Transformer to add general use gfci to 208 vac light pole?

spencer_electricianNovember 9, 2009

Thinking that this is impractical but if anyone knows of a way let me know. In a parking lot the building owner wants to add a receptacle to plug in a holiday sign. The pole light has 208 line to line and pulling in extra conductors would not be worth it for this use. Is there any transformer for this application that could be used as a step down from 208 to 120? Most I have seen from looking into a bit are more for control circuits and seems the price is very high even for under 1kva. Appreciate any thoughts before I tell him it can not be done.

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Ron Natalie

They make relatively small (and I mean less than 200A not physically small) 208->120 step downs, but even at the small size they're still pricey ($500) and they aren't rated for outside so you'd have to find some enclosure for them. So I suspect you're looking at at least $1000 before you even begin to consider the other issues.

What sort of holiday sign? Any chance of just getting the sign relamped or whatever it would require to run it off the 208?

    Bookmark   November 9, 2009 at 6:37AM
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spencer_electrician

I think they just want to plug in a few Christmas lights. Found some xformers as well $400+ Could one be mounted in a 3r enclosure or is there an actual wet rated xformer?

    Bookmark   November 9, 2009 at 10:26PM
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azlighting

Without spending a lot of money, I can't see how this would work besides using a step-down xfmr as stated before.

    Bookmark   November 9, 2009 at 11:15PM
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bus_driver

The 208 single phase supply to the pole is an oddity. Taken from a 208Y/120 transformer set? Wouldn't it be cheaper to have the POCO pull a neutral drop from the transformer set to the pole? That would supply the desired 120 volts.

    Bookmark   November 10, 2009 at 7:46AM
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spencer_electrician

Yes, the pole is an underground branch circuit derived from a 208y fed panel in the building. Nothing utility owned, middle of a hospital parking lot.

    Bookmark   November 10, 2009 at 10:23AM
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bus_driver

For the temporary situation, could the regular pole light be disconnected, the supply to the pole changed to 120 at the panel for the decorative lights, and then all restored when the lights are removed?

    Bookmark   November 10, 2009 at 11:42AM
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saltcedar

Why not 220v lights?

Here is a link that might be useful: 220V 10M 100 LED String Fairy Lights Color

    Bookmark   November 10, 2009 at 3:03PM
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spencer_electrician

Being a portion of a branch circuit (other pole lights through the lot) the voltage really can not be altered. I'll suggest that option of finding whatever lights they need in a European version. Then install a 208 receptacle with an in-use cover and make the appropriate ended SO cord.

    Bookmark   November 10, 2009 at 8:51PM
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aspen31

i think you should decide how large the xfmr NEEDS to be. new LED holiday lights don't draw much. if you can get by with 150va or less, then it might just fit inside the pole. if you need something larger and there isn't room on the existing circuit, then you've got another problem. i wouldn't source 240 volt lights, you'd just be creating another problem for the next guy, ie sourcing more lights when they're finished in 3 or 4 years.

rick

    Bookmark   November 11, 2009 at 10:05AM
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bus_driver

What if 24 volt LEDs could be found? A 208 to 24 volt transformer is quite common and low priced. But they are typically limited in VA size.

    Bookmark   November 11, 2009 at 1:13PM
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pharkus

Christmas lights with non-polarized plugs? If so, there is already uncertainty as to which conductor is hot at any given time, so I would have no ethical qualms about making one of them "float".

I'd get identical pairs of christmas light strings (ie, two 50-lamp strings, two 100s, etc) and wire them in series.

Since you'll be making series pairs for 240V, and supplying them with 208V, they'll be just ever-so-slightly dimmer than normal, but I'll bet any normal person would be hard-pressed to notice.

    Bookmark   November 14, 2009 at 8:27AM
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pharkus

This could be implemented very easily on some sets of christmas lights. Simply cut off both of the plugs, find the loop on the end of the first set, cut it, and attach the wires that formerly went to the plug on the second set. Fit an appropriate 208/240 plug onto the remaining wires (that used to go to the plug of the first set). Voila. 240V christmas lights.

    Bookmark   November 14, 2009 at 9:00AM
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spencer_electrician

Turns out what they are looking to power is a big deal. 4 foot deep footings to be installed and a bunch of assembly. Whatever it is they are only using for one week. The light pole has 3 or 4 poles ahead of it and heads off to an electric room on the 2nd floor of the building. I think given the temporary circumstances, they are better off running an extension cord over head to the roof of the building or using a generator. I'll try to find out what light is inside of it and why it can't be 208. Thanks for the help and won't bother to spend to much more thought/ time on this. The multi-millionaire that owns the building and a bunch of hospitals actually designed this whole idea up himself and the maintenance guys I'm talking to have been told very little from him.

    Bookmark   November 14, 2009 at 3:17PM
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pharkus

Here's a thought... it's a functional solution, but I'm pretty sure it's not code-compliant since there's absolutely no way for the "neutral" to be grounded... and it's just as temporary as temporary can get.

Pick up a 240V variac. Plug it into the 208. Adjust it for an output of 120V.

It's no worse than "balanced power" (two 60V hots and a ground).

    Bookmark   November 14, 2009 at 7:00PM
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