# Corner Ground Delta Mess.



## JohnR (Apr 12, 2010)

A Job I hope to get to clean up.
Site, old industrial building turned rented spaces, commercial now.

Situation, 2 meters, 1 main, 1 IDK, 4 tenants. 240V closed delta, corner grounded.
When a tenant don't pay the bill, everyone looses power. So lets try to install 4 meters. 
The electric supply in this building is very entangled, and some is very unsafe.
I am not sure about all the codes concerning 240V closed delta that is corner grounded. 

For instance, When running a feeder, and the "c" phase is grounded, do you need to run another ground for the "ground"?

Main 400A disco above CT cabinet.










Trough from CT cabinet out to main panel, tapped to disco's
It's kind of small.8X8X60, cover missing.










Main Panel 400A rated, yes that is a factory buss.
Grounded leg is in the Neutral position.
Note the 1" conduit to the left. * it is fed from the 60A breaker second down on left. It is ON.











Disconnect to left of Main panel.
Center leg is the grounded one.









Panel fed from main panel. That ground bar has no bond jumper to the panel can.


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## JohnR (Apr 12, 2010)

Now we follow that 1" from the left of the MDP. It goes through the wall under the 10KVA transformer that supplies the 120v loads.











I eliminated some personal stuff on this pic













 240V delta live right about shoulder height.


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## JohnR (Apr 12, 2010)

I disconnected those wires from the breaker. I will be letting the owner know what a hazard that was.

Now for some questions,
I have read the older posts about these systems and how to safely wire them. I plan to use a 4 gang meter breaker combo, 3ph, for the new service, coming off the large disconnect. I don't know about running out to the individual panels in each space though. 
Do I need to run a separate ground? or can the C' phase be grounded at each panel? This doesn't seem right to me.

How should I properly address the grounding of the system?

I plan to use the little 10kva single phase transformers to supply 120 loads at each tenant, inside each tenant space.

The line diagram will follow this pattern for each. 
OH drop-400A disco-Meter bank-tenant disco-tenant panel-120v transformer-tenant 120v panel. 
Is there a better way to do this?


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## JohnR (Apr 12, 2010)

Oh, yeah, Can't forget the water meter ground, and the power pole.


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## JohnR (Apr 12, 2010)

So far, as I understand it, I need to make the grounded phase white, and run an equipment ground along with the phase conductors. 

Does anyone know where I could source a couple of those 240/480 high to 120/240 secondary transformers, about 10Kva?


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## Outdoorguy (Sep 5, 2011)

What a nightmare. I've always dreaded running into that kind of stuff. Especially corner grounded deltas. Have fun.:blink:


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## Wireman191 (Aug 28, 2011)

I ran into this about two weeks ago. Crazy stuff for sure! Looking on the Internet should answer some questions.


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## varmit (Apr 19, 2009)

The pictures look better than most of the junk that I have to work on.

A corner grounded delta system is not a problem to work with. Think of the grounded phase as you would a "neutral" ( By definition- a grounded conductor.) Yes, you need an bonding/grounding conductor to the equipment also. If the tenant service is 240/120 only, I would use standard single phase transformers. You would run two phases to each transformer. Example: Unit 1- A & B phase, unit 2- B & C phase, unit 3- C & A phase, etc. There are three code compliant methods to do the over current protection:
A. Three pole circuit breakers
B. Two pole fusing, or breakers and the grounded phase on the neutral bar.
( Be sure that the breakers are rated for this application.)
C. Use three pole disconnects with a "dummy" fuse in the grounded phase.
( Fuse manufacturers make these dummy fuses. They are just a jumper across the fuse holder.)

Good luck.


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## frenchelectrican (Mar 15, 2007)

Genrally corner grounded delta system is not super hard to work with it once you understand the basic of GCD's they are not the same as convental Delta system.

The quirk you may snag is the metering arrangement if they can work on CGD { this part you may want to check with POCO to see what listing they approved for CGD network set up }(otherwise the POCO may ask you to reconferated to full 4 wire delta or go with Wye format )

How much triphase load are you expecting there ?

I was looking at the photo and the pole pigs they are not very large IMO total capaity is 30 KVA if the pigs did have imprint of " 10 " on the can if other numbers then change the figures.

And look like you have equal pig sizes so it can be pretty easy to change if the situation required.

