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Old 02-17-2015, 05:57 PM   #1
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Default Romex Wire derating if buried in insulation

Hello Everyone,
I was wondering if anyone can shine some light on this. Im doing some residential work in mass. I will be running three new circuits for the basement up to a second floor apartment. Im using 12/2 romex, and it will be run behind a insulated wall. In the mass amendments it states that i need to use the 60c column for derating and not the 90c for derating if installed in thermal insulation. To me i'm thinking it only has to do with foam insulation. Correct me if im wrong.
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Old 02-17-2015, 06:05 PM   #2
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Does the local amendment really say to use the 60 deg col for derating?

Or the 60 deg is the lowest ampacity allowable and to use the 90 deg for derating.
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Old 02-17-2015, 06:15 PM   #3
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Yes the new amendments that were passed for the 2014 saids that if installed in thermal insulation the amapacity of the conductor shall be of 60c. back in 2011 the local amendments stated you can use 90c for derating but not go lower then the 60c ampacity. I guess i will need to run 10/2 because the three circuits are bundled up.
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Old 02-17-2015, 06:15 PM   #4
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this appears to be what it says

Quote:
320.80(A). Delete the last sentence, which reads: "The 90C (194F) rating shall be permitted to be used for
ampacity adjustment and correction calculations; however, the ampacity shall not exceed that for a 60C
(140F) rated conductor."
Quote:
334.80. Delete the second paragraph and revise the first paragraph to read as follows:
334.80 Ampacity. Type NM, NMC, and NMS cable shall have conductors rated at 90C
(194F). Where installed in thermal insulation, the ampacity of conductors shall be that of 60C
(140F) conductors. The ampacity of Types NM, NMC, and NMS cable installed in cable tray
shall be determined in accordance with 392.11.
http://www.mass.gov/eopss/docs/dfs/o...27cmr12-00.pdf
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Old 02-17-2015, 06:21 PM   #5
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Quote:
Originally Posted by WireGuy36 View Post
Yes the new amendments that were passed for the 2014 saids that if installed in thermal insulation the amapacity of the conductor shall be of 60c. back in 2011 the local amendments stated you can use 90c for derating but not go lower then the 60c ampacity. I guess i will need to run 10/2 because the three circuits are bundled up.
do they define "bundled" ?
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Old 02-17-2015, 06:23 PM   #6
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yes that is exactly what it saids wildleg, so am i reading it wrong or not understanding it. lol So i have to go with 60c column for and derate from the 60c column seeing im in insulation or can i use the 90c for derating still.
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Old 02-17-2015, 06:56 PM   #7
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As I see that you can use 90C for de-rating but 60C thru insulation. Now if the cable does not go thru insulation then it may be used at 75C however the notes to the table will limit the overcurrent protective device for the small size branch circuits anyway.
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Old 02-17-2015, 07:15 PM   #8
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Quote:
Originally Posted by WireGuy36 View Post
Yes the new amendments that were passed for the 2014 saids that if installed in thermal insulation the amapacity of the conductor shall be of 60c. back in 2011 the local amendments stated you can use 90c for derating but not go lower then the 60c ampacity. I guess i will need to run 10/2 because the three circuits are bundled up.
You can use the 12/2, they simply deleted the second paragraph and edited the first and third paragraph, read 240.4(D)...

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Old 02-17-2015, 07:25 PM   #9
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Okay thanks guys i figured i would be okay, just reading this local amendment was making my head spin.They word something very hard to understand that you have to read it over and over again.
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