Hi I have recently bought a new compressor (3HP) it starts and runs from a generator (3.5Kw) but the compressor cuts out when it gets warm and not up to pressure. If I run the compressor of a mains supply it runs all day no problems.

So I'm guessing the problem is something to do with the generator supplied power (sine wave)? not been the same as mains.

So the question is is there anything I can buy to place between genny and compressor to solve the problem?

All the other kit runs with no problem with the genny, pressure washer, hoovers etc.

As I wrote that I also realise that my electronically controlled polisher doesn't run of the genny it sort of pulses for want of a better description.

Probably you're getting a square wave or some such from the generator, not a true sine wave, and the compressor doesn't like it. You'd need an oscilloscope to check.

The cutting out is probably due to a thermistor in the motor windings, which cuts the current if it overheats, to save the windings burning out. It's telling you not to keep doing it.

Apologies if I spout bollox, I'm more mechanical though I think that's right.
I'm almost certain you are right, my wine reduced brain cells seem to remember something about that, have to be a ble to solve the problem though I would have thought.
What make is your Genny? quite a few 3.5kw's have AVR's fitted, maybe there is an issue with your genny electronics


Book Reviewer
is the genny rated twice the compressor? not great with electronics but when I used to do site work we couldn't run any kit with electronics like saws and routers unless we had at least twice the genny power available as the fluctuations used to fry the motor controllers. gennys IIRC are rated at max power but aren't happy once they go over half of its rating cept in short bursts.

looking at specs online a 3hp compressor needs 2.2kw of smooth power so you would need a 5kw genny just for the compressor.

joiners I used to know would use the petrol compressors on site unless they were just starting out when they would charge them up at home and hope for the best.
Thanks for your replies I think you maybe spot on grumblegrunt, I was talking to some fella in the bar last night that turned up in a van suggesting he was a sparky and he suggested the same thing.

However it seems to start the compressor very easily so me thinks its time to have some bod look at the genny to see what happens when load is applied. Anyone got a 5.5 Kw diesel genny for sale?


Book Reviewer
charging an empty tank is easy but once you get pressure the genny wont be able to match the demand.

take the compressor down to a hire shop and test it on one of their bits of kit.
Thread starter Similar threads Forum Replies Date
R DIY 126
sirbhp Health and Fitness 31
alloydog DIY 13

Similar threads

Latest Threads