GFCI breaker trips

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Old 01-01-14, 05:29 PM
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Unhappy GFCI breaker trips

I wired a 50A double pole GFCI subpanel for a spa and the breaker trips immediately every time. I need someone with more knowledge than I to figure it out. What I know is....
1) It is wired correctly. I've checked and rechecked the instructions and online. The neutral wire from the breaker goes to the neutral bus
2) It's not the spa. I disconnected the load (spa) and the breaker still trips immediately
3) The house wiring is complicated. I inherited a job on an old farm house that was started by someone else. The meter socket has a disconnect and the ground runs to ground from there. It's my assumption that ground and neutral are bonded at this point. Two hots, neutral and ground go to the main service panel. Ground and neutral are isolated in the panel. There are no issues with GFCI outlets in the hose. A 100A breaker leads to a "primary" subpanel in the addition which was just built. Ground and neutral are again isolated. From the primary subpanel there are 2 other subpanels. One 50 amp to the spa. Ground and neutral are isolated and there is also a separate ground rod running from the spa in addition to the house ground. I have tried disconnecting the additional ground from the system but the breaker still trips. There is also a 100A feed from the primary subpanel to a remote subpanel in a spring house. This panel has neutral bonded as it's in a separate building (700ft away) and has a separate set of ground rods. The 20A GFCI outlet in the spring house passes with a GFCI outlet tester.
4) The wire for the spa was laying in place under the house for around a year before getting to this point.
5) I've read several on-line forums. Multimeter tests indicate continuity between ground and neutral at the spa and primary subpanel. Wouldn't you expect this if neutral and ground are bonded up stream?? I got the multimeter for XMas so it's a new gadget to me.

If the wire is wet I assume it will eventually dry. Anybody have suggestions??
 
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Old 01-01-14, 05:38 PM
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The wire for the spa was laying in place under the house
Cable not wire correct? What type of cable, UF, NM-b, SE?
 
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Old 01-01-14, 06:53 PM
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correct - cable. NM-B. It runs inside the wall, then through plastic conduit underneath gravel under concrete, through a crawl space and finally up through the floor to the subpanel.
 
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Old 01-01-14, 08:02 PM
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You've run type NM cable in conduit undeground ? That is not correct. NM cable is not considered water resistant and is not used underground or outside.

UF cable must be used outdoors or THWN conductors in your conduit.


However......with that aside........

In the spa panel should be a neutral block, a ground block and two hot terminals.
The white should go to the neutral bar which cannot have a connection to ground at that point.
The bare should go to the ground block.
The red and black wires go to the hot terminals supplying the GFI breaker.
The white tail wire coming off the GFI breaker goes to the neutral block.

At this point..... if you've wired it this way and it trips the breaker with no load connected.....the breaker is bad.


If you wanted to check underground wiring for water issues you'd first need to disconnect both ends of the cable. You'd set your meter to the highest ohms scale or auto if it's a digital meter. You would check from each of the 4 conductors to a known ground. There should be NO readings between any wire and ground. There should be no reading between any two wires either.
 
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Old 01-02-14, 06:45 AM
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I'm OK with the wire type. Under the concrete in the family room it runs through flexible plastic impermeable conduit until it exits under the crawl space, but maybe that's not totally code. The wire never actually exits the house foundation.

Your description of the breaker is exactly how it's wired. I've reviewed the wiring several times.

I also thought about checking the wire as you suggested after disconnecting both ends but I've not done that yet. I was going to check the various wires for continuity after disconnecting them but I'll check them both ways that you suggested.

Thanks for your help. I'll let you know what I find.
 
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Old 01-02-14, 07:56 AM
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flexible plastic impermeable conduit until it exits under the crawl space,
It is also condensate from air infiltration that can cause conduit to fill with water. Once it does the paper packing in the NM-b becomes wet, probably for ever. While PJ's test is good only a Megger can show a small leakage between wires and you only need 5ma to cause a GFCI trip. If you continue to have a problem I'd suggest replace the cable.

Meggers cost a lot more then new cable but there is a another way perhaps slightly more accurate to test the existing cable using 120 volt GFCI receptacle that might be more revealing then a multimeter. Disconnect on both ends. Pick two wires to test. Connect 120 volts to one end and a GFCI receptacle to the other. If the GFCI won't hold you have a problem. Test all wire combinations including bare ground and each insulated wire. The 120 volt supply ground is not connected when testing.
 

Last edited by Posternine; 01-02-14 at 08:18 AM.
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