NFPA 70 Practice Questions with Correct
Answers
Given: After all demand factors have been taken into consideration for an office
building, the demand load is determined to b 90,000 VA; the building has a 120/240-volt
single phase electrical system. What MINIMUM size copper conductors with
THHN/THWN insulation are required for the ungrounded serive-lateral conductors?
Consider all termination lugs are rated for 75 C.
A. 400 kcmil
B. 350 kcmil
C. 300 kcmil
D. 500 kcmil
D. 500 kcmil
GIVEN: A commercial building is to be supplied from a transformer having a
480Y/277-volt, 3-phase primary and a 208Y/120-volt, 3-phase secondary. The secondary
will have a balance computed demand load of 416 amperes per phase. The transformer
is required to have a MINIMUM kVa rating of _____
A. 100 kVa
B. 150 kVa
C. 86 kVa
D. 200 kVa
B. 150 kVa
,Manhole covers shall be OVER _____ pounds or otherwise designed to require the use
of tools to open.
A. 25
B. 50
C. 75
D. 100
D. 100
The branch circuit conductors supplying one or more units of information technology
equipment shall have an ampacity of NOT less than _____ Percent of the connected
load.
A. 80
B. 100
C. 115
D. 125
D. 125
IN regard to a 7 1/2 hp, 480-volt, 3-phase ac motor with an 80 percent power factor and
a full-load ampere rating of 19 amperes indicated on the nameplate, and service factor
of 1.15; when the initial setting of the overload device you have selected is no sufficient
to carry the load, what is the MAXIMUM setting permitted for the overload protection?
A. 21.85 amperes
B. 23.75 amperes
,c. 24.70 amperes
D. 26.60 amperes
D. 26.60 amperes
The ampacity adjustment factors for conductors addressed in Section 310.15(C)(I) of
the NEC(R) are not required to be applied when the conductors are installed in a metal
wireway unless, the number of current-carrying conductors within the wireway exceeds
at least ____ at any cross-section area of the wireway.
A. 20
B. 30
C. 35
D. 24
B. 30
What MINIMUM voltage is required after 1 1/2 hours to serve emergency lightning
from a storage battery when the normal source voltage of 120 volts is interrupted?
A. 60 volts
B. 90 volts
C. 105 volts
D. 120 volts
C. 105 volts
Determine the MAXIMUM ampere setting permitted for an overload protective device
responsive to motor current, where used to protect a 20 hp, 240-volt, 3-phase, induction
type ac motor with a temperature rise of 48 degrees C and a FLA of 54 amperes
, inducted on the namplate.
A. 54.0 amperes
B. 70.2 amperes
C. 62.1 amperes
D. 75.6 amperes
B. 70.2 amperes
Where Type SRD multiconductor cable consist of size 8 AWG conductors and only two
(2) conductors in the cable are the current-carrying, what is the ampacity of the
conductors?
A. 20 amperes
B. 30 amperes
C. 40 amperes
D. 50 amperes
C. 40 amperes
Aluminum or steel cable trays shall be permitted to be used as equipment grounding
conductors, provided ____
I. The cable tray sections and fittings are identified as an equipment grounding
conductor
II. The cable tray sections and fittings are durably marked to show the cross-sectional
area of the metal
Answers
Given: After all demand factors have been taken into consideration for an office
building, the demand load is determined to b 90,000 VA; the building has a 120/240-volt
single phase electrical system. What MINIMUM size copper conductors with
THHN/THWN insulation are required for the ungrounded serive-lateral conductors?
Consider all termination lugs are rated for 75 C.
A. 400 kcmil
B. 350 kcmil
C. 300 kcmil
D. 500 kcmil
D. 500 kcmil
GIVEN: A commercial building is to be supplied from a transformer having a
480Y/277-volt, 3-phase primary and a 208Y/120-volt, 3-phase secondary. The secondary
will have a balance computed demand load of 416 amperes per phase. The transformer
is required to have a MINIMUM kVa rating of _____
A. 100 kVa
B. 150 kVa
C. 86 kVa
D. 200 kVa
B. 150 kVa
,Manhole covers shall be OVER _____ pounds or otherwise designed to require the use
of tools to open.
A. 25
B. 50
C. 75
D. 100
D. 100
The branch circuit conductors supplying one or more units of information technology
equipment shall have an ampacity of NOT less than _____ Percent of the connected
load.
A. 80
B. 100
C. 115
D. 125
D. 125
IN regard to a 7 1/2 hp, 480-volt, 3-phase ac motor with an 80 percent power factor and
a full-load ampere rating of 19 amperes indicated on the nameplate, and service factor
of 1.15; when the initial setting of the overload device you have selected is no sufficient
to carry the load, what is the MAXIMUM setting permitted for the overload protection?
A. 21.85 amperes
B. 23.75 amperes
,c. 24.70 amperes
D. 26.60 amperes
D. 26.60 amperes
The ampacity adjustment factors for conductors addressed in Section 310.15(C)(I) of
the NEC(R) are not required to be applied when the conductors are installed in a metal
wireway unless, the number of current-carrying conductors within the wireway exceeds
at least ____ at any cross-section area of the wireway.
A. 20
B. 30
C. 35
D. 24
B. 30
What MINIMUM voltage is required after 1 1/2 hours to serve emergency lightning
from a storage battery when the normal source voltage of 120 volts is interrupted?
A. 60 volts
B. 90 volts
C. 105 volts
D. 120 volts
C. 105 volts
Determine the MAXIMUM ampere setting permitted for an overload protective device
responsive to motor current, where used to protect a 20 hp, 240-volt, 3-phase, induction
type ac motor with a temperature rise of 48 degrees C and a FLA of 54 amperes
, inducted on the namplate.
A. 54.0 amperes
B. 70.2 amperes
C. 62.1 amperes
D. 75.6 amperes
B. 70.2 amperes
Where Type SRD multiconductor cable consist of size 8 AWG conductors and only two
(2) conductors in the cable are the current-carrying, what is the ampacity of the
conductors?
A. 20 amperes
B. 30 amperes
C. 40 amperes
D. 50 amperes
C. 40 amperes
Aluminum or steel cable trays shall be permitted to be used as equipment grounding
conductors, provided ____
I. The cable tray sections and fittings are identified as an equipment grounding
conductor
II. The cable tray sections and fittings are durably marked to show the cross-sectional
area of the metal
