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26401-20 - Load Calculations: Feeders And Services: Questions With Complete Answers
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26401-20 - Load Calculations: Feeders And Services:Questions With Complete Answers
What NEC Article covers feeder circuits? Right Ans - NEC Article 215
The conductors and equipment for delivering electric energy from the serving
utility to the wiring system of the premises served is a? Right Ans - Service
The overhead conductors between the utility electric supply system and the
service point is _____? Right Ans - Service drop
What sections make up electrical Calculations? Right Ans - Feeders,
Services, & Branch Circuits
What NEC Article covers loads being supplied as continuous duty? Right
Ans - 215.2(A)(1)(a)
Which NEC article discusses adjustment factors for more than 3 current
carrying conductors in a raceway? Right Ans - 310.15(C)(1)
Which NEC article discusses the correction factors for the ambient
temperature the conductors will pass through? Right Ans - 310.15(B)(1)
Which NEC article discusses the not mandatory rule of increasing conductor
size when voltage drop exceeds 3% for feeders and 5% for combination
feeder & branch circuits? Right Ans - 215.2(A)(1)(b) Informational Note
No. 2
A continuous duty load is a load that operates without interruption for more
than ______hours straight? Right Ans - 3
When figuring voltage drop, where do you find conductor resistance in the
code book? Right Ans - NEC Chapter 9, Table 8
Which NEC table lists allowable ampacities for insulated conductors rated up
to and including 2,000V Right Ans - 310.16
, How do you calculate load center length? Right Ans - Multiply each tap load
by its physical routing distance from the supply, add the product of these
together and divide them by sum of the individual loads (total load I)
producing load center length (L)
What should you do when calculating amperage of a circuit, but the wire is
rated at 75 degree C and the lugs are rated at 60 degree C? Right Ans - Size
ampacity off the 60-degree column
If a feeder is rated at _____ the 60-degree rating for the feeder conductor is
used unless all feeder components are rated higher temperature. Right Ans
- Less than or equal to 100A
The formula I = VA/V is for calculating what? Right Ans - Feeder ampacity
for a single-phase circuit
The formula I = VA/ (VX1.732) is for calculating what? Right Ans - Feeder
ampacity of a 3-phase circuit
How do you determine VA when given a value in KW? Right Ans - Multiply
by 1,000
Where is the overcurrent protection device on a tap conductor? Right Ans -
Ahead of the point of supply
Which statement is true about the 10' tap rule? Right Ans - Tap conductors
cannot extend beyond the switchboard, panelboard, or control device it
supplies
Which statement is true about the 25' tap rule Right Ans - Must be rated no
less than 1/3 the capacity of the device protecting the feeder
Which statement is false about taps supplying a transformer - primary and
secondary not over 25'? Right Ans - Primary tap conductors must have an
ampacity of 1/4 the overcurrent device protecting the primary conductors.
According to NEC section 220.61, what would be the unbalanced load a
neutral would be subjected to if phase A carried 50A and phase B carried 40
amps? Right Ans - 10
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