COMMENT 5-199 250.112(B)

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I'm looking for constructive criticism on the following, and if you think it is merited, support in the form of comments from you on 5-199. Thanks, Jim Williams

4 Comment:

250.122 Size of Equipment Grounding Conductors.

(B) Increased in Size. Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire type equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.

(B) Increased in Size. If wire type equipment grounding conductor(s)s are present, where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation because of ambient temperature correction factors, exposure to sunlight on a rooftop, adjustments for more than three current carrying conductors, or for reduction in voltage drop, the following calculations shall be made (all areas in circular mils or mm?):

new ungrounded area / original ungrounded area = ratio
original equipment grounding area ? ratio = new equipment grounding area

The new required size of the equipment grounding conductor(s) shall be the next standard size that is equal or greater than the new equipment grounding area.

5 Statement of Problem and Substantiation.

The original text is so chopped up that just displaying the new text is clearer. Suggest that the reasons for increasing size be explicit and that calculation be expressed as a usable formula rather than suggested by the wording.

 

[don_resqcapt19]

...

(B) Increased in Size. If wire type equipment grounding conductor(s)s are present, where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation because of ambient temperature correction factors, exposure to sunlight on a rooftop, adjustments for more than three current carrying conductors, or for reduction in voltage drop, the following calculations shall be made (all areas in circular mils or mm?):

new ungrounded area / original ungrounded area = ratio
original equipment grounding area ? ratio = new equipment grounding area

The new required size of the equipment grounding conductor(s) shall be the next standard size that is equal or greater than the new equipment grounding area.

5 Statement of Problem and Substantiation.

The original text is so chopped up that just displaying the new text is clearer. Suggest that the reasons for increasing size be explicit and that calculation be expressed as a usable formula rather than suggested by the wording.

The list of reasons has the same problem as the original rule that applied to voltage drop. The intent is to have an increased sized EGC of the wire type anywhere you use a conductor larger than permitted by the NEC.
I also question the words "increased in size from the minimum size that has sufficient ampacity for the intended installation". If a code rule requires an increase in conductor size, then you have not made an increase from a conductor that has sufficient ampacity for the intended installation. If this rule is to work, it has to be based an increase from the minimum size conductor that would be permitted by the ampacity tables.

 

[fmtjfw]

Thanks, good clarification.

Thanks, good clarification.

The list of reasons has the same problem as the original rule that applied to voltage drop. The intent is to have an increased sized EGC of the wire type anywhere you use a conductor larger than permitted by the NEC.
I also question the words "increased in size from the minimum size that has sufficient ampacity for the intended installation". If a code rule requires an increase in conductor size, then you have not made an increase from a conductor that has sufficient ampacity for the intended installation. If this rule is to work, it has to be based an increase from the minimum size conductor that would be permitted by the ampacity tables.

what about "increased in size from the minimum size that has sufficient ampacity for the intended load". Does that fix the first problem?

" The intent is to have an increased sized EGC of the wire type anywhere you use a conductor larger than permitted by the NEC." I thought I listed the 4 reasons you increase the size of an ungrounded conductor. Is it not clear or did I leave something out?

 

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add?

Informational Note: Increases in size for the grounded conductor alone do not require the equipment grounding conductor to be increased in size.

 

[don_resqcapt19]

what about "increased in size from the minimum size that has sufficient ampacity for the intended load". Does that fix the first problem?

I don't think so. It has to be based only on the table ampacity. Sufficient ampacity for the load would require complicance with the various derating rules as they change the conductor ampacity.

" The intent is to have an increased sized EGC of the wire type anywhere you use a conductor larger than permitted by the NEC." I thought I listed the 4 reasons you increase the size of an ungrounded conductor. Is it not clear or did I leave something out?

"It was just what I had on the truck that day". That type of answer was the reason that the words "increased for voltage drop" were removed from this code rule.

 

[don_resqcapt19]

add?

Informational Note: Increases in size for the grounded conductor alone do not require the equipment grounding conductor to be increased in size.

Not sure if that is needed, but I don't think that you can add a new idea at the comment stage.

