Electrical Level 3 Module 1 Load Calculations and Branch Feeder Circuits Questions and Correct Answers

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Electrical Level 3 Module 1 Questions and
Correct Answers

63.55' is the load center distance for a 208V, four-wire, three-
phase branch circuit with fixed


noncontinuous loads from the source of 60A at 45', 40A at 60',
30A at 75', and 25A at 100'. Ans: Here is the solution:


Load 1 = 45' ×60A = 2,700


Load 2 = 60' ×40A = 2,400


Load 3 = 75' ×30A = 2,250


Load 4 =100' ×25A = 2,500


155A 9,850



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Total load (I) = 155A


Load center length (L) = 9,850


9,850 ÷ 155A = 63.55'


the ampacity of branch circuit conductors must be derated when
there


are more than three current-carrying conductors in a raceway.
Ans: According to the NEC®,


Aluminum THWN - 50A [from NEC Table 310.15(B)(16)]


Correction factor - 0.88 [from NEC Table 310.15(B)(2)(a)]


50A × 0.88 = 44A Ans: ambient temperature of 38°C is 44A. Here
is the solution:


must be derated when installed in conduit on or above rooftops
Ans: Conductors


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