Grounded Conductor required?

[Dale001289]

This is where you need to read 90.5(A) & (B)

Please do and if it's accepted you can come back and tell us that is required at that time, as of now it isn't.


This is where you need to read 90.5 (A) & (B) again.

You're welcome

90.5 bears no direct relevance to this conversation but nice try anyway.
And you are also welcome
Dale


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[roger]

90.5 bears no direct relevance to this conversation but nice try anyway.

Sure it does, you just refuse to see it the same as you refuse to see the others posting that the Grounded Conductor is not required to be brought to the first means of disconnect in an SDS are correct.

If you can show us where the NEC states it "shall be" you will substantiate your claim, until then you are just believing something that isn't true.

Note under 250.24(C) it says

(C) Grounded Conductor Brought to Service Equipment.
Where an ac system operating at less than 1000 voltsis grounded at any point, the grounded conductor(s) shall
be routed with the ungrounded conductors to each service
disconnecting means and shall be connected to each disconnecting
means grounded conductor(s) terminal or bus.

Show us where Grounded Conductor Brought to Separately Derived Systems can be found

Roger

 

[Dale001289]

Sure it does, you just refuse to see it the same as you refuse to see the others posting that the Grounded Conductor is not required to be brought to the first means of disconnect in an SDS are correct.

If you can show us where the NEC states it "shall be" you will substantiate your claim, until then you are just believing something that isn't true.

Note under 250.24(C) it says

Show us where Grounded Conductor Brought to Separately Derived Systems can be found

For SDS it’s implied - not actually stated. Keep in mind the code isn’t a perfectly written document that’s why it changes every three years.
In the above diagram the system bonding jumper takes a ground fault back to the transformer via EGC and then to the CB - which trips (hopefully)
- but this is not the ONLY condition for fault. There are others. Grounding and bonding isnt an exact science and always subject to interpretation but I prefer to err on the side of safety and reliability - a few extra bucks for an additional white insulated copper conductor is not a major concern of mine. But then again the smallest project I’ve worked in in the last ten years is $2 BN. I can see how cost may be an issue for a small business owner subcontractor.
In spite of some very enlightening posts I intend to stick to my interpretation.


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[infinity]

For SDS it’s implied - not actually stated. Keep in mind the code isn’t a perfectly written document that’s why it changes every three years.
In the above diagram the system bonding jumper takes a ground fault back to the transformer via EGC and then to the CB - which trips (hopefully)
- but this is not the ONLY condition for fault. There are others. Grounding and bonding isnt an exact science and always subject to interpretation but I prefer to err on the side of safety and reliability - a few extra bucks for an additional white insulated copper conductor is not a major concern of mine. But then again the smallest project I’ve worked in in the last ten years is $2 BN. I can see how cost may be an issue for a small business owner subcontractor.
In spite of some very enlightening posts I intend to stick to my interpretation.

It's not actually stated because as numerous posters have it said it's simply not required. If you think that it should be then as suggested sent in a PI and see if the CMP agrees with your substantiation. Until then accept the fact that you're assertion that it's implied is merely an opinion.

 

[roger]

For SDS it’s implied

No it's not even though you wish it was.

Keep in mind the code isn’t a perfectly written document that’s why it changes every three years.

Granted it changes for clarification and correction but also because methods, materials, and products change. This is where you need to submit your PI if you want it to change.

but I prefer to err on the side of safety and reliability - a few extra bucks for an additional white insulated copper conductor is not a major concern of mine.

So if you're paying the uneccessary cost have at it but that doesn't change the fact that it is not required.

But then again the smallest project I’ve worked in in the last ten years is $2 BN. I can see how cost may be an issue for a small business owner subcontractor.
In spite of some very enlightening posts I intend to stick to my interpretation.

The size of the projects do not change the NEC and your sticking to your interpretation is your prerogative.

Most my projects are in the multi millions and up to 160 men so, from experience I know if it's a 1-2 man project or a 100 - 200 man project, the code reads the same.

With that said, if it's included in the bid documents fine, if not and someone wants it later I will happily submit a CO.

