Help me diag a 3hp 220v compressor motor...please

[kevs79]

So Ive had this motor for a while and had not been ran in a while. I hooked it up to my "new" compressor and it worked fine for a test. Pumped it up to 150psi a couple times and then I shut it down. A few days later I moved the compressor to my garage and plugged it in...nothing, no clicks, no humming..nothing. I made sure I have 110v to both legs going into the motor and 110v on each leg going to the capacitor. Could it be a bad capacitor? The capacitor looks fine but doesn't have any voltage when I unplug the motor.

 

[Bert_]

Checking line to ground and getting "110" tells you nothing. Check line to line and see if you have voltage.

When dealing with 240v loads (motors/ect) always check LINE to LINE, just because you measure 120v to ground does not mean you have 240.

Check to make sure you have power at your outlet. check the pressure switch ect.

 

[kevs79]

Checking line to ground and getting "110" tells you nothing. Check line to line and see if you have voltage.

When dealing with 240v loads (motors/ect) always check LINE to LINE, just because you measure 120v to ground does not mean you have 240.

Check to make sure you have power at your outlet. check the pressure switch ect.

Well....you sir just solved my problem! Thanks!. Im not too familiar with 220v and assumed checking each leg would be a valid check...not! A wire in my plug came loose! I feel very stupid but live and learn!!

 

[Whitworth]

I'd first move the motor back to where it worked a few days ago. That will answer motor fault or fault with circuit it's plugged into.

 

[thewatusi]

If you're getting 110v on each hot leg I'd be calling the Poco

 

[kevs79]

Got it all running now. One of the hot wires in the plug had came loose. Now I have a different issue. The other day it was working fine(outside) now it pumped up to 150ish and then started slowing down and I shut it down. I let the air out and tried again and the motor is laboring and won't turn it fast enough now. The unloader is unloading it is so slow. I can spin the pump by hand easily so I don't think that is the issue.
It is a Quincy 310 w/the centrifugal unloader. My motor is a 12 amp 3450 rpm so a little below 3hp. I have a 3.25 pulley on the motor and the pump has 14 inch pulley so it should be running approx 800 rpm. Maybe I am taxing the motor too much and need a smaller pulley???

 

[kevs79]

Well, I got a new belt and I adjusted the pulley down a little. The new belt along with the pulley adjusted down is making good contact now and seems like it is running good now. Ran it all the way from 0-150 no problem. I think the belt might have been slipping before because the pulley was hot and now it isn't. I need to figure out what CFM it is now.
0-100 8 min
100-125 3 min
125-150 2 min
60 gallon tank

 

[CGT80]

5-7 cfm

http://www.egnergy.com/calculator.html

 

[kevs79]

5-7 cfm

http://www.egnergy.com/calculator.html

Thanks! Kind of disappointing to be honest. I was expecting more...

 

[American Locomotive]

You might want to do a couple of timed trials and recheck afterwards. Changing the compressor oil might also help as well.

It also makes a big difference if its a two-stage or single stage pump. Single stage pumps drop way off in efficiency at higher pressures. Remember that two pistons does not mean two stage.

 

[larry_g]

Now that you have a working system you need to do an amp draw check. You should be nearing 12 amps on a 230 volt single phase, http://www.engineeringtoolbox.com/elctrical-motor-full-load-current-d_1499.html . If your under that then you have room to increase the motor pulley size.

Another rule of thumb is ~4cfm per hp, so it your nearing 8 cfm then your in the ball park.

lg
no neat sig line

 

[The Tool Tyrant]

Well, I got a new belt and I adjusted the pulley down a little. The new belt along with the pulley adjusted down is making good contact now and seems like it is running good now. Ran it all the way from 0-150 no problem. I think the belt might have been slipping before because the pulley was hot and now it isn't. I need to figure out what CFM it is now.
0-100 8 min
100-125 3 min
125-150 2 min
60 gallon tank

FYI, the 310 is a 2 stage pump...specs from Quincy: Typical HP. range: 1-1/2 to 3, Min. RPM 400, Max RPM 920, CFM F.A.D. @ 175 PSI MIN RPM:4.06, CFM F.A.D. @175 MAX RPM 9.35.
Personally, I prefer the 1725-1750 RPM motors with a larger diameter pulley to help eliminate belt slippage. Just about all heavy duty (industrial) compressors come standard with the 1725-1750 RPM motors.

 

[kevs79]

Thanks everyone for the info! I do think the small pulley is making it hard to prevent the belt from slipping. I think it is tight now and not slipping though. Maybe a little on start up...maybe.
I did some more "time trials" and it is more what I expected. To me the crucial one is when the cutoff switch comes on and off. 120-150. That CFM is 10. The 70-100 and 0-150 is only 7 though...weird.
Oh well, enough dwelling on the CFM, it is what it is.
Thanks again for all the input, I really appreciate it.

 

[wyliesdiesels]

Well....you sir just solved my problem! Thanks!. Im not too familiar with 220v and assumed checking each leg would be a valid check...not! A wire in my plug came loose! I feel very stupid but live and learn!!

If one of the hot wires was loose I dont see how u were able to get 120v from that leg to ground...

....
It is a Quincy 310 w/the centrifugal unloader. My motor is a 12 amp 3450 rpm so a little below 3hp. I have a 3.25 pulley on the motor and the pump has 14 inch pulley so it should be running approx 800 rpm. Maybe I am taxing the motor too much and need a smaller pulley???

yea thats probably about 2.5hp. Most 3HP motors are a little closer to 17a- 14-15a...

 

[kevs79]

If one of the hot wires was loose I dont see how u were able to get 120v from that leg to ground...

Forgot to mention also the neutral wire shorted to the one hot wire that was hooked up also....What a mess!!!!

 

[kevs79]

This was in the male plug btw. Temporary till I get it hard wired

 

[wyliesdiesels]

Forgot to mention also the neutral wire shorted to the one hot wire that was hooked up also....What a mess!!!!

Why do u have a neutral wire for 230v motor?

And if there was a short the breaker shouldve tripped.

Are u using a double pole breaker?

This was in the male plug btw. Temporary till I get it hard wired

Since its about 3HP u can use a plug and receptacle.

No need to hardwire unless of course u want to.

 

[kevs79]

Yes, two pole breaker
My terminology was wrong...should have said ground. There are two hot wires and one ground wire that go to the pressure switch. Anyway, problem solved now. I am going to hard wire it in once I get some time. I keep the breaker off unless I am using it. I have a big heavy duty long 220v extension cord that I run from my 220 outlet across the garage to the compressor now to just make sure everything works good before I get the permanent line ran.

 

[wyliesdiesels]

Did the breaker trip when the hot and ground shorted?

 

[PT Doc]

Kevs79. Happy. Hear you got things sorted out.

This forum is awesome. The knowledge base is immense. Search out for answered when unsure. Having all kinds of loose wires can be disastrous.

Be safe.

 

[kevs79]

No it didnt but I could see where it shorted. It was burnt in that area. It might have shorted when I uplugged it from extension cord the first time I had it running outside. I might have flipped the breaker off when I walked by and not paid attention to it being tripped.
Is it possible the one leg of 110 was back feeding through the pressure switch and that is why I was showing 110v on both legs at the switch and the motor?