voltage drop

[jumper]

Well, close, but not exactly 11 AWG. Because the AWG scale is not a linear function of the cross sectional area, or even of the resistances. But in concept you are correct that its performance will be somewhere between the two gauge sizes that you run for both halves of the circuit.

It is probably most accurate to add up the resistances and divide by two to get the equivalent combined KCMIL of the series assembly. So the inverse of the KCMIL. I get an equivalent 8.02 kcmil when combining #10 and #12 in series, which is less than the Wikipedia value for #11 AWG (8.23 kcmil).

I am nominating you for The Egghead of the Week Award.

The winner gets free pi for a month.

 

[Smart $]

Well, close, but not exactly 11 AWG. Because the AWG scale is not a linear function of the cross sectional area, or even of the resistances. But in concept you are correct that its performance will be somewhere between the two gauge sizes that you run for both halves of the circuit.

It is probably most accurate to add up the resistances and divide by two to get the equivalent combined KCMIL of the series assembly. So the inverse of the KCMIL. I get an equivalent 8.02 kcmil when combining #10 and #12 in series, which is less than the Wikipedia value for #11 AWG (8.23 kcmil).

Actually, the AWG scale is linear. It is the whole-number-incremental-equivalent-cross-sectional area which is not.

Anyway, when doing the more traditional 2KIL÷V_D=CSA calculation, one usually rounds up to the next larger gauge, but typically a common and useful gauge.

Anyway, the point on sizing the EGC to the ungrounded conductor is a valid one which I had not considered, i.e. #12 ungrounded only requires #12 EGC.

Another point which pretty much goes ignored is that regarding feeder (and I believe service...) conductors, the ampacity of a grounded conductor which is not connected to any ocpd does not have to include a 125% factoring of the continuous load. Therefore, even without 220.61 reduction, a grounded feeder conductor could be smaller.

 

[wwhitney]

Actually, the AWG scale is linear. It is the whole-number-incremental-equivalent-cross-sectional area which is not.

I don't follow you. Things are not linear, it is only relationships that are or are not linear. The relationship of cross-sectional area (or diameter) to AWG is exponential.

Cheers, Wayne

 

[Smart $]

I don't follow you. Things are not linear, it is only relationships that are or are not linear. The relationship of cross-sectional area (or diameter) to AWG is exponential.

"Things", i.e. a scale, can be linear or non-linear. Have you not seen or heard of a logarithmic scale, for example. Technically, a scale of the logarithms is linear. The values the logarithms represent are not. If a scale, such as an axis on a graph, is labeled with the representative values incrementally (i.e. linearly) spaced, only then is the scale logarithmic (0, 1, 10, 100, 1000, etc). If that same scale is labeled with only the logarithms, the scale itself would be linear (0, 1, 2, 3, etc.).

Backtracking to my comment, I apologize to Carultch because I took part of his comment out of context (i.e. I stopped at linear rather than including the rest of his statement).

 

[wwhitney]

"Things",

Sorry, sloppy choice of words on my part. I meant quantities or numbers.

i.e. a scale,

Scales are in fact relationships. Between the quantity being expressed and the space on the page. Otherwise, I agree with your comments.

Cheers, Wayne

 

[electric_girl]

Wait a minute, if voltage drop isn't an issue, why are you upsizing the wire? Why a 20A OCPD on an 8A load?
I believe, if voltage drop isn't an issue, it isn't necessary to upsize your ground.

Sent from my SM-G920P using Tapatalk

 

[Dennis Alwon]

Wait a minute, if voltage drop isn't an issue, why are you upsizing the wire? Why a 20A OCPD on an 8A load?
I believe, if voltage drop isn't an issue, it isn't necessary to upsize your ground.

Sent from my SM-G920P using Tapatalk

If you upsize the conductors generally it is for voltage drop however the wording "for voltage drop" was removed years ago. The op did mention voltage drop

250.122(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.