ggappa
Member
- Location
- Nicollet, MN
what is the best way to de-rate nm cable? and the best way to find the proper values?
2011 code. thank you
2011 code. thank you
NM derating
- Thread starter ggappa
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
You derate by starting at the 90C column and reducing down based on factors such as bundling, temp, etc.
ggappa
Member
- Location
- Nicollet, MN
what i meant was nm pipe fill, no just general derating. sorry about that. like what size pipe would be needed for 3-12/2 nm and 1-10/3 nm.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
ggappa
Member
- Location
- Nicollet, MN
the only reason i ask is because there are similar questions on a exam that i am taking. the reason its ran through a pvc pipe is because they are just using it as a short chase (nipple) into a panel. and the question asks how to size the pipe if nm is going through it.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
See Dennis answer above. note 2,chap 9.
short nipples, 24" or less, are note 4. nipples are not sleeves.
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- Location
- New Jersey
- Occupation
- Journeyman Electrician
Nipples would have a maximum fill of 60%, raceways would be 31%, 40% or 53% fill.
ggappa
Member
- Location
- Nicollet, MN
i know how to do pipe fill im trying to find out how to do it for nm i see what you mean about what percent to use but how do you know what value to use (approximate area in.2) for a 12/2 or a 10/3 or any nm? this is a question on the minnesota journeymans exam.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
You need the diameter/2=radius.
pi*radius^2=area.
Dennis gave one spec sheet.
pi*radius^2=area.
Dennis gave one spec sheet.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I hope they don't expect you to know that info off the top of your head.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
The formula or the area for every cable? The formula should be expected to be known IMO.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Yes but not the dimensions of the cable.
kwired
Electron manager
- Location
- NE Nebraska
Proper answer is if running NM cable in a raceway you are wasting time and money by not running THHN/THWN.
If it is just a sleeve there is no maximum fill requirements.
If it is just a sleeve there is no maximum fill requirements.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I knew what you meant, I am bored and being onerous.
Where is Bob? I would rather tangle with him, ' course I usually lose. Damn yankee.
But then again, I usually lose most of my harebrained arguements
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