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roy167

NEC Code questions

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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? 

 

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image.png.92c3b9ebc2650fa4efc2e01894517cf6.png

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.  

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On 3/3/2019 at 9:33 AM, roy167 said:

image.png.92c3b9ebc2650fa4efc2e01894517cf6.png

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

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On 3/3/2019 at 11:01 AM, roy167 said:

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? 

 

 

On 3/3/2019 at 11:33 PM, roy167 said:

image.png.92c3b9ebc2650fa4efc2e01894517cf6.png

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 .

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