5hp 240 Volt Air compressor Install

[Bert_]

#10 thhn is fine. No need to change that part. Romex is limited to lower ampacity than thhn.

Agree with sberry that 40 is about the right size breaker. I would really consider a 30 to be to small. You are actually allowed up to a 70A breaker according to the NEC.

 

[sberry]

I believe if it was 70 might have to be 8 wire ???? I have ran them from 30, my bud had a 28A one ran 30 for 30 yrs. I have a 24A that runs 30,,, I had the breaker in hand, it never caused a problem. But there isn't a problem putting a little headroom in.

 

[Bert_]

I believe if it was 70 might have to be 8 wire ???? I have ran them from 30, my bud had a 28A one ran 30 for 30 yrs. I have a 24A that runs 30,,, I had the breaker in hand, it never caused a problem. But there isn't a problem putting a little headroom in.

No restriction on wire size vs breaker size. If you had an application were the motor wouldn't reliably start on a 70A (250% of FLC). You are actually allowed to go up to a 100A breaker (max 400% of FLC). All this is allowed on #10 thhn or #8 Romex.

I agree that many will run fine on a 30. But if you're wiring it from scratch I can't think of a single reason to use less than a 40. A 30A leaves the possibility of nuisance trips in my book.

 

[sberry]

I can be wrong here,, so,, fwiw,, if a guy was to use 100 would need 8 wire. Seems I did this in study somewhere along the way but some other part of code applies, 10 to 60, 8 to 100. 12 on 50,, like the welder, it may run on 14 but has to have the breaker reduced to 30

 

[sberry]

6 for 200A, cant attach a wire smaller than its short circuit rating?????

 

[AllThingsOld]

They didn’t have the wire I went to buy, the guy working was zero help, but they had the 6 THHN, so I just bought it and will use it in place of the romex. I didn’t want to make 2 trips.

 

[Bert_]

They didn’t have the wire I went to buy, the guy working was zero help, but they had the 6 THHN, so I just bought it and will use it in place of the romex. I didn’t want to make 2 trips.

There is absolutely no need for #6 anywhere on this project.

The sizes you need are,
#8 for any Romex
#10 for any thhn

Anything else is a waste of money.

 

[Bert_]

6 for 200A, cant attach a wire smaller than its short circuit rating?????

I don't think there is any wording like that in the NEC section pertaining to motors.

 

[sberry]

It isn't in motors, it's some other part that escapes me at the moment. It's been so long since I really read it I have troube with 250, 310 and 630,,,, ha

 

[Kaizen]

They didn’t have the wire I went to buy, the guy working was zero help, but they had the 6 THHN, so I just bought it and will use it in place of the romex. I didn’t want to make 2 trips.

Overkill but will work fine. Make sure you use insulator bushings or screw in ones on that flex. Also easier to push wire through before connecting to both sides.


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[AllThingsOld]

I am half way there, I just need to wire the compressor in now

 

[AllThingsOld]

And it doesn’t work. Everything is wired properly, not tripping the breaker, it’s definitely getting 120 on each side of the switch. I can hear the motor trying to start, but it doesn’t. Now when I flip the pressure switch on, I get nothing, no sound.. I want to pull my hair out

 

[alfredeneuman]

Seems I did this in study somewhere along the way but some other part of code applies, 10 to 60, 8 to 100.

The size of a ground wire is 10 to 60A, 8 to 100A, and 6 to 200.
I know of no such rule applicable to the circuit wires.

 

[pattenp]

Verify you have 240V across the hots at the compressor connection.

 

[wyliesdiesels]

And it doesn’t work. Everything is wired properly, not tripping the breaker, it’s definitely getting 120 on each side of the switch. I can hear the motor trying to start, but it doesn’t. Now when I flip the pressure switch on, I get nothing, no sound.. I want to pull my hair out

Are you using a double pole breaker?

Did you test line to line at the switch?

Bad capacitor?

