# 3 Phase delta question???



## RePhase277 (Feb 5, 2008)

romexrocket said:


> I have an existing 3 phase delta 120/208/120 to nuetral 240/240/240 phase to phase. I installed a new 3 ph panel in a residence remodel that maybe at one time needed 3 ph, but now have no reason for it other than to help with load. question is this: I have a 240 v 1 phase water heater and a 208/240 1 phase condensor on roof would their be anything wrong with involving the high leg to get supply voltage to either of these units, also i was thinking i should probably stay off the high leg with the range and dryer because of the nuetral in these and wouldnt want 208v on 1 side to damage any 120v loads it may be tappin off 1 side. any opinions or advice?? thanks in advance


No, you can use the high leg and another phase for any single phase single-voltage equipment.

And yes, I agree that using the B phase on a MWBC such as a dryer or range would be a bad idea:no:


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## Dennis Alwon (May 9, 2009)

I agree with Inphase. The dryer uses 120V for the dryer motor so with a phase to neutral you don't know which leg the dryer is using for the 120v part.


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## romexrocket (Oct 3, 2007)

Would it also be good practice to label the a/c unit and water heater that is supplied by a high leg or not needed?


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## Dennis Alwon (May 9, 2009)

romexrocket said:


> Would it also be good practice to label the a/c unit and water heater that is supplied by a high leg or not needed?


The high leg should be marked in the disco with orange tape.



> 110.15 High-Leg Marking.
> On a 4-wire, delta-connected system where the midpoint of one phase winding is grounded, only the conductor or busbar having the higher phase voltage to ground shall be durably and permanently marked by an outer finish that is orange in color or by other effective means. Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present.


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## RePhase277 (Feb 5, 2008)

Dennis Alwon said:


> The high leg should be marked in the disco with orange tape.


I agree that orange marking would be safer, it isn't necessary unless the neutral is present in the box. On a 2-wire water heater circuit, the two hots could be any hot colors, neither of them would be required to be orange.


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## CFL (Jan 28, 2009)

InPhase277 said:


> I agree that orange marking would be safer, it isn't necessary unless the neutral is present in the box. On a 2-wire water heater circuit, the two hots could be any hot colors, neither of them would be required to be orange.


The op would be using the grounded conductor and the high leg for the water heater. I think that's what Dennis was referring to.


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## Electric_Light (Apr 6, 2010)

120/208 isn't Delta. That's the typical 208Y/120 common in apartments and offices. Why are you installing 240v delta? I believe they're meant for users with significant number of three phase motor loads and a sparing amount of 120v plug-in stuff, such as a machine shop with an office.

What does the code have to say about any conductor higher than 120v with respect to ground on a residential property?


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## RePhase277 (Feb 5, 2008)

CFL said:


> The op would be using the grounded conductor and the high leg for the water heater. I think that's what Dennis was referring to.


Hmmm... I took it to mean that he wanted to use two phases, one of them being the high leg phase, which is OK.

I would NOT use the neutral and high leg to power any 208 V loads. For one, you must use a single pole breaker that's straight-rated, which is not all that easy to come by. And for two, the system just wasn't designed to be used that way. I wouldn't want to put any more load on the neutral than it was intended to carry.


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## Norcal (Mar 22, 2007)

If a single phase load is fed by the high leg, a 120/240V slash rated breaker cannot be used, a 240V rated 2-pole from what I have heard is pricey.


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## Dennis Alwon (May 9, 2009)

CFL said:


> The op would be using the grounded conductor and the high leg for the water heater. I think that's what Dennis was referring to.


No I wasn't referring to the water heater but rather to a dryer or range where a neutral is present. It would be insane to try and use the high leg in this case. 

I would also tape it orange whether a neutral was present or not. Not req. but I would do it anyway.


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## Hairbone (Feb 16, 2011)

Dennis Alwon said:


> I would also tape it orange whether a neutral was present or not. Not req. but I would do it anyway.


That is a great practice to do!! Bought 6 ballasts the other day because one of the guys didn't realize he was dealing with a delta service . A real odd ball in my area!


