30A, 60sec, 7", less than 105C, what AWG?

I need to put a ground strap in a device I am working on and it needs to be able to handle 30 A for 60 seconds without rising above 105C (assuming ambient of 25C). What is the smallest diameter wire I can use? It needs to be 7" long. I have googled high and low and not found anything useful in this case.

Reply to
acannell
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Get ground strap stuff and install in your application. Stick 30A through it for 60 seconds and measure how hot it gets.

Adjust accordingly....

Job Done

DNA

Reply to
Genome

I get 14 AWG having a 62 K temperature rise after passing 30 A for 60 s. (This assumes that none of the heat gets out of the wire.) 16 AWG had a 155 K rise and so would not meet your requirements.

I put together a little spreadsheet for calculating temperature rises in PCB traces and wires. Let me know if you would like a copy of it.

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-Harold Hill

Reply to
hhill

Try some of this stuff:

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Good Luck! Rich

Reply to
Rich Grise

See the book "National Electrical Code" aka NFPA 70. It should be available at your local college library.

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JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
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Reply to
joseph2k

The NEC is going to say 10ga copper, not what he asked. Maybe the Neher McGrath formula in 310.15 would be relevant. Gut feel? 18 or 16 would do what he asked. What is the ambient temp and insulation?

Reply to
gfretwell

Believe it or not! I have used "solder wick," the non-fluxed kind, for ground straps and it works well. And it can handle the temperature!

Al

Reply to
Al

Without flux? That's not solder wick. Its just braided wire, which was around for a LONG, LONG time before any flux was added to make solder wick. Braided wire was used to ground the back of the engine block to car and truck bodies so you could listen to a radio, rather than ignition noise.

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Reply to
Michael A. Terrell

By the most astounding coincidence, we just happen to have great heaping bunches of low cost solder wick at

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Many thanks,

Don Lancaster                          voice phone: (928)428-4073
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Reply to
Don Lancaster

You can make your own braid by taking certain forms of coax apart.

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Many thanks,

Don Lancaster                          voice phone: (928)428-4073
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Reply to
Don Lancaster

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part number: 75-1-5 et al

Al

Reply to
Al

Not just coax. I had about 6,000 feet of three conductor CATV converter control cable with a fine copper braid salvaged from a CATV repair center I ran back in the mid '80s. A bottle of Kester RMA flux was always on my bench, and I used the wet wick method to repair thousands of circuit boards. After pulling the wires and paper out of the shield it would collapse into a flat 1/8" wide braid. I wrapped it on old solder spools and empty solder wick holders. I still have some of the cable left, and a quart or two of Kester RMA flux.

BTW, I have used the shield RG174 and cheap copper shielded RG-59 coax for larger parts, but I haven't done much with through hole for about 10 years. The only small coax I have on hand is silver plated teflon, and I'm not going to waste it by using it as solder wick.

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Reply to
Michael A. Terrell

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