High Amp Reading in house

Status
Not open for further replies.
S

sunny4444

Member
Location
New Bedford,MA
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.
 
sunny4444 said:
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.
Click to expand...

How long does the breaker stay on before tripping. It sounds like a dead short somewhere.
 
sunny4444 said:
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.
Click to expand...

Yes, many of us have run into this before.

It is a called a short circuit or ground fault.
 
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?
 
sunny4444 said:
I thought it was a short too, but wouldnt that trip the breaker instantaneously?
Click to expand...

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.
 
iwire said:
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.
Click to expand...

Don't forget the size of the supply transformer, and size and distance of service and feeder conductors ahead of the breaker.
 
sunny4444 said:
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?
Click to expand...

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.
 
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
 
sunny4444 said:
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
Click to expand...

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.
 
sunny4444 said:
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
Click to expand...
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.
 
kwired said:
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.
Click to expand...


Thats a great idea, thanks kwired
 
GoldDigger said:
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.
Click to expand...

thanks for the response GD
 
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.
 
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.
 
bobbymari said:
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.
Click to expand...

Which puts more resistance in the circuit and lowers amount of current flow.
 
Status
Not open for further replies.
Top