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## Shockdoc (Mar 4, 2010)

Smoke..........the product of a high leg feeding a 120 volt load. I would keep a high leg strictly to HW heaters, compressors, motors or any other straight 220 load that does not require a neutral.


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## Shockdoc (Mar 4, 2010)

I have actually run a 220 AC off a single pole 20 on a high leg to neutral. Worked with no difference. Go on throw your stones, it was temporary.


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## Magnettica (Jan 23, 2007)

I worked on a high-leg service today. A new 240 circuit for an old air compressor. Used one of the high legs (208 volts) and one of the 120 volt legs. The high leg is 208 volts to ground but when measured phase-to-phase the voltage is 240 volts. I would suggest to anyone to check the supply voltage before quoting or doing any work. Sometimes you can get lucky and see the utility transformer set up and know just by looking before actually taking the panel cover off.


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## Magnettica (Jan 23, 2007)

Shockdoc said:


> I have actually run a 220 AC off a single pole 20 on a high leg to neutral. Worked with no difference. Go on throw your stones, it was temporary.


How the hell did you do that?


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## Smoke (Feb 25, 2011)

its actually illegal to put 3ph in a residential dwelling where i live. i saw it once but it went to a garage, not the house, outside where a small machine shop was set up.


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## don_resqcapt19 (Jul 18, 2010)

Electric_Light said:


> 120/208 isn't Delta. ...


He didn't say 120/208. He said 120/208/120 hot to neutral and 240 phase to phase. That is a wild leg delta system.


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## Shockdoc (Mar 4, 2010)

Magnettica said:


> How the hell did you do that?


It will run high leg to ground . it was a 200 volt high leg and the AC ran fine until POCO fixed the primary for the low pot transformer.:thumbsup:


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## Smoke (Feb 25, 2011)

don_resqcapt19 said:


> He didn't say 120/208. He said 120/208/120 hot to neutral and 240 phase to phase. That is a wild leg delta system.


ok i am going to ask a stupid question because i havent had time to look into it. we had a delta system here in the past that had no voltage to b phase and there was no neutral. it ran 3 phase equipment like a champ but there was no neutral so it was only used for industrial applications, only 3 phase loads. you are saying there is a 3 phase delta with a neutral and a wild leg?
i am totally learning something here, thanks for your education.


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## Magnettica (Jan 23, 2007)

Shockdoc said:


> It will run high leg to ground . it was a 200 volt high leg and the AC ran fine until POCO fixed the primary for the low pot transformer.:thumbsup:


The reason why ask is because the high leg on a "Red Leg" service is 208 volts to ground, and a parallel circuit. 

A double-pole circuit is a series circuit. 

I don't see how it would work if the A/C required a 240 volt circuit.


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## desar (Feb 6, 2011)

I think the system your talking about with the 3 phase with no voltage from B phase to ground would be called a 3 phase corner grounded delta where on hot phase is both a phase conductor and also a grounded conductor. old system not really used any more. Very dangerous on trouble shooting ,because you think one phase is blown because you don't get a reading from hot to ground like the other two phases. Used for areas that have mostly 3 phase loads with small 120 volt loads.

The other system with the 208 to nuetral is 3 phase 4 wire delta with a mid tap across on winding.


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## RePhase277 (Feb 5, 2008)

Smoke said:


> ok i am going to ask a stupid question because i havent had time to look into it. we had a delta system here in the past that had no voltage to b phase and there was no neutral. it ran 3 phase equipment like a champ but there was no neutral so it was only used for industrial applications, only 3 phase loads. you are saying there is a 3 phase delta with a neutral and a wild leg?
> i am totally learning something here, thanks for your education.


That is a corner grounded or "Grounded B" delta. One of the phases is tied to ground, so usually you use a single phase panel with it, even though it is 3 phase.


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## don_resqcapt19 (Jul 18, 2010)

desar said:


> I think the system your talking about with the 3 phase with no voltage from B phase to ground would be called a 3 phase corner grounded delta where on hot phase is both a phase conductor and also a grounded conductor. old system not really used any more. Very dangerous on trouble shooting ,because you think one phase is blown because you don't get a reading from hot to ground like the other two phases. Used for areas that have mostly 3 phase loads with small 120 volt loads. ...


