New to air compressors. In need of some help

William Caves · Jul 18, 2017

Hello,

First time posting and any help would be appreciated. New to air compressors but recently purchased one from Craigslist. 60 gallon 5HP single phase 240v 22AMP. Model US560V. For home use. This is one relatively similar (or identical, except that one is two stage) to the Harbor Freight model that comes up when you google the model number and also a BelAire linked here
https://www.mastertoolrepair.com/stationary-air-compressor-parts-218v-p-20126.html .
When I purchased it (for very cheap) it didn't run and I tested the capacitor and it was out of spec. Replaced the capacitor and it runs but it turns itself off and smokes a bit after about 20 seconds on. Have it ran to a dryer plug that is Nema 10-30 rated at 30 amps and 125-250 volts on a 30amp breaker and this is the only outlet on the circuit. I know this is not up to code as a compressor legally needs a ground and I only have a neutral (almost hoping that is my problem). I intend on using the compressor rather rarely and only having it plugged in while using it and under supervision as my dryer needs to be plugged in often. After scouring the internet it seems as this is a "workable" method, but not the safest. I am not sure if I am doing something wrong or if the motor is bad. I have tried it disconnected from the pump pulley as well as connected. I have tested the leads and the two power leads test at 120 volts. It does not build pressure it seems during the 20 second run cycle but it does turn. I feel like I must have configured it wrong electrically or something. Also, I believe that the pressure switch was changed (looks extremely new) and it seems to not resemble OEM and is rated at 20 amps, which is obviously lower than the 22 amp draw from the motor. Some pictures attached of the wiring and motor documentation. Any help would be greatly appreciated. Thank you.

Infinia · Jul 18, 2017

Check the centrifugal switch inside the motor, it should disconnect the start circuit after it comes up to speed. The 3 wire dryer wiring should be OK a dedicated branch ckt. E.g no current or voltage drop from neutral to ground.
Yes 22A is a lot of current. make sure you have at least 230V measured at the motor when loaded down, light duty wiring and switches can drop too many volts causing motors to overheat. A 5 volt drop to each leg is allowed for 240V nominal.

how did you test the capacitor that you found out of spec? There is probably 2 start caps and 1 run capacitor make sure if replaced they are rated for that duty.
If its not building any pressure for 20 seconds from zero pressure you have more troubleshooting! Possibly 2 separate problems, failed pump and motor.

William Caves · Jul 18, 2017

Capacitor was tested with a capacitance tester. Tested the start capacitor and it was at about half the capacitance (like 110 microfarad instead of 230). Run capacitor was also tested and was fine. The three shrouds on the top of the motor is occupied by one large starter capacitor, one run capacitor, and it seems a reset switch. Thermal reset maybe? Just a switch on the shroud with a black and blue wire in the shroud. The starter capacitor certainly says "start capacitor" on it and is rated the same as the one that came out, run cap doesn't say anything in particular but seems reasonably sized. Will look into the centrifugal switch. Was something I was able to find someone recommending being at fault for overheating, but was unsure how to check it. Will dig deeper
Thank you so much

Infinia · Jul 18, 2017

William Caves said:
The three shrouds on the top of the motor is occupied by one large starter capacitor, one run capacitor, and it seems a reset switch. Thermal reset maybe?

No the thermal switch is buried deep inside the motor, investigate more after you get the motor apart. This must be an overcurrent breaker maybe NFG?

William Caves · Jul 18, 2017

Have not checked the centrifugal switch or thermal switch yet. Checked the voltage when I power on the compressor but I am only letting it run for about 4 seconds. ~117v on the white in, ~117v on the black in, ~117v on the blue which leaves the connection that the white and black connect to and then enters the motor compartment. I am guessing that blue is supposed to have ~240v to run the motor as it is the only other wire in that little panel area that isn't a ground or my two hot wires?

Infinia · Jul 19, 2017

I am guessing that blue is supposed to have ~240v to run the motor as it is the only other wire in that little panel area that isn't a ground or my two hot wires?

Look at the motor it has a diagram. Measure it right at the terminals 2&4. This is 240V gear. Don't use ground (neutral) for power measurements! The neutral has become safety ground (green) in your setup not useful as a measurement reference.
Measure at motor, then pressure switch finally at the plug. Then you can see where the various drops are. Switch contacts , plugs , and reworked terminations can and do go bad esp. at 22A. I'm not so sure if I'm comfortable with directing you at this point. This is dangerous for experts let alone rookie folks guessing and poking around high energy stuff> Just inspect things and manually re-work some of those sketchy connections. Don't plug it in again until your done with trouble shooting and inspecting. Constantly running it over and over cant be good for the motor OR with your face in there! Danger this is high energy stuff.
Sorry you took a gamble on some else's botched repair job.. Time to call in a professional, they can probably give you an estimate in 30 minutes!!

William Caves · Jul 19, 2017

I appreciate the help and respect your decision to not direct me to my shocking death. Again, thank you for the assistance to this point!

