Replacing Halide Roadway lights with LEDs


Thread Starter

David Flora


If you could help me I'd really appreciate it. I have about 30 Metal Halide roadway lights that I would like to replace with LED lights. LED nameplate says they will run on 277V, existing lights have 3 conductors going to them: 1 is ground/green, across the other 2 is 480V, either one of the 2 wires alone to ground is 277V. Can I use just one 'hot' wire and ground to power the new LEDs? I'm thinking I can if I make sure loads are balanced.

<b>Moderator's note:</b> This question was originally posted to an old thread. I made it a new thread.

Bob Peterson

I think you would be better served by taking this question to a forum better suited to it like

In general I think what you want to do is a very bad and unsafe idea. The green (ground) wire is not supposed to ever be a current carrying conductor unless there is a fault, and then it conducts only for the few milliseconds it takes for the fault to clear.
<b>***No, do not do that!***</b>

Running normal non-fault current in a grounding (as opposed to groundED) conductor is dangerous and that you would even ask the question indicates you should not be tackling this project without qualified help.

However....just so you know how much work and cost will be involved when you get someone to do it, don't forget that you have a spare conductor placed there with the intention of carrying normal non-fault current -- the second 480V wire. Now it will need to be moved to a different connection on the panel/transformer end, and might need to be taped to a different color, such as white, to indicate a grounded conductor, but you shouldn't need to pull any new wires. A given number of watts will require more amps at 277 than at 480, so the wires might be too small, except that the LED lights are probably enough lower in wattage that they can use the same wires even at 277. In any case, your electrician can tell you how many amps the wires can safely carry and you can choose your LEDs accordingly.
Thanks for your answer. I would very much like to get out of the "you're not trained call someone who is' situation. I understand this from a safety standpoint but more knowledge in this area would be helpful to me.

Any suggestions for resources?

Thanks You again for your answer.

Bob Peterson

Some of this stuff is non-trivial and does not lend itself well to a 2 or 3 paragraph answer.

There are all kinds of issues and it is hard to give answers to someone who does not even know what questions to ask.

There are all kinds of things you might be able to do but what you suggested initially you wanted to do is potentially quite hazardous.

You said these are roadway lights. Is this a government road? If so you will have to abide by all the various government rules that apply, many of which are fairly arcane, and vary widely from entity to entity.

The least expensive answer might (and I emphasize might) be to add a small 480:277 V xfmr at each pole. It would need primary and secondary fuses, but would not need to be real big. just large enough to handle whatever current the new LED light at the pole requires. Depending on how it is currently wired you might be able to get by with fewer transformers. Someone competent would need to look at the existing wiring diagrams and figure out how best to approach it.

It is hard to give you any serious advice because we have very little in the way of actual information with which to base such suggestions.