Use of 90 degree C column of 310.16

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Michael15956

Senior Member
Location
NE Ohio
Chris6245 said:
So by this you mean that terminating NM to a 75C breaker is also a violation? Isn't NM only rated at 60C?

Chris,

No, the above is not what I meant.

"In a nutshell," the NEC sets the determination of termination of equipment under 110.14(C)(1)(a) and (C)(1)(b). This sections states that T310.16 shall be used for conductor ampacities. It further provides termination provisions for equipment under 100A and equipment for over 100A. Also, stated under (a)(3) and (b)(2), "Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors." What this means is that the 90C column for NM can be used for conductor ampacities if all the equipment/connections/terminations/splices/CB etc. within that circuit are also rated for 90C.

Hope this helps,


Michael
 

kpepin

Senior Member
Chris6245 said:
So by this you mean that terminating NM to a 75C breaker is also a violation? Isn't NM only rated at 60C?

Just because a 60 amp disconnect is rated at 60 amps doesn't mean you can't put 40 amp fuses in it..as long as you don't exceed the rating you are OK...so IMO a 75C wire on a 90C lug is in no way a violation as long as it is fused properly

If you look at 110.14(C)(1)(a) it basically states (almost) everything 100A or less has to be rated at 60? anyway. Has anyone ever seen Type NM cable size 1 or larger?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
kpepin said:
If you look at 110.14(C)(1)(a) it basically states (almost) everything 100A or less has to be rated at 60? anyway. Has anyone ever seen Type NM cable size 1 or larger?


NM cable is only made up to size #2 AWG. Other cable types and most conduit and wire #1 and smaller can still be used at 75 degrees if the terminations are all rated for 75 degrees.
 

Chris6245

Senior Member
Location
Ohio
Michael15956 said:
Chris,

No, the above is not what I meant.

"In a nutshell," the NEC sets the determination of termination of equipment under 110.14(C)(1)(a) and (C)(1)(b). This sections states that T310.16 shall be used for conductor ampacities. It further provides termination provisions for equipment under 100A and equipment for over 100A. Also, stated under (a)(3) and (b)(2), "Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors." What this means is that the 90C column for NM can be used for conductor ampacities if all the equipment/connections/terminations/splices/CB etc. within that circuit are also rated for 90C.

Hope this helps,

Michael

I wasn't disputing that fact...I may have missunderstood the statement I quoted as to mean you can't put a lower rated wire on a higher rated terminal just because it was rated higher than the wire. Now that I have read it several more times I think I am getting what was being said......
 
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