# residential house 3 phase???



## Stub (Apr 19, 2010)

Murphy said:


> the other has 3 phase breakers in it..


What's a 3 phase breaker? A 3 pole?

How many wires coming into the house from the pole?


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## william1978 (Sep 21, 2008)

I have seen several house's with 3 phase in them. One of them was a 1000a or 1200a.


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## MDShunk (Jan 7, 2007)

william1978 said:


> I have seen several house's with 3 phase in them.


They're normally really big houses, but every once in a while I run across a fairly normal looking house with a 3-phase service. Makes me wonder why. Near as I know, there's always been a substantial fee from the power companies to originally supply a dwelling with 3-phase.


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## MF Dagger (Dec 24, 2007)

I've seen only a couple like that that are smaller houses. 1 used to be a post office long ago and the other used to be a grocery store then a butcher shop and then the ramshackle dump that I had the pleasure of working in.


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## william1978 (Sep 21, 2008)

MDShunk said:


> They're normally really big houses, but every once in a while I run across a fairly normal looking house with a 3-phase service. Makes me wonder why. Near as I know, there's always been a substantial fee from the power companies to originally supply a dwelling with 3-phase.


 Yea, One of the had a chiller and it was right on a golf course, so to my knowledge 3 phase was right there at the house. This house had 7 people that worked at the house full time to keep it up. I was just blown away.


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## william1978 (Sep 21, 2008)

I just remembered I wired a condo building several years ago and all of the units on the top floor had 3 phase in them 200a and 400a panels in them, and the only thing that was 3 phase was the RTU's.


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## Rudeboy (Oct 6, 2009)

I've seen a few 3-phase service drops in residential. Usually there's some sort of shop on the property which utilizes it.


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## Murphy (Dec 10, 2009)

Stub said:


> What's a 3 phase breaker? A 3 pole?
> 
> How many wires coming into the house from the pole?


 
yea i will have to observe more when i go there tommorrow.. but my point is ....if anything shouldnt this be 2 phase because there are only two phases running down the street..? the guy was an engineer.. i think he basically has two phases coming in his house.. and the one panel with the three pole breakers is probably using a combination of the two phases to mimic three phase.. again,,,ill have to read some lables and see what these breakers are.. I have yet to see anything around the house today that would have taken 3 phase


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## MDShunk (Jan 7, 2007)

Sometimes they'll arrange the 3 phase conductors on the poles in a diamond configuration, and it might look at first glance like you've only got two.


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## Murphy (Dec 10, 2009)

MDShunk said:


> Sometimes they'll arrange the 3 phase conductors on the poles in a diamond configuration, and it might look at first glance like you've only got two.


 na this pole just has the classic one on each side


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## Magnettica (Jan 23, 2007)

Murphy said:


> yea i will have to observe more when i go there tommorrow.. but my point is ....if anything shouldnt this be 2 phase because there are only two phases running down the street..? the guy was an engineer.. i think he basically has two phases coming in his house.. and the one panel with the three pole breakers is probably using a combination of the two phases to mimic three phase.. again,,,ill have to read some lables and see what these breakers are.. I have yet to see anything around the house today that would have taken 3 phase


Check the A/C condensing units. That would be a great candidate for the 3-phase supply. :thumbsup:


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## MDShunk (Jan 7, 2007)

Magnettica said:


> Check the A/C condensing units. That would be a great candidate for the 3-phase supply. :thumbsup:


The equipment is also a heck of a lot cheaper, and longer lived, if you can serve it with 3-phase. When you start to get around 5-ton and bigger, that's when you start to think seriously about whether you can reasonably serve it with 3-phase.


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## Murphy (Dec 10, 2009)

Magnettica said:


> Check the A/C condensing units. That would be a great candidate for the 3-phase supply. :thumbsup:


yea they both said 1 ph on the motor


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## Murphy (Dec 10, 2009)

thanks for all the suggestions guys.. ill come back with more details tommorrow


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## Magnettica (Jan 23, 2007)

Murphy said:


> thanks for all the suggestions guys.. ill come back with more details tommorrow


And pictures :thumbsup:


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## micromind (Aug 11, 2007)

My house is served by a 120/208 3 phase wye. Mostly because of all the 3 phase shop equipment that I had before I built it. My A/C units and my well pump are 3 phase too.

