Bussbar ampacities

[steveve1]

Seems to me there is a ampacity rating of 1/4 cu bussing based on sq. inches or the like. Can you shed a little light on this subject? Thanks always.

 

[charlie]

Re: Bussbar ampacities

I used to design transformers and we used either 750 or 1000 amperes per square inch for loading a bus bar. The last time I worked in that area was 1969 so the details are really fuzzy. It seems like we used 750 for Al. and 1000 for Cu. A ?" X 4" bus would be 1 square inch.

Keep in mind that I am going from memory and I was working for a manufacturer. I can't find where the Code addresses this issue.

 

[tshea]

Re: Bussbar ampacities

Search google--Here's one of the better sites I found
copper.org
They have a tremendous amount of information.

 

[jim dungar]

Re: Bussbar ampacities

A word of warning, do not try to compare bus sizing in a Listed product with any "standard" for current density. Manufacturers apply bussing based on actual temperature rise which includes factors like air flow and configuration.

 

[dillon3c]

Re: Bussbar ampacities

The only place in the code book that I know of, that address buss sizing..

NEC'05, 366.23(A) Auxiliary Gutters

NEC'02, 366.7(B)

 

[charlie]

Re: Bussbar ampacities

Thanks Dillon, I couldn't find it.

 

[charlie]

Re: Bussbar ampacities

By the way, bus is spelled bus. However Bussmann people really like it when you use their spelling of buss.