Power Factor for voltage drop calculations for a commercial building .95?

[Cartoon1]

Hello all,

Typically what do you use for PF when doing voltage drop calculations for a typical commercial building from its switchboard (480/277) to the subpanels? Nothing crazy, typical LED lights, Receptacles, Offices setup, step down transformers to 208/120V, and A/C. Is .95 reasonable or maybe even Pf of 1 since it is mostly resistive load?

Thank you

 

[ptonsparky]

Hello all,

Typically what do you use for PF when doing voltage drop calculations for a typical commercial building from its switchboard (480/277) to the subpanels? Nothing crazy, typical LED lights, Receptacles, Offices setup, step down transformers to 208/120V, and A/C. Is .95 reasonable or maybe even Pf of 1 since it is mostly resistive load?

Thank you

Are you doing fault current calculations or simple VD?

 

[Cartoon1]

Are you doing fault current calculations or simple VD?

Simple VD%

 

[wwhitney]

Are you asking because (a) you have Watts and need to use an average PF to get VA to get the currents or (b) for AC voltage drop, even once the current is known, the power factor of the loading has an effect because of the reactance of the conductors?

For (b) the effect is small unless the conductors are physically quite large, as the reactance per foot is fairly constant with size, and only at very large sizes is the resistance per foot low enough that the impedance isn't simply dominated by the resistance.

If this is for a feeder with physically large conductors (MCM range, IIRC), then I would suggest looking at Chapter 9 Table 9 Note 2 and calculating the "effective Z" for PFs of 0.85 (easy, given in the table), 0.9, 0.95, and 1.0, and seeing if it makes much difference.

Cheers, Wayne

 

[ron]

Since the only code requirement for voltage drop is in the energy code, and doesn't indicate any criteria, I use pf=1 for simplicity.

 

[David Castor]

0.95 is a reasonable pf for this service.