Exam 4: Branch Circuits

Multioutlet branch-circuit ratings are limited to 15-, 20-, 30-, 40-, and 50-ampere except on premises, where they may have a higher rating.

When all conductors of the same alternating-current circuit are in the same raceway, the magnetic flux around each conductor the magnetic flux of the other circuit conductors.

Law proves that in a given circuit, the higher the impedance, the lower the current flow.

On what is the resistance of a conductor dependent?

During the process of laying out an electrical system, when are branch circuits assigned?

For motors, the OCPDs are .

Although several different types of insulation are listed in the NEC, there are only three different temperature ratings: 60 degrees C, 75 degrees C, and degrees C.

Where would insulation with high-temperature rating be needed and why?

The allowable ampacity of a 4 AWG THHN conductor is 95 amperes.If we have four 4 AWG THHN conductors, what is the adjusted ampacity?

Whenever a grouping of more than current-carrying conductors exists, an adjustment factor from NEC Table 310.15(B)(3)(a) must be applied.

What is thermoset insulation?

In general, the letter-type designation R formerly referred to a -based covering and now indicates thermoset insulation.

NEC Table 310.15(B)(16) places the wires available for building construction into two categories: and aluminum.

When sizing conductors and overcurrent protection, you must take 100 percent of the noncontinuous loads plus percent of the continuous loads.

Count the neutral conductor of a 4-wire, 3-phase, wye-connected circuit when the major portion of the load is electric discharge lighting (fluorescent, mercury vapor, high-pressure sodium, etc.), data processing, and other loads where the neutral conductor carries current.

Several factors or conditions can cause conductors to overheat, but often overlooked is the possibility of .

Metal raceways not properly grounded could become " " and present a shock hazard.

If the ambient temperature anywhere along the length of a raceway is less than 78 degrees F or higher than degrees F, the ampacity of the conductors in the raceway, or cable, must be modified by a correction factor.

How does oxidation affect aluminum conductors, and how can this be averted?

An exception to the rule where two different temperatures are encountered for the same conductors permits the application of the higher ampacity (lower temperature) if the length of the conductors that enter a higher temperature is not more than 10 ft (3.0 m) or not more than 10% of the total circuit length.