# ?? 3-wire 3-phase service



## farmantenna (Nov 22, 2012)

I unfortunately got involved with a restaurant remodel (yes a group is reopening an old closed for while restaurant during panic pandemic where indoor dining was just allowed at reduced occupancy) and one of the two overhead services is interesting. There's a single phase service too.

I looked at the service at 3:30 pm on a Friday so... 

The service is an overhead 3 phase service with 3 wires. No neutral just a ground wire wrapped around a screw in the meter enclosure and going to a ground rod. The meter only interrupts 2 legs so I measured 120v to ground on load side of the center terminal of the meter. All line legs measure 120v to ground and 208v between them. 

What I don't understand, and I might try this, is if there is a fault to ground where does the fault current go? Usually it's carried back on the neutral which is bonded to ground but this only has a ground rod. The service is only 50' away. Maybe it's an ungrounded service?


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## Dennis Alwon (May 9, 2009)

Is it a corner grounded delta system?


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## MotoGP1199 (Aug 11, 2014)

Dennis Alwon said:


> Is it a corner grounded delta system?


I don't think it is. He said all legs are 120v to ground. 

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## Bird dog (Oct 27, 2015)

@farmantenna 
get with the POCO & verify what it is. Then you can go from there.


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## B-Nabs (Jun 4, 2014)

It sounds like a Wye service that for some reason doesn't have a neutral coming to the building from the pole.

Is it an overhead service? What is the incoming cable? Triplex? Quadplex?

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## splatz (May 23, 2015)

@farmantenna, can you post a picture or two or three of the transformers on the pole?


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## Bird dog (Oct 27, 2015)

splatz said:


> @*farmantenna*, can you post a picture or two or three of the transformers on the pole?


and a close up of the wiring.


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## splatz (May 23, 2015)

.... 

this board server / software is all jacked up


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## paulengr (Oct 8, 2017)

If it’s truly ungrounded the first ground fault makes it corner grounded but no trip which is what OP is describing. Ungrounded systems are still bonded and grounded just no neutral.

The second ground can also be harmless if create a line-ground-line fault.


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## farmantenna (Nov 22, 2012)

what hell is happening? hahaha

I'll post photos Monday while I'm there. At some point in history they wanted 3 Phase for RTUs and fans but I have never seen 3 wire 3 phase 208v system like this. There are 3 transformers on the pole just for this building and the single phase comes from the 120/240 lower wires


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## HackWork (Oct 2, 2009)

farmantenna said:


> what hell is happening? hahaha


I apologize for Travis calling you a DIYer and destroying your thread. He is doing it to every thread so don't feel bad.

Once you post the pictures we can hopefully get this back on topic.


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## paulengr (Oct 8, 2017)

farmantenna said:


> what hell is happening? hahaha
> 
> I'll post photos Monday while I'm there. At some point in history they wanted 3 Phase for RTUs and fans but I have never seen 3 wire 3 phase 208v system like this. There are 3 transformers on the pole just for this building and the single phase comes from the 120/240 lower wires



Wait a minute. From the same three transformers? If one of them is 240/120 that’s high leg delta but your phase to ground voltage is 120 on two phases and 208 on the third, and phase to phase voltages are 240, not 208. Are you talking about a separate transformer or is the ground missing on 240/129 too?

208/120 is a common commercial voltage when you mostly need 3 phase for HVAC and most loads are 120. 240/120 high leg delta is common when you have mostly 240/120 loads and just a couple three phase. Both are often wired with three single phase transformers but high leg delta can be wired with just two transformers if your three phase load is limited.


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## Bird dog (Oct 27, 2015)

paulengr said:


> high leg delta can be wired with just* two transformers* if your three phase load is limited.


Is that also called an open delta?


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## Dennis Alwon (May 9, 2009)

Please stop the bickering-- you two need to get a room somewhere... geez.....


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## JoeSparky (Mar 25, 2010)

travis theory said:


> that isnt a 3 phase set up. thats a normal set up.
> there is ALWAYS a "neutral" feeding such a place.
> the neutral is that bare wire, going to ground. the other two are the two hot legs...that makes three wires.
> 
> ...


:stupid::stupid::stupid::stupid::stupid::stupid:


Oh my god, you Fùcking moron! Are you even an electrician? You definitely are not Chicken Steve. The chicken man is an idiot and a fùcking dolt and a communist, but he definitely knows more than this about electricity.




@farmantenna , Ignore this moron!

You said there were 2 services on the building. I've run into in on some commercial/industrial buildings. At some point in the building's life, they added some 3 phase loads. Left the existing 120/240 1ph service and added a 3 phase open delta service. 

At that point there were only 2 transformers feeding this service on the pole. It was either at the pole ungrounded straight 240 or corner grounded 240 and poor quality 240 between phase and ground. Corner grounding is just for safety, not for current carrying purposes.

