Bonding of CT can and disconnects

[sw_ross]

Disregard the termination of the first disconnect- it was changed after the picture was taken!

This is a 600-amp service that a j-man put together that I work with.
My question is about the bonding.
Each of the 3 disconnects have their bonding screw installed. There is a 6-lug ground bar located in the CT can that a #4 ground wire from each disconnect goes to.
To the left of the CT can (out of picture) is the meter and a #4 ground wire from there goes to the ground bar in the can. Also, the ufer ground GEC comes to the can from the house.
My question basically is that the neutral terminal block in the can is also bonded to the can. It seems to me that there is the issue of objectional current on the #4 ground wire because it’s basically creating a parallel path for neutral current. But I also understand that if you have a fault in the can you need a return path back to the transformer.

The J-man and I were having a discussion about this bonding today before the poco came to hook it up.
What are your thoughts about this setup?
Thanks

 

[infinity]

There should not be a green conductor feeding any of the service switches.

 

[tom baker]

My poco has a very detailed drawing on CT cans and how to bond. Have you checked with your POCO?

 

[texie]

There should not be a green conductor feeding any of the service switches.

I agree. If the CT can has a bonded neutral then that meets 250.92 and you should not put a wire type bonding jumper as that deliberately creates a parallel path. And since the OP used PVC nipples no other bonding is required.
Edit to add: the nipple to the first disco looks like it could be metallic as it looks too close to be PVC with MAs. If it is metal one end of it will need to be bonded.

 

[LarryFine]

Simply put, up to the service main, where the premises equipment grounding system begins, where the local electrodes land, and where the premises neutral zero-voltage reference is, the neutral and any metallic enclosures and raceways are considered to be one conductor.

To quote myself from another thread:

The basics: On the line side of whichever enclosure(s) houses the main disconnect(s) (and ignoring the metering), there is no EGC, there is only the neutral.

The main disconnect is where the premises grounding system begins as separate conductors, and its connection to the service neutral is the main bonding conductor. The grounding electrodes (Ufer or rod(s), water pipe, building steel, etc.) must also connect to the service neutral at (or before) this point.

Any circuits leaving this enclosure, whether branch circuits or feeders, must include an EGC separate from the neutral (if there is one), and said neutral should never be bonded to ground again. Except for switching, fusing, etc., we treat the neutral as we would any ungrounded (hot) conductor.

 

[Buck Parrish]

I agree with Tom , Larry and Rob.
I'll add,

View attachment 2564903 View attachment 2564903


The J-man and I were having a discussion about this bonding today before the poco came to hook it up.
What are your thoughts about this setup?
Thanks

You need to teach your journeymen some basic electrical construction. Although since it's a CT can that may be confusng to some. .So I wouldn't go hard on him.
The green is an equipment ground, not a bond. ( I'll probably get some feed back on that.)
You don't use the equipment ground until you leave the first disconnect(s) At the service the neutral does it all. It bonds and grounds the can. .

 

[hillbilly1]

Georgia Power does their own bonding, and doesn’t want to see any of your grounds in there. Varys greatly from poco to poco.

 

[Joe Villani]

How else would you bond the CT Cabinet?

It appears the neutral termination is insulated? Would not those just be supply side bonding jumpers?

If the grounded conductor termination in the CT cabinet is insulated from the can I dont think Id have a problem with the wire(s). (cant verify the sizing though)

 

[texie]

I would also add that

How else would you bond the CT Cabinet?

It appears the neutral termination is insulated? Would not those just be supply side bonding jumpers?

If the grounded conductor termination in the CT cabinet is insulated from the can I dont think Id have a problem with the wire(s). (cant verify the sizing though)

I think I see a field added bonding jumper from the neutral block to the can. I do how ever question the size of the jumper as it would have to meet 250.102.

 

[LarryFine]

How else would you bond the CT Cabinet?

There needs to be a jumper between the neutral terminal block and the terminal bar behind the red wires.

It appears the neutral termination is insulated? Would not those just be supply side bonding jumpers?

A POCO-supplied CT can would have a neutral terminal block factory bonded to the enclosure.

 

[LarryFine]

I think I see a field added bonding jumper from the neutral block to the can. I do how ever question the size of the jumper as it would have to meet 250.102.

You're right on both points. It's there and it appears to be too small.

Added: The ends of the top PVC nipple need water-proofing.

 

[texie]

Two other thoughts since we are "inspecting" this...
Many POCOs will not allow the GEC the connect in the meter or CT can.
Those expansion joints would appear to be above any straps below. They should be the first thing out of grade.

 

[tom baker]

CT cans I have done use a large multihole ground bar for the neutrals. One neutral goes to the can. We use cans with mounting blocks for the CTs. No self tapping screws allowed

 

[texie]

There needs to be a jumper between the neutral terminal block and the terminal bar behind the red wires.


A POCO-supplied CT can would have a neutral terminal block factory bonded to the enclosure.

No matter who supplies the CT can I have seen many that do not have a factory bond.

 

[LarryFine]

No matter who supplies the CT can I have seen many that do not have a factory bond.

Must be my local POCO's thing.

 

[hillbilly1]

I alway use a bond bushing on my side, that way the can is grounded even if the poco doesn’t bond on their side. Bond bushing is not required on both sides.

 

[sw_ross]

There should not be a green conductor feeding any of the service switches.

That’s what I’m thinking as well.
I’m also thinking that the neutral block should be bonded to the can also?

 

[sw_ross]

My poco has a very detailed drawing on CT cans and how to bond. Have you checked with your POCO?

Good suggestion, I’ll check

 

[sw_ross]

I agree. If the CT can has a bonded neutral then that meets 250.92 and you should not put a wire type bonding jumper as that deliberately creates a parallel path. And since the OP used PVC nipples no other bonding is required.
Edit to add: the nipple to the first disco looks like it could be metallic as it looks too close to be PVC with MAs. If it is metal one end of it will need to be bonded.

It is all pvc

 

[sw_ross]

I agree with Tom , Larry and Rob.
I'll add,


You need to teach your journeymen some basic electrical construction. Although since it's a CT can that may be confusng to some. .So I wouldn't go hard on him.
The green is an equipment ground, not a bond. ( I'll probably get some feed back on that.)
You don't use the equipment ground until you leave the first disconnect(s) At the service the neutral does it all. It bonds and grounds the can. .

In the can the terminal block for the neutral is isolated from the can so I’m thinking a bonding wire/screw needs to be added?