motor guy]

I forgot that I have a 30 amp Y power cord adaptor that I can plug the compressor into. Will this help more? It was much warmer today and I plugged it into the normal 20amp socket and it only surged slightly one time right after starting. I forgot this compressor kind of hesitates to start when it's cold outside even when plugged into a wall outlet.