 

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add?

Informational Note: Increases in size for the grounded conductor alone do not require the equipment grounding conductor to be increased in size.

The section already states that it refers only to the ungrounded conductors so why would the added wording be needed? IMO if you need to add explanations to every code section then the book would be 5000 pages long.

 

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Change must have been a long time ago.

Change must have been a long time ago.

I don't think so. It has to be based only on the table ampacity. Sufficient ampacity for the load would require complicance with the various derating rules as they change the conductor ampacity.


"It was just what I had on the truck that day". That type of answer was the reason that the words "increased for voltage drop" were removed from this code rule.

I looked at 2002 through 2012 and found the 250.122(B) text to be identical. There were change bars in 2002 for the paragraph, but that's the oldest edition I have.

Can you suggest a phrase that would identify the original size, before any derating is applied?

I don't understand how "It was just what I had on the truck that day" has anything to do with "increased for voltage drop"?

Looking for some help here. Thanks

 

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Don't know what the "rules" are.

Don't know what the "rules" are.

Not sure if that is needed, but I don't think that you can add a new idea at the comment stage.

I would think that since you can suggest substitute text, that the text could be organized into main and info.

 

[fmtjfw]

You are probably right

You are probably right

The section already states that it refers only to the ungrounded conductors so why would the added wording be needed? IMO if you need to add explanations to every code section then the book would be 5000 pages long.

It would not be the first "lame" Info Note.

 

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ROP entries around 250.122(B)

ROP entries around 250.122(B)

The 5-197 entry is a hold from the Technical Correlating Committee because the text is not clear and concise.

The 5-198 entry adds "of the wire type" but the justification is based on understanding and calculating the ampacity of metallic raceways, which is not in the added text?

The 5-199 entry is even stranger. It adds the current proposed text that I find very difficult to read. BUT the justification is that we really don't need to increase the sizes because the grounding conductor loads are expected to be very brief???

The 5-200 entry is rejected, it wants to allow the reduction in size based on engineering supervision.

Maybe Code, like sausage, is something you don't want to watch being made.:roll:

 

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REVISED VERSION COMMENT 5-199 250.112(B)

REVISED VERSION COMMENT 5-199 250.112(B)

I'm looking for constructive criticism on the following, and if you think it is merited, support in the form of comments from you on 5-199. Thanks, Jim Williams

4 Comment:

250.122 Size of Equipment Grounding Conductors.

(B) Increased in Size. Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire type equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.

(B) Increased in Size. If wire type equipment grounding conductor(s) are present, where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity before any adjustments for derating for (1) ambient temperature correction factors, (2) exposure to sunlight on a rooftop, (3) adjustments for more than three current carrying conductors, or (4) for reduction in voltage drop, then the required grounding conductor size shall be calculated using the following equation:


Agnew = Agorg ? (Aunew ? Auorg)

where:
Agnew = new area required for grounding conductor
Agorg = original area of grounding conductor
Aunew = new area for ungrounded conductor after all adjustments & deratings
Auorg = original area for ungrounded conductor before any adjustments or deratings
all areas in circular mils or mm?

The new required size of the equipment grounding conductor(s) shall be the next standard size that is equal or greater to the Agnew area.

Informational Note: Increases in size for the grounded conductor alone do not require the equipment grounding conductor to be increased in size.

5 Statement of Problem and Substantiation.

The original text is so chopped up that just displaying the new text is clearer. Suggest that the reasons for increasing size be explicit and that calculation be expressed as a usable formula rather than suggested by the wording. Parens not needed.

Informational note indicates larger grounded conductor (for harmonics for instance) does not trigger larger EGC.

 

[don_resqcapt19]

The "how to calculate" is not needed. "Proportional" does that job without all of the other text. I don't see a need for the "laundry list". The only thing that needs to be cleared up is the "starting point" for the ungrounded conductor size increase. In general, if you use a conductor with an OCPD that is smaller than the maximum permitted OCPD for that conductor, based only on the table amapcity of the conductor and the overcurrent protection rules, you trigger the need for an increased size EGC.