Article 210 provides the requirements for branch circuits. As with most NEC articles, it has its own general requirements. Like the arrangement in many articles, those consist of Part I.
Any GFCIs or AFCIs you use cannot be reconditioned [Sec. 215.3]. There’s more to this meaning than how you source green installation receptacles. It also covers “field reconditioning.” Let’s say you get a service call where the business or home got flooded. The owner wants you to clean and dry the receptacles, check the wiring, and put the receptacles back. There are three important concepts you need to convey to the owner: Nope, nope, and nope. Not only is this time-intensive and risking a callback for you, it’s also a safety risk that is prohibited by the Code.
The next set of general requirements is for multiwire branch circuits (MBCs). The NEC does not define what an MBC is. Suppose you are looking at a 120V circuit in a residence. It has a black wire (hot), white wire (neutral), and ground wire (green). That’s three wires, or multiple wires, so it’s a multiwire circuit — right? Not so.
A key characteristic of an MBC circuit is it uses two or more ungrounded conductors that share a neutral. In that same residence, you then look at a 120V circuit that originates at a handle-tied pair of circuit breakers. It’s got two hot wires (red and black), one to each breaker. The 240V circuit next to it in the panel has the same wiring colors, but it originates at a two-pole breaker. Both of these are multiwire circuits.
All conductors of an MBC must originate at the equipment containing the overcurrent protective device (OCPD) for that circuit [Sec. 210.4(A)]. At the point where each MBC originates, it must have a means by which all ungrounded conductors can be simultaneously disconnected [Sec. 210.4(B)]. Circuit breakers inherently provide this, fuses do not. So, if you have fuses as your OCPD for the MBC, you must also have a disconnecting switch that will simultaneously disconnect all ungrounded conductors.
MBCs can supply only line-to-neutral loads [Sec. 210.4(C)]. But there are a couple of exceptions to this rule. An MBC can supply line-to-line loads if:
- It supplies only one utilization equipment, or
- All of its “ungrounded conductors are opened simultaneously by the OCPD.”
The second exception appears to negate Sec. 210.4(C), since Sec. 210.4(B) requires that all ungrounded conductors be opened simultaneously. But notice “by the OCPD”. If you are using fuses, the OCPD doesn’t open all ungrounded conductors simultaneously; the disconnecting switch required for complying with Sec. 210.4(B) is not an OCPD.
The final general requirement for MBCs is that the conductors be grouped per Sec. 200.6(B). Essentially, this means at some point within the enclosure you bundle that circuit’s conductors (grounded, grounding, ungrounded) using cable ties, markers, or similar means. The point is to keep them from being tangled up with or confused with conductors from other circuits. In a nicely dressed panel enclosure, these would be cable-tied (or similar) to appear to be a cable bundle, and they would be routed (and perhaps secured) accordingly.
