Electrical and Mechanical Systems Flashcards

What is the minimum depth of working space required in front of a residential electrical panel operating at 0–150 volts to ground?

Answer: 36 inches

NEC 110.26 requires a minimum 36-inch-deep clear working space in front of panels operating at 0–150 volts to ground.

What is the minimum width of the working space in front of a residential service panel?

Answer: 30 inches or the width of the equipment, whichever is greater

The working space must be at least 30 inches wide or the width of the equipment, whichever is greater.

What is the minimum vertical clearance for overhead service-drop conductors above a residential driveway?

Answer: 12 feet

Service drops over residential property and driveways not subject to truck traffic require 12 feet of clearance.

An inspector finds two conductors secured under a single breaker terminal that is not listed for two wires. How should this be reported?

Answer: A double-tap defect that can cause loose connections and overheating

Double-tapping a terminal not listed for multiple conductors can loosen connections and cause arcing or overheating.

In a properly wired residential system, where should the neutral and equipment grounding conductors be bonded together?

Answer: At the main service disconnect only

Neutral-to-ground bonding occurs only at the service equipment; subpanels must keep neutrals and grounds separated.

Solid single-strand aluminum branch-circuit wiring installed in many homes from about 1965–1973 is primarily a concern because of what?

Answer: Its connections are prone to overheating and fire

Aluminum expands, oxidizes, and creeps at terminals, leading to loose, overheating connections.

What is the maximum overcurrent protection allowed for 14 AWG copper branch-circuit conductors in a dwelling?

Answer: 15 amps

14 AWG copper is limited to 15-amp overcurrent protection under the small-conductor rule.