Compressor/electrical help

[wythors]

I have this Craftsman compressor. It is plugged into a dedicated 20 amp circuit. According to the manual, it needs only a 15 amp circuit. When I originally purchased it, it blew the circuit breaker the first time it cycled "on" after the initial fill. It did this sporadically through the first several times I used it. Not popping the breaker every time it cycled, but maybe one out of three times. I had an electrician in to check the circuit, the breaker and the panel. He said everything was fine. At this point, I called Sears and arranged for an exchange. I just ran the new one through it's break-in cycle and filled it. I attached my blow gun, drained it down and it popped the circuit breaker again. Any ideas why this is happening or what can be done to alleviate the problem?

 

[Charles (in GA)]

While an electrician has checked the circuit, that does not mean there are no problems. Having swapped the compressor out, and that it is a new one, I'll discount the compressor, so that leaves the circuit as the problem. Did you try swapping out the breaker for another one, or a new one? Rare is it to find a bad one, but........ How far is the panel from the receptacle or better yet, about how many feet of wire is in the circuit? Is the wire 12 gauge? For sure? What is the quality of the receptacle in the wall? Is it a 59 cent version, or the three dollar version. There IS a huge difference in quality. Do you feel the cord or especially the plug, heat up after running the compressor?

The specs say the compressor draws 15 amps, therefore it will require a 20 amp circuit, as generally you should not exceed 80% of the capacity of a electric device, thus the max capacity of a 15 amp circuit is 12 amps and the capacity of a 20 amp circuit is 16 amps. This is a general rule that will keep you out of trouble, I think there are exceptions to it, but its best to stay on the cautious side.

Lastly, have you tried the compressor on any other circuit?

Charles

 

[wythors]

Hmmmm....

Yes, the breaker has been swapped for another one. The recepticle is at the opposite end of the house from the box, probably fifty feet as the crow flies. I have no idea as to how much wire is strung between them, or the guage of the wire. The house was built in 1964 and the outlet is original. I haven't felt the cord when this occurs, but I will next time I use it. It seems to me, that I should take your last suggestion and fly with that. If it works without a problem there, that should verify that there's a problem with that circuit.

Thanks for the thoughts.

 

[rodrelic]

There's a chance someone has tapped into it for something else. I'd run a new line, quality single outlet receptacle and breaker. Haven't bought any conduit lately but shouldn't cost over 50 bucks for all the stuff

 

[BoilermakerFan]

I'd have to agree. Unless you ran the circuit yourself or the electrician chased it down and verified it's truely dedicated, I'd be it's been tapped for other outlets.

I would run a new line. Use 10ga wire on the 20A circuit so you won't have a voltage drop issue. I suspect your getting just enough voltage drop over that run to cause the breaker to trip. In addition, the under voltage condidtion puts a real strain on the motor and significantly shortens it's life. Did the electrician confirm your voltage at the recepticle?

 

[bmwpower]

I have the same compressor. Same problem. This has been talked about before on here.

http://www.garagejournal.com/forum/showthread.php?t=2610

Apparently, it's a common problem.

I have my compressor on a 20A circuit, not far from the panel...still trips the breaker to this day. I still haven't done the fix for it (listed in the thread).

 

[rockwithjason]

You can measure voltage at the recepticle until doom's day and it will tell you nothing. You need to measure the voltage under load and at start up. If the voltage drops below say 100 volts you have a problem. Being as it was built in the 60's there is a chance that the house is wired with aluminum branch circuits. Voltage drop is a real nightmare on these systems. I agree with the 10awg wire and the dedicated circuit solution. If the compressor trips that setup then give up and get a new compressor.

 

[sberry]

This happens all the time with small comps, its just the nature of the type of load and equipment quality can be a factor. V drop at that distance isnt that much of a factor, the run current is 15 maybe less. Get a number 12 wire a single recept a 30A breaker or tape off the other half of the duplex and run a dedicated circuit. You will not overload the wire with this unit, the motor has its own thermal protection. I post a sign or write on the recept, This circuit for comp only, not for general use. Its the only thing that is going to work, upsizing the wire to 10 will not help, may even hurt by allowing for the delivery of more current. Just as a test take one of the cheap ext cords, a number 16 25 or 50 ft and see if the breaker trips with this.

 

[sberry]

I dummy off one side of the recept so it cant be used and is labeled.

