NEC Code questions

[roy167]

This is a thread to ask NEC code related questions. 

Example16: What is the ampacityto size the feeder conductor if it supplies the following two motors?
1.One 7.5-hp, 230V, single-phase motor
2.One 5-hp, 230V, single-phase motor
Ans: Table 430.248 gives 40 A and 28 A as individual FLC of the two motors. Per Article 430.24, the feeder must be sized to 40x125%+28 = 78 A.
Size the conductor for 75 C terminals: Ans. 4 AWG (85A)

I would think the feeder conductor should be sized for 60C since it is less than 100 amps and motor design codes are not given. Can someone verify? 

 

[roy167]

XHHW can be found in 75C and 90 C insulation.  This problem may have been solved using previous years code. According to 2017 code, does wet location mean 75C insulation? I have not been able to find that.  

 

[eatsleep]

View attachment 12644

XHHW can be found in 75C and 90 C insulation.  This problem may have been solved using previous years code. According to 2017 code, does wet location mean 75C insulation? I have not been able to find that.  

I think i remember reading somewhere that most of the terminal equipment is rated at 75C, so 75 C is chosen as its more common? I'm not completly sure on that, just wanted to provide some input

 

[Sthabik PE]

This is a thread to ask NEC code related questions. 

Example16: What is the ampacityto size the feeder conductor if it supplies the following two motors?
1.One 7.5-hp, 230V, single-phase motor
2.One 5-hp, 230V, single-phase motor
Ans: Table 430.248 gives 40 A and 28 A as individual FLC of the two motors. Per Article 430.24, the feeder must be sized to 40x125%+28 = 78 A.
Size the conductor for 75 C terminals: Ans. 4 AWG (85A)

I would think the feeder conductor should be sized for 60C since it is less than 100 amps and motor design codes are not given. Can someone verify? 

View attachment 12644

XHHW can be found in 75C and 90 C insulation.  This problem may have been solved using previous years code. According to 2017 code, does wet location mean 75C insulation? I have not been able to find that.  

If no other adjustments or correction factors are given use 75degC. You can see in NEC'17_Annex D Example D7 doing the same .

 

[tpkjr2006]

Purchase Tom Henrys book for NEC2017 it helps greatly.