Feeders: Texas Journeyman Electrician Practice Questions

Which conductors are "feeders"?

Feeders run from the service equipment, a separately derived system or other source to the final branch-circuit overcurrent device. Branch circuits start after that device.

Feeder conductors that supply continuous and noncontinuous loads must have an ampacity of at least:

Only the continuous portion is increased to 125%; the noncontinuous load is added at 100%.

The equipment grounding conductor run with a feeder is sized based on:

Equipment grounding conductors are sized from the rating of the overcurrent device protecting the circuit, using the table in 250.122.

A feeder supplies 80 A of continuous load and 30 A of noncontinuous load. What minimum ampacity must the feeder conductors have (no adjustment or correction factors)?

Take the continuous load at 125% and add the noncontinuous load at 100%.

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.