... "I’m used to using Table 9 in the NEC for R, and using the formula VD=F*(L*R*I)/1000, where F is 1.73 for three phase circuits, and 2 is for single phase circuits."

Referring to the question in the prior post, you can see that the F factor is already accounted for in the tabular data that Revit uses. Thus, it is not necessary to multiply by such a factor.

Why does the voltage drop for single phase (single-pole) circuits in Revit seem to be about half what I’m calculating using the NEC R factor, and the formula 2*(L*R*I)/1000?

The 2 in the formula is used to compute Line-to-Line voltage drop. For a single pole circuit, typically, you account for the Line-to-Neutral voltage drop, which is half of the Line-to-Line voltage drop (and thus, no 2 factor is necessary). As stated in the documentation, the voltage drop for each circuit is reported as line-to-line for 2-pole (single phase) and 3-pole (three phase) circuits. The voltage drop is reported as line-to-neutral for 1-pole circuits.

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