E2 Conductor Ampacity and Derating 2

Question 1

When more than 3 current-carrying conductors are installed in a conduit, NEC Table 310.15(C)(1) requires a derating factor. What is the correction factor when 7 to 9 conductors are bundled together?

Accepted Answer

0.70

Answer

0.50

Answer

0.60

Answer

0.80

Question 2

A 4 AWG THHN copper conductor has a 75°C terminal rating. Using NEC Table 310.16, what is the ampacity used for circuit calculations?

Accepted Answer

85A

Answer

70A

Answer

95A

Answer

100A

Question 3

Which NEC article provides the general rules for conductor ampacity calculations including adjustment and correction factors?

Accepted Answer

Article 310

Answer

Article 240

Answer

Article 300

Answer

Article 230

Question 4

Six current-carrying 12 AWG THHN conductors are installed in a single conduit at an ambient temperature of 30°C. What is the derated ampacity per conductor?

Accepted Answer

15A

Answer

12A

Answer

20A

Answer

24A

Question 5

Under NEC 310.15(E), what is the minimum allowable ampacity for a conductor used as an equipment grounding conductor?

Accepted Answer

It is not required to be derated for bundling

Answer

It must match the phase conductor ampacity

Answer

It must carry full fault current without derating

Answer

It follows the same derating rules as phase conductors

Question 6

A 500 kcmil aluminum XHHW-2 conductor is installed in a raceway in an ambient temperature of 50°C. What correction factor from NEC Table 310.15(B)(1) applies?

Accepted Answer

0.71

Answer

0.58

Answer

0.82

Answer

0.91

Question 7

Two sets of 350 kcmil THHN copper conductors are installed in parallel. Each set is in its own conduit. How is the ampacity of each conductor set determined?

Accepted Answer

Each conductor carries its full table ampacity without derating for the parallel set

Answer

Ampacity is halved for each conductor

Answer

Both sets are treated as one bundle requiring derating

Answer

Ampacity is limited to the smaller conductor size