If the house in question is served by overhead power lines, there must be 3 or 4 of them to get a 3 phase service. With two, you can only get single phase. 

Most POCOs will use two or 3 single phase pole-mount transformers to supply 3 phase, but I've seen a single pole-mount can that had 3 bushings on top for the primary, and 4 on the side for the secondary, and fed an obvious 3 phase motor. 

Just because there's a 3 pole breaker installed in a panel by an electrical engineer doesn't mean there's 3 phase power available.

Rob


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## MDShunk (Jan 7, 2007)

micromind said:


> Just because there's a 3 pole breaker installed in a panel by an electrical engineer doesn't mean there's 3 phase power available.
> 
> Rob


Yeah, could have been a few free breakers he got from work, and he's using them on three different 12-2's or something. 

I do some work for a couple that owns a bunch of gas stations, and they provided me with a box of used breakers to use for their basement remodel. Many of them were switched neutral breakers. I figured, "what the heck" and used a few switched neutral breakers as a novelty. That'll really mess with the next guy's head.


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## varmit (Apr 19, 2009)

Murphy said:


> OK so i believe i know how transformers work and the difference between 3 ph and 1ph..
> 
> my co worker and I were at a fairly large house today.( an owner a while back was an electrical engineer) the house has two panels. one has single and double poles only.. the other has 3 phase breakers in it.. there is a ct cabenit right before the two panels... I did not open it.( i will tomorrow) anyway, i dont think its three phase because there's only two lines running down the street.. there were two regular single phase transformers on the powerpole..(again, didnt get a good look at the connections, will do tommorrow) but without a phase converter how is it possible to have 3 phase in this setup. my co worker was saying its a 3 phase transformer on the pole..but that dosnt make sense to me.


From what you describe, I would say that this is a 230/120 volt "High Leg" service. These were very common, in the past, on small commercial. Yes, on this system only two phases are required on the primary side. Normally there are 2 transformers connected on the primary. The "High Leg" will read about 208 VAC to ground. The other 2 phases will read 120 VAC to ground. between any 2 phases will read about 230 VAC. THE "HIGH LEG" PHASE CAN ONLY BE USED ON 230 VOLT EQUIPMENT OR 3 PHASE LOADS WITH NO 120 VOLT EQUIPMENT ATTACHED. The 120 VAC loads are connected phase to neutral on the other 2 phases.


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## Murphy (Dec 10, 2009)

varmit said:


> From what you describe, I would say that this is a 230/120 volt "High Leg" service. These were very common, in the past, on small commercial. Yes, on this system only two phases are required on the primary side. Normally there are 2 transformers connected on the primary. The "High Leg" will read about 208 VAC to ground. The other 2 phases will read 120 VAC to ground. between any 2 phases will read about 230 VAC. THE "HIGH LEG" PHASE CAN ONLY BE USED ON 230 VOLT EQUIPMENT OR 3 PHASE LOADS WITH NO 120 VOLT EQUIPMENT ATTACHED. The 120 VAC loads are connected phase to neutral on the other 2 phases.


 
varmit you are the man!.. that is exactly what it is... thanks for the knowledgable input.. Im glad i have a straight forward answer to explain to everyone.


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## waco (Dec 10, 2007)

Tipoff will be four wires coming off a single transformer. Probably a better system than what we have for residential now. Well, better for the consumer, not so much better for the PUCO.


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## jw0445 (Oct 9, 2009)

MDShunk said:


> They're normally really big houses, but every once in a while I run across a fairly normal looking house with a 3-phase service. Makes me wonder why. Near as I know, there's always been a substantial fee from the power companies to originally supply a dwelling with 3-phase.


MD- In our area PPL just charged my customer $ 1720.00 for getting 3-phase installed and said there would be a one time equipment charge if he didn't use enough power but I forget what the minimum was. FYI it's an 800 amp.


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## MF Dagger (Dec 24, 2007)

Murphy said:


> varmit you are the man!.. that is exactly what it is... thanks for the knowledgable input.. Im glad i have a straight forward answer to explain to everyone.


