I want to add GFCI to a pool light circuit. I traced the circuit to a Square D XO subpanel. The XO series breaker box is obsolete and the only breakers I can find are regular used ones (no GFCI breakers for XO). It would be a huge job to replace the entire subpanel just for this circuit, because it contains a maze of other old circuits. Is there any GFCI breaker that will plug into the XO box? Is there a GFCI device that I can connect to the junction box in the pool equipment room? Maybe a simple one switch circuit breaker box that can connect through a knockout.. something that would install without turning it into a huge construction job?

You can simply add a GFI outlet in the pool equipment room somewhereon that circuit before the pool lighting, or use a blank GFI beforethe pool lighting like this: offer the same protection. You could probably mount the box onthe breaker cabinet with a knockout, or somewhere on a wall in theequipment room.

How to add GFCI to circuit with obsolete breaker box?

May 30, 2009 26 Replies

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RBM 17 years ago

The GFCI device senses the current going out on the hot leg and returning on the neutral. If they are not equal, current is leaking to ground, and the device cuts out. Where your landscape lights are concerned, the neutral wire is probably broken, so to make the lights work, he just connected the bare ground as a neutral replacement. That circuit won't work on a GFCI device as there would always be leakage into ground on the bare wire, causing an imbalance. It is also a potentially dangerous situation for anyone that may touch one of these fixtures. If they happen to be touching anything that is better grounded than the ground wire, they could become part of the circuit.

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Nate Nagel 17 years ago

no.

the GFCI must be in a box where both hot and neutral are available - it has connections for both. The GFCI compares currents between the two wires, and if they differ by more than 5 mA or so, it'll shut off the power. this is why it also can't be used to replace a switch used in a "switch leg" configuration, because there's no neutral available there.

nate

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Mark 17 years ago

I simply pulled the old non-gfci circuit that ran to my detached garage out of the panel, then ran a short line to a surface mounted box a few feet from the panel with a gfci outlet. I then pulled the garage line into that so now I have a much needed outlet near my panel and the garage and underground line leading out to it is protected.

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iwdplz 17 years ago

That wiring makes sense and I tried it just now, but the GFCI trips immediately so the pool light never turns on. I also noticed that the landscape light doesn't turn on anymore - so I jumpered the feed neutral to the pool light neutral like it was before, and now landscape light turns on ok via the other switch. So the pool light and landscape light must be using the same neutral. I am puzzled why the GFCI is tripping and how I should wire it given this new info..

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iwdplz 17 years ago

Update:

When I add the landscape light to the Load terminal in the GFCI combo device (instead of a separate switch), it works. Now the GFCI works for both the pool light and landscape lights. Except now I don't have independent control over them. That's fine because the landscape lights are next to the pool anyway. So this way I have GFCI protection for ALL of the outdoor lights near the pool.

Why does this GFCI tripping happen with a separate landscape light switch? My guess is that by turning on the landscape switch, it causes the current to drop unevenly in the circuit legs and the GFCI senses a slight mismatch. So by combining them together the current drop is evenly matched.

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iwdplz 17 years ago

This is the best/correct hookup because now I can use the outlet regardless whether the switch for the lights is turned on or off.

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iwdplz 17 years ago

I think this is what happened:

"Multiwire circuits have two or more ungrounded conductors sharing a common neutral, as in a 120/240V, single-phase circuit or a 208Y/120V, 3-phase circuit."

"GFCI receptacles can be used on multiwire circuits, but they must be wired such that the neutral on the load side of the GFCI is not shared by two ungrounded conductors. Failure to observe this requirement will result in a differential current any time a load served by an ungrounded conductor not connected to the GFCI is energized, immediately tripping the GFCI."

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