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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7497
Experience:  Proven Professional 48 years Experience
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I have an outside electric circuit on a pool pump. Water got

Customer Question

I have an outside electric circuit on a pool pump. Water got into the conduit and now the GFI trips under load even though the water has been drained from the circuit. The circuit does not trip under no load. Any suggestions on what to check?
Submitted: 3 years ago.
Category: Electrical
Expert:  Mike G. replied 3 years ago.
Hi, I'm Mike and I'll be glad to assist you. Disconnect the motor and try the GFCI again. You may have to dry out the motor as well.
Customer: replied 3 years ago.

The GFI trips under any load (although I haven't tried a very low load like a 10 watt lamp). I tried the heat gun and a rotary tool and it tripped under each load. It does not trip without a load.

Expert:  Mike G. replied 3 years ago.
Where are you appling the load? At the breaker or on the circuit at the pump.
Customer: replied 3 years ago.

I am plugging the load into a new receptacle installed at the end of the circuit (at the pump location in a shed). I read 118 volts across the receptacle and also from the hot lead to ground. I read no voltage from the receptacle neutral to ground. The circuit worked fine before water got into the conduit but I changed the receptacle in order to raise it off the pump shed floor. The source of water was not in the pump shed, it was rain infiltration in the pull box near the house. The only other access I have to the wires is an intermediate pull box about half way from the house to the pump shed. I read the same voltages there.

Expert:  Mike G. replied 3 years ago.
Let me suggest that you temp a receptacle at the panel on the GFCI. Now put a load that tripped it when you had it in the shed. If it hold, the breaker is good and there is a fault in the circuit. If it trips then the breaker has failed and needs to be replaced.
Customer: replied 3 years ago.

I'll try it. If there is a fault in the circuit, will it eventually dry out or will I need to pull new wire?

Expert:  Mike G. replied 3 years ago.
What did you use for wire in the conduit?
Customer: replied 3 years ago.

Hard to remember, it was 20 years ago. Up to the first pull box where the water infiltrated it appears to be regular 3 conductor #12 wire (it has a white outer sheath). From that connection I pulled individual #12 wires because of the long run (it was easier to pull individual wires). None of it is gray covered outdoor cable.

Expert:  Mike G. replied 3 years ago.
If ou used a NM cable, that is more than likely what faulted. If can only be indoors. Any wiring outside is considered a wet location and the circuit should be either a THHW or THW in conduit or a UF cable.
Customer: replied 3 years ago.

I'm 99% certain it's THHW or THW. The fact that it worked fine for 20 years until the rain infiltration is somewhat revealing. If it's THHW or THW should I give it more drying time before biting the bullet and pulling all new wire?

Expert:  Mike G. replied 3 years ago.
Do the test that I suggested and let me know how it went. You said the cable had a white sheath, and that makes me think it was NM cable. If it was only means you were lucky for 20 years. If it is NM, replace it.
Customer: replied 3 years ago.

I will try the test. What I don't understand is why it only trips under load. If there is a fault in the circuit, wouldn't it trip without a load?

How do I get ahold of you after I try the test? It might be tomorrow.


Expert:  Mike G. replied 3 years ago.
Just return to the last post, as you have been. The question remains open.
Customer: replied 3 years ago.

Ok - I'll let you know. Thanks for your help.

Expert:  Mike G. replied 3 years ago.
You're welcome.
Customer: replied 3 years ago.
Mike - the problem is solved. Actually it's not solved yet but I know where the circuit fault is. Prompted by your suggested test, instead of hooking up a load at the GFI circuit breaker, I tried the load at the intermediate junction/ pull box that I mentioned earlier about 3/4 of the way between the house and the pump shed. The GFI held so the fault was between this box and the shed. I ran a new temporary feed from this box to the shed and the circuit is running.

Although the original problem was water infiltration into a junction/pull box at the house, the new fault was not caused by the water. I assume that when I raised the receptacle I nicked two or three wires when I hand cut the 3/4 inch conduit to add the new riser. I was carefully, but not careful enough. So now I'll pull new wire through this 25 foot run for the permanent fix.

I still don't understand why it held until a load was applied. Do you have an explanation for that? By the way, I am satisfied with your help.
Expert:  Mike G. replied 3 years ago.
I can't say for sure why it held, except that it was Murfey's Law. Glad it's resolved.
Customer: replied 3 years ago.
Expert:  Mike G. replied 3 years ago.
Please hit one of the rating selections to close the question. Thanks.

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