Garage sub panel issues

[Yakemovicz92]

Hello, I’m having trouble determining the issue that I’m having in my garage. I have several shop lights, 110v air compressor, and a ammco 110v brake lathe. When everything is running At the same time, the double poll 60 amp breaker in my basement which is 65 feet away from my garage keeps tripping. It’s 6 gauge wire connecting the garage to the house. Why is it blowing the breaker in my basement, shouldn’t it be blowing at the sub panel in the garage? There are 3 breakers in the sub panel. All the breakers are 15 amp. compressor goes to one, lathe goes to the other, and the shop lights and outlets on the others. I’ve already tested the double breaker in the basement and I have a total of 240v between both, and 110v tested individually. All outlets in the garage have been checked for correctness with a circuit tester. All fine. Any ideas of what direction I need to go in next?

 

[westward10]

One for @Megawatt

 

[Pete999]

Hello, I’m having trouble determining the issue that I’m having in my garage. I have several shop lights, 110v air compressor, and a ammco 110v brake lathe. When everything is running At the same time, the double poll 60 amp breaker in my basement which is 65 feet away from my garage keeps tripping. It’s 6 gauge wire connecting the garage to the house. Why is it blowing the breaker in my basement, shouldn’t it be blowing at the sub panel in the garage? There are 3 breakers in the sub panel. All the breakers are 15 amp. compressor goes to one, lathe goes to the other, and the shop lights and outlets on the others. I’ve already tested the double breaker in the basement and I have a total of 240v between both, and 110v tested individually. All outlets in the garage have been checked for correctness with a circuit tester. All fine. Any ideas of what direction I need to go in next?

Are you overloading the breaker in the basement? what are the loads at the sub panel?

 

[Yakemovicz92]

Are you overloading the breaker in the basement? what are the loads at the sub panel?

Im not sure, I'm going to be getting an amp clamp tomorrow off of a co-worker to figure that out. I highly doubt that I'm drawing a total of 60 amps

 

[Marvo]

Check the motor start currents especially for single phase motors when you get your hands on the clamp tester.

 

[Megawatt]

Im not sure, I'm going to be getting an amp clamp tomorrow off of a co-worker to figure that out. I highly doubt that I'm drawing a total of 60 amps

With that much load you shouldn’t be Tripping the 60 amp main breaker. I bet with all your equipment running at the same time you wouldn’t pull 30 amps max. Could there be something wrong with the wiring on the lathe or air compressor. Which is the last machine you turn on when it trips. The possibility of the breaker tripping in the main panel could be that the breaker in the basement has a higher interruption RMS than the main in your main panel. The interruption should be labeled 10 RMS For house panels. I believe it is a peace of equipment that your trying to run
[automerge]1574639396[/automerge]

With that much load you shouldn’t be Tripping the 60 amp main breaker. I bet with all your equipment running at the same time you wouldn’t pull 30 amps max. Could there be something wrong with the wiring on the lathe or air compressor. Which is the last machine you turn on when it trips. The possibility of the breaker tripping in the main panel could be that the breaker in the basement has a higher interruption RMS than the main in your main panel. The interruption should be labeled 10 RMS For house panels. I believe it is a peace of equipment that your trying to run

Good luck and check you machinery I believe that’s where you will find your problem. Let’s us know what you find
[automerge]1574640325[/automerge]

With that much load you shouldn’t be Tripping the 60 amp main breaker. I bet with all your equipment running at the same time you wouldn’t pull 30 amps max. Could there be something wrong with the wiring on the lathe or air compressor. Which is the last machine you turn on when it trips. The possibility of the breaker tripping in the main panel could be that the breaker in the basement has a higher interruption RMS than the main in your main panel. The interruption should be labeled 10 RMS For house panels. I believe it is a peace of equipment that your trying to run
[automerge]1574639396[/automerge]


Good luck and check you machinery I believe that’s where you will find your problem. Let’s us know what you find

What all do you have plugged into your receptacles, some where in your space you have got a short circuit
[automerge]1574640436[/automerge]

With that much load you shouldn’t be Tripping the 60 amp main breaker. I bet with all your equipment running at the same time you wouldn’t pull 30 amps max. Could there be something wrong with the wiring on the lathe or air compressor. Which is the last machine you turn on when it trips. The possibility of the breaker tripping in the main panel could be that the breaker in the basement has a higher interruption RMS than the main in your main panel. The interruption should be labeled 10 RMS For house panels. I believe it is a peace of equipment that your trying to run
[automerge]1574639396[/automerge]


Good luck and check you machinery I believe that’s where you will find your problem. Let’s us know what you find
[automerge]1574640325[/automerge]

What all do you have plugged into your receptacles, some where in your space you have got a short circuit

Is the breaker in your subfed panel a 60 amp also
[automerge]1574641574[/automerge]

With that much load you shouldn’t be Tripping the 60 amp main breaker. I bet with all your equipment running at the same time you wouldn’t pull 30 amps max. Could there be something wrong with the wiring on the lathe or air compressor. Which is the last machine you turn on when it trips. The possibility of the breaker tripping in the main panel could be that the breaker in the basement has a higher interruption RMS than the main in your main panel. The interruption should be labeled 10 RMS For house panels. I believe it is a peace of equipment that your trying to run
[automerge]1574639396[/automerge]


