Compressor Help, 2 motors blown in 2 days!

[NWill]

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.

 

[matt_i]

Usually if a motor is going to die, its going to release some amount of magic smoke. It might not be a full mushroom cloud but at least up close something typically smells "burned".

It seems like your first test proved the pressure switch good but I would take each of those motors and clamp them to the bench and try to start them via another means (drum switch, use a pencil eraser to manually close the contacts on a motor starter/contactor, etc. etc).

If both of those motors are bad you might need a legit 208/230 motor (with that stamped on the nameplate). Another question is: if you have 208vac do you have 480vac or 3 phase. You could solve a lot of durability problems with a contactor, and a 208-230/460 3-phase motor.

 

[LXCam]

Sounds like the contacts in the starter might be burned up. Take them out and inspect before doing much more.

 

[NWill]

Usually if a motor is going to die, its going to release some amount of magic smoke. It might not be a full mushroom cloud but at least up close something typically smells "burned".

It seems like your first test proved the pressure switch good but I would take each of those motors and clamp them to the bench and try to start them via another means (drum switch, use a pencil eraser to manually close the contacts on a motor starter/contactor, etc. etc).

If both of those motors are bad you might need a legit 208/230 motor (with that stamped on the nameplate). Another question is: if you have 208vac do you have 480vac or 3 phase. You could solve a lot of durability problems with a contactor, and a 208-230/460 3-phase motor.

I checked for that burnt smell when it happened, didn't notice anything.

I also hardwired the HF motor to bypass the switch all together, no luck.

I am thinking best-case scenario is the first motor just overheated and I got a lemon from HF. If I can confirm this then I will get a buck boost for the next motor. No 480/3 phase.

 

[MrSurly]

Do you have three phase service? I'm trying to sort out how it is that you have 208 there.
Something is wrong if you have 208 across two 'hots'.
I think you need to do a little more detective work back at the load center to rectify (no pun) the voltage situation, first. Check voltage before/after the breaker, etc.

I mean, you *could be* on a 208y/120 service but that would seem unusual. Is your place a part of a multi-family apartment/condo or similar?
If you are on a 208/120 service, you should then locate a 208V rated motor (combo 208/230) and you should be good to go.

 

[NWill]

Single phase. I get 208-210v across L1/L2 and 120v from either one to ground.

 

[OccupantRJ]

Measure that circuit back at the main panel, and also the incoming power to compare. Could have a voltage drop situation.

 

[TRWham]

Single phase. I get 208-210v across L1/L2 and 120v from either one to ground.

Is this in a commercial space?

 

[NWill]

Is this in a commercial space?

Yes. Mostly glorified storage units with offices in a commerical complex area. Light commercial I guess.

 

[Aceman]

There are several things to check, in no particular order.

1. Incoming voltage
2. Incoming voltage at startup
3. Motor pulley sizes
4. Motor RPM
5. Motor HP
6. Starter/Pressure switch contacts
7. Unloader valve
8. Amperage under load

A customer called me a couple weeks ago, they had replaced their compressor motor and breaker, but it was still tripping. They had purchased a 3450 RPM motor, instead of a 1750 RPM.

 

[TRWham]

Yes. Mostly glorified storage units with offices in a commerical complex area. Light commercial I guess.

So probably 4 wire 3 phase service to the complex (either from PoCo or local transformer) but each unit only has single phase 208V/120V.

Did the circuit breaker trip with either failure? Did either motor overheat? I would check continuity through each motor winding and winding to ground.

 

[NWill]

Neither circuit breaker or motor tripped in either case. The HF motor didn't feel abnormally warm. I wasn't at the shop when the original motor quit.

 

[walta]

Questions

1 Did you try pushing the red reset button on the new motor?
2 Was the original motor 3HP?
3 Was the original motor 3400 RPM?

If the motor starts with a zero PSI tank and stops when the tank is full but cannot get started again to refill. You may have a bad unloaded that mechanically take the pressure off the compressor for restarts.

