Equipment Grounding Conductor Sizing For Voltage Drop

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Yes. Thank you for finding the exact scenario where you have to use the values in the book to get the correct answer on a test. :lol:

The code rule is based on circular mils provided in Table 8, Chapter 9.

Submit a proposal to amend the table if you find it to be unacceptable, but I will continue to use the book values in the field and in class.
 
George Stolz said:
Yes. Thank you for finding the exact scenario where you have to use the values in the book to get the correct answer on a test. :lol:

The code rule is based on circular mils provided in Table 8, Chapter 9.

Submit a proposal to amend the table if you find it to be unacceptable, but I will continue to use the book values in the field and in class.
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There are more scenarios than just that one.

Where does the NEC actually say that???

As for submitting a proposal, I just may... someday. But it won't be on changing the values in Table 8. The cmil values are calculated from [rounded] AWG diameters in one or more standards which the NEC cannot change. If anything, it will be about rewording the Code section to determine upsizing AWG sizes based on the AWG size difference where no kcmil sizes are involved.
 
George Stolz said:
I would be so much happier if you just corrected the tables. Having to remember two methods for this requirement is a greater burden, IMO.
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The probability of getting the Table values changed is, in my estimate, about the same as me changing lead to gold. :happyyes:

Using AWG size difference is actually quite easy compared to doing cmil ratio calculations...

Up ungrounded one AWG size, up EGC one AWG size;
up ungrounded two AWG sizes, up EGC two AWG sizes;
up ungrounded three AWG sizes, up EGC three AWG sizes;
and so forth.

Can't get any easier than that... :blink:
 
George Stolz said:
You already did. Going by chapter 9, table 8 your example proved it. It's a circular mil off, requiring the next larger conductor.
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Two things:

1) Where does it say we have to use the cmil values listed in C9T8?

2) Where does it say if the ratios calculate to be off by 1 cmil or more we have to go to next larger size EGC?
 
Smart $ said:
Two things:

1) Where does it say we have to use the cmil values listed in C9T8?

2) Where does it say if the ratios calculate to be off by 1 cmil or more we have to go to next larger size EGC?
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1. 90.3
2. 250.122(B)

Why do you believe you can pick an outside source for your values as opposed to using the NEC? Why do you believe you can round down?

The simple fact of the matter is that all we have when we try to defend an installation or pass a test is the NEC provided.
 
George Stolz said:
1. 90.3
2. 250.122(B)

Why do you believe you can pick an outside source for your values as opposed to using the NEC? Why do you believe you can round down?
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90.3 said:
Chapter 9 consists of tables that are applicable as referenced.
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250.122(B) does not reference C9T8...

250.122 said:
(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors.
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...and specifies no rounding rules.

I chose the earlier example specifically in anticipation rounding being questioned. If we apply significant figure rounding rules, assuming of course there are four significant figures applied to the values in C9T8, then the 1.5907 and 1.5906 values given in my example [technically] round to 1.590 [four significant figures], and as such have no disparity. If we do not apply this significant figure rounding, I estimate approximating half of the upsizing ratios exhibit disparity with the AWG size difference method. The ratios with disparity would result in one AWG size larger EGC per "your method".

"Why do you believe you can pick an outside source for your values as opposed to using the NEC?"
Take a look at the informational note below C9T8. The NEC itself consistently uses outside references, and in many cases does not transpose relevant contextual matter.

George Stolz said:
The simple fact of the matter is that all we have when we try to defend an installation or pass a test is the NEC provided.
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You are aware of many sections where we have to consider the intent as overriding the literal interpretation of the wording... are you not???
 
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