Fine Print Notes

[swen]

Article 215.2(A)(3) FPN No. 2 discusses excessive voltage dropes in branch and feeder circuits. Fine Print Notes are not mandatory. Does the NEC require that conductor sizes be increased if the voltage drope in a branch circuit becomes more than 3 pecent or the voltage drop in a branch plus a feeder becomes more than 5 percent?

 

[charlie b]

No, it does not require that. Good engineering practice would, and the client might have something to say on the topic, but not the NEC.

Welcome to the forum.

 

[Pierre C Belarge]

See 90.5(C) Explanatory Material.



The NEC is a safety document.

Design issues generally fall on the designer, which may necessitate exceeding the minimum requirements of the NEC.

 

[ron]

If your jurisdiction requires compliance with the energy code (IECC), then you must comply with voltage drop limitations from there, but not the NEC.

 

[hurk27]

See 90.5(C) Explanatory Material.



The NEC is a safety document.

Design issues generally fall on the designer, which may necessitate exceeding the minimum requirements of the NEC.

I have always wondered why they never made it mandatory since it can be a safety problem, if the voltage drop is enough it can keep the OCPD from opening, especially in a 430 install?

I could see a 10% being a mandatory limit, that would still provide OCPDs safety?

 

[ron]

In Subsection 8.2.1, ASHRAE 90.1 requires that feeder and branch-circuit voltage drop not exceed 2 percent and 3 percent, respectively.
This is the energy code reference if your adopted energy code has incorparated the ASHRAE Standard.
I do not think that the IECC has it on its own.

 

[nakulak]

I have always wondered why they never made it mandatory since it can be a safety problem, if the voltage drop is enough it can keep the OCPD from opening, especially in a 430 install?

I could see a 10% being a mandatory limit, that would still provide OCPDs safety?

I thought overcurrent devices worked strictly off current ?

 

[cpal]

I thought overcurrent devices worked strictly off current ?

significant Vd will cause a decrease in current inverse trip breakers will be affected respectively.

 

[hurk27]

I thought overcurrent devices worked strictly off current ?

Resistance is current limiting, which is what causes the voltage drop in the first place.

 

[W6SJK]

NEC only limits voltage drop in Fire Pump motor feeders. (and welding feeders as I recall but it's been a while. )