3 Phase Resi?

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jmellc

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Durham, NC
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Facility Maintenance Tech. Licensed Electrician
I haven't heard this question in a long time but I think I am right in saying that most power companies will not supply 3 phase power to a residence. Am I correct on this?
 
Kind of depends on the residence, doesn't it? In most of the USA, it seems like they'll easily go 400amp, or even 600, before going 3-phase. OTOH a friend in Australia just upgraded his house from single to three phase because of the `15+ KW of solar he now has. PoCo there was happy to do it, just pull out three wires of one size, pull in four slightly smaller, connect at the street and service switch; sounded like this isn't uncommon at all.
 
jmellc said:
I haven't heard this question in a long time but I think I am right in saying that most power companies will not supply 3 phase power to a residence. Am I correct on this?
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How many apartments are around you that have three phase feeding them?
Three phase costs more. There’s minimum bills, higher service charges, more CIA..

Not many want to pay that for what little they will use three phase.
 
jmellc said:
I haven't heard this question in a long time but I think I am right in saying that most power companies will not supply 3 phase power to a residence. Am I correct on this?
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I have designed PV systems for hundreds of single family residences, mostly in Texas. I have seen three phase services to them a handful of times. Most were 208/120V but a couple were 240/120V high leg. I can only remember one that wasn't a mansion; it was a smallish house with a very old 240/120V high leg service.
 
In the hot weather areas, it was not uncommon, many years ago, to find 3 phase high leg service with a delta breaker feeding a dwelling unit with air conditioning. However a new installation of 3 phase for a dwelling would be rare.

Here is some info about that use from an home inspection blog.
HighLegDelta2.jpg

​

A Short History of The High-Leg Delta Service​

It’s now just an interesting bit of electrical history, but in the 1950s and ‘60s residential air conditioning was in its infancy and a type of 3-phase service called “HIgh-Leg Delta” was used for homes with larger air conditioning compressors. Three phase motors are more efficient than single phase and use less current. High-Leg Delta provides 240 volts phase to phase, and the third “High Leg” (center-tapped on the transformer) delivers 208 volts.
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Here is some info on this use from a Square D document.
“A Delta Breaker is a load-center breaker with 2 plug-in stabs and a wire from the third terminal that goes to the third leg of a transformer. This allowed you to use a single-phase loadcenter and get three-phase power by running a third wire back to the transformer. The breaker is no longer available, and any replacement breaker will require installation of a 3-phase load center.”{/quote]
Delta breakers are prohibited by the NEC starting with the 1978 code. The current code section for that rule is 408.36(C).
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ggunn said:
I can only remember one that wasn't a mansion; it was a smallish house with a very old 240/120V high leg service.
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This house had a gutter that fed one three phase disco and two or three single phase discos on the A and C phases. Everything was rusted up; it was a mess. 1950's construction sounds about right.
 
Three phase residential is very unusual in Britain. The only one I knew of was a huge palace of a place near Hyde Park in London.
 
I’ve only seen two single family residential with three phase, one was in the Dominican Republic, and the other was a hunting lodge in Albany Georgia. It was even 480 volt three phase with a transformer in a closet on each floor. Full commercial kitchen in the basement. His wife was a Victoria Secrets model.
 
hillbilly1 said:
I’ve only seen two single family residential with three phase, one was in the Dominican Republic, and the other was a hunting lodge in Albany Georgia. It was even 480 volt three phase with a transformer in a closet on each floor. Full commercial kitchen in the basement. His wife was a Victoria Secrets model.
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If it had a full commercial kitchen and a three phase transformer on each floor it's maybe a bit of a stretch to call it residential.
 
One issue is home appliances are rated 230V, some may be rated for 200/230 volt, but a 230 volt appilance used at 208 volts will have its heat output reduced.
 
Besoeker3 said:
If it had a full commercial kitchen and a three phase transformer on each floor it's maybe a bit of a stretch to call it residential.
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It was single family, it was the guy’s vacation home. Yeah, he was pretty loaded. It was built like a southern plantation home. He stayed in it when he was dove hunting on the at least 1000 acres it sat on. Had a horse barn and if I remember right, a 500 kw generator. We installed all the lights to pass inspection, then he hired someone else to take them all down to install fixtures from France that were not UL listed. Some were so large they were hung with log chain!
 
hillbilly1 said:
It was single family, it was the guy’s vacation home. Yeah, he was pretty loaded. It was built like a southern plantation home. He stayed in it when he was dove hunting on the at least 1000 acres it sat on. Had a horse barn and if I remember right, a 500 kw generator. We installed all the lights to pass inspection, then he hired someone else to take them all down to install fixtures from France that were not UL listed. Some were so large they were hung with log chain!
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The ones I was speaking of mostly looked like hotels although they were legally single family residences.

Some people just have too much money. :D
 
hillbilly1 said:
It was single family, it was the guy’s vacation home. Yeah, he was pretty loaded. It was built like a southern plantation home. He stayed in it when he was dove hunting on the at least 1000 acres it sat on. Had a horse barn and if I remember right, a 500 kw generator. We installed all the lights to pass inspection, then he hired someone else to take them all down to install fixtures from France that were not UL listed. Some were so large they were hung with log chain!
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Spectacular, splendid, sumptuous living! Not your usual resi!
 
depends on where the 3-phase lines are located. The house I know has three phase was at the end of a street which had ocean/harbor on 2 sides and the 3-phase was for an elevator. Don't know why. Didn't ask
 
I would think some the large mansions out there possibly have three phase service to them though they may be considered to be a single family dwelling they are more similar to some resorts
 
Around here, PG&E requires a permit and inspection from the AHJ for most anything, and the biggest issue would be getting an electrical permit on a parcel zoned residential, and showing a 3-phase service.

At least in my area, that would be an almost impossible sell to the building Dept.

Unless your wife was a VS model, then who knows. 😳🤣

Or the property was zoned Ag, then you might, but then you’d have to show what you were doing with it, to be sure you were conforming to zoning regs.
 
It was common in the Phoenix area to have 3Ø for a air conditioner & single phase for everything else. There is a shop nearby that has a 480/277V service & has a bootleg MIL unit attached, had 277V lighting in the kitchen & living room, they took them down hot to replace them with ceiling fans, ended up disconnecting it for them so it would not let the magic smoke out of the fans.
 
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