William Caves · Jul 19, 2017

Had to dig just a LITTLE bit deeper down the rabbit hole before I decide to give up on this one (hardheaded). Noticed something i had not noticed before, crusty windings. And they are just covered in it on this small section. The rest of the windings are quite clean. Tried to blow them clean and the smell they put out was the exact same as the smoke the compressor burned off. I am sure this is a symptom but I don't know if this basically dooms the motor as it seems it burned itself to a crisp :flamethro

But, yeah, when I was turning the motor on yesterday for a few seconds at a time terminal 2 and 4 tested at 120 volts on both the black and white wires. Not entirely sure how to test "at the motor" as that seems deeper than the terminal, and I don't know how to safely go any further with the compressor on and power being delivered. Continuity tested from the wall all the way to the two wires that insert into the windings and everything that I expected to have continuity, had continuity, up until the blue and yellow power wires connected to each of the two lead winding strands. Unless I want to remove the motor and look further into the shaft side of the motor (probably do it out of stubbornness :deadhorse

), guess I am done pursuing this motor. Win some - lose some! Thank you for the guidance and eliminating some doubts at certain steps along the way!

Infinia · Jul 20, 2017

Why on earth do you keep reporting 117-120V? This is 240V ! It's pretty silly to override any ckt breakers. If they are tripping you must stop and find the cause!! uhh it's put there for protection, you can cause damage to property ( an expensive motor ) and life or limb... ugh 2 reasons why I lost confidence in your knowledge and experience.
I suspected the start winding was never disconnected after spinning up, looks now burned. The centrifugal switch is right in front you, shown on your image. Under voltage is another cause but you could troubleshoot things in a safer sequence..

FWIW look into industrial power injuries, they get burned and hit by molten shrapnel, Not necessary to come in contact with live conductors. When stuff is smoking it's insulation melting after then it's likely to become a short circuit, making flames and sparks... ever seen a Roman candle close up? In order to stay safe, knowledge and /or experience is important. I have responsibility to keep you and any others that read this thread safe.

William Caves · Jul 20, 2017

Sorry if I have been frustrating! I really do appreciate the concern.
Seems as though I was wrong, but I thought if two terminals with the same end-point were at 120v then the destination would be at 240v. Tested the terminals a few days ago individually and they were 117 each. After your most recent post I put it all back together and tested them together (each multimeter lead on one of the terminals?) and was at 235v. Not sure that is what I was supposed to do the whole time. Not even certain if that is even the proper way to test for 240v. Not sure if each terminal is supposed to be 240v when tested with one multimeter lead to ground. I was able to freely move the centrifugal switch manually and every time I turned the compressor off I heard something that sounded exactly like the switch moving. Not sure if the sound was present when engaging the motor, as it was quite loud.
I don't imagine I will be continuing on with the motor. As stated, my lack of knowledge combined with the motor seeming like it is likely fried anyway makes this a high risk and likely no reward scenario.
Might just purchase a new motor. I know I can bolt and unbolt things. Feeling apprehensive about that too though considering you mentioning the pump might also be failing. When turning manually the pulley/flywheel turns mostly smoothly and I can feel air leaving the breather and I can hear some groaning of air. But considering how much i spun my wheels on the motor, I might not be cut out for a used air compressor, not until I am more familiar with the operation of one.

American Locomotive · Jul 20, 2017

You measure 240v by measuring across both hot legs. That motor is toast. Just go out and grab a new one, they're not too expensive.

redmondjp · Jul 20, 2017

American Locomotive said:
You measure 240v by measuring across both hot legs. That motor is toast. Just go out and grab a new one, they're not too expensive.

Well hold on a minute there - let's stop to consider that there may be something wrong with the compressor portion that caused the motor to fail. So just throwing a new motor on may not permanently fix the problem.

American Locomotive · Jul 20, 2017

Then the motor overload protection should have protected the motor if that were the case.

jimmy-ray · Jul 20, 2017

I can smell that motor just from the pic

Kenskip1 · Jul 20, 2017

This post is a perfect example of why I will not make a purchase off craigs list or ebay. You do not have any idea as to what you are purchasing, or the cost to make repairs. I do understand individuals just starting out on a budget. Why was this compressor not checked out prior to purchase?I will make a bet that he will not get his monies returned.Anyway I hope that you get this problem solved, Ken

redmondjp · Jul 21, 2017

American Locomotive said:
Then the motor overload protection should have protected the motor if that were the case.

Not necessarily, and especially for a low-buck motor like that one. If it had a proper motor starter with properly-sized (NEMA) or set (IEC) overload protection, then I would agree.

