Conductors with _____ marked on the insulation are NOT approved for use in a wet location.
a. THW
b. THHW
c. THHN
d. THWN - ANSWERTHHN
As shown in Table 310.104(A), conductors with THHN insulation are approved for use in dry and damp locations only and conductors with THWN, THHW, and THW insul...
Conductors with _____ marked on the insulation are NOT approved for use in a wet location.
a. THW
b. THHW
c. THHN
d. THWN - ANSWERTHHN
As shown in Table 310.104(A), conductors with THHN insulation are approved for use in dry and
damp locations only and conductors with THWN, THHW, and THW insulation are recognized for use
in dry and wet locations.
Given: A one-family dwelling unit with a demand load of 200 amperes is supplied with a 120/240
volt, single-phase, electrical system from the local utility company. What is the MINIMUM size
aluminum THW conductors required for use as service-entrance conductors for this residence?
a. 1/0 AWG
b. 4/0 AWG
c. 3/0 AWG
d. 2/0 AWG - ANSWER4/0 AWG
Section 310.15(B)(7)(1) permits one-family dwelling 120/240 volt, single-phase, service-entrance
conductors to be sized at an ampacity of not less than 83% of the service rating. Therefore, 200
amperes x 83% = 166 amperesTable 310.15(B)(16) indicates size 4/0 AWG THW aluminum
conductors with an allowable ampacity of 180 amperes should be selected for this dwelling.
Where a 150 kVA, single-phase transformer having a secondary voltage of 120/240 is installed at a
multi-family dwelling, the full-load current rating, in amperes, of the secondary is _____.
a. 625 amperes
b. 265 amperes
c. 526 amperes
d. 1250 amperes - ANSWER625 ampreres
To find the full-load current rating of the single-phase transformer apply the single-phase current
formula as shown:
I = (150 kVA x 1000) / 240 volts = 15,000/240 = 625 amperes
, Which one of the following listed circuit breakers is NOT a standard ampere rating?a. 75 amperes
b. 90 amperes
c. 110 amperes
d. 225 amperes - ANSWER75 amperes
Table 240.6(A) illustrates the standard ampere ratings for fuses and circuit breakers. A circuit breaker
with an ampere rating of 75 amperes is not a standard ampere rating.
When a galvanized eye-bolt is to be used as the point of attachment for an electrical service, the NEC
requires the eye-bolt to be installed NOT less than _____ above finished grade.
a. 8 ft.
b. 10 ft.
c. 12 ft.
d. 15 ft. - ANSWER10 Ft
The intent of Section 230.26 is to provide adequate vertical clearance of the conductors and prevent
physical damage to the conductors and prevent persons from making accidental contact with the
conductors which may create a shock hazard or electrocution. In no case shall the point of
attachment of the service-drop conductors to be less than 10 ft. above finished grade.
Why is electrical continuity required for metallic conduit?
a. To reduce voltage drop.
b. To limit galvanic corrosion.
c. To establish an effective ground-fault path and facilitate the operation of the overcurrent
protective device.
d. To reduce electrolysis. - ANSWERTo establish an effective ground-fault path and facilitate the
operation of the overcurrent protective device.
Electrical continuity is required for metallic conduit to establish an effective ground-fault path and
facilitate the operation of the overcurrent protective device. Reference Section 250.4(A)(4) and (5).
In dwelling units, receptacle outlets installed for countertop surfaces, must be located above, but
NOT more than _____ above the countertop or work surface.
a. 12 inches
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