MEP-831A will not start air compressor

[Leonardo]

Hello new member here. I bought an MEP-831A from a gov auction and took it home and cleaned it up, It has only 8 hours on the hour meter. The thing ran bad and I noticed someone has removed the lead tampers on the throttle and messed with the settings. I put everything back to how it is suppose to be and adjusted the controller. The generator now actually works ok except that I cant start my 2hp compressor. That kills the power unless I hold the switch next to the green light manually, in this case it will start the compressor and then I can let the switch go and the compressor will continue to run.

Do you guys think a 2hp compressor is too much for this generator? The compressor takes about 13 amps to run hen plugged into a wall and using a kill a watt. BTW I have the inverter set to 115 mode. Shouldnt the generator be able to put out 25 amps when set this way? 120v x 25 = 3000?

 

[kloppk]

In general motor driven items draw about 4X the nameplate current at startup until they get up to speed. That high startup current is what's tripping the 831.

 

[DieselAddict]

The 831 is very sensitive to high starting loads. Mine will not start a 120v construction compressor where my 802 starts it without a grunt.

I put a hard start capacitor on the compressor to see if that made a difference and nope. Trips immediately when I turn It on.

 

[Coug]

Most inverter type generators won't start motor loads the same way as a conventional generator will.

Conventional style it's the rotating mass that helps power past the initial peak current.

With inverters it's electronics controlling everything, and either they can't respond fast enough or just can't handle the load.

 

[Evvy Fesler]

I’m curious to know if your compressor has an air unloader valve? I agree with the other comments though, but in general, the trick is to unload the compressor’s startup task. With an air compressor the unloader valve is one of the few things you can try.

 

[Guyfang]

Or maybe open the water drain valve on the tank, and then start it? Still, if the tank is empty, would the start up load still be high? Never had a problem like that.

 

[Light in the Dark]

The only thing an 831 is good at starting is a receding hair line.

 

[Leonardo]

Thanks for the replies and allow me to clarify things. First thing I guess is that I should state I am very well versed in general electrical muckery as far as a layman goes. Never went to school for it but I understand ac power really well for a layman and have done many projects sucessfully like converting a 120v genset to 120/240. or converting a 12v alternator to 36v. There was a time when I even made my own printed circuit boards for diy projects.

With that said I do have a bit of dislexia so If I mix something up I will apologize in advance.

Anyways, So far when I have talked about starting the compressor I should have pointed out that I was trying to start it with zero tank pressure. I figure this gives the generator the best chance of starting the compressor. Also the tank is dry. I am anal about that. One thing i failed to mention in my first post is that when my generator overloads and trips the circuit interrupter it does not light up any warning lights? What is the overload warning light for if it does not light up during an overload? (i did push the test button and the light works). Just using intuition here I would imagine that during an overload situation the overload light should come on to warn the operator. but my overload light never comes on unless I press the test/reset button.

I notice that there are no obvious circuit breakers on the panel like a typical residential generator has, aside from the 10a breaker for the convenience outlet. But as far as the main power lugs go, there is not an obvious circuit breaker. It seems to me that this generator is using the circuit interrupter as a circuit breaker. Is this correct or am I off here? This is my first military generator, although I have sense bought 1 more as well as a 10KW but that's for another thread.

Yesterday I found out the 831A WILL actually start the air compressor (which does have an unloader valve btw) if I hold the circuit interrupter on manually for about 1.5 seconds while the thing is cranking up. After ther compressor starts I can let the circuit interrupter go and the compressor will keep running fine on it's own and it will go great until the next off-on cycle where it trips the circuit interrupter. I am starting to think the circuit interrupter may be a bit too sensitive. Does anyone know if there is a way to adjust the circuit interrupter? Is it even adjustable? Am I barking up the wrong tree? And yes my kill a watt was freaking out and beeping at me during that 25a start!

i am just spitballing in the wind here but I am wondering if maybe this generator unit would benefit from a circuit interrupter bypass and instead it should have a circuit breaker like a conventional residential generator has. A few of you have said the 831a is not good at starting motors. maybe this is why? After all it is rated at 3000 watts at .8 power factor right? In my mind that should just barely be able to start a 2hp motor.

 

[kloppk]

You are correct, there is no typical circuit breaker on the 831 for the power to the lugs.
The inverter monitors the current load on L1 & L2 coming out of the inverter.
If the current monitor detects current in excess of the rated current it causes the contactor to open.
There isn't any way to adjust the trip threshold.

 

[Leonardo]

disappointing but understandable.

I have a 7hp tecumseh 3kw generator that will start this 2hp compressor every time, even allowing it to cycle on and off. it' is of course a different beast and not directly comparible, but I cant help wonder if this 831A could be tweaked in some way to help it start heavy inductive loads without tripping the circuit interrupter.

 

[peapvp]

disappointing but understandable.

I have a 7hp tecumseh 3kw generator that will start this 2hp compressor every time, even allowing it to cycle on and off. it' is of course a different beast and not directly comparible, but I cant help wonder if this 831A could be tweaked in some way to help it start heavy inductive loads without tripping the circuit interrupter.

i would use a VFD (Variable Frequency Drive) sized to fit compressor to control inrush current into compressor when started.

 

[gelane]

Micro Air softstart kit.
Call them and ask them. Tell them what you got and see
if they can help you.
(not associated with them)

 

[Kenny0]

Said you are running on 120v only, did you connect a jumper wire between L1 an L2. If not that would do it. The switch for 120v or 120/240v is on top of the inverter. Could be too much for an inverter generator.