Breaker tripping when turning on compressor

[bmwpower]

Compressor is one of those Craftsman 33 gallon types, 15A on name tag. For the past 2 years, I've not had a single problem with turning it on (on a 15A circuit). Recently occasional its been tripping the breaker on a 15A circuit. Resetting the breaker and turning it on again usually works. Sometimes, however, it will trip again until it finally turns on.

I even took it into my new garage and put it on a dedicated 20A circuit and it tripped the breaker.

Any idea what's going on? Is the motor getting ready to die?

 

[Weekend_warrior]

My guess is that your getting a partial short on the motor and its drawing to many amps. I'd have it checked out for sure.

 

[bmwpower]

Who do I get to check this kind of thing?

 

[6t7gto]

bmw,
most compressors "unload" the head after it cycles.
maybe yours is not and it's trying to start up with pressure in the head.
does your compressor exhaust a little bit of air when it reaches the preset operating pressure?

david

 

[rockwithjason]

Your breaker may be getting lazy too. Try swapping it with anouther. If you are using an extention cord try plugging directly into the wall. The closer you get to the panel the better.

 

[bmwpower]

bmw,
most compressors "unload" the head after it cycles.
maybe yours is not and it's trying to start up with pressure in the head.
does your compressor exhaust a little bit of air when it reaches the preset operating pressure?

david

I know it does normally. I guess the question is, does it do it all the time. I will have to check and see. I'll let you know.

 

[bmwpower]

Your breaker may be getting lazy too. Try swapping it with anouther. If you are using an extention cord try plugging directly into the wall. The closer you get to the panel the better.

I tried it multiple breakers in my new garage. And one in the old garage where I used it for a couple of years with no problems. Now it's starting to do it in there, too. It did the same thing several times in the new garage

I'm not using an extension cord and even tried an outlet closer to the panel...same results.

 

[GearHead_1]

Unless the environment has gotten significantly colder (heavier oil) than what you normally see I would think the motor is showing signs of wear.

 

[bmwpower]

Unless the environment has gotten significantly colder (heavier oil) than what you normally see I would think the motor is showing signs of wear.

New garage is heated...

 

[ranger_dood]

do compressor motors have a kick-start cap? maybe that cap isn't doing its job anymore and is putting more strain on the line.

 

[Charles (in GA)]

bmw,
most compressors "unload" the head after it cycles.
maybe yours is not and it's trying to start up with pressure in the head.
does your compressor exhaust a little bit of air when it reaches the preset operating pressure?

david

David is correct, this is the most common problem with compressors, especially (and I don't know why) portable units.

When the pressure switch opens and removes power from the motor, the mechanical motion of the arm in the switch pushes on a valve that bleeds pressure off the head of the compressor. So, as David describes, just as the compressor shuts off, you should hear a hissing from this valve at the pressure switch. If you do not, feel around and see if the arm and valve are exposed so you can manually operate it, most compressors have this feature so you can shut off a compressor before the pressure switch does, and then manually bleed off the pressure. The valve may just be sticking. My old Craftsman does on ocassion.

Second possible problem. The pipe from the compressor pump to the tank has a check valve in it. This keeps tank pressure from backing up to the head of the pump and making it difficult to start up. When you have a bad check valve, you get a situation where the bleed valve will hiss air constantly until the tank depletes, unless of course, the unloader valve is sticking along with the bad (leaking back) check valve.

Motors just don't go out very often. Sometimes start capacitors do, and more often than that, the centrifugalswitch that takes the start capacitor out of the circuit sticks and the capacitor stays electrically in the circuit and keeps the compressor from coming up to speed, it shortly blows the breaker, but the compressor does start up........

Pics are of my one horse portable Craftsman (I stated two hp in another post, sorry) which is a good 35 years old. One pic shows the check valve at the bottom of the large tube from the head, the other arrow shows the manual/auto head unloader valve at the bottom of the small tube. Second pic shows my digit on the manual unloader lever. Note that the compressor is so old it did not come with a belt guard, it was an optional accessory I never bought.

Charles

 

[Charles (in GA)]

Compressor is one of those Craftsman 33 gallon types, 15A on name tag. For the past 2 years, I've not had a single problem with turning it on (on a 15A circuit). Recently occasional its been tripping the breaker on a 15A circuit.

From a later post, it sounds like a compressor problem, rather than a circuit problem, HOWEVER, you should never be loading a circuit this heavy. One of the first and a basic rule of electricity, no matter if AC, DC auto, home, aiirplane, whatever, is to never exceed 80% of the designed capacity of a circuit, with the normal, running load. Certainly you will have momentary surges at startup of almost anything, but your 15 amp compressor is a 15 amp normal running load. A 15 amp circuit should not be loaded more than 12 amps (thats 80% of 15 amps) total on the circuit, and a 20 amp circuit should not be loaded more than 16 amps, total on the circuit.

