NEC Questions Practice Test-15
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Question 1 of 10
1. Question1 points
What is the maximum voltage drop recommended by NEC for both branch conductor and feeder conductor?Correct
Question 2 of 10
2. Question1 points
The connected load of all-electric restaurant is 140 KVA which is supplied by a 120/208 V three phase supply. What is the required service conductor ampacity?Correct
Total connected load = 140 KVA
Refer : NEC Table 220.88
First 200 KVA load is at 80% so
Total demand load 140 * 0.8 = 112 KVA
ampacity I = VA / [E * 1.732 ] = (112 * 103 ) / (208 * 1.732)
= 311 amperes
Question 3 of 10
3. Question1 points
What size branch circuit protection is required for 20 A motor compressor connected to 240 volts single phase supply?Correct
Refer : NEC 440.22 (A)
The branch circuit protection ratings should be 175% of motor current rating.
branch circuit rating = 20 * 1.75 = 35 amperes
Question 4 of 10
4. Question1 points
A 30 ampere branch circuit with heavy duty lamp holders is permitted to supply fixed lightening units in …………………..Correct
Refer : NEC 210.23(B)
30 ampere branch circuit with heavy duty lamp holders is permitted to supply fixed lightening units other than dwelling unit .
Question 5 of 10
5. Question1 points
What is the minimum general lightening load required for 1500 square foot single family dwelling unit as permitted by NEC?Correct
Refer : NEC Table 220.12
for dwelling unit minimum general lightening load is 3 VA / square foot
Total load = 1500 * 3 = 4500 VA
Question 6 of 10
6. Question1 points
What size service conductor is required for a 120/240 volts single phase with a demand load of 48 KVA?Correct
Refer : I = P / E
I = 48000 / 240 = 200 amperes
Question 7 of 10
7. Question1 points
In calculating the load for a commercial kitchen with one electric appliance, which of the following demand factor is allowed?Correct
Refer: NEC 220.56
For load calculation of a commercial kitchen with only one electric appliance should be rated at 100%. For applying deductions there must be at-least three or more appliances should be available.
Question 8 of 10
8. Question1 points
The ampacity of 2/0 THHN conductor is 195 amperes ( 900 C). What is the maximum allowable ampacity of 2/0 THHN conductor in a conduit with 5 other current carrying conductors?Correct
If more than 3 conductors are placed in a conduit the conductor ampacity must be derated.
Refer: NEC Table 310.15(B)(3)
For 5 conductors in a conduit the de-rating factor is 80%
maximum allowable ampacity = 0.8 * 195 = 156 amperes
Question 9 of 10
9. Question1 points
An isolated ground receptacle shall be identified by :…………….Correct
Refer : NEC 406.3 (D)
An orange triangle located on the face of the receptacle.
Question 10 of 10
10. Question1 points
If a panel board contains a snap switch with rating of 30 amperes must be protected not in excess of :Correct
Refer : NEC 408.36 (A)
the maximum rating of Panel boards containing 30 amperes or less snap switches should be less than 200 amperes.