Air compressor

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I just aquired this 13gal campbell hossfield compressor and have a question.It occasionally (like every couple uses) trips the breaker when the motor starts to kick on.  Like it will get a couple of revolutions winding up and will blow the breaker..Can happen at initial start up or when in use and it gets below that point that it auto kicks on.  Its on a 20 amp breaker and it worked fine for many years on this same breaker.  Not sure what its problem is
Reply:I can't tell for the picture angles whether it is an oilless or oil lubed compressor...and it probably doesn't matter. Sounding like it might be the pressure relief valve is stuck and when your compressor cycles on it is working under a heavier load that what the motor was designed to handle due to the built up pressure in the compessor. Does the compressor give off a slow hiss at the end of each compression cycle to indicate the compressor is bleeding off the stored air in the compression chamber...head not the air tank? If not, it is probably the problem.You have me on saying the compressor is recently acquired AND also that it has worked fine for years on this circuit???Lincoln PrecisionTig 275Miller 251Miller DialArc 250Bridgeport millHossfeld bender & diesLogan shaperJet 14 X 40 latheSouth Bend 9" 'C'Hypertherm 900Ellis 3000 band saw21"Royersford ExcelsiorTwo shops, still too many tools.
Reply:I think Roy is right.  Your unloader may not be working.  Does it start up ok with no pressure on the tank and stay running until it kicks off for the first time.  Usually the unloader is attached to the pressure switch and will bleed air every time it shuts off.Dan
Reply:Its possible.  Where would this pressure valve be?  It does give a 3-4 second hiss when i turn it off, but. The his comes from the arear with the switch and regulator an whatnot on the right side.  Should it be doing this from the pump also? It does this with an empty tank and full.  Also once when it was doing it bad, the tank was empty and i held the manual pressure releaser open till the motor got to full speed an released it an it aired up great
Reply:Now it's sounding more like it may be your motor's starting capacitor. You'll need a more experienced man than me for a diagnosis because I don't know if a starting cap will slowly go bad...what it is sounding like here...or whether they just do a go-no go from good to bad. You say the unloader is working...the hiss you mentioned, and also that the compressor worked great once you let it build up to speed by holding the manual pressure release (pop-off valve?) open? Tripping the breaker MAY be from a weakening start capacitor not giving the motor enough initial power to kick it up to running speed and the motor is laboring which would cause a heavy amp load and your tripped breaker. My best guess, but take it for what it's worth...Lincoln PrecisionTig 275Miller 251Miller DialArc 250Bridgeport millHossfeld bender & diesLogan shaperJet 14 X 40 latheSouth Bend 9" 'C'Hypertherm 900Ellis 3000 band saw21"Royersford ExcelsiorTwo shops, still too many tools.
Reply:Thank you for your help.  I also kind of thought it could be the capacitor, but I am not very knoledgable on electrical things like that.  Which capacitor do you think is for starting? The small or large one?  Also I say I recently aquired it, but I knew its history because I got it from a good friend who i have used it with many times in the past
Reply:Above my pay grade, but your best bets are (1) take it in to a motor repair shop, (2) trace the wiring back from the centrifugal switch, per the diagram below, to the start capacitor, which is usually on the non-driven end of the motor connected to the end of the rotor shaft or (3) Google the motor serial number and manufacturer off the Internet and see what you come up with. Personally, with your asking the level of questions you're asking, I'd guess that #1 would be your best bet. Not trying to be snide...I take most of my own motor problems in to a motor shop along with a 12 pack of the owner's favorite beer to get what I need.Lincoln PrecisionTig 275Miller 251Miller DialArc 250Bridgeport millHossfeld bender & diesLogan shaperJet 14 X 40 latheSouth Bend 9" 'C'Hypertherm 900Ellis 3000 band saw21"Royersford ExcelsiorTwo shops, still too many tools.
Reply:Since it ran good on your friends 20 amp bkr I'd try installing a new breaker before taking the motor to a shop. Breakers do get tired.                                          MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:I had exactly the same problem with my compressor. Initially, it would fill and then not be able to restart until the tank pressure was well below the low pressure switch point. Turned out it was the check valve that prevents the tank pressure from backfeeding to the pressure piston in the pump head. With the check valve gone, your motor is unable produce enough to be able to push past the pressure exerted on the piston and the electrical draw is what is knocking out your breaker; remember, highest amperage draw for any motor is at startup under load. Replace the Check Valve, you can get a universal at Princess Auto (Canada's HF) for a measly $6 (take out the old valve and take it with you to insure that you get the correct size. The correct size wasn't available one time and I got the next size up and just mountede the new one inside the old one for fit. Same thing happened to the compressor at work, too, exactly the same as yours, same issue, same solution. If I'm wrong, (doubt it) $6 is less than the Bench Rate at your local repair guy. Let us know how it all works out! (BTW check valve is the brass fitting that the copper or Alu pipe from the pressure head goes into. Follow that copper pipe from the head on the LS of the unit, it goes into the check valve. It's mounted on the tank, it's a one way valve that won't allow (air) pressure out the other way. Take a photo of the other side of the unit, I'll repost it with an arrow pointing to the valve) Start caps are binary, either they work or they don't, no middle ground. Also, that 3-4 second hiss most likely comes from the head releasing the unused pressure that didn't get to the tank. Last edited by bearston; 02-19-2013 at 04:10 PM.When a welder tells you to "stick it", what do they really mean?"In a time of universal deceit, telling the truth is a revolutionary act." - George Orwell
Reply:Are you plugged in direct or to a extension cord. Direct would be best.Millermatic 252millermatic 175miller 300 Thunderboltlincoln ranger 250smith torcheslots of bfh'sIf it dont fit get a bigger hammer
Reply:Originally Posted by mla2ofusSince it ran good on your friends 20 amp bkr I'd try installing a new breaker before taking the motor to a shop. Breakers do get tired.                                          Mike
Reply:Hey Mlasal1, just curious what happened here, did you figure out whether your compressor has power supply breaker issues in or is it unloader/check valve that caused the problem and is it resolved yet? Thanks for the update.  When a welder tells you to "stick it", what do they really mean?"In a time of universal deceit, telling the truth is a revolutionary act." - George Orwell