Charles

 

[bmwpower]

From a later post, it sounds like a compressor problem, rather than a circuit problem, HOWEVER, you should never be loading a circuit this heavy. One of the first and a basic rule of electricity, no matter if AC, DC auto, home, aiirplane, whatever, is to never exceed 80% of the designed capacity of a circuit, with the normal, running load. Certainly you will have momentary surges at startup of almost anything, but your 15 amp compressor is a 15 amp normal running load. A 15 amp circuit should not be loaded more than 12 amps (thats 80% of 15 amps) total on the circuit, and a 20 amp circuit should not be loaded more than 16 amps, total on the circuit.

Charles

I was under the impression that the compressor should be fine on a 15A circuit as 14 gauge wire is actually rated for, I believe, 20A short term. Also, the plug on the compressor is a normal 15A plug, not a 20A plug configuration. If Craftsman wanted me to only plug it into a 20A circuit, I would think the plug would be of the 20A type, no?

 

[bmwpower]

More testing...

I actually got a chance to test a couple theories out tonight.

I turned on the compressor tonight to fill up some tires. I plugged it into a dedicated 20A circuit in my new garage. Flipped the switch on the compressor and.... the breaker tripped. Turned off the compressor and reset the breaker. Turned on the compressor again and it kicked on and filled the tank. When the pump stopped filling the tank, I could hear the hiss of air as it bled the pressure off the head.

After I was done, I turned off the compressor and drained the tank.

Later tonight, I went back out and tried to kick on the compressor...no dice. It tripped the breaker on first start up. I reset everything and tried again. It started this time, so I let it fill up. Heard the air bleed at tank full. After it was full, I drained some air with the switch on and the compressor kicked on to refill the tank.

So....

It appears the compressor will not kick on AFTER the tank is drained, but has no problem starting up after a decrease in tank pressure.

 

[6t7gto]

two thoughts...
contacts in pressure switch may be burned..try cleaning them.
try it with the belt off. may isolate problem to motor.

david

 

[bmwpower]

two thoughts...
contacts in pressure switch may be burned..try cleaning them.
try it with the belt off. may isolate problem to motor.

david

I'll take a look at the pressure switch. I hope it's not bad cause I looked on the Sears site and it costs ~$90 to replace (ouch).

There is no belt on this one. It's one of those low end Craftsman types without a belt. The piston rod is directly connected to the motor shaft.

 

[JDIII]

Take a look at this : www.compressor.pro-menu.com

 

[bmwpower]

Take a look at this : www.compressor.pro-menu.com

That's my compressor! Well a couple generations newer judging from the model number, but it looks just like it.

I guess it's time to take it apart and see if this is my problem.

Thanks JD for the link. I'll take a look, hopefully tonight, to see if this is the problem.

 

[Charles (in GA)]

Well, do I get partial credit, professor? I did mention the centrifugal switch.........

This must be a common problem. This guy has done an excellent job of documenting a fix..........

To comment on the amp draw and rating of components. Yes the standard electric plug we are all used to is only rated at 15 amp. This is largely an NEC thing I suspect, to make sure that you don't plug a real high draw item into a lower rated circuit (high draw items should have the plug with one crosswise prong on it). The actual components of the circuit, the plug the 14 ga cord (as long as it is short) and the receptacle, are quite capable of handling the 15 amps. The biggest problem area is the circuit breaker and the 14 gauge wiring in the walls. A moderate length run of 14 gauge house wire, with 15 amps passing thru it will get warm, probably not enough to hurt anything, but any time a wire heats up, you are losing efficiency. The circuit breaker is the real problem, it is running on the edge when you are pulling 15 amps thru a 15 amp breaker. They will weaken and eventually trip prematurely and you will end up replacing them.

Case in point. I have a Sears stack washer/dryer, the big one, but one unit, one 240 v plug/cord. Internally, the motor for the dryer, and the washer are both 120v motors and the heat element is 240v. According to the wiring diagram the two motors are supposed to be on opposite sides of the incoming current. One on the netural and one hot, the other on the netural and the opposite hot. Thus the load is spread fairly evenly. Wrong. The factory actually wired the unit (contrary to the wiring diagram) with both motors on the same side of the hot circuit. I did not know this until the circuit breaker began tripping. I found it hot and using a clamp on amp meter I measured the current draw on each hot leg, finding that the two motors together, and with the dryer running on high heat, were loading one side of the circuit to the breakers capacity. It had been overheated so many times that it weakened and I eventually had to replace it.

Charles

 

[Silver73]

New guy here, Yep if it has a capacitor mounted externally( usually mounted to the outside of the motor), take it off and take it to a local motor shop, they may check it for free, it only takes a few seconds to check. Capacitors are pretty inexpensive, I would also check ALL WIRING and connectors to make sure there are no loose connections. If it does have and unloader make sure it works.

 

[DaveL.]

Me too

I had the same problem with my Sears 33 gallon Compressor. I even had a dedicated line with a 20 amp circuit breaker. I told my electician who wired my new home/garage about the circuit breaker tripping all the time. First thing he asked was do I have a Sears compressor. He said he ran into the same problem many times. He inserted a 30amp breaker in my box and I have had no problems since.