Wire Size for Large Compressor

[EasyE]

Update:

Got everything wired up and started 1 motor first. Idle voltage is 214, voltage drop on startup was 205V, running was 208V.
The second motor is wired on a 6 second time delay. It started and voltage dropped to 195V, while running it maintained right around 199-200V.

I checked amps next. Each motor is pulling around 37-38 amps on all legs. Total draw is 76-78 amps depending on tank pressure.

This seems a bit high to me since the FLA is ~28 amps on the motor plates. I rewired the lines to the motors from the control box with 10awg after checking the above numbers, but I doubt that will change much since these leads were only 24" in length.

My next thought is to change the sheaves on the motors to a slightly smaller size to get the amperage back in spec.

Any thoughts?

 

[wyliesdiesels]

Update:

Got everything wired up and started 1 motor first. Idle voltage is 214, voltage drop on startup was 205V, running was 208V.
The second motor is wired on a 6 second time delay. It started and voltage dropped to 195V, while running it maintained right around 199-200V.

I checked amps next. Each motor is pulling around 37-38 amps on all legs. Total draw is 76-78 amps depending on tank pressure.

This seems a bit high to me since the FLA is ~28 amps on the motor plates. I rewired the lines to the motors from the control box with 10awg after checking the above numbers, but I doubt that will change much since these leads were only 24" in length.

My next thought is to change the sheaves on the motors to a slightly smaller size to get the amperage back in spec.

Any thoughts?

that is pretty high.

What are your overloads set to? They shouldve tripped. rewiring the feeds wont solve that issue

 

[EasyE]

I set the overloads at about 31 amps. This thing builds air so fast that I don't think its really giving anything a chance to heat up and trip. I have the pressure switch to cut on a 105-110 and cut out at 135.

With both pumps going that only takes maybe 3 minutes.

 

[sberry]

Depending on my scheme might have a time to use 1 motor instead of starting 2 for short runs.

 

[EasyE]

That would work fine with the amount of air I need except the motor is still pulling over its rated amps.

 

[Aceman]

What rpm are the pumps?

What rpm are they turning now?

Have you serviced the pumps?

Wire size for 10HP 208v motors should be #8 thhn.

 

[sberry]

Yes, I understand, was simply considering equipment for 1 motor, 1/2 the cost of making them both work. 2 of them would be super for some sandblast especially if a guy sized the equipment to it.
I see that show American restoration and one of the things they should do is rig up a second blaster and get a truck of sand. They got enough man hours that some more whiz bang could save some time.

 

[EasyE]

What rpm are the pumps?

What rpm are they turning now?

Have you serviced the pumps?

Wire size for 10HP 208v motors should be #8 thhn.

Not sure on pump RPM - I have tried emailing champion (Cant find a phone number) with the serial numbers to see if I can get some information.
I suppose I could calculate the RPM based off the sheave sizes and motor RPM.

I have changed the oil on them and it appears they were maintained well before my time.

I doubt I will see much of a difference going to #8 wire since its only ~18" of wire.