Breaker keeps tripping, potential ground fault?

[dustman]

Hi all.

We have a 120v 20 amp circuit to an accessory dwelling with a run of about 75' of direct bury #12. The breaker keeps tripping even when there is nothing connected to the circuit. What I've done so far:

Checked all connections in the circuit(outlets, etc)

Then, disconnected the circuit at the junction box just outside the structure, isolating the wire run between the breaker and accessory dwelling. It still tripped.

Just before this post I switched that circuit to another breaker, to see if it might be a faulty breaker; nothing yet...

Sometimes this happens right away, sometime it wont trip for hours, with nothing connected either way. This has happened in the past then the problem just went away for a while, then came back.

We have done lots of excavation over the 20+ years of owning this place, and I'm thinking it's not unlikely that a wire could have been damaged.

Long story short, I'm suspecting a ground fault. Any idea how to narrow this down more, some good tests to run without specialized equipment? I have multimeters and have done quite a bit of electrical work but this is a little confusing.

 

[Timbo]

Have you tried replacing the breaker?
Tag @Megawatt for USA

 

[davesparks]

Start with an insulation resistance test to confirm a damaged cable.

 

[Megawatt]

Hi all.

We have a 120v 20 amp circuit to an accessory dwelling with a run of about 75' of direct bury #12. The breaker keeps tripping even when there is nothing connected to the circuit. What I've done so far:

Checked all connections in the circuit(outlets, etc)

Then, disconnected the circuit at the junction box just outside the structure, isolating the wire run between the breaker and accessory dwelling. It still tripped.

Just before this post I switched that circuit to another breaker, to see if it might be a faulty breaker; nothing yet...

Sometimes this happens right away, sometime it wont trip for hours, with nothing connected either way. This has happened in the past then the problem just went away for a while, then came back.

We have done lots of excavation over the 20+ years of owning this place, and I'm thinking it's not unlikely that a wire could have been damaged.

Long story short, I'm suspecting a ground fault. Any idea how to narrow this down more, some good tests to run without specialized equipment? I have multimeters and have done quite a bit of electrical work but this is a little confusing.

It sounds like there is damage to the wiring underground. Do you know what kind of cable was used, in any underground wiring is used has to be UF cable which is approved for underground use. Why don’t you just install another cable and use UF cable and it needs to be 24 inches if not in conduit. Good luck and let us know what you find.