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Old 05-24-2019, 09:37 AM   #1
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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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Old 05-24-2019, 09:38 AM   #2
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Sorry I can’t figure out how to insert a photo
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Old 05-24-2019, 10:04 AM   #3
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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.


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Old 05-24-2019, 12:04 PM   #4
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Yes, it sounds like a corner grounded delta. It could also be an ungrounded delta with one phase accidentally grounded.
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Old 05-24-2019, 12:52 PM   #5
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Look at the service & verify with the POCO.
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Old 05-24-2019, 01:26 PM   #6
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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.


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Old 05-24-2019, 06:15 PM   #7
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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/c...d-delta-196961
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Old 05-24-2019, 06:47 PM   #8
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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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Old 05-25-2019, 07:40 AM   #9
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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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Old 05-25-2019, 11:15 AM   #10
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Quote:
Originally Posted by canbug View Post
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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Old 05-26-2019, 10:26 AM   #11
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Quote:
Originally Posted by Robbie Rob View Post
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
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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Old 05-26-2019, 12:07 PM   #12
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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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Old 05-26-2019, 12:18 PM   #13
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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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Old 05-26-2019, 08:01 PM   #14
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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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Old 05-26-2019, 08:05 PM   #15
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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/kk62oxy4ks...65838.jpg?dl=0

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Old 05-26-2019, 08:55 PM   #16
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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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Old 05-28-2019, 01:08 PM   #17
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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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Old 05-28-2019, 02:29 PM   #18
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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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Old 05-28-2019, 02:48 PM   #19
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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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Old 05-28-2019, 02:54 PM   #20
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"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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