William Caves · Jul 24, 2017

Kenskip1 said:
This post is a perfect example of why I will not make a purchase off craigs list or ebay. You do not have any idea as to what you are purchasing, or the cost to make repairs. I do understand individuals just starting out on a budget. Why was this compressor not checked out prior to purchase?I will make a bet that he will not get his monies returned.Anyway I hope that you get this problem solved, Ken

Thanks man. You are not wrong, I normally don't buy used items I am not greatly familiar with. However, I never buy non-essentials that cost $800 or more like this compressor would have cost new. The compressor didn't start when i bought it, but the start capacitor was out of spec. Like 130 microfarad or something instead of 250. So I thought (hoped) that might have brought it back. Story still rings true though, don't buy used from Craigslist if you don't have a working understanding of it. Still only spent like $150 on it, so if the pump is functional, still didn't make out too bad.

Kenskip1 · Jul 24, 2017

Bill,I hope that you get it working.Myself I am not an electrician. My work is generally brakes shocks,that sort of thing.I also do a bit of small engine repair, sharpen chainsaw chains.Here is where schooling comes into play as I envy you with your electrical knowledge.Many individuals make there living with there minds. I do my limited repairs working with my hands and tools.Get this thing working.Thanks for the reply,Ken

William Caves · Jul 25, 2017

jimmy-ray said:
I can smell that motor just from the pic

Yeah, the smell was a smell I am not used to. I can sometimes smell when a little electronic component in a car burns out, but this was something different. Can smell it the next day. Super unique smell

William Caves · Jul 25, 2017

redmondjp said:
Well hold on a minute there - let's stop to consider that there may be something wrong with the compressor portion that caused the motor to fail. So just throwing a new motor on may not permanently fix the problem.

Yeah, this is something I had some reserves against for the reason you highlighted. That being said, it seems that as long as you can turn the fly wheel, the pump should be working (unless you have crazy gasket leaks?), right? I just went through a very technically simple method of trying to test the pump. I took my drill with a socket bit to the flywheel bolt and spun it, for a few minutes at a time, several times. The pressure in the system (60 gallon tank) increased from 1psi to 1.8psi. No audible leaks at this low of a pressure, but when i open the drain valve, it definitely sounds like a good amount of air is in there. I can turn the pump sort of freely, but right before it presses air it is a bit harder, but not so hard that my 18v (NON-IMPACT) drill couldn't turn it fairly easy from the CENTER bolt. So I imagine a motor would see that as moving freely. Am I missing something again?

redmondjp · Jul 25, 2017

William Caves said:
Yeah, this is something I had some reserves against for the reason you highlighted. That being said, it seems that as long as you can turn the fly wheel, the pump should be working (unless you have crazy gasket leaks?), right? I just went through a very technically simple method of trying to test the pump. I took my drill with a socket bit to the flywheel bolt and spun it, for a few minutes at a time, several times. The pressure in the system (60 gallon tank) increased from 1psi to 1.8psi. No audible leaks at this low of a pressure, but when i open the drain valve, it definitely sounds like a good amount of air is in there. I can turn the pump sort of freely, but right before it presses air it is a bit harder, but not so hard that my 18v (NON-IMPACT) drill couldn't turn it fairly easy from the CENTER bolt. So I imagine a motor would see that as moving freely. Am I missing something again?

I don't think you're missing anything - it sounds OK and it's normal for there to be more resistance during the compression stroke.

Infinia · Jul 25, 2017

Holding very low tank pressure for a long time is good, it allows us to observe the pump in operation...
Spinning the pump for 20 seconds under its own motor power gives no tank pressure movement, Spinning it for " a few minutes + repeated several times" on your drill chuck saw less than 1-2 psi. Observations "Houston we have a problem."

I probably could get that motor working again, but it wouldn't be a especially safe to do, at least long term. Did you ever look at the rotor switch to determine the cause and effect of that burned winding? I suggest you could ohm (buzz out) the start circuit to the rotor switch, To fix it maybe it just needs a little grease on the shaft and clean the contacts. As a last resort, IDK perhaps you use your drill setup to start the motor manually ( disconnect the start cap ). Indeed very good learning experience could be had here! IMO..At least you paid for it.

Infinia · Jul 29, 2017

what happens when the start winding switch gets stuck.

William Caves · Aug 6, 2017

So the video you linked looked exactly like i was dealing with. Smoke out of the motor after a short run period.

As an update, i got another cheap motor and replaced the previous motor. I just ran the compressor for about one minute, maybe 2 and it got the PSI to 60. I figure that is a decent rate for a 60 gallon compressor. Everything seems to be working fine, ran an impact wrench I had picked up at a garage sale and it worked well. I turned the compressor off because my tank is rated at 165 PSI but the pressure switch is rated at 175 max PSI, so I am looking for a way to adjust (or if i need to change) the pressure switch. I am quite cautious about this thing blowing up on me. haha.

Thank you so much for the advice and getting me started with this thing. People like you allow me to have confidence that I can get into these "high priced" (for a non-professional) and very specialized tools to learn how to actually do super cool stuff like painting a car and sandblasting cabinets without having to spend $1200 just for the compressor! Thank you!

New to air compressors. In need of some help

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