Wire Ampacity chart

I started here...

Maybe these will help.

What do you want to wire?

Ampacity depends on ohmitude and allowable fahrenheitery, but is largely independent of voltaciousness.

I experimented on ribbon cables as regards current limits. They have unique geometry and allow some interesting choices of spacing and parallelism. Of course the limits depend powerfully on air flow.

I have in mind some modules plugged into a rackmount chassis, each doing 12 channels of a test function, with four common busses. I'll have short ribbon cable jumpers between modules to extend the function in groups of 12. A 20-wire cable could use 5 wires per buss, or 4 with grounds between, or something. Or use a 16 wide ribbon with 4 per. Fortunately, there will be predictable air flow.

Why play chess or do crosswords when you can design electronics?

other situations in which the nominal ampacity rating of wiring must be derated (reduced) due to other factors, a common one being multiple conductors in a run of conduit where the heat dissipation might not be so good, requiring a derating to 70% or less of nominal.

Yes wire sizes for amperage can vary all over the place. It depends on how much hear rise you can stand and if it is open air or enclosed such as in a transformer or conduit.

About the only 'real' chart is one that I saw where the wire would melt out in open air.

Saw where some wire was being sold in dropcords and listed as say # 12 wire but was actually a few wire sizes smaller like # 14. Reason being given wes the insulation was rated for a higher heat. Still does not compensate for the voltage drop.

How 'bout this? People usually don't get paid for doing crosswords or playing chess. That makes it fun. People get paid tons and tons of money to design electronics so that makes it work.

Some of it is work. But designing is fun.

A co-worker from long ago would say the difference between work and play depended on which way the money flowed. I was lucky to find something I liked doing and was able to do it all of my working years. Now I can sit around and wonder how people can possibly get along without my experience and wisdom. Think old fart at the coffee shop.

Where I worked about 3/4 of the time was fun. The other 1/4 of the time was work because I did not enjoy that part. If I could have paid the bills I would have done the 3/4 time for nothing. Is it work or fun for the people doing sports ? Even the chess can be a job or for fun or both. Golf is probably the best paying job for fun. Not much physical abuse to the body compaired to other sports.

Yes, "Yes wire sizes for amperage can vary all over the place." is exactly what I found. I used the calculator that was linked and it shows that AWG 40 was suitable for 1 amp at 1 foot long ? I thought the rule etched it stone was the #10 was used for 30 Amp, #12 for 20 Amps, and #14 for Amps, where does this standard come from ? And why can't I find a chart that follows the AWG down into the 2? AWG gauges ? Years ago I had a shop class where the instructor stated that 18 AWG was good for 3 amps and another instructor stated that 18 AWG was good for 5 amps maximum. I just thought it would be simple to find a chart that definitively shows the small AWG(s)

Thanks

There's no definitive answer, unless you have to follow recognized standard. A rule of thumb for copper wiring fusing current is 80*d^1.5 (d = diameter in mm) and then to design with a safety factor (say 1/20th of that).

I searched for 24 awg ampacity. Several tables for small wire gauge showed up. \

That's just someone's definition. Electronic design is fun, but the followups - parts selection, documentation, testing, compliance - can get tedious.

My reference says that the fusing current of #40 is 1.77 amps. So 1 amp would be mighty hot.

The ITT "Reference Data for Radio Engineers" is a good book to have around. Old copies should be cheap.

Yikes. (1/20)^2 is 1/400. Seems pessimistic.

Dean, I have seen that table before. it shows two numbers described as "Maximum amps for chassis wiring" and "Maximum amps for power transmission". Not really sure what these definitions mean other than the literal interpretation ?

For 14 AWG the chart shows 8.282 Amps and 32 Amps respectively ?

Thanks Sid.

Short answer is chassis wiring is in an enclosed box. the other is in open air.

For power transmission the chart assumes the wire will be routed in a bundle with other power wires, thus the ability to dissipate heat will be reduced, so the current capacity will be lower.