North Carolina Limited Electrical Contractor (L)

EMT must be fastened at intervals not exceeding 10 ft generally, but within 900 mm (3 ft) of each box, cabinet, conduit body, or other termination.

NEC 250.22 absolutely prohibits grounding of certain circuits (e.g., crane circuits over combustible fibers in Class III locations), whereas 250.21(A) lists systems that are allowed to remain ungrounded but are not mandated to be so.

Under standard NEC rules a conductor's ampacity must equal or exceed 100% of the overcurrent device rating, but in supervised industrial installations with devices rated over 800 A and two specific conditions met, ampacity need only be 95% of the device rating.

When the bonding jumper is at the source it connects the grounded conductor to the supply-side bonding jumper and the non-current-carrying metal enclosure; when it is at the first disconnect, the grounding electrode conductor must also be connected at that same disconnect point.

Feeder conductors must have ampacity equal to noncontinuous load plus 125% of the continuous load; noncontinuous loads are counted at 100% with no adder.

A one-family dwelling requires a service disconnect rated at least 100 amperes 3-wire, while an installation with no more than two 2-wire branch circuits requires only 30 amperes.

Edison-base fuseholders are permitted only as replacements in existing installations with no evidence of overfusing or tampering; once overfusing is found, Type S adapters must be installed so only correctly rated Type S fuses can be used and cannot be removed or shunted.

Interrupting Rating is the highest current at rated voltage a device is identified to interrupt under standard test conditions, whereas Fault Current is the actual current delivered at a point on the system during a short-circuit condition.

When connected solely to a rod, pipe, or plate electrode the GEC need not exceed 6 AWG copper; the concrete-encased electrode rule requires at least 20 ft of rebar but does not cap the GEC size under 250.66(A).

Luminaires in permanently installed fountains must operate on supply circuits of 150 volts or less between conductors, whereas submersible pumps and other submersible equipment may operate at up to 300 volts between conductors.

Tap conductors not over 25 ft long must have ampacity of at least one-third the feeder overcurrent device rating; the 10-ft tap rule requires a higher fraction (at least one-tenth is not applicable here — NEC 240.21(B)(2) specifies one-third for 25 ft taps).

Both rules set a floor of 1/0 AWG, but 310.10(G)(1) governs phase, neutral, or grounded circuit conductors connected in parallel, while 250.24(C)(2) specifically governs the grounded (neutral) service-entrance conductor run in parallel in each separate raceway or cable.