ECN Forum Forums Code Related Discussion NEC & other Code issues Single Phase or Three Phase?

Can a residential apt that is about 2200 sq. ft. have three phase service? or is it only for commercial? Is this a NEC issue or local building dept.?

It would be up to the POCO as to whether they would or would not make it available.
edit for spelling.

[This message has been edited by electricman2 (edited 12-20-2004).]

This is probably more a power company issue than anything else.

It is unlikely that a residence will have three phase power, with one exception:

Some larger apartment buildings have three phase power. Each apartment has there own panel with a three wire feeder, using two of the phases and the neutral. The wiring inside the apartment looks like single phase, but you only have 208V line to line, and you _always_ have to count the neutral as a current carrying conductor.


-Jon

I agree with you John. Our utility will feed condo projects with three phase transformers and feed 2 live legs and a nuetral (network) to the individula units. Our policy is three phase services are only allowed on our commercial or industrial rates, not residential rates.

For what it is worth, we have some residential 3Ø services.

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Charlie Eldridge, Indianapolis, Utility Power Guy

A little off-topic for NEC discussions, but here in Britain 3-phase is very rare for residential. Apartment blocks will take a 3-phase service, but each "flat" will get only a 2-wire single-phase service tapped from the 3-phase risers.

Continental Europe is a different ballgame. 3-phase residential power is very common there, even for quite low-power services.

 
In North America this seems to be a highly regional decision. NEC or local code may prohibit >150V-to-ground in residential structures—limiting interior circuits to 208Y/120V. Three-phase service in single-family homes has become more common in NorCal, for once prohibited at all costs, to permitted if at a commercial tariff, to permitted for larger service, but the cost of all additional {above 1ø} utility-provided facilities paid for prior to a single kilowatthour sold.

In some regions, 3ø single-family residential is old hat. 1200-ampere boards are not unheard of.

There is a home about a mile from me that has a 600-ampere switchboard, with dedicated 75kVA 208Y/120 padmount. Well pump and hermetic refrigeration compressors are 3ø, which clearly have much higher reliability that their 1ø equivalents.

[On Paul’s comments, there was a recent usenet thread re “standard” 15½-ampere 3ø 230/400V service for (assumedly single-family) residences in an area of Portugal.]

Mr. Eldridge,

I'm going to be ready to bring my newly refitted linear accelerator on line again soon and now this thing's going to need at least 3Ø. Do you have any advice on how I should approach my power company. By the way they are PG&E, If that matters.

Rknikko, I appologize for being off topic.

Editted because I never get it right the first time.

[This message has been edited by Physis (edited 12-29-2004).]

Hello Sam. Send me a PM on the other forum and I'll give you the name, address, and phone number of a friend at PG&E.

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Charlie Eldridge, Indianapolis, Utility Power Guy

 
Phys — You may be in luck. Based on some rules-of-thumb for data-center planning, if you want your own 600-ampere distribution circuit, you can get 12,000kVA of capacity on one of PG&E’s 12kV lines, or, up to 21,000kVA on a dedicated 21kV circuit. [Decent LINACs always need lots of extra focus-magnet power… and, or course, air conditioning on those balmy afternoons.]

If you want to go full tilt, and if it’s in their best interests, PG&E will serve as low as 2,000kVA demand at 69 or 115kV.




[This message has been edited by Bjarney (edited 12-29-2004).]