Calculating the ampacity of a solid metal strip/block?

Question

I am designing a 12vdc system where I will have a row of fuse holders. I would like to connect the row using a "bus bar" type strip of solid aluminum. If I know the exact dimensions of the strip is there a formula for calculating the amperage it can handle?

What I'm looking for is a formula to calculate current capacity based on material specifics. (density, dimensions etc). I can look at the piece and guess what gage wire it's close to. BTW where do you come up with 60AMPs? The NEC allows 119amps on a 2AWG copper THHN conductor in free air.

Answer 1

The easiest way would be to convert the bar to the closest circular mils.
This would give you a close enough value to use a standard lookup chart on AL wire.

If you need more info, post the dimensions.


Here is a site for a free calculator for 20 days. Near the bottom. You have to RUN the app from the site and it will install it.

Answer 2

The voltage is irrelevant to this problem. I don't know exact amperage's but I would approximate the bus bar thickness (at its narrowest point) and compare it to a similar gauge for a copper wire. Using a bus made for small glass fuses I would assume your bus is at least 5-7mm thick. That would be equivalent to a 2 gauge copper wire which is rated a 60 amps (conservatively) This will give you 12 x 60 = 720 watts total load.

Answer 3

Al resistance is 0.028 ohm*cm.
For a current I flowing through it we have:
I^2*R, this energy is converted into heat hence:
I^2*R=k(Tc-Ta) where k=thermal conductivity of Al, Tc=conductor steady state temperature C, Ta= ambient temp C, R=total resistance of conductor ohm, I=current in amps
From these equations you can find I the ampacity at steady state.

Answer 4

Change that aluminum to copper and u will have less to worry about.

Answer 5

YES!