Voltage drop

[RemerElectricllc]

If I have a run of 130' with a breaker rated for 60 amps is it code for me to use 3x #4 thhn because of voltage drop or would I be safe with 6/3 Romex?

 

[infinity]

Voltage drop compensation is not required by the NEC but if you're designing for it you would need to know the actual load in amps.

Welcome to the Forum.

 

[drktmplr12]

If I have a run of 130' with a breaker rated for 60 amps is it code for me to use 3x #4 thhn because of voltage drop or would I be safe with 6/3 Romex?

limits to voltage drop are typically only required by state building code under the energy conservation chapter. most plans reviewers won't pick up on it. for Florida, its 5% max branch+feeder.

what voltage, how many phases, and what current is expected?

Using Table 9 for AC resistance and reactance:
worst case (48.1 amps should trip your thermal mag in 3 hours) you are working with 120V single phase:
130', 120V single phase, 48 amps at 0.8 pf (inductive load) in PVC, or no conduit, VD=2.9%
130', 120V single phase, 48 amps at 1.0 pf (resistive load) in PVC, or no conduit, VD=2.9%

jumping up to 230V single phase:
130', 230V single phase, 48 amps at 0.8 pf (inductive load) in PVC, or no conduit, VD=1.5%
130', 230V single phase, 48 amps at 1.0 pf (resistive load) in PVC, or no conduit, VD=1.7%

running in steel conduit would increase the voltage drops a bit. if you run it through any online voltage drop calculator available, the values might vary because there are many ways to approximate. Either way, I don't expect that you have an issue unless the location of the panelboard is a long distance from the source.

here is some educational material for yourself with approximation fomulas at the end. they appear to ignore the effects of steel conduit, which will increase the effective reactance of the cable, and therefore increase voltage drop for inductive loads. Cable reactance has no impact on resistive loads. This should get you 95% of the way there.

http://adamselectric.coop/wp-content/uploads/2015/02/Voltage-Drop.pdf

 

[tom baker]

The only nec article that has a voltage drop requirement is 695 fire pumps ( disclaimer, may be requirement in COPS article, which most have never used or even read)

 

[ptonsparky]

The only nec article that has a voltage drop requirement is 695 fire pumps ( disclaimer, may be requirement in COPS article, which most have never used or even read)

Verifying your suspicion.
COPS?

 

[tom baker]

Article 708 critical operations power systems.
I did not see a volt drop requirement in it.
COPS is very detailed on wiring methods, testing, maintenance, etc. For example feeders must be protected in a 2 hour wiring method, wiring must be in RMC,IMC or MI cable….

 

[don_resqcapt19]

The only nec article that has a voltage drop requirement is 695 fire pumps ( disclaimer, may be requirement in COPS article, which most have never used or even read)

There is one in 647.

647.4(D) Voltage Drop.
The voltage drop on any branch circuit shall not exceed 1.5 percent. The combined voltage drop of feeder and branch-circuit conductors shall not exceed 2.5 percent.

There may be another.

 

[tom baker]

Thanks Don. I had to look up Art 647. It like Art 708 are not commonly used.
Next time I will say "there are only a few articles that require voltage drop, one is Art 695 Fire Pumps"

 

[mayanees]

There is one in 647.


There may be another.

HAH! There are actually sixteen mentions, easily found using the "NFPA Link" search function. For $99/year I'm a believer!