Feeders: Massachusetts Journeyman Electrician Practice Questions

According to the NEC, the conductors running from the main service panel of a house to a subpanel in a detached garage are:

Conductors between the service equipment and the final branch-circuit overcurrent devices (here, in the garage subpanel) are a feeder.

According to the NEC, unless the equipment is listed for 100% operation, feeder conductors must have an ampacity of at least the noncontinuous load plus what percentage of the continuous load?

Section 215.2(A)(1) requires the feeder ampacity to be at least the noncontinuous load plus 125% of the continuous load (before any adjustment or correction).

According to the NEC, the rating of a feeder overcurrent device must be at least:

Section 215.3 sizes the feeder overcurrent device at no less than the noncontinuous load plus 125% of the continuous load, unless the assembly is listed for 100% operation.

According to the informational note in the NEC feeder rules, what voltage drop limits give reasonable efficiency of operation?

The informational note to 215.2(A) suggests no more than 3% voltage drop on the feeder and 5% overall. Being an informational note, it is a recommendation, not a requirement.

According to the NEC, when a feeder carries the total load supplied by service conductors with an ampacity of 55 A or less, the feeder ampacity must be:

Section 215.2(A) requires feeder conductors to be no smaller in ampacity than the service conductors when the feeder carries the total load of service conductors rated 55 A or less.

According to the NEC, a common neutral may serve up to how many sets of 3-wire feeders?

Section 215.4(A) allows a common neutral for up to three sets of 3-wire feeders or two sets of 4-wire or 5-wire feeders.

According to the NEC, when feeders share a common neutral and are installed in a metal raceway, what is required?

Section 215.4(B) requires all conductors of feeders using a common neutral to be enclosed in the same metal raceway or enclosure, to prevent inductive heating (see also 300.20).

According to the NEC, before a feeder installation begins, what may the authority having jurisdiction require?

Section 215.5 lets the AHJ require a diagram showing feeder details before installation, including area in square feet, connected load, demand factors and conductor type and size.

According to the NEC, when must a feeder include an equipment grounding conductor?

Section 215.6 requires a feeder that supplies branch circuits requiring equipment grounding conductors to include or provide an equipment grounding conductor that the branch-circuit EGCs connect to.

According to the NEC, the equipment grounding conductor run with a feeder is sized based on:

Section 250.122(A) sizes equipment grounding conductors from Table 250.122 using the rating of the overcurrent device ahead of the circuit. Look the value up in your code book.

According to the NEC, if feeder ungrounded conductors are increased in size to reduce voltage drop, what happens to the wire-type equipment grounding conductor?

Section 250.122(B) requires the wire-type EGC to be increased proportionally to the circular mil area of the upsized ungrounded conductors, so the fault path keeps up with the larger circuit.

According to the NEC, when a feeder is run with parallel conductors in two separate raceways, how is the wire-type equipment grounding conductor installed?

Section 250.122(F) requires an EGC in each parallel raceway, each sized from Table 250.122 for the overcurrent device protecting the feeder.

According to the NEC, is a wire-type equipment grounding conductor ever required to be larger than the circuit conductors supplying the equipment?

Section 250.122(A) states that the equipment grounding conductor is not required to be larger than the circuit conductors supplying the equipment.

According to the NEC, where a building has feeders from more than one nominal voltage system, how must the ungrounded feeder conductors be handled?

Section 215.12(C) requires ungrounded feeder conductors to be identified by phase or line and system at all termination, connection and splice points when more than one voltage system exists, with the identification method documented at each feeder panelboard.

According to the NEC, in a panelboard supplied by a 4-wire delta system with a high leg, which phase position must the high leg occupy?

Section 408.3(E)(1) requires the high leg to be connected to the B phase in panelboards and switchboards (arranged A, B, C from front to back, top to bottom or left to right).