# Strange Service



## Robbie Rob (May 14, 2017)

Good morning, I am a electrical contractor working on an old old building. This factory was running during world war one. I’ll attach photos of the equipment to see. This factory is moving their facility and need all their equipment re-located. The majority of equipment is unlegible and nameplates can’t be read. So I want to match the voltage that feeds each machine and make sure I have that voltage in the new building. 
The problem I’m running into is the voltage coming into the building is strange. It looks to me like a three phase system (4) wire but I’m getting 236V- ground on A phase 
236V- ground on B phase 
0V- ground on C phase 
And 236 V between A B and C 
This is with the main disconnect shut off and reading from the power company. A couple of the machines are legible and say they are three phase 230V-460v I put a call into the power company and they said that they do not have A service at that voltage. So I believe there is something wrong with the power coming in. I’m concerned if they correct it then transformers throughout the facility they put out a different voltage on the secondary. Depending on how they tapped these transformers. I guess what I am looking to understand is if anyone has ever heard of a voltage like this or have any suggestions. I just don’t want to hook up these new machines To 230V- 460V and find out they will not run at the new building. 
Thank you in advance. Rob


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## Robbie Rob (May 14, 2017)

Sorry I can’t figure out how to insert a photo


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## ElectricMatt (Dec 29, 2016)

It sounds like you have a corner ground delta 120/240 to me. Most POCOs I deal with work inside 5-10% tolerance. 

Per example a couple of the plants I am running run 508v when the plant is down. They run hot so when the plant has a load on it it will run at 483-485. If not they would end up with 460-470. 


Sent from my iPhone using Tapatalk


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## CoolWill (Jan 5, 2019)

Yes, it sounds like a corner grounded delta. It could also be an ungrounded delta with one phase accidentally grounded.


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## Bird dog (Oct 27, 2015)

Look at the service & verify with the POCO.


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## canbug (Dec 31, 2015)

Is there a chance the utility is providing a site specific/one off xformer to maintain the older equipment? 
Otherwise, yes to the open delta.


Tim.


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## Cow (Jan 16, 2008)

The old building per your description has 240v 3 phase, either a corner or ungrounded system.



That tells me your new building should have 240v 3 phase for this equipment if you want to keep it at the same voltage.


Read this thread, varmit does a good job with explaining voltages at the bottom:


https://www.electriciantalk.com/f2/corner-grounded-delta-196961


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## Jerome208 (May 10, 2013)

You are also probably going to have to come up with a plan for 120 volts to office equipment and such. Maybe supply your own transformer. Also does any of the equipment require a neutral for 120v controls and the like? You won't have that here.



Around here we would ask the power company to convert the service to 120/240 high leg delta. But I understand they only like to supply 208 in other parts of the country so it might be best not to go there with them and keep it like it is.


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## CTshockhazard (Aug 28, 2009)

C phase conductor marked white and has no OCPD - Corner grounded

C phase conductor not marked white and has an OCPD - Ungrounded



Curious, what's the service at the new building?


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## MechanicalDVR (Dec 29, 2007)

canbug said:


> Is there a chance the utility is providing a site specific/one off xformer to maintain the older equipment?
> Otherwise, yes to the open delta.
> 
> 
> Tim.


In NJ a pre WWI building could have been something that the owner had some contractor build up a system for to power the equipment he was going to install.

I've seen some houses with attached shops in old areas that looked like Frankenstein's lab in the basement.


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## Southeast Power (Jan 18, 2009)

Robbie Rob said:


> Good morning, I am a electrical contractor working on an old old building. This factory was running during world war one. I’ll attach photos of the equipment to see. This factory is moving their facility and need all their equipment re-located. The majority of equipment is unlegible and nameplates can’t be read. So I want to match the voltage that feeds each machine and make sure I have that voltage in the new building.
> The problem I’m running into is the voltage coming into the building is strange. It looks to me like a three phase system (4) wire but I’m getting 236V- ground on A phase
> 236V- ground on B phase
> 0V- ground on C phase
> ...


I share the opinion that your POCO should supply you with a Delta service and one transformer center tapped for your 120 volt loads.
I would put all of the straight 3 phase loads in one panel and the 120 loads in a seperate single phase panel.


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## Bird dog (Oct 27, 2015)

Southeast Power said:


> I share the opinion that your POCO should supply you with a Delta service and one transformer center tapped for your 120 volt loads.
> I would put all of the straight 3 phase loads in one panel and the 120 loads in a seperate single phase panel.


IIRC the center tap can only be lightly loaded for 120v loads. If this is true how do you calculate this?


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## micromind (Aug 11, 2007)

Southeast Power said:


> I would put all of the straight 3 phase loads in one panel and the 120 loads in a seperate single phase panel.


This is how I usually arrange high-leg systems. 

The panels are next to each other and I chase them together.


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## Southeast Power (Jan 18, 2009)

Bird dog said:


> IIRC the center tap can only be lightly loaded for 120v loads. If this is true how do you calculate this?


What we usually have here in our jurisdiction is two transformers, one about 30% larger than the other. The larger transformer is center tapped.


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## Southeast Power (Jan 18, 2009)

Southeast Power said:


> What we usually have here in our jurisdiction is two transformers, one about 30% larger than the other. The larger transformer is center tapped.