 

[AllThingsOld]

Yes, first thing I checked was power at the switch, I have 120 per side. The motor is making some strange sound, like an electric humm. I hope it isn’t the kiss of death for the motor.

 

[AllThingsOld]

Yes, double pole breaker

 

[Bert_]

Yes, first thing I checked was power at the switch, I have 120 per side. The motor is making some strange sound, like an electric humm. I hope it isn’t the kiss of death for the motor.

Motor doesn't care about 120 to ground. It needs 240 volts line to line. That is where you need to connect your meter, line to line. Testing to ground tells you nothing.

 

[AllThingsOld]

Sorry, yes line to line is 240

 

[AllThingsOld]

I didn’t do anything with this wiring, I probably should have checked it.. who am I kidding, I would not even know what to check.

 

[Bert_]

You have 240 in the motor?

Is there a reset button on the motor?

 

[AllThingsOld]

There is a reset button

 

[AllThingsOld]

230 yes... I just turned the switch on, motor started making that hmmm sound, I hit the reset button and it tripped the breaker

 

[wyliesdiesels]

could be a dead cap

 

[Bert_]

That's not a good sign. This is a new compressor, right?

 

[Terry D]

Try taking the belts off and see if the motor will start on its own

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[AllThingsOld]

No, it’s not a new compressor, used. It’s the Harbor Freight 93274 2 stage... I have spent so much money at this point, that I let the “good deal” cloud my decision making and I cannot believe I bought it without hearing it run. Long story short. I bought a blast cabinet, didn’t realize how much air I actually needed.This is the 3rd compressor I have bought in a short amount of time, the others just undersized. Bought this used and the guy delivered it.. I’m a complete idiot and took him at his word that it ran great, no issues etc.. This blast cabinet adventure has cost me a fortune and I’m not up and running yet.

 

[wyliesdiesels]

How long ago did you buy it?

Could be a simple capacitor.

 

[AllThingsOld]

10 days

 

[Bert_]

I agree it could be a capacitor. It would be under a round cover on the side of the motor. It's worth checking.

 

[AllThingsOld]

Motor has 2 round covers, should I just check both of them ? Should I just check the part # and order 2 or ?

 

[Bert_]

You can kind of test them with an ohm meter. Won't be able to tell you and exact value but can usually tell you good / bad.

Pull the covers and just look at them visually first. Oftentimes the problem is obvious.

 

[Terry D]

I would still isolate the motor from the compressor, to make sure its not a compressor problem. make sure the compressor spins freely, make sure it wasn't ran without oil. If you bought it from some one that you don't know, make sure its even the right capacitors for that motor. If it doesn't say on the motor, google it.

 

[AllThingsOld]

Compressor spins freely, which is sort of a relief, I guess. I have called the seller and sent him a text, no reply of course. Which it’s my fault, I should have made the time to insure it ran, instead of taking his word and him delivering it, such a stupid move by me. I’m about to look at the capacitors now.

 

[AllThingsOld]

Not sure if this is right or wrong, but it doesn’t seem right. 2 different capacitors and wired differently. I am hoping this is the issue, so that I can just replace one or both. I can see the the top of the second one appears to be leaking. I believe the one in the first photo has been replaced already, possibly, but it only has 2 wires, while the second capacitor has 3... Also they are much different in size, is this correct ?

 

[sberry]

The leak isn't good, not going to get any better,,,, I think that is the start, replace it.

 

[wyliesdiesels]

The cap with 3 wires is most likely a dual cap- typically start and run, built into one canister.

If one is leaking, then its going bad and should be replaced.

 

[pattenp]

Neither of those caps are dual. There would be three separate insulated connectors. The metal one is a run, the plastic one is the start.

 

[AllThingsOld]

I m trying to figure out if both capacitors are the stock units or if they have been replaced. I found this one on amazon, I believe this is what I need

 

[wyliesdiesels]

Neither of those caps are dual. There would be three separate insulated connectors. The metal one is a run, the plastic one is the start.

whoops youre right- i didnt look close enough. I see its dual terminals off of one tap.