Compressor motor wired wrong-what damage was done?

[midwest farms]

I'm, hesitant to send this request due to it being the result of assuming on my part. Bought a new (to me) Gardner Denver compressor. I wired up the power whip yesterday afternoon and noticed on startup that the motor started up slower than expected and that the rpm was maybe a little lower than expected. I stopped, checked connections, contacters on the pressure switch, took the belt off the pump ect. Everything seemed to check out ok. Started again and ran for maybe a minute and it STOPPED-nothing, no humm no anything. Interestingly it didn't pop a breaker. After checking deeper found that the previous owner had whip wired backwards into the pressure switch....the green wire running to power and the red running to ground!? I saw the pump run in his shop and it ran fine so I am convinced he had it hooked up "correctly" albeit with the wrong color combination.

Where should I start? Start capacitor, run capacitor? Both? There is no hum under power. The motor didn't "let the smoke out". I feel foolish for not checking someone else's work. I know better than that. Motor is Leeson 3 hp single phase. Any thoughts?

Thanks in advance!


A side note, it is interesting that having power hooked to the ground didn't make the whole compressor "hot". I know that I touched the compressor when it was running for the short minute. I feel fortunate I didn't get hit with one leg of 220v. I'm beyond calling the previous owner up and letting him know how dangerous this was-I just want to get it fixed!

 

[jhelrey]

Depends how he has it wired up at the plug or at the panel. If he followed his color choices, it may have been fine. If you wired up the whip and this whip has a plug but you didn't change/check how the plug was wired, then you may have wired it incorrectly.

 

[midwest farms]

Thanks for the reply. He had it wired correctly albeit with wrong color coding of the wiring. When I wired it into the panel at my shop, I followed traditional wire color coding (green nuetral, red L1, black L2) however his whip had green at L1 and red as ground!

So basically I wired it wrong, attaching one leg of the 220 to ground on the compressor. It ran wired this way for about a minute then it shut down. Again no smoke, sparks, crackles or even a burnt smell. It just stopped. The start capacitor cover was warm but not hot. If I would have checked the wiring at the pressure switch I would have noticed it was wired backwards but I didn't. Again the danger of assuming.

Any ideas on where to start to diagnose what I fried in the process?

 

[hidollartoys]

Start by wiring the motor "correctly". And as a side note, green can not be used as a neutral (per code). The green in this case is ground if the motor is wired as 240v.

Next check capacitors. Use a meter that has a capacitor test. Next check the motor for open or grounded windings.

 

[sberry]

Also,,, is your panel wired correctly, this should have blown a breaker instantly.

 

[Gary S]

At this point, I would try wiring it right and giving it one more chance. It just might be OK.

Years ago my brother was building his house and the only power available early in the construction was a temporary box on the pole that the power company supplied. During the dirt work on the road, they broke the blade support off the road grader. The piece that broke was 2" thick iron, so no small welder was going to fix it. My brother borrowed a large 240v commercial welder from a friend and hauled it to the site. We had to temporarily hard wire it into the box. When doing that, we opened the welder and found that it was wired wrong internally. It could have not worked that way unless his friend also had his garage miswired with the same error.
We corrected the wiring inside, and connected it to power and used it for a couple of hours. Before we returned it, we put the wiring back (incorrectly) inside the welder. We informed the owner to have his wiring corrected. He was using the green wire as a hot.

 

[larry_g]

Also,,, is your panel wired correctly, this should have blown a breaker instantly.

Not necessarily. Even though the one hot leg was wired to the frame the frame was not grounded. Ground wire was isolated in the motor circuit. So no short in place. The hot to ground through the motor did not pull enough current to pop the breaker.

Does the motor have a thermal overload that is popped?


lg
no neat sig line

 

[Charles (in GA)]

Does this compressor have a motor starter with it. I would think a G-D would.

Charles

 

[bsaint]

Meg the motor.

 

[nehog]

1. Rewire with correct color codes.
2. Check the voltage at the outlet box (or junction box, if hard wired) and make sure you have 240 volts.
3. Check the ground to ensure that it is still good back to the panel.

It is (at least to me!) clear that you were running the motor on 120 volts, using one line and the ground (tied to neutral at the box). That should not have damaged the motor if the motor was not overheated (did you smell anything?) What I suspect happened is the tandem breaker may have been damaged, and you are not getting 240 volts at the motor now.

Yes, you were lucky as the dickens you were not zapped as that compressor was sitting at 120 volts on its frame. What kind of floor was it on, if bare concrete, that could easily have grounded the line. You owe the good-luck fairy $25...

 

[Tim The Tool Man]

I have actually seen this done a couple times once with a 4-way light switch and once with an electric range. In each case the guy that originally miss-wired the circuit was also color blind! They couldn't tell the difference between red and green

 

[midwest farms]

Thanks for all the suggestions and advice. I was able to diagnose the problem and found additional wiring gaffs from the prior owner. All is well and the compressor is back online!
Thanks so much!