I have only seen, or even bothered to notice a closed delta.
I have a pic somewhere.










https://www.dropbox.com/s/kk62oxy4kslu93g/20190131_065838.jpg?dl=0


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## Jerome208 (May 10, 2013)

You find closed deltas on occasion around here. (PG&E.) Center tapped of course. But the vast majority are open delta presumably because they serve only one or two small machines. Anything of any size these days is built with a pad mount anyway.


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## Robbie Rob (May 14, 2017)

Thank you everyone for the advice. I’m going to speak with the power company and get some pricing on transformers. I’ll let you guys know how it worked out.


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## Tonedeaf (Nov 26, 2012)

red leg delta corner grounded very common in NJ
three phase 240V
center tap one winding for 120V-240V single phase


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## CoolWill (Jan 5, 2019)

Tonedeaf said:


> red leg delta corner grounded very common in NJ
> three phase 240V
> center tap one winding for 120V-240V single phase


A corner grounded 4 wire delta? That would leave the 120 V neutral ungrounded. In that kind of system, you'd have some 120 V circuits that required 2 pole breakers.


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## Jerome208 (May 10, 2013)

"Red leg" ("orange leg"?) and corner grounded are mutually exclusive as far as I can tell.


If not please provide pictures.


I think this may be a confusion in terms.


Out here there are corner grounded systems but they are not allowed for new service for many years (decades?)


All the ones I see have 3 open wires on wood poles which are invariably falling over, or have warped so much over the years they might as well be.


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## Tonedeaf (Nov 26, 2012)

CoolWill said:


> A corner grounded 4 wire delta? That would leave the 120 V neutral ungrounded. In that kind of system, you'd have some 120 V circuits that required 2 pole breakers.


3 hots +1 neutral = 4


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## Bird dog (Oct 27, 2015)

Tonedeaf said:


> 3 hots +1 neutral = 4


 Do you have a drawing of that with voltages?
High Leg Delta












Open Delta














Corner Grounded Delta


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## CoolWill (Jan 5, 2019)

Tonedeaf said:


> 3 hots +1 neutral = 4


Right, but look at what grounding one of the phases would do, especially if the grounded phase was on the center-tapped transformer. That's a downright wacky setup, and probably a code violation that I'm too lazy to look up.


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## varmit (Apr 19, 2009)

To the OP: You have a corner grounded system or a system with a ground fault on one phase. On an ungrounded system, if there is a ground fault on any ONE phase, nothing will happen and everything will continue running as normal. If there is a ground fault on a second phase fuses blow/breakers trip.There is no neutral on a system like this.

In the old days, it was common to have two services, one an open delta or corner grounded delta of 240 or 480 volts, and a second 120/240 single phase service for lighting and general use outlets. Few utilities today will supply two services to a building unless it is huge. Now days, you install a customer owned transformer powered from a single service to provide different electrical characteristics.

I will repost my old post below.

There seems to be more confusion about corner grounded systems and high leg systems than any other subject on this forum. Neither are complicated, but high leg systems require a little more thought when connecting loads. Especially 120 volt loads on a 240/120 high leg service. 

A corner grounded delta system is very common in older industrial facilities. These were usually equipment power only, with either another service, or on site transformer(s) for general 120 volt lighting and outlets. 

WHEN WORKING AT A LOCATION, ALWAYS CHECK/TEST TO SEE WHAT TYPE SYSTEM YOU ARE DEALING WITH. Wear your PPE when doing this.

Note: Names will vary regionally. Voltages listed are nominal rating. This is a basic description of what you should find.

Delta, open or ungrounded 230 (or 460) volt
A to B 230 (460)
B to C 230 (460)
A to C 230 (460) 
Any phase to ground will read random values. Usually different on each phase.

Corner grounded Delta (One phase conductor is connected to the grounding electrode system. Normally the grounded conductor is A or B phase- but you never know until you test.
A to B 230 (460)
B to C 230 (460)
A to C 230 (460) 
A to ground 230 (460)
B to ground 0 (0) grounded phase conductor in this example
C to ground 230 (460)

High leg system ( Usually 240/120, but I have seen other voltages on rare occasions.) The B phase position is normally the high leg- but always verify. This system has a "neutral" (grounded conductor) for use on 120 volt loads connected to THE NON HIGH LEG PHASES.
A to B 240 
B to C 240 
A to C 240 
A to ground 120
B to ground 208 (high leg phase conductor in this example)
C to ground 120 

Resistance grounded ( A large resistor is connected to the supply transformer center tap and connected to the grounding electrode system. This helps to limit fault current to an acceptable level on larger services.Usually 460 volt or higher.)
A to B 460
B to C 460
A to C 460
All phases to ground will read a random value that will be about the same on all three phases.


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## varmit (Apr 19, 2009)

Cow said:


> The old building per your description has 240v 3 phase, either a corner or ungrounded system.
> 
> 
> 
> ...


Thank you for the compliment.


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## varmit (Apr 19, 2009)

Probably, your best plan would be to install a 480/277 service at the new location. Feed from this service to one (or more if needed) 480 to 230 volt transformer(s) and panel(s) for the old equipment. For 120 volt loads, install a 480 to 120/208 transformer and panel. Both of the transformers are very common.

If these machines are very old, the motors may not work well on 208.


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