Good luck and check you machinery I believe that’s where you will find your problem. Let’s us know what you find
[automerge]1574640325[/automerge]

What all do you have plugged into your receptacles, some where in your space you have got a short circuit
[automerge]1574640436[/automerge]

Is the breaker in your subfed panel a 60 amp also

How long have you had this equipment and what changed when it started tripping
[automerge]1574641689[/automerge]

With that much load you shouldn’t be Tripping the 60 amp main breaker. I bet with all your equipment running at the same time you wouldn’t pull 30 amps max. Could there be something wrong with the wiring on the lathe or air compressor. Which is the last machine you turn on when it trips. The possibility of the breaker tripping in the main panel could be that the breaker in the basement has a higher interruption RMS than the main in your main panel. The interruption should be labeled 10 RMS For house panels. I believe it is a peace of equipment that your trying to run
[automerge]1574639396[/automerge]


Good luck and check you machinery I believe that’s where you will find your problem. Let’s us know what you find
[automerge]1574640325[/automerge]

What all do you have plugged into your receptacles, some where in your space you have got a short circuit
[automerge]1574640436[/automerge]

Is the breaker in your subfed panel a 60 amp also
[automerge]1574641574[/automerge]

How long have you had this equipment and what changed when it started tripping

How long does this equipment run before it trips

 

[Yakemovicz92]

With that much load you shouldn’t be Tripping the 60 amp main breaker. I bet with all your equipment running at the same time you wouldn’t pull 30 amps max. Could there be something wrong with the wiring on the lathe or air compressor. Which is the last machine you turn on when it trips. The possibility of the breaker tripping in the main panel could be that the breaker in the basement has a higher interruption RMS than the main in your main panel. The interruption should be labeled 10 RMS For house panels. I believe it is a peace of equipment that your trying to run
[automerge]1574639396[/automerge]


Good luck and check you machinery I believe that’s where you will find your problem. Let’s us know what you find
[automerge]1574640325[/automerge]

What all do you have plugged into your receptacles, some where in your space you have got a short circuit
[automerge]1574640436[/automerge]

Is the breaker in your subfed panel a 60 amp also
[automerge]1574641574[/automerge]

How long have you had this equipment and what changed when it started tripping
[automerge]1574641689[/automerge]

How long does this equipment run before it trips

SO there are 5 basic light fixtures in my detachted garage with T8's that are on at all times, my air compressor only runs when the pressure in the tank gets to low so it doesn't run for long. It will usually trip the 60 amp breaker in my main box that's in my house when I'm cutting rotors on my brake lathe. The Lathe runs perfect with the lights on, small radio, a few rigid battery chargers plugged in, and a small mini fridge. That all runs fine together, then once my compressor kicks on, it will run for a few seconds the blow the breaker.

Compressor - 15amps
Lathe - 15/7 amps (whatever that means?)

^this is what it says on the equipment. no idea what the lights and other things draw.

 

[westward10]

Assuming the compressor has some kind of inertia start/run switch which should open very quickly, it may be stuck or the motor is not achieving the rpm to switch it.

 

[Megawatt]

SO there are 5 basic light fixtures in my detachted garage with T8's that are on at all times, my air compressor only runs when the pressure in the tank gets to low so it doesn't run for long. It will usually trip the 60 amp breaker in my main box that's in my house when I'm cutting rotors on my brake lathe. The Lathe runs perfect with the lights on, small radio, a few rigid battery chargers plugged in, and a small mini fridge. That all runs fine together, then once my compressor kicks on, it will run for a few seconds the blow the breaker.

Compressor - 15amps
Lathe - 15/7 amps (whatever that means?)

^this is what it says on the equipment. no idea what the lights and other things draw.

That 15/7 means at 120vac it will pull 15 amps and at 240 vac it will pull 7 amps so it’s a multi tap machine. It does not sound like an overcurrent situation it sounds like a dead short. If the compressor kicks on and you say the breaker trips immediately, what’s the current on the name plate on the compressor say

 

[westward10]

The compressor is 15A, assuming that is flc its start current could be nearly 80A.

 

[Megawatt]

The compressor is 15A, assuming that is flc its start current could be nearly 80A.

I agree thats why we have to do calculations and size the breaker because of the in rush current which like you stated it can be quite high

 

[westward10]

For a compressor I assume a cap start, cap run motor. As I said previously it may be staying too long in start for some reason prolonging the start in rush current.

 

[Megawatt]

The compressor is 15A, assuming that is flc its start current could be nearly 80A.

@westward it’s hard to figure some things that we read, it makes you want to be there and find the problem if what he says about the compressors amperage I think it should be on a 30 amp breaker not a 15 amp and most air compressors I’ve worked on has 1 pressure switch and a motor with no contactors.

 

[Marvo]

Test the offloader valve on the compressor...and the check valve whilst you're at it. The offloader should open and make a hiss noise when the compressor stops running so next time it starts it doesn't have to fight against full head pressure. The check valve prevents the pressurised air flowing backwards from the receiver tank into the compressor head.

Here's a thread where someone had similar problems from a few years ago but the info is still valid.

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