You should verify that this is what it is and then mark it. Enough people are confused by them that do commercial a lot that it is bound to cause problems down the line.


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## slickvic277 (Feb 5, 2009)

I've seen some really old homes in the historic parts of Philadelphia that have had 2 phase power. The only homes I've seen with 3 phase are large luxury houses that are new. I always found it interesting.


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## william1978 (Sep 21, 2008)

Magnettica said:


> And pictures :thumbsup:


 Pictures would be great.:thumbsup:


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## jwjrw (Jan 14, 2010)

Murphy said:


> varmit you are the man!.. that is exactly what it is... thanks for the knowledgable input.. Im glad i have a straight forward answer to explain to everyone.


 
I'm not going to say it is not a high leg but it would make no sense not being able to use the B phase in a residence. Almost all loads in a house are 120v. If it is you probally have a lot of empty spaces on the B phase.


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## Murphy (Dec 10, 2009)

jwjrw said:


> I'm not going to say it is not a high leg but it would make no sense not being able to use the B phase in a residence. Almost all loads in a house are 120v. If it is you probally have a lot of empty spaces on the B phase.


 correct.. they put the 208 leg on the c phase.. witch is completely empty lol... i dont understand why this house had it installed this way. maybe back in the day it was needed.. certainly just a hassel now. and ill try to get some pics monday.sorry for the wait


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## Electric_Light (Apr 6, 2010)

"two phases" is the norm for apartments and dormitories if the building has elevator(s), because the building would already have three phase service. 208/120 is a true two phase, but 240/120 from center tapped delta isn't because it's just one of the phases that's center tapped. 

The individual units are wired A/B, B/C, A/C in such a way to maintain a reasonable phase balance. 

The elevator(s) and any other large shared motors(central HVAC) utilize three phase.

One of the apartments I lived in had a thermostat that only controlled the fan and all the heating/cooling water was provided by basement equipment room. The chiller was thermostatically controlled based on outdoor temperature. The management only used manual over ride if there was enough complaints.

Aside from those stair climbers, pneumatic and winch type light duty residential elevators, the elevator car weighs as much as a road car and the motor is usually large enough to require three phase(by utility regulations) service.


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## slickvic277 (Feb 5, 2009)

Electric_Light said:


> "two phases" is the norm for apartments and dormitories if the building has elevator(s). 208/120 is a true two phase, but 240/120 from center tapped delta isn't because it's just one of the phases that's center tapped.
> 
> The individual units are wired A/B, B/C, A/C in such a way to maintain a reasonable phase balance.
> 
> ...


Nope. a true 2 phase system is a five wire system. 4 hots and one neutral.

It works like this,

Line A1 to Line B1 = 240v

Line A1 to neutral = 120v

line B1 to neutral = 120v 

Line A2 to Line B2 = 240v

Line A2 to neutral = 120v

Line B2 to neutral = 120v

Now to confuse you even further,

Take either A1 or B1 and go to Either A2 or B2 and you get some where between 160 - 175 volts.
I believe the phase were 90 degrees apart. Or almost.

It's an old system and it's only in use still in some very old area's.

There is also other voltages that were used in the old 2 phase system but the ones above are the only ones still in use, that I've seen.

There's also a 2 phase 4 wire system with no neutral but I've never seen one active.


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## Electric_Light (Apr 6, 2010)

slickvic277 said:


> Nope. a true 2 phase system is a five wire system. 4 hots and one neutral.


:001_huh: I guess I'm not old enough to know this. I wiki'd it. Are the two phases separated by 90 degrees?

What I meant by "true two phase" though, is that the phases are shifted, not simply mirroring each other with inversion (or center tap) and a 180 degree difference. 

Both 0, 90 as well as 0, 120 are capable of induction motors on their own.


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## slickvic277 (Feb 5, 2009)

Electric_Light said:


> :001_huh: I guess I'm not old enough to know this. I wiki'd it. Are the two phases separated by 90 degrees?


