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?
Fine Print Notes
- Thread starter swen
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- Lockport, IL
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- Semi-Retired Electrical Engineer
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.
Welcome to the forum.
Pierre C Belarge
Senior Member
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- Westchester County, New York
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.
The NEC is a safety document.
Design issues generally fall on the designer, which may necessitate exceeding the minimum requirements of the NEC.
ron
Senior Member
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- New York, 40.7514,-73.9925
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
Senior Member
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- Portage, Indiana NEC: 2008
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
Senior Member
- Location
- New York, 40.7514,-73.9925
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.
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.
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 ?
significant Vd will cause a decrease in current inverse trip breakers will be affected respectively.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Resistance is current limiting, which is what causes the voltage drop in the first place.
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