The metering for open delta is only 2 wires, because there are no phase to ground loads and you are always drawing power from 2 legs and both transformers anyways.

I bet what really is happening here is building used to have an open delta service for the above reasons. One of the neighboring buildings needed a 3 phase wye service from the same pole. So the power company added a 3rd transformer and wired them all together wye. Your service never got changed. You are reading 208v between phases. 

The 120v you are reading is traveling through the grounds of the building. Most liklely to a point where both services are grounded to the same metal. The current is traveling back through the neutral of the single phase service and to the poles where the neutrals and grounds of both services are tied together at the pole with the 3 cans on it


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## HackWork (Oct 2, 2009)

Dennis Alwon said:


> Please stop the bickering-- you two need to get a room somewhere... geez.....


"you two"???




Apparently Dennis and the other guy will allow Travis to spread complete electrical misinformation for the handful of posts he makes that are actually about electricity, because the other 95% of his posts are liberal garbage that they slurp up.


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## CoolWill (Jan 5, 2019)

Two hots and a bare with 120 to ground and 208 between the hots is two phases of a three phase system, so single phase.


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## MotoGP1199 (Aug 11, 2014)

You guys are all mean. I dont think you understood the stero analogy correctly. 

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## Quickservice (Apr 23, 2020)

Lordy... what a screwed up thread.


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## splatz (May 23, 2015)

Bird dog said:


> Is that also called an open delta?


I believe you can do a high leg delta with an open delta...


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## Bird dog (Oct 27, 2015)

splatz said:


> I believe you can do a high leg delta with an open delta...


Trying to figure the voltages is confusing for some reason & it didn't dawn on me that it is a limited high leg delta until it was pointed out.








...


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## paulengr (Oct 8, 2017)

Bird dog said:


> Is that also called an open delta?



Yes. Any delta with just two transformers is an open delta.

The other common instrumentation version used 2 line-line voltage (PT) transformers instead of three.


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## JoeSparky (Mar 25, 2010)

@farmantenna service is definitely currently fed Wye. He said he got 208 from all 3 phases and 120 to ground from all 3. That rules out any corner or center grounded delta.


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## Bird dog (Oct 27, 2015)

JoeSparky said:


> @*farmantenna* service is definitely currently fed Wye. He said he got 208 from all 3 phases and 120 to ground from all 3. That rules out any corner or center grounded delta.


Something still isn't right. It should also have a neutral that is at least sized for fault current.


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## joe-nwt (Mar 28, 2019)

Bird dog said:


> Something still isn't right. It should also have a neutral that is at least sized for fault current.


it's an old service from back before fault currents were told it's not OK to use the ground.:wink:


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## JoeSparky (Mar 25, 2010)

Bird dog said:


> Something still isn't right. It should also have a neutral that is at least sized for fault current.


Like I posted yesterday. It was probably an open delta feed when it was installed. POCO has since upgraded it to wye without replacing the drop or touching the service on the building.


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## farmantenna (Nov 22, 2012)

*Updated photos*

it is difficult to see the transformer connections in the photo and in person but looks like a wire from each is connected together with a wire going to the ground of the lower set of single phase run. also sloppy weird connections up there.


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## JoeSparky (Mar 25, 2010)

farmantenna said:


> it is difficult to see the transformer connections in the photo and in person but looks like a wire from each is connected together with a wire going to the ground of the lower set of single phase run. also sloppy weird connections up there.


Looks like exactly what I guessed. That was an open delta service. It is now fed from a wye transformer configuration. Looks like those transformers feeds someplace off to the right as well.
With the service in it's current configuration, you should not power any 120v loads from the 3 phase service. That service has no neutral. Your meter says it will work, but it is reading through ground to the single phase 120/240 service and out through the neutral of that service. Sooner or later, you would overload it or have problems with crusty old ground connections.


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## Cow (Jan 16, 2008)

I would be getting in contact with the power co. ASAP to get that corrected.

Looks like 120/208Y to me. Time for a service change.


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## cuba_pete (Dec 8, 2011)

wow...I love coming in to these threads a day late.

It's like Steve and Cletus had a love child.:vs_OMG:


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## JoeSparky (Mar 25, 2010)

Cow said:


> I would be getting in contact with the power co. ASAP to get that corrected.
> 
> Looks like 120/208Y to me. Time for a service change.


Nothing that scares me on that service. If the OP wants to sell a 400a 3-phase service upgrade, then sell away. The building probably has 2 HVAC units and a hood fan that needs 3 phase. Everything else is single phase. Plenty of capacity there for that.