 

[wyliesdiesels]

Do you have three phase service? I'm trying to sort out how it is that you have 208 there.
Something is wrong if you have 208 across two 'hots'.
I think you need to do a little more detective work back at the load center to rectify (no pun) the voltage situation, first. Check voltage before/after the breaker, etc.

I mean, you *could be* on a 208y/120 service but that would seem unusual. Is your place a part of a multi-family apartment/condo or similar?
If you are on a 208/120 service, you should then locate a 208V rated motor (combo 208/230) and you should be good to go.

Lots of commercial buildings and apartments get 208Y/130 3 phase coming in and its distributed to each unit as single phase- 2 hots and neutral and ground.

Not unusual at all.

 

[FordTruckWench]

Lots of commercial buildings and apartments get 208Y/130 3 phase coming in and its distributed to each unit as single phase- 2 hots and neutral and ground.

Wouldn't this still be "two of three phases?" The two 120V hots are going to be only 120 degrees apart, not the 180 degrees of a center tapped single phase 240V feed.

 

[TRWham]

Wouldn't this still be "two of three phases?" The two 120V hots are going to be only 120 degrees apart, not the 180 degrees of a center tapped single phase 240V feed.

Exactly, that's why it's 208V line to line for all 3 single phase combinations (AB,BC and AC). Each is 120V line to neutral (a wye neutral made at the transformer from all 3), but because of the 120 degree phase angle, the line to line is only 208V phase voltage.

 

[TRWham]

Q...
If the motor starts with a zero PSI tank and stops when the tank is full but cannot get started again to refill...

This is a good point. I had not thought of the possibility the motor is stalling trying to restart and tripping on internal overload. However, even if that were the case with the 2 hp, I would think the 3 hp might have enough torque to start it.

 

[walta]

The more I think about it if the motor where operated at the wrong voltage it should trip its overload a few time without damage.

I think you should not have a problem getting exchange on the motor.

Walta

 

[AntonLargiader]

This is a good point. I had not thought of the possibility the motor is stalling trying to restart and tripping on internal overload. However, even if that were the case with the 2 hp, I would think the 3 hp might have enough torque to start it.

Every compressor like that I have used has a depressurizing vent on the pressure switch, so the compressor starts up without fighting the tank pressure. I was looking at a lot of compressors about a year ago and the Kobalt 60g is very similar to my Black Max 60g.

 

[alfredeneuman]

Questions
2 Was the original motor 3HP?

It's 3.7HP

"However, even if that were the case with the 2 hp, I would think the 3 hp might have enough torque to start it. "
See above

 

[TRWham]

Every compressor like that I have used has a depressurizing vent on the pressure switch, so the compressor starts up without fighting the tank pressure. I was looking at a lot of compressors about a year ago and the Kobalt 60g is very similar to my Black Max 60g.

Yes, but unloaders fail from time to time.

It's 3.7HP

"However, even if that were the case with the 2 hp, I would think the 3 hp might have enough torque to start it. "
See above

Somewhere I got the mistaken impression the original was a 2 hp.

 

[wyliesdiesels]

It's 3.7HP

"However, even if that were the case with the 2 hp, I would think the 3 hp might have enough torque to start it. "
See above

Where did he say 3.7HP?

Only thing i saw was that the replacement motor is 3HP...

 

[AntonLargiader]

Lowes says 3.7HP, but the 16.2 amp rating suggests 3.

I suspect the 208V is the problem.

EDIT: An interesting read: http://www.brithinee.com/technical-articles/240-vs-208-volts-do-motors-care/

 

[alfredeneuman]

Lowes says 3.7HP, but the 16.2 amp rating suggests 3.
I suspect the 208V is the problem.

It states right in the .pdf manual that it won't run suitably on 208, but the original lasted 18 months?

 

[CGT80]

x2 on checking the running amperage.


On 208v, the amperage may be higher than the motor is rated for. If it has a service factor of 1.15, you can multiply the name plate amperage by 1.15 and find out the max amperage that is safe for that motor.


A clamp on amp meter will tell you how much load that pump really puts on the motor. Is the pump in good shape and does it spin easily by hand?

