Electrical Exam Prep Help?
- Thread starter 110.14(D)
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- New Jersey
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Sure, what can we help you with?
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
I assume this is what you are questioning. It is pretty straightforward but how one is expected to enforce this is another question
Preparing to take a Master Electrician Exam, just looking for some help along the way. I'll be posting questions as needed to get through the course, currently in Unit 6 - Conductor Sizing and Protection Calculations.
That's my user name, not a question.
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
We are anxiously waiting
Feeder Sizing @ 90°C
Feeder Sizing @ 90°C
Page 249 Figure 6-16
If 300A continuous load @ 100% with 90°C wire on 90°C terminals is permitted, using the 90°C column for XHHW wire the first conductor size over 300A is 300kcmil at 320A. Why is the answer for this example 400 kcmil @380A? I thought I understood this concept in the 2017 NEC Handbook Section 215.2, but I can't get the right answers in any of the examples in the Exam Prep Book.
What am I missing?:?
Feeder Sizing @ 90°C
Page 249 Figure 6-16
If 300A continuous load @ 100% with 90°C wire on 90°C terminals is permitted, using the 90°C column for XHHW wire the first conductor size over 300A is 300kcmil at 320A. Why is the answer for this example 400 kcmil @380A? I thought I understood this concept in the 2017 NEC Handbook Section 215.2, but I can't get the right answers in any of the examples in the Exam Prep Book.
What am I missing?:?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
300 x 125%= 380
The question seems to imply that the breaker is rated 100% but if that is not the case then 400 kcm is correct. The wording, to me, is a bit off.
The question seems to imply that the breaker is rated 100% but if that is not the case then 400 kcm is correct. The wording, to me, is a bit off.
I failed to mention the 400A breaker.
The point of the example seems to be that 90° wire can be used at full 90° ampacity on 90° terminals permitting a smaller size for that segment. 125% full load doesn't apply to that 90° segment, but I completely missed that 300 kcmil XHHW (320A @ 90°C) would be enough for the load but undersized for the breaker.
The point of the example seems to be that 90° wire can be used at full 90° ampacity on 90° terminals permitting a smaller size for that segment. 125% full load doesn't apply to that 90° segment, but I completely missed that 300 kcmil XHHW (320A @ 90°C) would be enough for the load but undersized for the breaker.
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