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What Amperage Are These Fuses

You may need to turn them over so you can see the labels? :p

At least they got rid of their ant problem!
 
If we assume that the pipe shown is 1/2" schedule 40 brass, then it has an OD of 0.840" and an ID of 0.622". So the cross sectional area is pi/4 * (.840^2-0.622^2) = 0.250 in^2. A cmil is pi/4 square mils, so that's 318,716 cmils.

A random web page claims lead free brass has an electrical conductivity of 28% IACS (copper = 100%), so the resistance per unit length would comparable to 89,240 cmils copper wire. That's between #1 AWG copper (83690 cmils) and #1/0 (105600 cmils).

Another random web page claims the fusing current for #1 copper is 1594A, and for #1/0 copper is 1897A. Now the rate of heat generation in the pipe for a given current will be comparable to 89240 cmil copper wire (ignoring skin effect, which may or may not be valid), but the brass pipe has different thermal characteristics from the equiresistant copper wire. The density and heat capacity are close, but the brasss weight is 3.57 times higher (slower to warm up, but won't affect equilibrium temperature directly), while the outer diameter is greater (more area to radiate heat, so lower equilibrium temperature for a given input heating rate).

The upshot is that I'll guess it's 1500A-2000A, but it could be higher due to the greater surface area. Obviously this is pretty rough, especially the last paragraph above.

Cheers, Wayne
 
I've seen the copper plumbing tubing used before on a throw-switch and Present Lincoln hiding behind a fuse a couple of times, both on house trailers.
 
wwhitney said:
If we assume that the pipe shown is 1/2" schedule 40 brass, then it has an OD of 0.840" and an ID of 0.622". So the cross sectional area is pi/4 * (.840^2-0.622^2) = 0.250 in^2. A cmil is pi/4 square mils, so that's 318,716 cmils.

A random web page claims lead free brass has an electrical conductivity of 28% IACS (copper = 100%), so the resistance per unit length would comparable to 89,240 cmils copper wire. That's between #1 AWG copper (83690 cmils) and #1/0 (105600 cmils).

Another random web page claims the fusing current for #1 copper is 1594A, and for #1/0 copper is 1897A. Now the rate of heat generation in the pipe for a given current will be comparable to 89240 cmil copper wire (ignoring skin effect, which may or may not be valid), but the brass pipe has different thermal characteristics from the equiresistant copper wire. The density and heat capacity are close, but the brasss weight is 3.57 times higher (slower to warm up, but won't affect equilibrium temperature directly), while the outer diameter is greater (more area to radiate heat, so lower equilibrium temperature for a given input heating rate).

The upshot is that I'll guess it's 1500A-2000A, but it could be higher due to the greater surface area. Obviously this is pretty rough, especially the last paragraph above.

Cheers, Wayne
Click to expand...


That was a lot of brain work, but it was also hella funny.

Andy.
 
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