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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?
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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