 

[Charles (in GA)]

There is a real good chance that a 1960's house, esp an early '60's one is wired with 14 gauge on the outlets. A 50 ft plus circuit on 14 gauge could not properly operate this compressor. A 12 gauge wire with this high a draw at this distance is questionable also. As others have noted, it could be aluminum wire also. If you have aluminum wire, you need special CO/ALR marked receptacles and paste on all wire ends during assembly. Been there, done that, with a AL wired house I bought one time, that the wiring was burning up in the walls at the receptacles.

As others have also noted, run a 10/2 w/grd wire and a good Leviton Pro grade outlet. Get one that has the backwire feature that you put the wire in, and tighen the screw on the side and it pinches the wire inside with a serrated plate. Very effective installation and doesn't require that you wrap the wire around the screw. DO NOT use the outlets with the push in back wire (now restricted to 14 gauge wire anyhow). A good Leviton Pro Grade receptacle will cost you about three bucks or more, and well worth it. I put them throughout my house and workshop. A real bear to plug and unplug from, but they won't get loose and don't wear out.

Charles

 

[sberry]

Charles, there wont be an issue with V drop on a 12 with this unit, the cause is from something else, leaking unloader or motor start contacts and may be minor and hard to spot or even eliminate. Its a good idea to have something like this on its own circuit anyway just in case it needs tailoring because of problems such as this. There is a feature in the breaker I believe that tends to ratchet up for lack of a better term, my chop saw would trip every half a dozen starts, its just the nature of running hi torque motor starts and the code makes provisions for this. I dont much care for setups like this running from 120V in the first place, I never see running from 120V as much of an asset, its a liability from my point of view unless you really really absolutely have to move it. Welding machines the same way, you really need a dedicated circuit, might as well run 240 right from the start and be done with it and get a way better unit at the same time for very few more dollars. But now its a case of you got to run what you brung so you got to make the best of it.

 

[bmwpower]

So running these things on a dedicated circuit, using 12 gauge wire and a 30A single pole breaker is the (possible) solution? I'm going to stop at Home Depot and get a 30A and try it out.

 

[KeukaDan]

upsizing the wire to 10 will not help, may even hurt by allowing for the delivery of more current.

This statement confuses me, the wire doesnt determine current draw, only resist it by heating up. Maybe there is something I am missing here.

 

[Charles (in GA)]

So running these things on a dedicated circuit, using 12 gauge wire and a 30A single pole breaker is the (possible) solution? I'm going to stop at Home Depot and get a 30A and try it out.

30amp breaker is not correct for 12 gauge wire, need to stick with a 20 amp breaker.

Charles

 

[bmwpower]

30amp breaker is not correct for 12 gauge wire, need to stick with a 20 amp breaker.

Charles

Charles,
You can upsize the breaker IF the motor circuit is dedicated to the compressor.

I stopped tonight and picked up the 30 amp breaker, installed it and no more problems (yet). The compressor cycled like it was supposed to.

 

[Charles (in GA)]

Charles,
You can upsize the breaker IF the motor circuit is dedicated to the compressor.

I stopped tonight and picked up the 30 amp breaker, installed it and no more problems (yet). The compressor cycled like it was supposed to.

Actually, within limits, that is true, and I was going to correct my post after pondering over it and studying it, but when I went to...................... no internet connection!!!!!!!!!!!!! (Charter Cable broadband) and it only began functioning about 9:30 this morning.

Charles

 

[oldskewl61]

them there compresers just draw alot of amps on start up if it were me id use a 30 amp breaker you got inserince right? its a slim chance youll have problems cause it only draws more on hot restarts

 

[sberry]

Yes, its the start current and its instanteneous, it doesnt last long enough to overheat the wire. A 30 wouldnt overheat a 12 wire anyway but on many dedicated circuits similar to this the breakers main function becomes a disconnect and to provide short circuit protection, shorts can draw hundreds of amps on a 12 wire without heating. The motor itself has thermal protection which protects the wiring, essentially the machine itself is the limiting factor, it just will draw only so much current. This is the reason to make this dedicated, we wouldnt want to plug a heater on the same circuit as the comp and have a breaker in the system that will not fully protect the wire, its not an issue with a single appliance on that wire. This is a common problem, there isnt much you can do except change it out. Even if you could manage to tune that comp the problem would likely return next week.