Need help with air compressor

[kzitekmpls]

That is maybe a 2hp motor. A real 3hp motor would be rated for 25-30 amps on 120v, and for that reason, they don’t really exist.

Regardless, I’m surprised it taps out that fast. It’s certainly not a heavy duty unit, but I bet something’s wrong with it aka faulty. Put an amp clamp on it to confirm.

I'm thinking try slightly smaller pully and throw and amp clamp on as next step.

 

[DerekV]

Triple checked it's wired for 120v

Try the wiring for “240v” for grins, maybe the diagrams are reversed

 

[American Locomotive]

There are two things going on here:

1) The motor you bought is not actually 3HP
2) Your old motor is also not 3HP

At 17.2A FLA @ 230v, your old motor is about 4HP. I suspect it's actually "3.7 HP", as that is a very common rating for newer compressors,. Your new motor, with a 9A FLA @ 230v is going to be around 2HP at most. Just seeing that it consumes half the amps should be a clue that it's got about half the power.

You're going to need to drop the pulley size down dramatically for this to work, unfortunately.

 

[The Cobbler]

go here , see what your current rpm is on the pump, adjust to 400 or better and see what size pulley you need https://www.blocklayer.com/pulley-belteng

 

[kzitekmpls]

Try the wiring for “240v” for grins, maybe the diagrams are reversed

Wouldn't hurt....

 

[kzitekmpls]

go here , see what your current rpm is on the pump, adjust to 400 or better and see what size pulley you need https://www.blocklayer.com/pulley-belteng

I'll measure and try this out

 

[kzitekmpls]

There are two things going on here:

1) The motor you bought is not actually 3HP
2) Your old motor is also not 3HP

At 17.2A FLA @ 230v, your old motor is about 4HP. I suspect it's actually "3.7 HP", as that is a very common rating for newer compressors,. Your new motor, with a 9A FLA @ 230v is going to be around 2HP at most. Just seeing that it consumes half the amps should be a clue that it's got about half the power.

You're going to need to drop the pulley size down dramatically for this to work, unfortunately.

Good info, I guess I shouldn't trust the manufacturer on HP ratings

 

[N_Jay]

What speed was the old motor?

 

[kzitekmpls]

Same, 3450 RPM

 

[cannuck]

There are two things going on here:

1) The motor you bought is not actually 3HP
2) Your old motor is also not 3HP

You forgot their might well be a 3rd thing going on. Motor was made in China so entirely possible the knee bone ain't connected to the thigh bone.

 

[Jswain]

The other motor was not dual voltage. I moved and no longer have 220v. I tried to run 220v motor on generator and blew the motor. Threw a 120v motor on to use at current house.

Yeah so if it was 17fla @ 240v then your new motor is half as powerful. You will need to cut whatever size pulley you have on the motor in half, which might lead to not having enough grip or even if you do not spinning the pump fast enough. Worth a shot if it's all you got though

 

[kzitekmpls]

Very helpful guys. Using the pulley calculator posted above. I should be able to switch to a 2.5 inch pulley from a 4inch and still have the pump spinning fast enough. I will give it a try and throw on an amp meter as well and report back.

I'm a construction guy I understand framing, electric motors not so much. So thank you all

 

[The Cobbler]

good luck with it, be sure to report back. that calculator will also tell you the required belt size too .

 

[Jswain]

If it gets you almost there but not quite you may be able to adjust the cutout pressure lower and live with slightly less pressure stored. Synthetic oil may also help, specifically on cold starts

 

[kzitekmpls]

Thank all of you for the help.

I would like to report that after changing the pulley to a smaller size and getting a smaller belt the air compressor runs perfect.

Builds to 135psi, kicks back on at 90

13.5 Amp draw at peak power and runs super smooth and quiet.

Success!

 

[Jswain]

Good save

 

[DALES]

I have a 60 Gallon Sanborn air compressor. I recently installed a 125v 3HP motor. Compressor runs great with valve on bottom of the tank open.

When valve is closed compressor will build pressure to 50psi (according to gauge on compressor) then slow down until motor cannot turn and just hums.

I suspected a bad check valve and have replaced it with no improvement. I have double and triple checked wiring. Side note motor will not start if tank has more than 30psi in it. But starts when tank is empty.

I'm stuck, please help!

Late reply, probably your run capacitor, change both start and run capacitors. A bad run capacitor will make motor hum, vibrate and overheat and kick breaker.