Varmit have one idea with it. I do belive it will work with the transfomers he suggest it and use the stragiht 240 volt meters { may have to get one with network verison if possible }

Otherwise go with full triphase transfomers for each tenant useing 240D-208Y120 tranfomer set up { that one of the other idea it may be a doable }

Merci,
Marc


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## JohnR (Apr 12, 2010)

frenchelectrican said:


> Genrally corner grounded delta system is not super hard to work with it once you understand the basic of GCD's they are not the same as convental Delta system.
> 
> The quirk you may snag is the metering arrangement if they can work on CGD { this part you may want to check with POCO to see what listing they approved for CGD network set up }(otherwise the POCO may ask you to reconferated to full 4 wire delta or go with Wye format )





frenchelectrican said:


> How much triphase load are you expecting there ?


I am not completely sure, I still have not been able to access the entire facility which has held up the estimate. The owner is very hard to get ahold of even when he says "yes, I will meet you at 4".


frenchelectrican said:


> I was looking at the photo and the pole pigs they are not very large IMO total capaity is 30 KVA if the pigs did have imprint of " 10 " on the can if other numbers then change the figures.
> 
> And look like you have equal pig sizes so it can be pretty easy to change if the situation required.
> 
> ...


 The Pigs are feeding two buildings and are the same sizes. I don't have access to the other building, it is a single tenant there. I hope not to need the three phase transformers, There isn't much room in the electrical closet.


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## Meadow (Jan 14, 2011)

JohnR said:


> So far, as I understand it, I need to make the grounded phase white, and run an equipment ground along with the phase conductors.
> 
> Does anyone know where I could source a couple of those 240/480 high to 120/240 secondary transformers, about 10Kva?


 
Usually get them from Grainger. Excellent selection:thumbsup:


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## Shockdoc (Mar 4, 2010)

Piss poor planning always leads to a piss poor installation. You have a bonafide mess on your hands.


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## RIVETER (Sep 26, 2009)

JohnR said:


> A Job I hope to get to clean up.
> Site, old industrial building turned rented spaces, commercial now.
> 
> Situation, 2 meters, 1 main, 1 IDK, 4 tenants. 240V closed delta, corner grounded.
> ...


When doing any work, the time to learn is not after you got the bid.


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## MF Dagger (Dec 24, 2007)

RIVETER said:


> When doing any work, the time to learn is not after you got the bid.


I disagree, sometimes you just gotta jump in there. Bid it to allow for your learning and your mistakes and go for it.


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## RIVETER (Sep 26, 2009)

MF Dagger said:


> I disagree, sometimes you just gotta jump in there. Bid it to allow for your learning and your mistakes and go for it.


Let your doctor know that when you need a kidney.


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## MF Dagger (Dec 24, 2007)

He's not talking about a kidney. He's talking about electrical repair and installation. It's not like he went from knowing no basics one day to bidding this job the next day. I run into new or oddball stuff all of the time and there is no way I could foresee or imagine half of it ahead of time. You gotta go with the flow.


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## Jlarson (Jun 28, 2009)

That doesn't even come close to being a bonafide mess. I'd give a lot to redo a system that clean once and a while. 





meadow said:


> Usually get them from Grainger. Excellent selection:thumbsup:


Grainger isn't exactly a cheap place to order transformers from. :no:


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## frenchelectrican (Mar 15, 2007)

JohnR said:


> I am not completely sure, I still have not been able to access the entire facility which has held up the estimate. The owner is very hard to get ahold of even when he says "yes, I will meet you at 4".
> The Pigs are feeding two buildings and are the same sizes. I don't have access to the other building, it is a single tenant there. I hope not to need the three phase transformers, There isn't much room in the electrical closet.


 
What type of commercal set up it will be like retail store or office space or wharehouse { storeage} ?

And a quick short cut is check with POCO with the history of load useage many time they will keep the records how much load they useing so you can get a basic idea where go from there.

For triphase most likely used with HVAC or RTU one of the two. I did reread it again and I did catch one statement that you have a master C/T cabent so you can split in 4 ways in set of 100 ampers for each tenent section { if not crazy with electrique loads }

Hope that help a bit.

Merci.
Marc


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## CTshockhazard (Aug 28, 2009)

Hey John, hope things are going good for you.

Wish I could help you out, but I have very limited experience with those systems.










Curious though, why did you take your pants off to take the pictures? :laughing:


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## ce2two (Oct 4, 2008)

CTshockhazard said:


> Hey John, hope things are going good for you.
> 
> Wish I could help you out, but I have very limited experience with those systems.
> 
> ...


Gotta love that glass or what ever hilbilly tape they used:thumbsup:hack special:blink:


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## JohnR (Apr 12, 2010)

I didn't even notice the pants were hanging there. No, they arn't mine. Mine would cover more of the trough than that. :whistling2:

CT, the shop is right across the highway from you. They have an auto mechanic, a garage for a wrecker, a Paint? garage (not sure what he does in there), and another shop that has ???machine shop? lives in back? not sure.:laughing:


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