Use of 90 degree C column of 310.16

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Richard S

Member
It is the opinion of a couple of project managers in my office that the 90 degree C column can never be used. This opinion is based on previous experience with local inspectors. Reading the code, I'm not so sure about this opinion.

If the equipment, terminations, conductors and conduit are all listed and rated at 90 degree C, I don't see any issures with using the 90 degree C column for sizing my conductor amapacity.

Does anyone have any experiences (pro or con) with using the 90 degreed C column of 310.16?
 

haskindm

Senior Member
Location
Maryland
You got it. In theory IF the equipment, terminations, conductors and conduit are all listed and rated at 90 degree C then the use of the 90 degree column would be perfectly acceptable. In practice you will not find any (at least I have not seen them) terminals listed for 90 degree so the 90 degree column may only be used for derating. When/if 90 degree terminations become available the NEC is ready. Keep in mind that 90 degree C equals about 200 degrees F so I am not sure that I would be comfortable with terminals that routinely operate that hot, but what do I know?
 

bob

Senior Member
Location
Alabama
Richard S said:
It is the opinion of a couple of project managers in my office that the 90 degree C column can never be used. This opinion is based on previous experience with local inspectors. Reading the code, I'm not so sure about this opinion.

If the equipment, terminations, conductors and conduit are all listed and rated at 90 degree C, I don't see any issures with using the 90 degree C column for sizing my conductor amapacity.

Does anyone have any experiences (pro or con) with using the 90 degreed C column of 310.16?
Richard
At this time I am not aware of any 600 volt equipment with 90C terminals.
If there were you could use the 90C rating. Until then you must use the 75C rating. 90C rating is used when derating of conductor is called for.
 

Richard S

Member
bob said:
Richard
At this time I am not aware of any 600 volt equipment with 90C terminals.
If there were you could use the 90C rating. Until then you must use the 75C rating. 90C rating is used when derating of conductor is called for.

Both Burndy and Ilsco have compression lines that list "UL 486A 90?C Listed and CSA Certified for 600 Volts" If I am using these lugs for my terminations and bolting these lugs to bussing I should be ok to use the 90?C rating.
 

smithacetech

Member
Location
Utah
Richard S said:
Both Burndy and Ilsco have compression lines that list "UL 486A 90?C Listed and CSA Certified for 600 Volts" If I am using these lugs for my terminations and bolting these lugs to bussing I should be ok to use the 90?C rating.

But you may still be limited by the feeding breaker.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Richard S said:
Both Burndy and Ilsco have compression lines that list "UL 486A 90?C Listed and CSA Certified for 600 Volts" If I am using these lugs for my terminations and bolting these lugs to bussing I should be ok to use the 90?C rating.

The NEC is concerned with the rating of the complete termination, not just the rating of the lug. The termination includes the heat dissipation of the enclosure. Most enclosures (even those housing 100% rated breakers) have had their ventilation designed for the 75C column.

UL does not have a listing for any overcurrent protective device using the ampacities from the 90C column. UL does have a 90C listing for some items (i.e. wire nuts, butt splices, and distribution blocks) but in general they are "joining devices" and not "terminations".
 

360Youth

Senior Member
Location
Newport, NC
haskindm said:
In practice you will not find any (at least I have not seen them) terminals listed for 90 degree so the 90 degree column may only be used for derating.

Here, here! Me either.

haskindm said:
When/if 90 degree terminations become available the NEC is ready.

Never realized that. NEC seems to have been waiting a long time, cause 90 degree table has been there as long as I can remember, not that I'm that old, ahem...ahemm. Sure is tempting to use that table, though. :roll:
 

RB1

Senior Member
What about this? I leave the panelboard enclosure with 75 degree conductors and set a junction box adjacent to the panel. I install a power distribution block identified for 90 degree terminations. On the other end of the run I set a juction box and convert back to 75 degree conductors before entering the enclosure for my equipment terminations. Is this permissible?
 

jdouglas

Member
Location
South Carolina
RB1 said:
What about this? I leave the panelboard enclosure with 75 degree conductors and set a junction box adjacent to the panel. I install a power distribution block identified for 90 degree terminations. On the other end of the run I set a juction box and convert back to 75 degree conductors before entering the enclosure for my equipment terminations. Is this permissible?

Love this kind of thinking. I always say give em what they ask for!
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
RB1 said:
What about this? I leave the panelboard enclosure with 75 degree conductors and set a junction box adjacent to the panel. I install a power distribution block identified for 90 degree terminations. On the other end of the run I set a juction box and convert back to 75 degree conductors before entering the enclosure for my equipment terminations. Is this permissible?

Yes.

Although I have never seen how much 75C cable is actually needed, I usually recommend 4ft min. because this is the amount that UL uses during the testing of terminations on enclosed circuit breaker and fusible switch lugs.
 

Michael15956

Senior Member
Location
NE Ohio
RB1 said:
What about this? I leave the panelboard enclosure with 75 degree conductors and set a junction box adjacent to the panel. I install a power distribution block identified for 90 degree terminations. On the other end of the run I set a juction box and convert back to 75 degree conductors before entering the enclosure for my equipment terminations. Is this permissible?


My thought is it is not permissible.

Because the 75C conductor(s) will be connected to a 90C termination.

110.14(C)(1)(a)(3) If the 90C temperature rating column is used for your wire rating, then all of the terminations/connections etc. must be rated at 90C.

Michael
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Michael15956 said:
My thought is it is not permissible.

Because the 75C conductor(s) will be connected to a 90C termination.

110.14(C)(1)(a)(3) If the 90C temperature rating column is used for your wire rating, then all of the terminations/connections etc. must be rated at 90C.

Michael

Correct. However if you change RB1's description slightly then this objection vanishes.

Rather than leaving the panelboard with 75C conductors, you leave the panelboard with conductors that have 90C insulation, but which are sized from the 75C column.

-Jon
 

RB1

Senior Member
Good catch Michael. What I meant was 75 degree ampacity for 90 degree conductors like Jon said.

Jim- I had a field rep from NEMA tell me exactly the same thing. Do you think the "4 ft. rule" should be put into code?
 

ITO

Senior Member
Location
Texas
Michael15956 said:
My thought is it is not permissible.

Because the 75C conductor(s) will be connected to a 90C termination.

110.14(C)(1)(a)(3) If the 90C temperature rating column is used for your wire rating, then all of the terminations/connections etc. must be rated at 90C.

Michael

This scenario is the exact example Stabiloy Al and Alcan sent me for submittal of thier XHHW-2 Al wire as a work around for the 90?C termination issue.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
RB1 said:
Good catch Michael. What I meant was 75 degree ampacity for 90 degree conductors like Jon said.

Jim- I had a field rep from NEMA tell me exactly the same thing. Do you think the "4 ft. rule" should be put into code?

No,

It is already part of the "listing and labeling" per UL 489(?) so additional NEC language should not be necessary.
 

Chris6245

Senior Member
Location
Ohio
Michael15956 said:
My thought is it is not permissible.

Because the 75C conductor(s) will be connected to a 90C termination.

110.14(C)(1)(a)(3) If the 90C temperature rating column is used for your wire rating, then all of the terminations/connections etc. must be rated at 90C.

Michael
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
 
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