Roger

 

[rbalex]

For SDS it’s implied - not actually stated. Keep in mind the code isn’t a perfectly written document that’s why it changes every three years.
In the above diagram the system bonding jumper takes a ground fault back to the transformer via EGC and then to the CB - which trips (hopefully)
- but this is not the ONLY condition for fault. There are others. Grounding and bonding isnt an exact science and always subject to interpretation but I prefer to err on the side of safety and reliability - a few extra bucks for an additional white insulated copper conductor is not a major concern of mine. But then again the smallest project I’ve worked in in the last ten years is $2 BN. I can see how cost may be an issue for a small business owner subcontractor.
In spite of some very enlightening posts I intend to stick to my interpretation.


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I don't usually step out of the Hazardous Location field, because there are so many other well qualified commenters in other subjects. I will say this, having been a Principal on four different NFPA Technical Committees over the years, nothing intended is "implied" or it is a violation of the NFPA Manual of Style (MOS) and gets corrected fairly quickly. The NEC has its own MOS as well but it is subordinate to the NFPA MOS. Both may be found from links on this page under "Resources".

I'm retired now but I was lead engineer on several muli-$BN jobs - back when a $BN was "real money".

 

[Dale001289]

It's not actually stated because as numerous posters have it said it's simply not required. If you think that it should be then as suggested sent in a PI and see if the CMP agrees with your substantiation. Until then accept the fact that you're assertion that it's implied is merely an opinion.

Look at 2017 NEC Handbook - EXHIBITS 250.1, 250.6, 250.7 250.14, 250.15 and 250.16....Each SDS is pictured with a Grounded, white conductor. In these pictures, it appears the grounded conductor is primarily acting as a neutral.
For SDS's without line to neutral loads if you want to omit the grounded conductor and claim the SSBJ does the same thing I wouldn't have a major problem with that as long as the SSBJ is bonded from the Neutral bar to the Xfmr XO and is taped white at both ends, it would (probably) be consistent with NEC.

 

[Dale001289]

I don't usually step out of the Hazardous Location field, because there are so many other well qualified commenters in other subjects. I will say this, having been a Principal on four different NFPA Technical Committees over the years, nothing intended is "implied" or it is a violation of the NFPA Manual of Style (MOS) and gets corrected fairly quickly. The NEC has its own MOS as well but it is subordinate to the NFPA MOS. Both may be found from links on this page under "Resources".

I'm retired now but I was lead engineer on several muli-$BN jobs - back when a $BN was "real money".

Hi Bob, nice to see you on this thread and thanks for the input. Perhaps the word 'implied' was not such as wise one. Maybe I should have said 'preferred' - but then again, this probably isn't acceptable language either.

 

[roger]

Hi Bob, nice to see you on this thread and thanks for the input. Perhaps the word 'implied' was not such as wise one. Maybe I should have said 'preferred' - but then again, this probably isn't acceptable language either.

Exactly, neither implied nor preferred are enforceable.

After your PI is accepted we can revisit this subject.

Roger

 

[rbalex]

From the NEC MOS:

3.2 Word Choices.
3.2.1 Unenforceable Terms. The NEC shall not contain
references or requirements that are unenforceable or vague. The terms
contained in Table 3.2.1 shall be reviewed in context, and, if the resulting
requirement is unenforceable or vague, the term shall not be used.

Table 3.2.1 Possibly Unenforceable and Vague Terms:
…
Prefer(red)
…

There are plenty of such terms.

Just a further note: A PI won't get resolved until sometime around 2022. You could try for an Formal Interpretation (See NEC Section 90.6) - they are a pain to get, but could be quicker and have the advantage that, IF it is answered, the CMP is obligated to create an unambiguous text. See Regulations Governing the Development of NFPA Standards, Section 6.

 

[Dale001289]

From the NEC MOS:

There are plenty of such terms.

Just a further note: A PI won't get resolved until sometime around 2022. You could try for an Formal Interpretation (See NEC Section 90.6) - they are a pain to get, but could be quicker and have the advantage that, IF it is answered, the CMP is obligated to create an unambiguous text. See Regulations Governing the Development of NFPA Standards, Section 6.

This is great info Bob. Looks like a Formal Interpretation is the best way to go.

 

[packersparky]

Look at 2017 NEC Handbook - EXHIBITS 250.1, 250.6, 250.7 250.14, 250.15 and 250.16....Each SDS is pictured with a Grounded, white conductor. In these pictures, it appears the grounded conductor is primarily acting as a neutral.
For SDS's without line to neutral loads if you want to omit the grounded conductor and claim the SSBJ does the same thing I wouldn't have a major problem with that as long as the SSBJ is bonded from the Neutral bar to the Xfmr XO and is taped white at both ends, it would (probably) be consistent with NEC.

