SDS Grounding

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TheElectrician

Senior Member
Hey Guys,

In the attached 3 three line I have bonded N-G on the first disconnecting means on both the primary and the secondary of the T/F to earth and connected the transformers G to earth as well. I followed NEC 230.30(A)(1) Exception No. 2, but just a doubt if the "first disconnecting means" just denotes that it should be bonded either on the primary or on the secondary or should it be on the both disconnecting means. Is there any other code that stated this?

Grounding.JPG

Thanks
 

TheElectrician

Senior Member
Hey Guys,

In the attached 3 three line I have bonded N-G on the first disconnecting means on both the primary and the secondary of the T/F to earth and connected the transformers G to earth as well. I followed NEC 230.30(A)(1) Exception No. 2, but just a doubt if the "first disconnecting means" just denotes that it should be bonded either on the primary or on the secondary or should it be on the both disconnecting means. Is there any other code that stated this?

View attachment 23338


Thanks

Also, Do we have to ground "Earth" where ever we have a N-G bonding as showed in the diagram as I see a lot of posts talking:

"he GEC connection and the SBJ can be... and it is required that they both be in the same enclosure." Post #4 - https://forums.mikeholt.com/showthread.php?t=183483
"The GEC connection is to be made at the same point as the bonding jumper is made at, not where the EGCs are connected" Post #6 & #7 - https://forums.mikeholt.com/showthread.php?t=56753

Which code says this?
 

TheElectrician

Senior Member
That appears to be a wye-wye which would NOT be an SDS (if connected the way I think it is).

Edit: in other words, there should not be a N-G bond.

So,

1) I should bond the N-G at the 89L disconnect (Primary side of the transformer), and should not bond in the 52IT (Secondary side of the transformer) because I can bond at the source or the disconnecting means but not at both the disconnecting means on primary and secondary is that right?
2) When does the exception 250.30(A)(1) Exception 2 apply? If this is a behind the meter connection, does it apply since we are powering a building?
3) I earth the system at 52IT and since the same wire goes via T/F I dont need to earth the T/F separately but I can bond ground to case in the T/F to continue the EGC, and also I have to earth the 89L because it is on the secondary of the T/F (and forms a new system basically)

Correct me if im wrong.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
That appears to be a wye-wye which would NOT be an SDS (if connected the way I think it is).

Edit: in other words, there should not be a N-G bond.

If the neutrals on both sides of the transformer are not bonded (to each other) I'm pretty sure it's separately derived.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I agree. I can't tell from the drawing if they are common.
Yeah, the drawing is pretty fuzzy when I try to make it bigger. It sort of looks like one of the phases is bonded on both sides, but that can't be right.
 
Yeah, the drawing is pretty fuzzy when I try to make it bigger. It sort of looks like one of the phases is bonded on both sides, but that can't be right.

We touched on wye-wye recently in another thread, and although I have never really bought any of the reasons people throw out there, there seems to be thinking that bonding the two neutrals together is a good thing, hence why I jumped to the conclusion that they were intended to be bonded. Hopefully OP can clarify.
 

TheElectrician

Senior Member
We touched on wye-wye recently in another thread, and although I have never really bought any of the reasons people throw out there, there seems to be thinking that bonding the two neutrals together is a good thing, hence why I jumped to the conclusion that they were intended to be bonded. Hopefully OP can clarify.

If you see the PDF attached, I have bonded the neutral on both the sides because 250.30(A)(1)(b) says, "where the system bonding jumper is installed at the first disconnecting means of a separately derived system (T/F), the system bonding jumper must connect the neutral conductor of the derived system to the metal disconnecting means enclosure" - Mike Holt NEC 2014 Solar Photovoltaic Systems book.

Which I interpreted as the first disconnecting means on both primary and secondary side.
 
If you see the PDF attached, I have bonded the neutral on both the sides because 250.30(A)(1)(b) says, "where the system bonding jumper is installed at the first disconnecting means of a separately derived system (T/F), the system bonding jumper must connect the neutral conductor of the derived system to the metal disconnecting means enclosure" - Mike Holt NEC 2014 Solar Photovoltaic Systems book.

Which I interpreted as the first disconnecting means on both primary and secondary side.

You only bod N-G on the secondary side
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
If you see the PDF attached, I have bonded the neutral on both the sides because 250.30(A)(1)(b) says, "where the system bonding jumper is installed at the first disconnecting means of a separately derived system (T/F), the system bonding jumper must connect the neutral conductor of the derived system to the metal disconnecting means enclosure" - Mike Holt NEC 2014 Solar Photovoltaic Systems book.

Which I interpreted as the first disconnecting means on both primary and secondary side.

The derived neutral is in the secondary of your transformer and there is no electrical connection to the primary unless you make one, and generally this is not done.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
You only bod N-G on the secondary side


It's correct that 250.30(A)(1) is only about the secondary side. But here's a loaded question:

Is 89L a service disconnect? If so then the N-G bond there is correct.
[MENTION=159145]TheElectrician[/MENTION]
We are not going to decide that question here, although you've got it drawn like it is a service disconnect. But you and the AHJ must be on the same page. Let us know if you need references to past threads on the forum.
 
It's correct that 250.30(A)(1) is only about the secondary side. But here's a loaded question:

Is 89L a service disconnect? If so then the N-G bond there is correct.

Yes, but it depends on what OP meant by "bonded on the primary". I kinda took this to mean there was a N (primary)-G bond in the transformer, in addition to the bond at the service equipment. Maybe he was just talking about the Bond at the service...?
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Yes, but it depends on what OP meant by "bonded on the primary". I kinda took this to mean there was a N (primary)-G bond in the transformer, in addition to the bond at the service equipment. Maybe he was just talking about the Bond at the service...?

In his OP he said "I have bonded N-G on the first disconnecting means on both the primary and the secondary of the T/F to earth". I was making the point that while one doesn't bond the 'first disconnect' on the primary side, it just so happens that this 'first disconnect' likely needs it for other reasons.
 

TheElectrician

Senior Member
Hey everyone, thanks for the useful comments, and I would like to clarify the confusion here about the bonding on the primary - what I meant here is that have a bond in the first disconnect on the primary side of the transformer (which is 89L in this case) and not inside the primary of the transformer.

The updates I made to the drawing is, I bonded the N-G in the 89L, removed the bond in the 52IT and I have put a ground rod (Earth) in the 89L and the 52IT.
 

TheElectrician

Senior Member
It's correct that 250.30(A)(1) is only about the secondary side. But here's a loaded question:

Is 89L a service disconnect? If so then the N-G bond there is correct.

@TheElectrician
We are not going to decide that question here, although you've got it drawn like it is a service disconnect. But you and the AHJ must be on the same page. Let us know if you need references to past threads on the forum.

Yes, it is a service disconnect here.
 
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