GFCI Breaker Tripping Spa Light

eaposition

I have a problem with GFCI breaker tripping on a Spa (hot tub) light. Here's the details.

This is a built-in spa (not premanufactured) built 20 years ago. There is a underwater Sta Rite (Pentair) enclosure built into the gunite wall. Installed in that niche is a Sta Rite 120 volt 250 watt fixture. The fixture is fed by a 16/3 captive cable that runs in a conduit from the niche to the equipment room on the other side of the wall. The 16/3 cable is connected via wire nuts in a jbox to 3 14 gauge stranded cables (black, white, green) in a conduit from the subpanel. The fixture is alone on a 20 amp GFCI breaker in the spa subpanel. The GFCI breaker trips as soon as it is set. Until recently, the light had been working fine. I swapped in a new breaker with the same results. Given that the fixture is 20 years old, I installed a new Sta Rite fixture. It also trips the breaker immediately.

I have tried a number of things to try and locate the problem but with no success. I took the new fixture and captive cable out of the spa and conduit and connected it directly to the breaker. That worked fine. With the fixture and cable back in place, I disconnected the ground wire in the jbox. The strange thing is that, with the ground wire disconnected, the breaker did not trip as long as the fixture was out of the water and not in its niche. As soon as the metal housing of the fixture touches the water, even slightly, the breaker trips. With the light fully installed back in the niche, one by one I disconnected the 3 wires in the jbox. With the ground wire and hot lead connected but the neutral disconnected, the breaker did not trip. The neutral connected by itself or the neutral and the ground connected caused the breaker to trip even without the light on. That tells me the fault is coming from the neutral. The problem is I can't imagine how the fault is occuring. It's a new fixture. The captive cable is new. There is nothing else on the circuit.

Any ideas?

Thanks.
Tom.

gregzoll

Stop using the spa before you kill someone, because the GCFI is telling you that there is a problem. Call a reputable electrician that knows pools and spa equipment, and have them fix it. If the GCFI is tripping, that is telling you there is a problem of current leakage from something (could be the pump, light, nearby underground electrical, etc.).

jbfan

Sound like the wire from the breaker to the connection of the light fixture.
If The ground and neutral touch, the gfci will trip.

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Speedy Petey

Well the only thing left is the wire.
Replace it with the correct #12 wire, OR replace the #14 as it is and also replace the breaker with a 15A.
It is NOT correct as it stands.

jbfan

Thanks Petey, missed the wire size part.

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Yes I am a Pirate, 200 years too late. "Jimmy Buffett"

eaposition

My apologies. The wire is #12.

Scuba_Dave

I hope the new light isn't a 250w light...that must help heat the spa
Maybe an LED instead ?
My pool light only takes 50w & lights up the whole 16x32 pool

eaposition

The last test was to eliminate the wire and conduit from the subpanel to the jbox as a possible source. The new fixture has 30' cable and only 10' was needed to get to the jbox. The addditional 20' has not been cut off yet. That 20' was long enough to reach the subpanel and connect it directly to the breaker. Same problem. The breaker tripped.

I had already put my megger on the breaker to jbox wire and it was good but decided to, as a last resort, eliminate that wire as a problem source. I can't use the megger on the new fixture because the new fixtures have built in heat overload circuitry.

Stubbie

With the light installed disconnect the the hot and ground in the j box. Connect only the neutral...see if the breaker trips.

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Stubbie

eaposition

It does trip. Here are the combinations:

hot only connected=no trip
hot and ground=no trip
neutral only=trip
neutral and ground=trip

My last resort is to get a new breaker and see what happens. The one in the subpanel now is 10 years old. The other breaker I tried was also an old one from another subpanel. I'm wondering if the old fixture was tripping due to a short in the cable or fixture and that the new fixture is tripping because the relatively old breaker can't handle the heat overload circutry in the new fixture. A last resort before I hang a flashlight over the spa and abandon the light :-)

Tom

Stubbie

Tom

If the breaker hot wire is disconnected at the jb and the neutral only is connected then you have current from another source getting on the neutral.

You said it trips as soon as the metal housing touches water in the spa ?

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Stubbie

eaposition

There was one other combination that was not included in the above list:

hot and neutral connected but ground not connected=no trip

This is an interesting combination. With the hot and neutral connected but not the ground, the breaker would hold if the fixture was out of the water. As soon as even a small part of the fixture housing hit the water, the breaker tripped.

Based on another recommendation I read, I tried the following. I shut off the breaker. The neutral wire to the load was removed from the breaker. The voltage between the disconnected load neutral wire and the neutral bar in the subpanel was around 5 mv. That seems good. Then the power to the subpanel was removed and the resistance between the disconnected neutral and the neutral bar was close to zero. That should have been infinite. When the ground wire to the fixture was disconnected the resistance went infinite.

Stubbie

Tom

What is the resistance between your neutral and ground wires if the are disconnected at the junction box and connected correctly at the fixture?

What is the resistance between the metal housing and the neutral at the fixture?

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" One nice thing about the NEC articles ... you have lots of choices"

Stubbie

eaposition

Neutral to ground is almost zero ohms. Doesn't sound right. It's as if the ground and neutral are connected within the fixture itself. It could be the thermal overloaded circuitry in the fixture that is causing this reading?

Ditto for the metal housing to neutral.

Tom

Stubbie

Well you have found your problem. Both tests should read open (infinite).

Doubtful its the thermal overload, it should be series with the hot wire
only..

Can you post pictures of the fixture and the niche?

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" One nice thing about the NEC articles ... you have lots of choices"

Stubbie