High Amp Reading in house

[sunny4444]

Hello,

I am working on a house with a 200A service. All the breakers have the right voltage when I meter them. There is one 15A breaker that kept tripping, so I checked the amperage when the breaker was one and it read 88 Amps and then would trip. I have unplugged everything that could be on that circuit, but i still have the high reading. Has anyone ran into this problem before, thanks in advance for any input.

 

[Dennis Alwon]

Hello,

I am working on a house with a 200A service. All the breakers have the right voltage when I meter them. There is one 15A breaker that kept tripping, so I checked the amperage when the breaker was one and it read 88 Amps and then would trip. I have unplugged everything that could be on that circuit, but i still have the high reading. Has anyone ran into this problem before, thanks in advance for any input.

How long does the breaker stay on before tripping. It sounds like a dead short somewhere.

 

[iwire]

Hello,

I am working on a house with a 200A service. All the breakers have the right voltage when I meter them. There is one 15A breaker that kept tripping, so I checked the amperage when the breaker was one and it read 88 Amps and then would trip. I have unplugged everything that could be on that circuit, but i still have the high reading. Has anyone ran into this problem before, thanks in advance for any input.

Yes, many of us have run into this before.

It is a called a short circuit or ground fault.

 

[sunny4444]

It will stay on for about 5 seconds, lights on another circuit will dim, i can hear the breaker struggle and then it trips. I thought it was a short too, but wouldnt that trip the breaker instantaneously?

 

[iwire]

I thought it was a short too, but wouldnt that trip the breaker instantaneously?

No, not always.

The length of the circuit, the size of the wire all effect the impedance of the circuit. Most likely you have a hard short or ground fault and 88 amps is the highest amount of current the circuit can deliver.

 

[Ragin Cajun]

Depending on how many times the breaker has tripped, you may consider replacing it after you find the short. Conductors may also have "issues".

RC

 

[kwired]

No, not always.

The length of the circuit, the size of the wire all effect the impedance of the circuit. Most likely you have a hard short or ground fault and 88 amps is the highest amount of current the circuit can deliver.

Don't forget the size of the supply transformer, and size and distance of service and feeder conductors ahead of the breaker.

 

[kwired]

It will stay on for about 5 seconds, lights on another circuit will dim, i can hear the breaker struggle and then it trips. I thought it was a short too, but wouldnt that trip the breaker instantaneously?

88 amps is a relatively low fault current, you likely have small transformer, long service conductors, and/or long distance between the breaker and the fault. Or a combination of more than one of those mentioned items.

Bring the source closer, increase the capacity of the source, increase branch circuit conductor size enough and you could easily have thousands of amps flowing into this fault. Trip time for that much current will be much closer to instantaneous.

 

[sunny4444]

I'm a little confused by some of the answers, this one 15A branch circuit is drawing 88 Amps and I do not have anything plugged into it. All other circuits are fine. So should i start taking apart anything thats on that circuit ie...junction boxes, ceiling fan, receptacles etc...what am i looking for? thanks

 

[kwired]

I'm a little confused by some of the answers, this one 15A branch circuit is drawing 88 Amps and I do not have anything plugged into it. All other circuits are fine. So should i start taking apart anything thats on that circuit ie...junction boxes, ceiling fan, receptacles etc...what am i looking for? thanks

Start by taking ohm reading of the hot to ground and hot to neutral. If there is no load connected at all you should get readings of infinity for both. You should get infinity to ground no matter what, you will have continuity to neutral through connected loads. This will help narrow down which conductors are shorted. Next step is likely to find a point about the middle of the circuit, take connections apart, and take readings again to see which direction from that mid point you need to continue looking. By doing this you immediately eliminate half of the circuit from being something to look at. Next step is to halve the remaining portion of the circuit again to determine which way to go from that point, and continue similar process until you find the problem or at least narrow it down to problem being somewhere between two outlets and maybe is buried in a wall somewhere. At that point you may have to decide whether or not to open walls or abandon the bad section and somehow replace it.

 

[GoldDigger]

I do not have anything plugged into it. All other circuits are fine. So should i start taking apart anything thats on that circuit ie...junction boxes, ceiling fan, receptacles etc...what am i looking for? thanks

Yes. The most likely problem is a miswired device or a faulty connection that has left a bare ungrounded conductor exposed. But it could also be an insulation tear from a bad pull or pinched wires.
Disconnecting the hot lead from the breaker and working your way around the circuit with an ohmmeter may get you close the problem. If you can isolate parts of the circuit by disconnecting junctions in boxes you may be able to find the bad part of the circuit that way. Just do not keep testing by tripping the breaker! An arc fault short could start a fire while you are testing.

 

[sunny4444]

Start by taking ohm reading of the hot to ground and hot to neutral. If there is no load connected at all you should get readings of infinity for both. You should get infinity to ground no matter what, you will have continuity to neutral through connected loads. This will help narrow down which conductors are shorted. Next step is likely to find a point about the middle of the circuit, take connections apart, and take readings again to see which direction from that mid point you need to continue looking. By doing this you immediately eliminate half of the circuit from being something to look at. Next step is to halve the remaining portion of the circuit again to determine which way to go from that point, and continue similar process until you find the problem or at least narrow it down to problem being somewhere between two outlets and maybe is buried in a wall somewhere. At that point you may have to decide whether or not to open walls or abandon the bad section and somehow replace it.

Thats a great idea, thanks kwired

 

[sunny4444]

Yes. The most likely problem is a miswired device or a faulty connection that has left a bare ungrounded conductor exposed. But it could also be an insulation tear from a bad pull or pinched wires.
Disconnecting the hot lead from the breaker and working your way around the circuit with an ohmmeter may get you close the problem. If you can isolate parts of the circuit by disconnecting junctions in boxes you may be able to find the bad part of the circuit that way. Just do not keep testing by tripping the breaker! An arc fault short could start a fire while you are testing.

thanks for the response GD

 

[RLyons]

Had a row of 120v pole lights reading 125a before tripping. Turned out to be a bad underground splice 125' away. Start opening junction boxes and separating the circuit until it holds or you found your problem.

 

[iwire]

Don't forget the size of the supply transformer, and size and distance of service and feeder conductors ahead of the breaker.

That would all be part of the circuit.

 

[jeremysterling]

... Just do not keep testing by tripping the breaker!

Start...separating the circuit until it holds...

I'm going with GoldDigger on this one.

I know pole lights are a pain to break open the bases to isolate faults, but you can't deliberately close in a breaker on a fault. We have meters to troubleshoot these issues.

 

[bobbymari]

another issue for the long time before tripping could be a weak ground i/e loose conduit or flex connectors where conduit/ flex is your ground. you could hear a nice looooong buzz before youd get a trip.

 

[kwired]

another issue for the long time before tripping could be a weak ground i/e loose conduit or flex connectors where conduit/ flex is your ground. you could hear a nice looooong buzz before youd get a trip.

Which puts more resistance in the circuit and lowers amount of current flow.

 

[kwired]

That would all be part of the circuit.

I know, was not sure if everyone participating in conversation knows though.

 

[kbsparky]

Bad underground to a post lamp can cause this type of condition. Be sure to check for things like that in your troubleshooting endeavors.