Transformer grounding detail

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hhsting

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Below is what I received as transformer grounding detail. It has not supply side bonding jumper instead the engineer has conductor bonded from the transformer to the ground rod. To me conductor from Transformer to ground rod is not in compliance with NEC 2017 Article 250.4(A)(5) and also transformer enclosure cannot be used as equipment grounding conductor path NEC 2017 Article 250.118, 450..10. I am not sure if this would be in compliance with NEC 2017 and would like to know what your thoughts are in regard to if this is acceptable or not?

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hhsting

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augie47 said:
In some cases, you can (read 250.30) but your sketch does not show a N-G connection at the transformer.
Click to expand...

Incoming EGC transformer primary is bonded to the transformer enclosure call it C1 but in attacent post #1 its called EG.

From secondary panel board their is GEC from
Neutral bar to rod. From rod their is conductor C2 which connects the transformer enclosure.

C2 is connected to neutral bar in secondary panelboard.

C1 and C2 form N to G bond at transformer via its enclosure.

Do you see it?
 
infinity

infinity

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It shows an EG on the primary so there is an EGC run to the primary. The GEC to the transformer case is not required.
 
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hhsting

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retirede said:
X0 of the secondary is not bonded in the transformer.
Click to expand...

X0 of the xfmr goes to N bar in panelboard.

N bar is connect to GEC. GEC is connected to bonding jumper which bonds xfmr enclosure.

Xfmr enclosure is connected to primary of EGC.

Second N to G bond is indirect in Xfmr via bonding jumper to xfmr case and primary EGC to xfmr case. Bonding jumper is bonded to N bar of secondary panelboard and thus connected to xfmr x0
 
don_resqcapt19

don_resqcapt19

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hhsting said:
X0 of the xfmr goes to N bar in panelboard.

N bar is connect to GEC. GEC is connected to bonding jumper which bonds xfmr enclosure.

Xfmr enclosure is connected to primary of EGC.

Second N to G bond is indirect in Xfmr via bonding jumper to xfmr case and primary EGC to xfmr case. Bonding jumper is bonded to N bar of secondary panelboard and thus connected to xfmr x0
Click to expand...
That is not a second connection to XO. The GEC would need to be directly connected to XO in the transformer for that to be an issue.

However, it is my opinion that, unless the transformer and panel are connected via a non-flexible metal wiring method, a supply side bonding jumper is required between the panel and the transformer metal parts.
 
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hhsting

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jaggedben said:
The primary EGC doesn't have another connection to the secondary neutral.
Click to expand...

See the red path. Egc bonds the bonding jumper from rod via xfmr case and bonding jumper from rod is connected N bar panelboard. All this creates 2nd N to G

3590aae27ae6085116194c97fbbf3c0c.jpg



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jap

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jaggedben said:
The primary EGC doesn't have another connection to the secondary neutral.
Click to expand...

Sure it does,,, from the case of the transformer, through the 2/0 to the ground rod, from the groundrod through the 2/0 to the neutral bar in the panel,, which is connected to XO back at the transformer.


Which would be the case any time you use anything other than a non-conductive conduit to contain the wiring between the load side of the transformer to the panel even if the 2/0 bonding jumper shown in the diagram from the transformer to the ground rod wasn't there.

Jap>
 
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hhsting

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jap said:
Sure it does,,, from the case of the transformer, through the 2/0 to the ground rod, from the groundrod through the 2/0 to the neutral bar in the panel,, which is connected to XO back at the transformer.


Which would be the case any time you use anything other than a non-conductive conduit to contain the wiring between the load side of the transformer to the panel even if the 2/0 bonding jumper shown in the diagram from the transformer to the ground rod wasn't there.

Jap>
Click to expand...

There are 2 N to G one at xfmr and one at secondary panelboard.

You need to be in either one not both NEC 2017 Article 250.30


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jap

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Yes there is, and, there is an absolute ton of parallel return paths just like this everywhere you look.

You see it on almost every electrical service around where the service conductors between the utility meters, transformers etc,,, and the service disconnect are contained in a conductive conduit.

JAP>
 
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jaggedben

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hhsting said:
There are 2 N to G one at xfmr and one at secondary panelboard.
Click to expand...
THE DRAWING DOES NOT SHOW ONE AT THE TRANSFORMER.

Are you just assuming there's a factory installed jumper in the transformer? If that's your concern then ask the person who submitted the drawing about it. Maybe they know something about their transformer that you don't.
 
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hillbilly1

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Does this have an isolated ground bar?For some reason the engineer is drawing a 2/0 from the ground bar to the can? 1” ground rod? Ok…. Usually they spec a 10’ also, so this must be a cad weld to it so it can be fully buried at 8’. They may make a direct burial clamp that accepts a 2/0, (which really needs to be no bigger than a #6) but I haven’t ran across one.
 
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