You can't use a 3 phase corner grounded delta system for 120 volt loads. You only have phase to phase voltages on that type of system.


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## desar (Feb 6, 2011)

On a corner grounded system if B phase is grounded and also a phase system you read 120 volt on Phase A and C to ground but on B phase you'll read 0 volts because the hot and the grounded conductor are the same.


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## desar (Feb 6, 2011)

Sorry I typed without thinking I am so wrong about my last statement.


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## Smoke (Feb 25, 2011)

InPhase277 said:


> That is a corner grounded or "Grounded B" delta. One of the phases is tied to ground, so usually you use a single phase panel with it, even though it is 3 phase.


that is incorrect, we used a 3ph panel and only fed 3ph motor loads
there was a separate service for receps and lts


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## kbsparky (Sep 20, 2007)

You can have a 240 Volt delta-connected 3 phase service without grounding a corner. 

Here is one example of a delta-connected transformer bank, followed by what is commonly called an "open bank" delta service.


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## Big John (May 23, 2010)

don_resqcapt19 said:


> You can't use a 3 phase corner grounded delta system for 120 volt loads. You only have phase to phase voltages on that type of system.


 I've seen CGD systems, but never worked on one. Why wouldn't you be able to add 120V single phase loads on a 120/240 CGD...?

-John


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## kbsparky (Sep 20, 2007)

Big John said:


> ... Why wouldn't you be able to add 120V single phase loads on a 120/240 CGD...?
> 
> -John


`Cause IF it's a corner grounded system, it ain't a 120/240 system!


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## Big John (May 23, 2010)

kbsparky said:


> `Cause IF it's a corner grounded system, it ain't a 120/240 system!


 Oh! It's all phase-to-phase voltages. I _knew_ that.... :wallbash:

-John


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## RePhase277 (Feb 5, 2008)

Smoke said:


> that is incorrect, we used a 3ph panel and only fed 3ph motor loads
> there was a separate service for receps and lts


I said usually. You can use a 3 phase panel and three pole breakers, but then you are switching the grounded conductor and totally wasting money on 3 phase panels. With a CGD system, a single phase panel is cost effective and perfectly operable.


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## Smoke (Feb 25, 2011)

InPhase277 said:


> I said usually. You can use a 3 phase panel and three pole breakers, but then you are switching the grounded conductor and totally wasting money on 3 phase panels. With a CGD system, a single phase panel is cost effective and perfectly operable.


i only worked on it once about 18 years ago and we used a 3ph panel.
your way is more cost effective but using your logic why even pull the third conductor? lets save 1/3 all the way, ground the middle phase right at the load (hoping you don't say that's how its done or ill really be blown away lol
im assuming it says somewhere in the code book, its legal to put a phase conductor on the neutral bar (assuming thats what you do).

to the untrained eye, if opened a panel wired like you say, it would definitely get a wtf, not saying your doing any thing wrong. those systems just aren't common around here.


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## RePhase277 (Feb 5, 2008)

Smoke said:


> i only worked on it once about 18 years ago and we used a 3ph panel.
> your way is more cost effective but using your logic why even pull the third conductor? lets save 1/3 all the way, ground the middle phase right at the load (hoping you don't say that's how its done or ill really be blown away lol
> im assuming it says somewhere in the code book, its legal to put a phase conductor on the neutral bar (assuming thats what you do).
> 
> to the untrained eye, if opened a panel wired like you say, it would definitely get a wtf, not saying your doing any thing wrong. those systems just aren't common around here.


In a CGD, one of the phases is grounded, and treated exactly like a neutral, it's even supposed to be white. You can't leave it out of the circuit because then you would only have two of the three phases at the load. For electrical purposes, it is a phase wire just as in any 3 phase system. For grounding purposes, it is treated just like a neutral and bonded at the main.

Yes, it can be mind boggling if you aren't expecting it. That's why labeling is so important in odd-ball systems like that.


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## don_resqcapt19 (Jul 18, 2010)

desar said:


> On a corner grounded system if B phase is grounded and also a phase system you read 120 volt on Phase A and C to ground but on B phase you'll read 0 volts because the hot and the grounded conductor are the same.


That is possible but a 120 volt corner grounded system is rare.


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