Breaker temp. rating

[u2slow]

I can't find the section in the code book regarding breaker temperature rating.

For example, does a 75 degree breaker limit the ampacity of a 90 degree conductor to that of a 75 degree conductor?

[neil seidner]

U2slow: This is some thing that I have never run into. I even pulled the dryer breaker out of the panel in my apartment so I could read the ratings. The breaker called for a conductor temperature rating of 75 degrees. This is a minimum temperature rating. I found nothing in the code book to indicate that the that ampacity of the wire is based on the rating marked on the o/c instead of the temperature rating of the wire. If this was in the code book it would be in 14-104, or possibly in 4-004.

Here is a thought. In scenario "A" you have a 75 degree breaker and a 90 degree conductor. In scenario "B" you have a 90 degree breaker and a 90 degree conductor. In scenario "B" there is more heat in the panel than in scenario "A" (this is indicated by the 90 degree breaker rating). Does it seem logical that in scenario "B" you would be aloud to use a smaller (based on 90 degree column) conductor than in scenario "A"(75 degree column of table 2/4)?

[u2slow]

I think its the breaker terminal that's rated for a maximum temperature... not a minumum conductor insulation rating. I had a look at some lugs at work today. They were stamped "90*C". I can't imagine a plain old lug requiring 90*C (or better) conductor insulation.

The NEC deals with the issue in 110.14 and here's a detailed explanation:
http://www.electricsmarts.com/conten...boy_110.14.asp

[neil seidner]

I understand what your saying now. It seems that the N.E.C. addresses this issue. But I still can't find anything in the C.E.C. on the subject.

[twh]

I don't think it's an issue where the load is non-continuous, or the 80 percent rule applies, and the tables used are 1 to 4. For underground runs, where a higher ampacity is allowed, compare the notes to Tables D9A and D9B.

[u2slow]

I found it in the bulletins! (BC that is)

Bulletin 0-8-0
Panelboard & Circuit Breaker Marking for 60/75*C Al/Cu Conductor

Some panelboard manufactururs are marking their products with ampere ratings based on 60/75*C insulation, or on 75*C insulation alone.

This marking is specific to the American market, whose standards are based on different criteria.

The Canadian Standards Association confirmed that the Canadian standards for these products are based on a minimum insulation rating of 75*C. This equipment is also approved for use with conductors having 90*C insulation.

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<font color="#a62a2a" size="1">[ March 07, 2004 12:08 AM: Message edited by: u2slow ]</font>