Odd GFCI Trip

[Little Bill]

I was on a call for GFCI receptacle tripping. Since the homeowner said he replaced the GFCI I figured he wired it wrong. I took out the GFCI and it had the line/load on the correct terminals. So I thought there is a ground fault somewhere.
Now this is an RV with both shore power and onboard, but I'm dealing strictly with the shore power.

I should have mentioned this first but didn't, the GFCI will reset but trips in about 30 secs. every time.
I see there is two load lines so I took them off and just added one at a time to see which one had the fault. After determining which of the lines had the fault I checked to see what was on each line. Turns out the one with the fault runs up to the driver's cabin. It goes to a junction box then on to a receptacle to plug in the TV. With nothing plugged in, the GFCI still trips.
Rather than tear the RV apart, I decided since this area (IMO) doesn't require GFCI, I decided to just feed this line off the "line" side. Everything worked after that. Oh, and I did check for line faults before doing this.

My question is why would it take 30 secs for the GFCI to trip?

 

[kwired]

I was on a call for GFCI receptacle tripping. Since the homeowner said he replaced the GFCI I figured he wired it wrong. I took out the GFCI and it had the line/load on the correct terminals. So I thought there is a ground fault somewhere.
Now this is an RV with both shore power and onboard, but I'm dealing strictly with the shore power.

I should have mentioned this first but didn't, the GFCI will reset but trips in about 30 secs. every time.
I see there is two load lines so I took them off and just added one at a time to see which one had the fault. After determining which of the lines had the fault I checked to see what was on each line. Turns out the one with the fault runs up to the driver's cabin. It goes to a junction box then on to a receptacle to plug in the TV. With nothing plugged in, the GFCI still trips.
Rather than tear the RV apart, I decided since this area (IMO) doesn't require GFCI, I decided to just feed this line off the "line" side. Everything worked after that. Oh, and I did check for line faults before doing this.

My question is why would it take 30 secs for the GFCI to trip?

Perhaps current leakage is right near the 4-6 mA trip range, if it would be higher current it would trip faster.

 

[growler]

I should have mentioned this first but didn't, the GFCI will reset but trips in about 30 secs. every time.
I see there is two load lines so I took them off and just added one at a time to see which one had the fault. After determining which of the lines had the fault I checked to see what was on each line. Turns out the one with the fault runs up to the driver's cabin. It goes to a junction box then on to a receptacle to plug in the TV. With nothing plugged in, the GFCI still trips.
Rather than tear the RV apart, I decided since this area (IMO) doesn't require GFCI, I decided to just feed this line off the "line" side. Everything worked after that. Oh, and I did check for line faults before doing this.

I don't know Bill I think there is a line fault. It probably takes 30 seconds for the wire to heat up to a point where it will trip a GFCI ( high resistance that breaks down once power is applied). Once the only protection is a regular breaker the problem could get worse

A GFCI normally gives a pretty good test of a line fault to ground.

 

[ptonsparky]

I don't know Bill I think there is a line fault. It probably takes 30 seconds for the wire to heat up to a point where it will trip a GFCI ( high resistance that breaks down once power is applied). Once the only protection is a regular breaker the problem could get worse

A GFCI normally gives a pretty good test of a line fault to ground.

I tend to agree with you. Wiring that is tripping a GFCI has a fault someplace. Equipment can pass enough ground current and be normal. Not so the wiring in a relatively short distance.

 

[Little Bill]

I don't know Bill I think there is a line fault. It probably takes 30 seconds for the wire to heat up to a point where it will trip a GFCI ( high resistance that breaks down once power is applied). Once the only protection is a regular breaker the problem could get worse

A GFCI normally gives a pretty good test of a line fault to ground.

There was no load connected when it tripped for me. If its a line to neutral fault, it should trip the breaker. I failed to mention in the OP that when testing, I left the EGC off and the GFCI held. So it has to be a ground fault to the neutral.

 

[synchro]

The voltage on the disconnected EGC relative to neutral may have given a clue whether it was a hot to ECG fault, or a neutral to EGC fault. The latter should measure no more than a few volts, but the former could be substantially more. It would still take some work to track down the fault location, but at least it would narrow it down some.