Domain 1 · Task 5 · 7% of the exam
NHIE electrical systems: the biggest single task
Nothing else on the exam carries 7%. Every other task in Domain 1 tops out at 6%. If you are deciding where an extra evening goes, it goes here — and most of what gets asked is dimensions, ampacity and clearances, which are the easiest marks on the paper to simply memorise.
| Subject | Figure |
|---|---|
| Working space at a panel | 36 in deep · 30 in wide · 6 ft 6 in headroom · highest handle ≤ 6 ft 7 in |
| Conductor ampacity | 14 AWG = 15 A · 12 AWG = 20 A |
| Continuous load | May not exceed 80% of the overcurrent device rating |
| Branch-circuit voltage drop | Under 3% — recommended, not required. The exam tests that distinction |
| Ground rod | Driven at least 8 feet into the earth, approved and accessible clamp |
| Direct-buried UF cable | At least 24 inches deep |
| NM (Romex) support | Every 4½ feet, and within 12 inches of each box |
| Overhead clearance — residential driveway | 12 feet |
| Overhead clearance — walking surface | 10 feet |
| Overhead clearance — beside or below an operable window or door | 3 feet |
| Overhead clearance — over pool water | 22½ feet |
Double taps
Two conductors under one breaker lug is only acceptable if the terminal is rated for two conductors. Not if the wires are the same gauge, not if the calculated load is under the ampacity, not if the panel has spare circuits. The manufacturer’s rating on the terminal is the whole answer.
When to stop and refer
An AFCI breaker tripping consistently is not something you diagnose on site. Nuisance tripping, suspected arcing, shared-neutral circuits in older wiring — the answer is an evaluation by a licensed electrician. Uncovered junction boxes in an attic are the same shape of question: multiple locations means it is systemic, and systemic means refer the whole system, not tape over the boxes.
On the exam, “recommend evaluation by a qualified electrician” is a real answer, not a cop-out.
What to hold on to
- 36 / 30 / 78 / 79 inches — depth, width, headroom, highest handle. Learn them as one set.
- 14 AWG = 15 A, 12 AWG = 20 A. Over-sized wire is not a defect.
- Continuous load ≤ 80% of the device rating. Voltage drop under 3% is a recommendation.
- A double tap is acceptable only if the terminal is rated for two conductors.
- Systemic electrical findings get referred to a licensed electrician, not patched.
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