Exam (elaborations)
JOURNEYMAN ELECTRICIAN (2020NEC)
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JOURNEYMAN ELECTRICIAN (2020NEC)
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JOURNEYMAN ELECTRICIAN (2020NEC)Conductors with _____ marked on the insulation are NOT approved for use in a wet
location.
a. THW
b. THHW
c. THHN
d. THWN - Answers -THHN
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 - Answers -4/0 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 - Answers -625 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 - Answers -75 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.
, The MINIMUM length of free conductor to be left at each junction box for the purpose of
splicing conductors, or making connections to luminaires or devices shall be _____ .a. 4
inches
b. 10 inches
c. 8 inches
d. 6 inches - Answers -6 inches
As per Section 300.14 at least 6 in. of free conductor is to be left at each junction box
for splices or the connection of luminaires or devices. The intent of this rule is to ensure
enough conductor slack for the terminal connections or splices to be made easily.
In general, overhead service-drop conductors shall NOT be smaller than _____.
a. 2 AWG copper
b. 4 AWG copper
c. 6 AWG copper
d. 8 AWG copper - Answers -d. 8 AWG copper
Section 230.23(B) requires overhead service-drop conductors to be not smaller than 8
AWG copper or 6 AWG aluminum or copper-clad aluminum. Do not get service-drop
conductors, the overhead conductors between the utility electric supply system and the
service point, confused with the service-entrance conductors, the conductors from the
service point from the utility company to the service disconnecting means.
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. - Answers -10 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. - Answers -To 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).
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