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## AU Facilities (Mar 25, 2015)

You sure that's 3 phase. That look line a single phase service. The pan looks like a 5 jaw bypass meter pan for a single phase meter. Here on LI they use 5 jaw meter pans so you could not turn the meter over and have it spin backwards to steal electric. Just because there are 3 transformers on the pole doesn't mean that service is connected to all 3 phases (I can't tell from the pic)


https://www.walterswholesale.com/mi...h-lever-bypass-5-jaw-1-position-200-amp-59831


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## farmantenna (Nov 22, 2012)

AU Facilities said:


> You sure that's 3 phase. That look line a single phase service. The pan looks like a 5 jaw bypass meter pan for a single phase meter. Here on LI they use 5 jaw meter pans so you could not turn the meter over and have it spin backwards to steal electric. Just because there are 3 transformers on the pole doesn't mean that service is connected to all 3 phases (I can't tell from the pic)
> 
> 
> https://www.walterswholesale.com/mi...h-lever-bypass-5-jaw-1-position-200-amp-59831


. 208v between all legs 3p MB 8 3-p CBs RTUs and fans. 

I hear yeah. That's why I posted this. It looks like single phase meter! The meter is removed and that center terminal is energized and at MB. I wanted to move the panel and it's still live!


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## farmantenna (Nov 22, 2012)

JoeSparky said:


> Looks like exactly what I guessed. That was an open delta service. It is now fed from a wye transformer configuration. Looks like those transformers feeds someplace off to the right as well.
> With the service in it's current configuration, you should not power any 120v loads from the 3 phase service. That service has no neutral. Your meter says it will work, but it is reading through ground to the single phase 120/240 service and out through the neutral of that service. Sooner or later, you would overload it or have problems with crusty old ground connections.


You're more observant than me and I'm there! You're absolutely correct. The ground rods for each meter, which are 1 foot apart, are 8" apart so the 3-phase service is getting it's ground from the single phase neutral which is connected to it's gnd rod.


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## JoeSparky (Mar 25, 2010)

Some less scrupulous folks then myself :whistling2: would power every 120v load in the building off of the B phase of the 3 phase service :surprise:


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## Cow (Jan 16, 2008)

JoeSparky said:


> *Nothing that scares me on that service.* If the OP wants to sell a 400a 3-phase service upgrade, then sell away. The building probably has 2 HVAC units and a hood fan that needs 3 phase. Everything else is single phase. Plenty of capacity there for that.


There isn't an effective ground fault current path back to the source. Does that seem reasonable to you?


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## JoeSparky (Mar 25, 2010)

Cow said:


> There isn't an effective ground fault current path back to the source. Does that seem reasonable to you?


Meh. Ground it to the same electrode as the other service. There's your path. Or sell the upgrade :thumbup:


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## CoolWill (Jan 5, 2019)

cuba_pete said:


> wow...I love coming in to these threads a day late.
> 
> It's like Steve and Cletus had a love child.:vs_OMG:


They already did. They named him "JoeSparky" for some reason.


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## JoeSparky (Mar 25, 2010)

CoolWill said:


> They already did. They named him "JoeSparky" for some reason.


I am not nearly as entertaining as those 2 clowns. 
If I had any feelings, they would be hurt right now lain:


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## CoolWill (Jan 5, 2019)

JoeSparky said:


> I am not nearly as entertaining as those 2 clowns.
> If I had any feelings, they would be hurt right now lain:


But you're a much better kisser.


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## JoeSparky (Mar 25, 2010)

CoolWill said:


> But you're a much better kisser.



Hacky said he wouldn't tell :surprise::sad::vs_mad:


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## CoolWill (Jan 5, 2019)

JoeSparky said:


> Hacky said he wouldn't tell :surprise::sad::vs_mad:


Hax didn't. Peter did.


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## HackWork (Oct 2, 2009)

This thread is gayer than Richard Simmons eating a custard donut at an Nsync concert.


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## CoolWill (Jan 5, 2019)

HackWork said:


> This thread is gayer than Richard Simmons eating a custard donut at an Nsync concert.


And you're as dumb as some thing that is doing a thing that is also dumb at a place.


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## HackWork (Oct 2, 2009)

CoolWill said:


> And you're as dumb as some thing that is doing a thing that is also dumb at a place.


I’m smart, I swear :vs_mad:


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## JoeSparky (Mar 25, 2010)

HackWork said:


> This thread is gayer than Richard Simmons eating a custard donut at an Nsync concert.


So, how was the concert?:devil3:


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## farmantenna (Nov 22, 2012)

*update*

I started this. I created a ground fault and there was definitely a flow of current! But only because it's going through the adjacent single phase ground/neutral. The ground rods for these services are 8 inches apart


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## paulengr (Oct 8, 2017)

farmantenna said:


> I started this. I created a ground fault and there was definitely a flow of current! But only because it's going through the adjacent single phase ground/neutral. The ground rods for these services are 8 inches apart



Too close.

Need to be one rod length apart or they start to act like just one rod. So typically eight feet apart, not 8 inches.


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