PORTABLE AIR COMPRESSOR AND GENERATOR?

[kenmac]

If you have a wire off the motor on the compressor that you can clamp an amp meter to ,you would know the amps that you are pulling at start up. A slow blow fuse is what I use sometimes on home a/c units. They are made a little different looking They are slow blowing as in handling high amp start ups.(Hope I explained it correctly)

 

[IslandTractor]

hi,more detailed info,
The generator is a sears120/240 volt 5500 watt not 6500
The compressor is a portercable twin tank 3 hp max amp load 15 amp
it is plugged in direct.ALAN

Not sure but with these corrected numbers the problem may be the start up requirements for a 3 hp motor exceed the generator's capacity. I forget the equation but I know that a 10KW generator has a max of about 5 hp electric motor.

 

[kenmac]

amps x watts = volts ? volts x watts =amps ?

 

[techman]

What you are experiencing is not all that unusual. When an induction motor (the type on the compressor) starts, it momentarily draws LRA - locked rotor amps. This can be several times the FLA - full load amps. Once it is accelerating up to speed, the current drops rapidly. Normally this lasts only a second or so, and can also be seen on things like central air.

Most consumer generators are built "on the edge" of specifications, nothing more than is needed and have very little reserve capacity. You often see a continuous and peak capacity, and the difference is only 20%-25%. When the compressor starts, it is drawing a lot of current (note your comment that the lights dim for a moment). With the generator, this high inrush can not be delivered, and the generator hits a current saturation and the compressor either is not spinning or turning very slowly, and not getting to speed to have the inrush current drop. The generator will bog down and the high current will trip your breaker. If the breaker did not trip, and the generator sat in that state, you would most likely burn out the generator if left trying to start. Saws and other tools do not use induction motors, but rather a series wound brushed type motor. These do not have the same starting charactistics and will spin up on most generators.

Unfortunately the solution is either a bigger generator, or an "industrial" grade generator that has a greater overload capacity.

paul

 

[kenmac]

Techman , I had no idea that his compressor might be doing that . LRA on a/c units is how I size a house generator If the cust. wants to run a/c on generator power.I have other installers ask my why I size the genset this way ? They say they only size by the max amps on the unit.Which in my opinion isn't the correct sizing method .

 

[BobRip]

hi,more detailed info,
The generator is a sears120/240 volt 5500 watt not 6500
The compressor is a portercable twin tank 3 hp max amp load 15 amp
it is plugged in direct.
It makes a pssssttt when it shuts ,off so id say the unloader is working.I took it apart also as my book said and checked it.
Apon further inspection i cant find the size of the resets in the generator,or manual,thought i read somewhere 20 amp.
No problem with the chop saws etc on the generator,i believe its working ok
book says it requires a slow blow fuse ?whats that? How do i install one?
SORRY about the wrong numbers the first time,should have looked it up and gave the facts
ALAN

Is that 5500 watt continuous or surge. Starting a compressor is a lot more difficult that starting a circular saw that is not in the wood. I thing you need a larger generator or smaller compressor. My generator (8000 watts continuous, 10000 surge) could not start my 1 HP well pump after Isabel. I ended up pulling up the pump and changing the wire from 12 guage to 10 guage. So a 16 horse power gasoline engine driven generator could not start a 1 HP pump. Compressors are not as bad, but still they have a flywheel and piston to spin up.

 

[techman]

LRA on a/c units is how I size a house generator If the cust. wants to run a/c on generator power.I have other installers ask my why I size the genset this way ?

I don't think it is that easy. You can not size by AC LRA. You would end up with a giant genset for a house. Much has to do with the generator construction and engine size. The cheaper gensets do not have much reserve to get a larger induction motor started turning. Better ones do.

As a rule of thumb, I would go with the genset peak output to be 2 x the FLA of an AC or other motor load. No guarante, but what I have seen that usually works. You should try it first (which is normally impossible) or talk to someone who has a comparible installation setup. The manufacturer of the genset should also be helpful with information on motor starting.

paul

 

[kenmac]

You'er correct , my mistake .sometimes I don't type or say what I'am thinking cause LAR on a 3.5 ton a/c unit is 102 which would require a 25 kw just for the a/c . Sorry for the screw up . Thanks for catching it . I size 2.5 x full load amps. which is a little much sometimes but, you got xtra if the need should arise.

 

[_RaT_]

Shouldnt my 6500 watt generator run my portacable twin tank portable air compressor? using it at my remote property it will trip the breaker[20amp] if it trys to start back up after its already been filled.It seems to work ok at the house ,although it dims the lights. I am plugging in direct.The only way i can use my nailers at camp , is to open the water drain valve slightly and let it run steady.What size generators are you contracters using to power your portable compressors? THANKS FOR ANY INFO.
ALAN

I have had success changing out the oil in my 1.5 HP Emglo with a synthetic oil. It really did make a difference when the compressor was cold. Ingersol Rand makes a synthetic for compressors available at Grainger's.

 

[hazmat]

Sorry for the late reply. It may be your breaker. I have a P/C twin tank with induction motor - 2.5 peak HP, 1.3 running. PC compressor

I bought this one specifically because it had a lower amp rating than others at the time as I was renovating a 100 year old house w/ not so modern electrical. It ran fine on the old electric. It would pop the 15amp arc fault breaker that the electritian installed while updating the electrical, but only when it cycled on again. It runs OK on regular 15 amp breaker & 14ga wire.

So - long story short, is your breaker "arc fault" (different than GFI).