Yeah there separated by 90 degrees. The original generators at Niagra falls were two phase generators here's an interesting read on two phase;
http://www.3phasepower.org/2phasesystems.htm


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## Magnettica (Jan 23, 2007)

Mike Holt had an interesting email newsletter a ways back on 2-phase wiring. From what I remember Philly had a lot of it in the city. I've never seen any 2-phase around here but I suspect Newark used years ago.


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## slickvic277 (Feb 5, 2009)

Magnettica said:


> Mike Holt had an interesting email newsletter a ways back on 2-phase wiring. From what I remember Philly had a lot of it in the city. I've never seen any 2-phase around here but I suspect Newark used years ago.



There's a lot in Philly but I would say the majority has been replaced in recent years. The greatest concentration would be in the "Olde City" section around 2nd and Market and that area.

It always creates confusion when it's first encountered in it's original equipment. Imagine opening a panel and seeing 5 wires.:laughing:

A while back I worked out in Pottstown PA in an old abandoned factory. There service and all the equipment was 2 phase 5 wire at 550v. I wish I would have took some pictures, very interesting stuff. It was all dead and we replaced everything.


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## slickvic277 (Feb 5, 2009)

Magnettica said:


> Mike Holt had an interesting email newsletter a ways back on 2-phase wiring. From what I remember Philly had a lot of it in the city. I've never seen any 2-phase around here but I suspect Newark used years ago.



Most heavily industrialized N.E. city's had it at one time. I'm sure it was used in Newark as well. Back before Philly had any high rises we had tons of factories we were very industrialized. Back in the day we were known as the "ELECTRIC CITY" because of the old Philadelphia electric company generating station on Delaware ave.

The building is still there, a lot of the 2nd transformers movie was filmed in that building.


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## danickstr (Mar 21, 2010)

So to summarize, this guy has a regular single phase panel and a high leg delta panel as well?

With the high leg landed on the C pole, if I have it right. I could see a guy doing it like that, since the POCO lands them there on the meter. now I of course wouldn't (ahem) but it would make sense if you hadn't seen them before, or an engineer/HO was watching over your shoulder..


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## micromind (Aug 11, 2007)

It was pretty common years ago around here to have the high leg on C phase. 

It was also common to have a single phase panel, and a smaller 3 phase one right next to it. Usually, they both had main breakers, and were double-lugged in the meter can.

I still see delta breakers sometimes, though it's pretty rare. Mostly 30s and 60s. Sometimes they fed a panel, sometimes just one or two motors.

Rob


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## frenchelectrican (Mar 15, 2007)

slickvic277 said:


> Nope. a true 2 phase system is a five wire system. 4 hots and one neutral.
> 
> It works like this,
> 
> ...


 
Let me add a item or two in here in the mix 

Three wire *two* phase it will look simaiur to leigt three phase supply however the both voltage and amp reading will be diffrent.

the L1 et L3 is normal phase format however the L1 aka Phase 1a while L3 aka Phase 2b I know I know you will say WTH .,,, while the L2 aka Phase 1b and Phase 2a combined the voltage will read couple volt differnt and the biggest issue is the B phase current will be higher IIRC 1.41 or somewhere there than other two lines are.

slickvic.,

I have see two phase sans netural it work the same way as you describe 2Ø5W format and only found in couple older buliding in Northeast wisconsin area but it just about history anyway.

In France it just about disappared almost 100% I know there is at least 3 customers I know of still using the two phase supply but it run in scott tee transfomer set up.

Merci,Marc


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## Marshall175 (May 23, 2009)

I appreciate you clearing that up, because what I think they were calling 2 phase is actually only 2 legs of a center-tapped, single phase.


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## slickvic277 (Feb 5, 2009)

Marshall175 said:


> I appreciate you clearing that up, because what I think they were calling 2 phase is actually only 2 legs of a center-tapped, single phase.



I don't understand. What I was calling two phase is just that, a now defunct system that was two phase 5 wire or two phase 4 wire.It was not a center tapped single phase.


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## McClary’s Electrical (Feb 21, 2009)

waco said:


> Tipoff will be four wires coming off a single transformer. Probably a better system than what we have for residential now. Well, better for the consumer, not so much better for the PUCO.


 Its done around here with a sceond xfmr for the delta phase


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