Air Compressor problem tripping the breaker the fix

[old]

Finally had some one send me an e-mail that truly explained thing in terms that where correct. Very simple math problem answered the question correctly. 3HP motor draws more then the tagged 15 amps plus add age of it to the equation amp draw was close to more then the 20amp break could handle. If I had a clap on amp meter I would have known that from the get go but I do not own one.
I installed a 30 amp breaker and it is still turned on and working.
Now to the new problem. So far it has pumped up to 40PSI and shuts down. Seems that the regulator is not working as it should be. So I am letting it run some to see if it might just be sticking due to not be used in a long time. If that does not fix it I'll install a new pressure switch and be done with if

 

[IH2444]

I hope you have at least 10 gauge wire on that circuit.
If 12 gauge possible overheat/fire risk.

 

[Jon Hagen]

You believe that HP rating I have seen 120V shop vacs rated at 6 hp.

Be carefull, dont let that thing run unattended. Good chance it has some shorted run windings.

 

[Indiana George]

Need more info to help you help yourself.Was it doing before?pressure switch might be bad, loose connections, make sure all connections are tight.
compressor bad.

 

[old]

Yes I understand the HP rating game. Many companies got sued over that a number of years ago.
As for letting it run with out me by it no problem since where I had it even if it shorted out nothing would have happened other then it smoking.
Just turned it off and it now come up to full pressure so the ATF in the system freed up a sticking regulator

 

[old]

My shop is all over wired. I use 10 gauge almost every place and other then my light duty extension cords my extension cords are all 10 gauge also. So most of my circuits are wired 10 gauge with 15 or 20 amp breakers

 

[Geo-TH,In]

Old, what do you mean you don't have a probe? I have an old analog one. Found at HF, they were selling a returned digital one for $4. People at HF said a man bought it and didn't know how to use it. I took a $4 chance, it works great. I think they sell for less than $20.

If I remember someone who had a comperssor like the one you are working gave you the advice to use a 30 amp.

Now if you bypass the pressure switch, and you can't get the pressure past 40, then like mine, it's very likely the piston/ring combo is junk.

George

 

[old]

This is the 2nd post on this compressor problem. Every thing is now working as it should be. Oil-less compressor that had sat who know how long. Was tripping 20amp breakers so tried 30 amp to see if it smoked or worked and it worked. Gave it a little ATF and let it run and the regulator freed up and when I turned it off it would kick on at 100psi and off at 120 just like it should

 

[old]

I have a VOM but not a clip on amp meter never really have had a need for one till this unit.
As for the breaker and going to 30 amp I think some one did say something but very late in the post. I had tried 5 different out lets to see if that helped but I wire my shop heavy on wire and lite in breakers so that I have not wire problems due to breakers being to heavy for the wire. I use 10 gauge wire with 15 and 20 amp breakers.
As for the regulator it was just a matter of letting the ATF I shot into the compressor to make sure it was lubed up to get to the regulator which in turned freed it up and when I turned it off it was kicking on at 100psi and off at 120 like it should

 

[jimg.allentown]

If it is cutting out at 40psi, the pressure switch would be the likely culprit. Also, there may be a thermal cutout on the motor. Given that it is drawing more than the 15 amp design current, the motor could be getting warmer than design and causing a thermal cutout to turn it off.
I would suggest checking the pressure switch for continuity when it cuts out. Continuity would indicate a problem with the thermal cutout in the motor.
Also keep in mind that when the pressure switch cuts out, it activates an unloader that relieves pressure on the compressor head for the next startup. If you hear the unloader pop off, then the pressure switch is the problem.
Grainger has a good assortment of pressure switches in the $30 - $35 range.

 

[old]

Odd seems some post got deleted for some reason. Yes I over wired my shop used 10 gauge wire when code calls for 12 etc and then under breaker things so again where code says a 30 amp breaker I use a 20 amp one instead

 

[old]

If you do the math a 3 HP motor should draw around 18.6 amps and then add the age of the machine is the reason a 20 amp breaker was not good enough. After giving it some ATF to clean things up and all the regulator on it freed up and it now kicks off at 120psi and on at 100psi like it should

 

[paul]

That sounds about right, but I wasn't going to get involved in that other thread.

Even tho your extension cord was a 10g, at 50 feet it likely wasn't helping any either.

Paul

 

[old]

By the way the feet number I used for that cord is guess probably a good bit shorter if not 25 or less I have never measured it. But either way the cord was not the problem it was the fact a 3HP motor draws 18.6 amps or more depending on age and wear etc

 

[Steve@Advance]

Something still not adding up...

A real 3HP motor draws 34 amps on 120v.!

You're best bet is to go by the "full load amp" rating on the motor tag.

Somehow the compressor mfg. have found a way to lie about the horsepower. See this a lot on the home shop type compressors, very deceptive and downright dishonest!

 

[old]

Yes being a former Navy E.T. and then a TV/radio repair man and a Maintenance electrician at Tracker marine and all I understand the only way to be sure of amps/hp is with the right gauges. Sadly a VOM does not cut if when your wanting to know amp draw on a compressor motor. Plus there are people who guess at things

 

[showcrop]

A three HP motor on a 15 Amp breaker is no more than a wish.

 

[souNdguy]

Most motors I see these days are rated at 'peak' hp.. for the non electrically inclined.. that's practically a lie.

I'd expect that motor to be actually around 2 hp...

soundguy

 

[old]

I started trying it on a 20 amp breaker which is still to light for a 3HP

 

[old]

Also if you read what I said the tag on the motor says it draws 15 and also if you keep reading you will see I said I was using a 20 amp breaker so where did you get a 15 amp breaker from????????????? Since I said nothing about a 15 amp breaker?

 

[GordoSD]

I bought one compressor and it stated in the service book, "Warantee void if used with extension cord"
I sold that one about a year later and moved up to 69 gal vertical. I gave the buyer the paperwork and showed him the extension cord note several days later I drove by his place and saw
it sitting in the middle of his yard with about 100 feet of electrical cord going to his shop. I came home and got a 50 reel of air hose and coupling so he could extend the air not the electricity. Plus the compressor would be INSIDE the shop. One reason everything he owns is either broke or about broke.

 

[Ken Macfarlane]

What exactly is shutting down? The motor starting from an empty tank will pull a bunch of amps but once running only maybe 1/2 rated amps until it starts getting up in pressure. It shouldn't hit full amps really ever but may get close near kickoff at peak pressure.

Is the motor correct for the compressor? If it's too small it will hit full amps before tank is full and thermal overload will kick out.

 

[RandyB(MI)]

see , Old , you didn't need any help, just some more time! Us old guys just take a little more time to learn sometimes. Usually because we are being TOO cautious and not wanting to cost ourselves $$$$$. Glad you figered it out.

 

[Brian Jasper co. Ia]

A true 2hp motor won't run on a 20 amp circuit. If your motor says it draws 15 amps at load, no way is it 3hp.

 

[showcrop]

(quoted from post at 20:37:10 03/15/14) A true 2hp motor won't run on a 20 amp circuit. If your motor says it draws 15 amps at load, no way is it 3hp.

Maybe it is a dual voltage motor and the 15 A rating is at 240V?