Electrical System Components Flashcards

What is the minimum size copper grounding electrode conductor required for a service with 2/0 AWG copper service-entrance conductors?

Answer: 4 AWG

Per NEC Table 250.66, 2/0 AWG copper service-entrance conductors require a minimum 4 AWG copper grounding electrode conductor.

Which component isolates the secondary winding of a control transformer from the primary and reduces voltage for control circuits?

Answer: Isolation transformer

An isolation transformer separates primary and secondary windings magnetically and provides voltage reduction for control circuit power supplies.

What is the maximum number of overcurrent devices (excluding the main) permitted in a lighting and appliance branch-circuit panelboard?

Answer: 42

NEC 408.54 limits lighting and appliance branch-circuit panelboards to a maximum of 42 overcurrent devices (poles).

In conduit fill calculations, what fill percentage is permitted when a conduit contains two conductors?

Answer: 40%

NEC Chapter 9 Table 1 allows 40% fill for conduits containing two conductors.

Which wiring method is most appropriate for connecting a motor to its controller in a location exposed to oil and coolant?

Answer: Liquid-tight flexible metal conduit (LFMC)

LFMC provides flexibility for vibrating motor connections and is listed for use in wet and oily environments.

A busway (bus duct) system offers which primary advantage over traditional conduit-and-wire feeders?

Answer: Easier tap-off at multiple points along the run

Busway systems allow plug-in tap boxes to be added at virtually any point along the run, making them ideal for industrial tap-off distribution.

What information is required to be marked on every listed luminaire (light fixture)?

Answer: Maximum lamp wattage and minimum conductor insulation temperature rating

Listed luminaires must be marked with the maximum lamp wattage and the minimum temperature rating of acceptable supply conductors to prevent overheating.