SSBJ - where to connect

[charlie b]

The secondary conductors of a step-down transformer will include an SSBJ sized per 250.102(C). Where are the two ends of that conductor terminated?

 

[Isaiah]

The secondary conductors of a step-down transformer will include an SSBJ sized per 250.102(C). Where are the two ends of that conductor terminated?

My experience is one end at XFMR, XO - which sometimes is connected to 4 hole nema
lug- then to the Grd buss in the panelboard for the other end


Sent from my iPhone using Tapatalk

 

[ron]

One of my often referred to images from MH

 

[LarryFine]

View attachment 2571924

Can't you alternately bond the neutral in the disconnect and omit the SSBJ as shown?

 

[jaggedben]

Can't you alternately bond the neutral in the disconnect and omit the SSBJ as shown?

Well, no, not exactly. The SSBJ is still required, although it's permitted to be a raceway or bus. And, you're supposed to move the GEC to the disconnect then, too. See 250.30(2) and (5).

 

[augie47]

Can't you alternately bond the neutral in the disconnect and omit the SSBJ as shown?

There is an exception in 250.30(A)(2) where under specific conditions the SSBJ can be omitted on outside transformers but generally as jaggedben states the SSBJ is required.

 

[Elect117]

450.10 if it is a dry type. Transformer Terminal bar to downstream OC EGC terminal bar.

 

[david]

Can't you alternately bond the neutral in the disconnect and omit the SSBJ as shown?

Let's label (the the bond the neutral) the system bonding jumper ((SBJ) in your question.

Your not being told that the SBJ cannot be moved to the first disconnect in the illustration if you choose to.

What would be "omitted" in the transformer would be the system bonding jumper and the grounding electrode system @ the transformer location


Because you moved them to the disconnect location

That's why as I believe your aware 250.30 (5) grounding electrode conductor "This connection shall be made at the same point on a separately derived system where the system bonding jumper is connected".

 

[Jpflex]

The secondary conductors of a step-down transformer will include an SSBJ sized per 250.102(C). Where are the two ends of that conductor terminated?

SSBJ was never included in any transformers i wired up, but after determining its size as you said to 250.102 C, I connected mine at the transformer EGC BUSS OR metal eclosure and other end to disconnect panel EGC buss or metal enclosure

Xo neutral also connects to EGC buss or metal disconnect cabinet. Variation depends where you place system bonding jumper at transformer xo or first point of disconnect for secondry

 

[Jpflex]

If th

Let's label (the the bond the neutral) the system bonding jumper ((SBJ) in your question.

Your not being told that the SBJ cannot be moved to the first disconnect in the illustration if you choose to.

What would be "omitted" in the transformer would be the system bonding jumper and the grounding electrode system @ the transformer location


Because you moved them to the disconnect location

That's why as I believe your aware 250.30 (5) grounding electrode conductor "This connection shall be made at the same point on a separately derived system where the system bonding jumper is connected".

If the transformer is located outside, then i believe the grounding electride conductor must be made at the source transformer. I think in this situation the system bonding jumper would also be located here. This was a confusing for me as well

 

[david]

If th

If the transformer is located outside, then i believe the grounding electride conductor must be made at the source transformer. I think in this situation the system bonding jumper would also be located here. This was a confusing for me as well

Post # 6

There is an exception in 250.30(A)(2) where under specific conditions the SSBJ can be omitted on outside transformers but generally as jaggedben states the SSBJ is required.

When the transformer XO is bonded and the required grounding electrode installed outside, you would want the grounded conductor to be the only bonded metal path from the transformer to the building.

Added bonded at the transformer, system bonding jumper at the building, grounded conductor bonded in two location

 

[Jpflex]

Post # 6

When the transformer XO is bonded and the required grounding electrode installed outside, you would want the grounded conductor to be the only bonded metal path from the transformer to the building.

Added bonded at the transformer, system bonding jumper at the building, grounded conductor bonded in two location

Yes one of my grounding and bonding books mentioned the grounded conductor could fulfill multiple roles as the SSBJ and grounded neutral conductor if sized for the larger of either.

However, it also said a separate SSBJ could be ran with the grounded conductor as long as a parallel path for objectionable current wasnt created - the earth ground rods path not counting as a path.

I would think under the method with a SSBJ and a grounded conductor, the source would have a system bonding jump and the first point of disconnect would not or vise versa but maybe not both.

This is what puzzled me in the past and I made many post here about this. If you are doing work in a breaker panel which is the first disconnect after the transformer secondary (previously instalked by someone else) but see no system bonding jumper to bond the neutral bus and ECG in the breaker panel are you to assume one was placed in the outside separetly derived transformer?

Or do you risk the violation of installing a redundant system bonding jumper at the first disconnect if there was one unknowingly alrrady installed in the upstream transformer (in door or out doors?)

 

[LarryFine]

Your not being told that the SBJ cannot be moved to the first disconnect in the illustration if you choose to.

What would be "omitted" in the transformer would be the system bonding jumper and the grounding electrode system @ the transformer location

Because you moved them to the disconnect location

This is what I meant. Moved, not eliminated.

 

[david]

Post # 6

When the transformer XO is bonded and the required grounding electrode installed outside, you would want the grounded conductor to be the only bonded metal path from the transformer to the building.

Added bonded at the transformer, system bonding jumper at the building, grounded conductor bonded in two location

First of all I misspoke in the above reply.
When I said building it should have said disconnect. I was coping and pasting and I messed up.

Yes one of my grounding and bonding books mentioned the grounded conductor could fulfill multiple roles as the SSBJ and grounded neutral conductor if sized for the larger of either.