 

[wyliesdiesels]

Lowes says 3.7HP, but the 16.2 amp rating suggests 3.

I suspect the 208V is the problem.

EDIT: An interesting read: http://www.brithinee.com/technical-articles/240-vs-208-volts-do-motors-care/

It states right in the .pdf manual that it won't run suitably on 208, but the original lasted 18 months?

x2 on checking the running amperage.


On 208v, the amperage may be higher than the motor is rated for. If it has a service factor of 1.15, you can multiply the name plate amperage by 1.15 and find out the max amperage that is safe for that motor.


A clamp on amp meter will tell you how much load that pump really puts on the motor. Is the pump in good shape and does it spin easily by hand?

Yeah when i read the 208v service comment by the OP and then motor 240v rating, I knew that could be a real problem. Motor probably overheated.

Never run a 230v rated motor on 208v...

 

[alfredeneuman]

Never run a 230v rated motor on 208v...

The tolerance for voltage variation under running conditions in NEMA Std. MG 1, 12.44, is ±10% of rated voltage at rated frequency.

https://www.ecmweb.com/motors/how-precise-are-motor-nameplate-ratings

230-208=22 230-10%=23

 

[AntonLargiader]

The tolerance for voltage variation under running conditions in NEMA Std. MG 1, 12.44, is ±10% of rated voltage at rated frequency.

https://www.ecmweb.com/motors/how-precise-are-motor-nameplate-ratings

230-208=22 230/10%=23

The article I linked to describes the problem with that.

 

[samss]

What's the voltage drop when the motor is running? Can you pull the breaker to check the buss connection?

 

[Bert_]

Cheap compressor motors are barely adequate and rated for 240v only. Low voltage will make the motor draw more amps and it should trip the overload, but if not it will burn up.

Get a name brand motor that is rated for use on 208V.

 

[BillK]

(I stole them off the same compressor I have at home)

If you have the same compressor at home then why not take the motor from it and give it a try ????? If that solves the problem you know what you need to do.

 

[MrDeerHunter]

Cheap compressor motors are barely adequate and rated for 240v only. Low voltage will make the motor draw more amps and it should trip the overload, but if not it will burn up.

Get a name brand motor that is rated for use on 208V.

This. Too many Amos for a cheap HF compressor duty motor. Find a motor for your electrical input.

Sent from my Moto Z (2) using The Garage Journal mobile app

 

[PWC Repair]

Any hvac supply house can order you a quality replacement motor. It's probably going to run you $300 plus.

 

[NWill]

I got the replacement HF motor installed on Monday morning. It has been working fine so far. Time will tell. At the very least it is a band-aid until I figure out my long term solution.

Thank you for the help everyone!

 

[wyliesdiesels]

I got the replacement HF motor installed on Monday morning. It has been working fine so far. Time will tell. At the very least it is a band-aid until I figure out my long term solution.

Thank you for the help everyone!

Is this motor rated 200v(or 208v) / 230v?

If not youre likely to burn it up again...

the long term solution was already mentioned- buy a properly rated motor...

 

[Bert_]

Why continue to waste money on cheap motors that won't work for you? If you want to be cheap even a used baldor or similar would work better than the HF special.

 

[Aceman]

Why continue to waste money on cheap motors that won't work for you? If you are being cheap even a used baldor or similar would work better than the HF special.

Some people have to touch a hot stove more than once....

 

[ez-duzit]

With some, cheap is a way of life.

 

[DSMR]

You need to put in a boost transformer so that you can use common 230vac motors. That or just put a vfd on it with a 3 phase motor.

With adding a transformer there are rules that you have to follow with regards to line/load fusing and also bonding req's based off of Xfmer size. This is clearly laid out in the NEC.

Running on lower voltage is not the answer.

 

[NWill]

Why continue to waste money on cheap motors that won't work for you? If you want to be cheap even a used baldor or similar would work better than the HF special.

Some people have to touch a hot stove more than once....

With some, cheap is a way of life.

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.