Compressor Help, 2 motors blown in 2 days!

[ez-duzit]

Where cheap is a way of life you will find easy and quick rationalization.

 

[American Locomotive]

Wasting money would be leaving my plasma sitting while I wait on a new motor. I have no problem spending the money on the correct motor, meanwhile HF had a cheap one in stock. If it lasts me a month while I source the correct one, great. The plasma paid for the motor twice an hour after I put it on.

You don't have to "source" anything. 3-5 HP 208-230v single phase motors are a stock item literally everywhere. You can probably even get one at Tractor Supply.

MSC, Grainger, McMaster-Carr and others could have had a new, properly rated motor at your door step by the next day. Messing around with incorrect components is not something to do if that that equipment makes money and holds paying customers up if it fails.

 

[Bert_]

You don't have to "source" anything. 3-5 HP 208-230v single phase motors are a stock item literally everywhere. You can probably even get one at Tractor Supply.

MSC, Grainger, McMaster-Carr and others could have had a new, properly rated motor at your door step by the next day. Messing around with incorrect components is something to do if that that equipment makes money, and holds paying customers up if it fails.

This,

There are several places 20-30 minutes from me that have name brand fractional - 10hp single phase motors in stock. Many are rated for use on 208 or have a 1.15 service factor.

 

[6PTsocket]

I have had a 60G Kobalt running my plasma table for the last ~18 months, no issues. Yesterday, the compressor stopped working. No humming, nothing. I replaced the run and start capacitors anyway (I stole them off the same compressor I have at home), no luck.

What I know so far....
Outlet: 208v across hot, 120v each leg to ground
Before compressor pressure switch: same readings.
After compressor pressure switch: same readings (if "ON")
At motor connection: ......same readings.

Specs:
Kobalt motor says basically "240V!!!!!"
I never really thought about it until today, I never checked the voltage coming into the building, oops. I thought maybe it finally overheated after running below recommended voltage. My fault...

BUT......

I ran to HF and grabbed a 230V 3HP compressor motor as I need my table running ASAP. I wired it in, mounted it up, bingo. Compressor is running again. Crisis averted.

Until 5 minutes later. I let it run up to 150psi where it shut off like it should. Cool, I go outside to blow out my car and hopefully find the giant spider that landed on my arm going 70mph on the highway. I go back in to turn off compressor, its at 90psi. WTF, it should kick on around ~120psi.

So the NEW motor (albeit, HF) lasted all of 5 minutes. This leads me to believe there could be another issue, or I just had **** luck with the HF motor. I am returning this one Monday and swapping out for another to be sure.

And no, I didn't find the f'ing spider either.

You are describing using 2 legs of 3 phase power. 208 leg to leg and 120 to ground or neutral. Some motors are rated 240-208 and run with a corresponding loss of power at 208. I am not sure all motors tolerate it. If you ran this long and the motor did not overheat I would suspect it was OK. Did you check to see if a thermal trip on your old motor popped ? If you find one, press HARD to reset. There are 208 to 240 step up transformers for this situation. I lived in an old apartment that was wired like your garage and had a window air conditioner that was rated for BTU at 240 and BTU at 208. The difference was enough that I bought a step up transformer to get 240 volt performance. If you can access the third leg, 3 phase motors are cheaper and out perform single phase 240 motors at lower current demand.

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