90-deg insulation derating

[l3city]

Hi guys,
Question:
Taking the 90-deg column from NEC Table 310.16 gives me a value for the wire (or wires). However, will I be limited by the 75-deg column ampacity even if I do not apply any derating factors (i.e. from table 310.15(B)(2) and/or temperature derating table) ?

If I derate by voltage drop only, will I be limited by the 75-deg column ampacity?
thanks ahead for any responses

 

[Dennis Alwon]

Hi guys,
Question:
Taking the 90-deg column from NEC Table 310.16 gives me a value for the wire (or wires). However, will I be limited by the 75-deg column ampacity even if I do not apply any derating factors (i.e. from table 310.15(B)(2) and/or temperature derating table) ?

If I derate by voltage drop only, will I be limited by the 75-deg column ampacity?
thanks ahead for any responses

You are always limited to the weakest link. Thus the 75C col. is the weak link. You can use the 90 to derate but you cannot be larger than the 75C col. This is assuming your lugs are rated 75C

 

[l3city]

You are always limited to the weakest link. Thus the 75C col. is the weak link. You can use the 90 to derate but you cannot be larger than the 75C col. This is assuming your lugs are rated 75C

Thanks, but how about no derating at all, will I still be limited to the 75-deg column?
thanks

 

[benaround]

Thanks, but how about no derating at all, will I still be limited to the 75-deg column?
thanks

Yes, unless you can find 90deg rated terminations, and by most in this Forum

are said to be non-existing.

 

[tom baker]

You can terminate to a buss bar and use 90 deg c ratings, Mike Holt has a picture in one of his books showing the lugs.

 

[l3city]

You can terminate to a buss bar and use 90 deg c ratings, Mike Holt has a picture in one of his books showing the lugs.

Thanks, well they can be shown in a book, but are these (90-deg termination lugs) existing or at least, easy to get?
thanks

 

[Dennis Alwon]

Thanks, well they can be shown in a book, but are these (90-deg termination lugs) existing or at least, easy to get?
thanks

Apparently there are a few manufacturers of certain types of equip that use 90C lugs. I have yet to see one. My bet is you need to use the 75C column.

 

[Smart $]

Thanks, well they can be shown in a book, but are these (90-deg termination lugs) existing or at least, easy to get?
thanks

90?C lugs that come to mind are fairly common. Take a look at your typical hi-press lug.

 

[jrannis]

90?C lugs that come to mind are fairly common. Take a look at your typical hi-press lug.

Mechanical lugs too. Even the piercing insulation type tap is 90 degree.