How to use: Cut out each card, fold along the center line, and read the term on one
side and the definition on the other — or just fold the answer under while you quiz yourself off the sheet.
Q
Minimum burial depth -- direct-buried cable, no GFCI, under a driveway (residential)
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A
18 in. is the general depth for direct burial without special protection under areas subject to residential vehicular traffic -- always cross-check Table 300.5 for the exact wiring method and voltage.
NEC Table 300.5
Q
Minimum burial depth -- rigid metal conduit (RMC)
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A
6 in., the shallowest depth in Table 300.5, because RMC provides its own strong physical protection.
NEC Table 300.5
Q
Minimum burial depth -- residential branch circuit, 120V or less, GFCI-protected, 20A max, under 20 in. of cover permitted
✂ — — — — — — — — — —
A
12 in. when GFCI-protected and 20A max, versus 18 in. without those conditions.
NEC Table 300.5
Q
All conductors of a circuit -- same raceway/cable rule
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A
All conductors of a circuit, including the neutral and all equipment grounding conductors, must be run together in the same raceway, cable, or trench (with narrow exceptions) so their magnetic fields cancel and induced heating is avoided.
NEC 300.3(B)
Q
Conductor fill limit in a single raceway
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A
Set by the conduit fill tables in Chapter 9 -- 53% for one conductor, 31% for two, 40% for three or more (percentages of the raceway's internal cross-sectional area).
NEC Ch. 9, Table 1
Q
Securing/support of nonmetallic-sheathed cable (NM)
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A
Must be secured within 12 in. of every box/fitting and at intervals not exceeding 4.5 ft along its run, with some flexibility allowed near the last support before entering equipment.
NEC 334.30
Q
Protection from physical damage -- cable through framing members
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A
Cables run through bored holes must maintain at least 1.25 in. from the nearest edge of the framing member, or be protected by a steel plate/bushing if closer.
NEC 300.4(A)
Q
Raceways/cables installed parallel to framing members
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A
Must be at least 1.25 in. from the nearest edge, or protected by a 1/16 in. steel plate, to guard against nail/screw puncture.
NEC 300.4(D)
Q
Wiring in ducts/plenums used for environmental air
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A
Only specific wiring methods listed for that use (e.g. plenum-rated cable) are permitted -- ordinary NM cable is not permitted in an environmental air plenum.
NEC 300.22
Q
Raceway seal requirement -- different temperature zones
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A
A raceway that passes from a warmer to a colder space (e.g. into a refrigerated area or from indoors to outdoors) must be sealed to prevent condensation from migrating through it.
NEC 300.7(A)
Q
Expansion fittings in raceways
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A
Required where a raceway crosses a structural expansion joint, or over long straight runs of PVC subject to significant thermal expansion/contraction.
NEC 300.7(B), 352.44
Q
Underground raceway/cable warning requirement
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A
Direct-buried cables and conduits not encased in concrete generally require a covering or other means to warn of their presence if dug into later (e.g. a warning ribbon above the raceway).
NEC 300.5(D)(3)
Q
Splices and taps in raceways
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A
Generally not permitted inside a raceway itself -- splices must be made in a box, conduit body, or other enclosure specifically permitted for splicing.
NEC 300.15, 300.17
Q
Induced currents in ferrous metal enclosures
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A
Where a single conductor passes through ferrous (steel) metal, it induces heating from the alternating magnetic field -- avoided by running all conductors of the circuit through the same opening/knockout.
NEC 300.20
Q
Raceways as a means of support
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A
A raceway is generally not permitted to be used as a means of support for other raceways, cables, or non-electrical equipment, except as specifically permitted.
NEC 300.11(B)