It would be a violation to mark the SSBJ with white tape.

 

[don_resqcapt19]

Yes you are required to bring it both for line to neutral loads and yes to clear a fault - with or without line to neutral loads.
A ground fault can occur downstream phase to conduit for example it doesn’t need a neutral to go to ground on branch circuits.
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If there are no line to neutral loads, there is no technical or code reason to run a grounded conductor from the transformer to the first OCPD. If your SDS is a grounded system and you are not installing a grounded conductor to the first OCPD, the system bonding jumper must be installed at the transformer. A Supply Side Bonding Jumper will be installed between the transformer and the OCPD. That is the fault clearing path.

 

[roger]

It would be a violation to mark the SSBJ with white tape.

Agreed.

Roger

 

[Dale001289]

It would be a violation to mark the SSBJ with white tape.

Actually, the tape could be omitted as well - a ground fault doesn't care if the conductor has green or white insulation. If the Xfmr vendor provides a jumper from the XO to the Xfmr Neutral bar then the SSBJ will work fine, provided it also lands on the Neutral bar. The problem with using only the SSBJ is that its not always adequately bonded directly to the Xfmr XO. This is the advantage of having the SSBJ plus a dedicated grounded conductor.

 

[packersparky]

Actually, the tape could be omitted as well - a ground fault doesn't care if the conductor has green or white insulation. If the Xfmr vendor provides a jumper from the XO to the Xfmr Neutral bar then the SSBJ will work fine, provided it also lands on the Neutral bar. The problem with using only the SSBJ is that its not always adequately bonded directly to the Xfmr XO. This is the advantage of having the SSBJ plus a dedicated grounded conductor.

The SSBJ is always adequately bonded to the grounded conductor. Its job is to provide a low impedance path to the source. It is required to be connected to the grounded conductor. See the definition of SSBJ.

 

[Dale001289]

The SSBJ is always adequately bonded to the grounded conductor. Its job is to provide a low impedance path to the source. It is required to be connected to the grounded conductor. See the definition of SSBJ.

There’s an option to bond to the EGC. The best path to the XO is via the grounded conductor


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[packersparky]

There’s an option to bond to the EGC. The best path to the XO is via the grounded conductor


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Who said anything about EGC's? You keep bringing things up that are not relevant to the discussion.

If the system bonding jumper was installed at the SDS, and the grounded conductor is brought to the disconnect, the grounded conductor would not play any role in clearing ground faults downstream of the disconnect. That is the job of the SSBJ. See the picture that Augie posted. The fault cannot return to the source from the disconnect on the grounded conductor when the system bonding jumper is installed at the SDS.

 

[Dale001289]

Who said anything about EGC's? You keep bringing things up that are not relevant to the discussion.

If the system bonding jumper was installed at the SDS, and the grounded conductor is brought to the disconnect, the grounded conductor would not play any role in clearing ground faults downstream of the disconnect. That is the job of the SSBJ. See the picture that Augie posted. The fault cannot return to the source from the disconnect on the grounded conductor when the system bonding jumper is installed at the SDS.

Go back and read the definition of SSBJ again. It gives an option of bonding to the EGC. The scenario by the other member is only ONE fault path - but there are others - this is why including a direct connection from neutral bar to neutral bar is desirable via the grounded conductor.
Lots of good Info on this string.
I plan to put together a formal input per BOBs suggestion that will clarify all above issues once and for all.

For now, my attention goes to a more important issue:
Houston Rockets defeating the GS Warriors tonight in Oakland for game six.




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[packersparky]

Go back and read the definition of SSBJ again. It gives an option of bonding to the EGC. The scenario by the other member is only ONE fault path - but there are others - this is why including a direct connection from neutral bar to neutral bar is desirable via the grounded conductor.
Lots of good Info on this string.
I plan to put together a formal input per BOBs suggestion that will clarify all above issues once and for all.

For now, my attention goes to a more important issue:
Houston Rockets defeating the GS Warriors tonight in Oakland for game six.

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If the system bonding jumper is installed at the SDS, a second connection of the grounded conductor to any normally non current carrying metal parts at the disconnect is a violation of 250.30(A). The SSBJ is connected to the grounded conductor at the SDS and the EGC's at the disconnect, hence the langauge in the definition.