Upsizing EGC for voltage drop

[JP23]

So what I'm gathering from this is that there is no requirement to use the smallest conductor size
possible based on the feeder rating so there is a little room for cheating by using #2 instead of
#3 CCC's as the basis for the calculations. Is this correct and generally acceptable?

 

[topgone]

So what I'm gathering from this is that there is no requirement to use the smallest conductor size
possible based on the feeder rating so there is a little room for cheating by using #2 instead of
#3 CCC's as the basis for the calculations. Is this correct and generally acceptable?

If you opt to compute, your results should be equal or bigger than what the NEC table says the EGC should be depending on the protective device setting/rating.

 

[Carultch]

So what I'm gathering from this is that there is no requirement to use the smallest conductor size
possible based on the feeder rating so there is a little room for cheating by using #2 instead of
#3 CCC's as the basis for the calculations. Is this correct and generally acceptable?

In NEC2014 and NEC2017, the language reads "the minimum size that has sufficient ampacity for the intended installation".

In otherwords, your starting point is the minimum size that you can use, if circuit length were not a factor. So pretend the circuit was only 20 ft long. What size can you use, with that configuration of wire QTY, wire type, conduit, load, circuit breaker/fuse, and environment? Local factors alone, what is the minimum local size?

So if adjustment and correction factors such as bundling require #4/0 on a 200A circuit, then #4/0 is your starting point for this rule. Even though #3/0 would otherwise be required if the bundling adjustment factor didn't apply. You forget about that, because it is not equivalent to the intended installation. So #4/0 with a #6 EGC would be the starting point, and you would scale the two sizes together proportionally according to kcmil, to get the corresponding new EGC when curtailing voltage drop.

 

[ramsy]

..so there is a little room for cheating by using #2 instead of #3

Property Insurers are not required to pay claims attributed to builders' lawlessness, or cheating, much less fire code violations.

If a breaker didn't trip before causing a fire, and insurance adjusters challenge by citing wrong size grounding wire per code, the burden of proof falls on contractor/installer's GL policy, and/or engineer/architect's plans E&O insurance.

If NEC ampacity tables show #3 before voltage drop, as code minimum after all adjustments, I believe exceeding minimum for future expansion is acceptable.

I believe under-sizing wire is where problems occur, and 310.15(C) only allows plans / "engineering supervision", which specify or modify this NEC ampacity table, to be "permitted" with approved ampacity formula's.