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Monday, June 27, 2016
Question:
Re: CQD answer published Tuesday June 14, 2016 -Voltage Drop
The issue of excessive voltage drop and causing a fire wasn't addressed in the answer provided, and I feel it important to point out that this isn't the case. If excessive voltage drop could cause a fire, then the NEC would address it with mandatory requirements. Voltage drop is strictly a performance issue, which the Code doesn't address as found in Section 90.1(B). Having too much voltage drop will either cause the equipment not to function properly, if at all. Or, it will result in energy lost as the wire that is too small won't perform efficiently. The question submitter needs to remember that it takes voltage to push the current through the cable (the resistance). Overcurrent is what overheats the conductor and causes a fire. If the voltage drops due to too much resistance in the conductor, then overcurrent will not occur.
Eddie Guidry, Principal, CMP 11
A
Answer:
Hey Eddie thanks for your comment. As you know the NEC does address voltage drop in an indirect way by 110.3(B) so if a manufacturer's instructions specify a minimum voltage or voltage range then that is required. You are correct, in many situations it is only a performance issue, or lack thereof. Lower voltages can be a problem for loads such as motors which should be taken care of by the protection required in Article 430 - if it is appropriately provided.