Will 12vac replacing 120vac mitigate stray current situation?

rmully · Sep 29, 2023

I have an inground pool with a 22 year old, 120vac light fixture in a niche connected to water-holding conduit running to a switch in an outbuilding. I removed the fixture to clean the niche. The fixture was just floating at the surface, still connected, with the wall switch off. A little extra wire coiled in the niche allows the fixture to be removed. I felt very noticeable stray current when putting my hand into the niche, a sharp tingle - not painful. I don't fully understand pool bonding, and doubt that mine has it because I have read that if properly bonded, stray current issues may be avoided. I also read that the hot can be switched off to something that is causing stray current, so I completely disconnected the fixture cable at the feed point at the switch in order to disconnect neutral and ground as well as hot, which was previously switched off. I could no longer feel any trace of current and stopped using the light, leaving it disconnected. Now I'd like to get the light working but the most attractive cost of a replacement housing I found is $600 - 800. I think that is stupid money for something like that. For about $150 I can leave the fixture in place, buy a 12vac 35w LED bulb, new fixture gasket and transformer, converting the thing from 120vac to 12vac. Assuming that the problem is in the fixture or its wire in the conduit, will that mean that because a 12v line is leaking through the water instead of a 120v line, the seriousness of the situation is minimized or eliminated?

DPG · Sep 29, 2023

I don't know anything about the regs over there, maybe our US member Megawatt can advise. But, I would definitely prefer a nice 12V powered fitting rather than the ancient 120V one!

Do you have GFCI protection on these circuits?

Megawatt · Sep 29, 2023

rmully said:
I have an inground pool with a 22 year old, 120vac light fixture in a niche connected to water-holding conduit running to a switch in an outbuilding. I removed the fixture to clean the niche. The fixture was just floating at the surface, still connected, with the wall switch off. A little extra wire coiled in the niche allows the fixture to be removed. I felt very noticeable stray current when putting my hand into the niche, a sharp tingle - not painful. I don't fully understand pool bonding, and doubt that mine has it because I have read that if properly bonded, stray current issues may be avoided. I also read that the hot can be switched off to something that is causing stray current, so I completely disconnected the fixture cable at the feed point at the switch in order to disconnect neutral and ground as well as hot, which was previously switched off. I could no longer feel any trace of current and stopped using the light, leaving it disconnected. Now I'd like to get the light working but the most attractive cost of a replacement housing I found is $600 - 800. I think that is stupid money for something like that. For about $150 I can leave the fixture in place, buy a 12vac 35w LED bulb, new fixture gasket and transformer, converting the thing from 120vac to 12vac. Assuming that the problem is in the fixture or its wire in the conduit, will that mean that because a 12v line is leaking through the water instead of a 120v line, the seriousness of the situation is minimized or eliminated?

The best thing that I can tell you is it’s supposed to be GFCI protected at all times. Even if you convert it to 12vdc will still have to be GFCI protected also. Good luck

Avo Mk8 · Sep 30, 2023

If you do go ahead with the plan to use a 12V supply, I would encourage you to use one that is made to the equivalent of the European Separated Extra Low Voltage (SELV) standard. Meaning that the primary and secondary side are separated by specific insulation techniques, so any single fault in the unit cannot result in anything higher than 12V ac appearing on the output (and hence get to the pool).
There are 12V transformers specifically made for swimming pool lighting, and although more expensive, if you shop around (reputable outlets, not on-line marketplaces!) you should be able to find the spec you need at a reasonable price.

DPG · Sep 30, 2023

Avo Mk8 said:
If you do go ahead with the plan to use a 12V supply, I would encourage you to use one that is made to the equivalent of the European Separated Extra Low Voltage (SELV) standard. Meaning that the primary and secondary side are separated by specific insulation techniques, so any single fault in the unit cannot result in anything higher than 12V ac appearing on the output (and hence get to the pool).
There are 12V transformers specifically made for swimming pool lighting, and although more expensive, if you shop around (reputable outlets, not on-line marketplaces!) you should be able to find the spec you need at a reasonable price.

Very good advice. Don't use any transformer that is termed 'auto-transformr' as it will not provide isolation from the mains side.

rmully · Sep 30, 2023

Thanks for the help. No matter what I do with the light, I'll put a GFCI breaker in the sub panel. The light is on a dedicated circuit. Regarding transformer advice, attached is a pic showing two products I was looking at. I'm assuming the gold highlighted wording with product A is what you are recommending. Not sure about loop coil in product B, but guessing it doesn't have that separation.

Avo Mk8 · Sep 30, 2023

Product A appears to fit the requirement, and does at least refer to the separation. Is the "not available for e-commerce purchase" a complication for you?
Product B contains what I know as a toroidal transformer, an alternative version of magnetic 'circuit' that has become quite popular, and I believe is a little bit more efficient, though that is not a serious consideration here. Nothing in the ad reassures me about its insulating or 'separation' qualities.
I suggest sticking to products that appear to be aimed at pool use, rather than those that are advertised for multiple uses "including pools"! if you see what I mean!