Master Electrician Practice Test

According to Section 220.82(A) the optional method of calculation is permitted only if the dwelling unit service-entrance conductors or feeder conductors have an ampacity of at least 100 amperes. This calculation method applies to a single dwelling unit, whether it is a separate building or located in a multifamily dwelling. It applies to dwellings served by a 120/240- volt, single phase system or a 208Y/120- volt, 3-phase system. Generally, the optional calculation method provides an easier and less complex calculation method than the standard (general) method for computing the total demand load for feeders and service-entrance conductors.

Due to the fact all the equipment on a farm will not be used simultaneously for an extended length of time, it is permitted to apply the demand factors shown in Table 220.103 when calculating the farm service-entrance conductors. This table shows the second largest individual load may be calculated at 75%.

Section 511.3(C)(3)(b) indicates where mechanical ventilation is not provided in the below floor level service pit of a major repair garage it shall be a Class I, Division 1 location. The Class I, Division 1 location below grade extends from the floor of the pit to the service area floor level.

The requirements for the location of conduit seals are to prevent an explosion from traveling through the conduit to another enclosure and to minimize the passage of gases or vapors from hazardous locations to nonhazardous locations. In Class 1, Division 1 locations, if the conduit enters an enclosure that contains arcing or high-temperature equipment, as required by Section 501.15(A)(1), conduit seals shall be installed within 18 inches of the enclosure.

As addressed in Section 404.8(B), permanent barriers are required between switches grouped in a box where the voltage exceeds 300 volts between the switches. Barriers are required between switches that are ganged in a box and used to switch 277-volt luminaires on 480Y/277-volt systems where two or more phase conductors enter the box. The barriers are required between the switches fed from two different phases of this system because the voltage between the phase conductors would be 480 volts and would exceed the 300-volt limit.

For the purpose of determining box size and fill, Table 314.16(B) shows the volume allowance, in cubic inches, required per conductor from sizes 18 AWG to 6 AWG. However, when sizing pull and junction boxes containing conductors of size 4 AWG and larger, the box dimension is to be calculated based on the diameter of the raceways entering the enclosure and the rules specified in Section 314.28 are to be applied.

Column 3 of Table 300.5, shows the conduit to have a permitted burial depth of not less than 18 inches from final grade, where given the conditions specified in the question.

The intent of Section 230.26, requiring the point of attachment of overhead service-drop conductors to be not less than 10 feet, is to prevent inadvertent contact with the conductors by persons, which may cause a shock hazard or electrocution and prevent physical damage to the conductors.

When electrical conduit or tubing enclose conductors of the same size, with the same type of insulation, where the raceway is more than 24 inches in length, Tables C.1 through C.12(A) of Annex C are permitted to be used when determining the maximum number of conductors permitted in the raceways. Table C.8 in this Annex indicates a trade size 3 in. RMC is required to enclose four (4) size 350 kcmil THWN copper conductors.

The general requirement for selecting the minimum size equipment grounding conductor is to select directly from Table 250.122 based on the rating or setting of the feeder or branch circuit overcurrent protective device(s). In this situation, the circuit breaker has a rating of 100 amperes, therefore a minimum size 8 AWG copper equipment grounding conductor is required to be routed with the air-conditioning unit supply conductors.

Potential transformers measure voltage.

A first aid kit should be provided for all jobs.