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230 3 phase or 120/208 3 Phase service?

I have been talking with Duquesne Light in Pittsburgh, PA about getting

3 phase to my commercial property. The field technician thinks I may be entitled to 3 phase at no cost because of the commercial building. However since I already have single phase service they "might" put up the transformers for a 230 3 phase at no cost to me. I would have to set a pole ~$600 + do the wiring. The only problem is that the 230 3 phase would not have a neutral. I could PAY for 120/208 3 phase but I don't know the cost of that yet. So this additional service would only be for 3 phase and I could not tap off to run my 110 outlets. I was hoping to be able to save money and tie it all together with on bill instead of having 2 different meters. I don't do a lot of 3 phase work but it would be nice to have for my occasional need to run my Mill, lathe, welder, compressor. They indicated that I could not get 480 3-phase for some reason. I don't want a huge bill every month and have read other stories where people were charged a minimum per month for the utility to justify the cost of installation.

Any thoughts would be appreciated on whether 120/208 would be more cost effective than 230 3 phase? Most of my equipment is 230/480V

Reply to
gtslabs
Loading thread data ...

Will your equipment run on 208? If not its an easy decision.

We beat this subject to death a few weeks ago...

Reply to
Chuck Sherwood

Chuck, can you provide the thread link?

Reply to
gtslabs

Can you justify buying a transformer to power the 110 circuits?

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Reply to
Jerry Martes

I have not priced them yet. But the problem with the 230 is that it does not have a neutral wire.

Reply to
gtslabs

Why don't you get 240 volt three phase, where they center-tap one of the transformers? Then you get 2/3 the number of

120 volt branch circuits that the 208 star setup gives.

Just stay away from the wild leg.

Jim

Reply to
jim rozen

There probably doesnt need for there to be a neutral on the 3 phase if the power company doesnt supply one. The neutral for the 110 circuits will be supplied by the step down transformer you buy.

Jerry

Reply to
Jerry Martes

Ask the power company if you can get 120/240V "Open Delta" 3-phase, especially if this will be the sole service to the shop - no separate

120/240V 1ph lighting panel. This is done all the time for residential buildings when most of the load is 1Ph, but there is a small 3Ph draw like a hydraulic elevator motor.

They install a regular (but large) 120/240V single-phase transformer that has a normal neutral, and can also be used to supply other neighbors with 120/240V 1ph power. The difference is they hang a second smaller 240V single transformer next to it on the pole.

The small transformer provides the third phase, but it is somewhere around 190V to ground instead of 120V like the other two supplied from the large transformer - so you have to be VERY careful to mark that "High" or "Wild" leg with orange tape as a warning. And never hook any 120V loads to it, or you will quickly let the smoke out of anything thats plugged in.

You can hook up 240V 1ph loads to the high leg and either of the other two, which will balance out the loads if you have several 240V

1ph loads running at once. (Yes, the syntax sucks on the first half of that sentence, but I dont feel like fixing it tonight.)

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Reply to
Bruce L. Bergman

Snip

NO YOU do NOT want to do that. Connecting loads to the leg which actually has the transformer is OK, but connecting single phase loads across the "Open" side of the delta tends to start to collapse the delta that you get.

jk

Reply to
jk

If you already have 240/120 single phase service all the electric co. does is hang two more pole transformers for the other leg. They could even get away with one transformer and give you open delta.

240 center tapped delta is what you want. The center tap gives you a neutral for the single phase 120/240.

John

Reply to
john

Hmmm... Never heard that one. I'll have to remember to research it if I ever come across another Open Delta service where they've hooked up 1Ph loads like that.

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Reply to
Bruce L. Bergman

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