However, it also said a separate SSBJ could be ran with the grounded conductor as long as a parallel path for objectionable current wasnt created - the earth ground rods path not counting as a path.

I would think under the method with a SSBJ and a grounded conductor, the source would have a system bonding jump and the first point of disconnect would not or vise versa but maybe not both.

This is what puzzled me in the past and I made many post here about this. If you are doing work in a breaker panel which is the first disconnect after the transformer secondary (previously instalked by someone else) but see no system bonding jumper to bond the neutral bus and ECG in the breaker panel are you to assume one was placed in the outside separetly derived transformer?

Or do you risk the violation of installing a redundant system bonding jumper at the first disconnect if there was one unknowingly alrrady installed in the upstream transformer (in door or out doors?)

250.30 (C) outside source
We are talking about that source being a transformer.

250.30(C) a grounding electrode connection at the transformer location

All it saying is ground the neutral at the transformer location and refers you to 250.50 and 250.30 (A)

250.30 (A) do not rebond on the load side of the system bonding jumper

250.30 (A) (1) when supplied by outside transformer. System bonding jumper at the grounding electrode conection.

Since we know the system bonding jumper bonds the neutral to the supply side bonding jumper we know we are required all three at the transformer location

The exception is only for a building being supplied by a feeder.

So from the transformer to the first disconnect where the feeder supply to the building originates you could apply the exception.

So for a building being supplied by an outside transformer, but not being supplied by a feeder.

The building supply from the transformer would have both a neutral and a supply side bonding jumper.
(The supply side bonding jumper could be metal conduit)

250.30(A) you cannot rebond the neutral since the system bonding jumper is required to be out at the transformer

There is no system bonding jumper at the building.
The supply side bonding jumper bonds to the eguipment ground and grounding electrode or electrodes at the building

 

[augie47]

With an outdoor transformer I think it is important to address the exceptions:
250.30(A)(1) System Bonding Jumper
Exception No. 2: If a building or structure is supplied by a feeder from an outdoor separately derived system, a system bonding jumper at both the source and the first disconnecting means shall be permitted if doing so does not establish a parallel path for the grounded conductor. If a grounded conductor is used in this manner, it shall not be smaller than the size specified for the system bonding jumper but shall not be required to be larger than the ungrounded conductor(s). For the purposes of this exception, connection through the earth shall not be considered as providing a parallel path.
and if you take advantage of that exception
250.30(A)(2) Supply Side Bonding Jumper
Exception: A supply-side bonding jumper shall not be required between enclosures for installations made in compliance with 250.30(A)(1), Exception No. 2.

 

[david]

With an outdoor transformer I think it is important to address the exceptions:
250.30(A)(1) System Bonding Jumper
Exception No. 2: If a building or structure is supplied by a feeder from an outdoor separately derived system, a system bonding jumper at both the source and the first disconnecting means shall be permitted if doing so does not establish a parallel path for the grounded conductor. If a grounded conductor is used in this manner, it shall not be smaller than the size specified for the system bonding jumper but shall not be required to be larger than the ungrounded conductor(s). For the purposes of this exception, connection through the earth shall not be considered as providing a parallel path.
and if you take advantage of that exception
250.30(A)(2) Supply Side Bonding Jumper
Exception: A supply-side bonding jumper shall not be required between enclosures for installations made in compliance with 250.30(A)(1), Exception No. 2.

Yes that means the disconnect and over current protection for the feeder supply would be at the transformer location or at a pedestal type location and the building feeder supply would have a neutral and a equipment ground from the feeder disconnect to the building

You're correct to emphasize the supply cannot create a parallel path

 

[wwhitney]

Yes that means the disconnect and over current protection for the feeder supply would be at the transformer location or at a pedestal type location and the building feeder supply would have a neutral and a equipment ground from the feeder disconnect to the building

No, the outdoor tap rule for transformer secondaries (240.21(C)(4)) would allow the OCPD to be at the building supplied, outside or inside nearest the point of entry. The result is that the feeder consists only of the circuit conductors, with the grounded conductor as the fault clearing path.

Cheers, Wayne

 

[wwhitney]

This is what I meant. Moved, not eliminated.

I'm a little late to the discussion, but it seems to me that other than the outdoor transformer case just discussed, there's always an SSBJ between the enclosures of the transformer and the first disconnect. Moving the SBJ (from one enclosure to the other) doesn't change that.

Cheers, Wayne

 

[david]

No, the outdoor tap rule for transformer secondaries (240.21(C)(4)) would allow the OCPD to be at the building supplied, outside or inside nearest the point of entry. The result is that the feeder consists only of the circuit conductors, with the grounded conductor as the fault clearing path.

Cheers, Wayne

Knowing that there are different kinds of separately derived systems. For the exception to apply the building supply would have to be a feeder. That applies to a generator or a transformer or whatever the derived source might be.

So what makes a source supply to a building a feeder.

An allowance for a building to be supplied directly from the secondary supply conductors to a building.

Does that make the building supply a feeder from a transformer secondary?
Does that make the building supply a tap from a transformer secondary?

When comes to location of overcurrent protection there are all kinds of exceptions for taps.

But when you talk about the location of the overcurrent protection of a supply that you identified as a feeder, overcurrent protection supply end or load end.

As you stated there is a location allowance in 240for the secondary supply conductors to be protected at there load end.

From what you posted your saying that defines those secondary supply conductors as a feeder

 

[augie47]

The exception basically allows you to treat a customer owned transformer the same as you would a utility (service) transformer provided all the stipulations are met.