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So, let us assume we have a set of conductors (hot/neutral/ground) going off to some piece of utilization equipment. Can I also run a set of conductors of appropriate ampacity off this circuit to a subpanel, thus making the conductors both a branch circuit and a feeder at the same time, provided their ampacity isn't exceeded by the combined load? Or can a set of conductors be either a branch or a feeder under the NEC, but never both at once?

  • It would be an unusual situation to be sure, like if you had a disused circuit. I wonder if the tap rules would come into play, i.e. could the utilization equipment be a tap, or could the subpanel be a tap protected by an appropriate sized main breaker therein. – Harper Jan 31 '17 at 6:07
  • @Harper -- yeah, I was planning to bring the tap rules into play in the context of a future question. – ThreePhaseEel Jan 31 '17 at 12:39
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I'd like to see a real world example of this, but I don't think one could/would exist.

If you had a piece of equipment that required a 30 ampere circuit, for example. If you tapped a panel off that circuit, then you'd have to increase the size of the circuit, and/or follow the tap rules. The tap rules require overcurrent protection where the tap conductors terminate, so you'd need overcurrent protection at the new panel and the equipment.

So basically, the branch circuit conductors would become a feeder, and tap conductors would be used to tap the feeder.

So no, I'm going to say you cannot tap branch circuit conductors. Maybe if it was a 15 or 20 ampere branch circuit, but what would be the point of that?

  • I have seen this done in industrial sites but not really residential other than taps for ovens but they don't have a separate breaker panel. but agree it could be done but not likely with the information provided. – Ed Beal Jan 31 '17 at 13:53
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    As a simple example, suppose power were run to a piece of high-current outdoor equipment e.g. a well pump) and one wanted to add operate some hard-wired low-current device that would never draw more than one amp in the absence of a severe electrical fault (e.g. a wireless data logger or a small luminary to aid in servicing or inspection). Running a separate 14-2 conductor purely for the purposes of powering the data logger or luminary would seem excessive compared with adding a waterproof enclosure to house a circuit breaker and the low-current devices. – supercat Jan 31 '17 at 23:28
  • I suspect that you're right insofar that a conductor feeding a subpanel and other loads independent of the subpanel is indeed a feeder and not a branch circuit, hence bringing the feeder tap rules into play. (Perhaps this'd happen if you were retrofitting an existing well or surface water pump for fire pump service as part of a sprinkler retrofit, but that's a real messy corner case...) – ThreePhaseEel Feb 3 '17 at 3:25

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