How much current does AWG 24 wire carry?

[Jwillis]

Theirs no rule that states that you can't pull more current through a wire than what is considered standard.

Yes there are such regulations based on C.S. Area, for installations covered by the Electrical Wiring standards in most countries.

But if you design equipment such as transformers, the standards are not based on conductor sizes.
However safety is then covered by insulation temperature rise standards.

The code only describes how the wire is to be installed. But does not regulate how it is to be used after installation. The NEC and UL/CSA  does not regulate end use. 

[pcprogrammer]

So, what wire gauge is recommend for the power cord (AWG18 vs 14),
wires between the IEC320 C14 Inlet Module with switch and the power supply as well as
the wires from the power supply to motor controller (one could output 4.2A and the
other 5.6A, not decided which to get yet)?

The power cord is a different story. It connects your power supply to the mains, which for you probably is 120V. If the stepper motor runs an average of 1A at 12V the current on the power cord is only in the order of 12 / 120 / efficiency of the supply (maybe 90%) part of the output current. So ~111mA. But there will be peaks to take into account. A standard power cord (AWG18) will do.

For the wires in between the power supply and the controller you can use something in between AWG24 and AWG18 depending on the length of the wires.

As for the actual current flowing through the wires it depends on a lot of factors. Measure the DC resistance of a single winding and divide the supply voltage by the resistance. This tells you the max current that can flow. Then there is AC behavior of the motor. To make it run the windings are actuated in turn, and this means pulsed voltages, reducing the average current.

To get a better understanding of it all I would suggest to read up on the basics of electrical engineering.

Edit: During my morning walk it dawned on me that I have the efficiency calculation wrong. Instead of multiply it should be divide. Amended the formula and result.

[soldar]

As a very rough starting point, rule of thumb and sanity check I use a guide of 3 A/mm2 for things like transformer windings and 10 A/mm2 for residential home wiring.

[soldar]

You really have to wonder what were they thinking when they invented the AWG

[johansen]

You really have to wonder what were they thinking when they invented the AWG

(Attachment Link)

its really not that bad. they were working with what they had at the time, which was various competing companies offering wire in different sizes.

By definition, No. 36 AWG is 0.005 inches in diameter, and No. 0000 is 0.46 inches in diameter. The ratio of these diameters is 1:92, and there are 40 gauge sizes from No. 36 to No. 0000, or 39 steps

of course they could have arbitrarily definied 0000 as .5 inches and made the math slightly easier, with no practical functional difference for anyone who actually works with their hands.

[Psi]

+1 for the powerstream table.

3.5A for wiring inside a device
0.57A for getting power somewhere.

It's more about heat and Vdrop, if you're ok with how hot the wire gets and the voltage drop then it's fine.
Wire with silicon insulation allows you to run it hotter.

Also if you coil the wire up you have to derate it because you have hot wire next to hot wire next to hot wire. So the hot wire in the middle sees the wires either side as ambient temp and so its temp shoots up from that point, not from actual ambient temp.  eg You get into runway very fast when you coil wires together.

[donlisms]

I think the AWG was heavily influenced by the Brown&Sharp gage that came before it. They chose two sizes that were clean sizes, (0.460 and... something) and then interpolated for the intermediates, and then rounded things off here and there.   The NBS has some papers that explain it all, with the general conclusion that it works just fine, given all of the other uncontrolled variables, eg how the wire is drawn, and the composition of the copper alloy, and all that stuff. Plus .34% per degree Centipede, of course.  All of this gage stuff is approximate, especially when you consider the resistance, which is where the real issues are.

History.  "Yes, Tommy, this is how we got here."

[inse]

Q: How much load can a donkey carry?
CQ: On the flat or up the mountain, for 5min or 5h, with PETA involvement or without?

[johansen]

Q: How much load can a donkey carry?
CQ: On the flat or up the mountain, for 5min or 5h, with PETA involvement or without?

i would love to see some of the armchair electrical engineers take apart their oven or range, only to find that 16 gauge wires run 14 amps through a 3500 watt oven heating element. oh the horror.

you can get about 3 pounds of wire out of them these days. good quality 105C rated wire. good for fixing cars and shit.

[coppercone2]

I think some of these values are nuts.

What exactly are you doing? the manufacturers need to COVA their ass.

I am lookin at a curve, at 35C above ambient for a single strand you get 3.75 amps. For a cable of four you get 2.8 amps.

If you have 80C rated cable, and your in normal places, you are still 45 C short of getting to the actual cable rating.

Then you have deviations like color of the cable, how its routed (race way or hanging in the air?).

If you are selling something to people you wanna definitely obey this stuff. If you are doing it for yourself then you have some leeway, so long you follow some precautions, like setting fuses. Different loads are different, how well behaved is your load? Can it stall out and draw massive amounts of current? Do you have a hard fuse or a poly fuse or a circuit breaker that you might keep resetting? What is the run time of your device?


For instance welding machine work cable is so different then NEC! 


If you followed NEC for welding machine work cable the results would be preposterous beyond belief.


I used a 20 AWG 4 strand cable with 80C rating to carry 12 amps! 

What is the result on this black TPE cable? After an hour of run time the cable gets warm to the touch. Its connected to a machine that makes alot of noise and its hanging in the air in a spiral shape. IF I take this machine out in the hot sun and let it run indefinately on the hottest day of the year, we might get close to the rating. The cable rating guideline is 0.8 * 6.5 amps (4 strand on 6.5 amp rating for single strand), aka 5.2 amps per wire, doubled up lets call it 10 amps. I ran it on 12 amps.

The table does not factor in the color, which has an effect on dissipation. This cable is braided with bare copper, no foil. The table just says to ignore shielding. Is this correct? Who knows. I imagine a braid might insulate this less then a foil. Maybe it just assumes insulated foil.


So oh no, I am running at 120% overload!!!!

But what does my hand tell me ? in a room temperature enviroment this cable is slightly warm after 2 hours. If it was zip tied into a strain relief, or jammed super tight inside of a cable routing thing inside of a box I might think hmm can this cause a problem??

 When its floating in the air my analysis tells me that its safe enough for a loud specialized tool that might run for a few hours of supervision. Am I going to redesign this for 18 AWG? NO! I am happy with it! Would I sell it ? No, because someone might get upset. But in my case this lab machine runs just dandy and there is IMO No hazard.


For a different example, a spot welder. It has 8 AWG silicone wire. I have to handle the wire and electrodes with my hands to use it. It welds at 1500 amps. If I use it alot, the wire gets hot. Hard to touch. If I was going to automate this machine I would up the gauge if its being used heavy because it gets seriously hot (but it goes into thick copper bus bars in the machine). is 8 AWG wire the wrong choice for 1500 amps? No, it makes sense for k-weld. Infact its what the manufacturer supplies you with! Would making thicker cables improve quality? Maybe, maybe not. The dexterity offered by the thinner wires might allow for better more repeatable probe position and more repeatable spot welds. If I am fighting heavy cables so the wires don't get hot, I might do it wrong and compromise the weld. Logically I think I should just leave it be!


How about my tig machine? If the wire gets hot on your leg then let it rest! No NEC here! Its not even a normal wire. They route argon through the weird super flex braid to cool it. So its a wire inside of a gas tube that cools when your passing tons of current through it. Leave it to manufacturer to decide.


How about my wall outlet? You bet your ass I won't deviate from the NEC recommendation when its powering welding machines and it deserves some extra copper! no fooling around in the wall

[MrAl]

Hello, different sources provide different answers. One stated 0.577A. The other 7A, etc. Which is correct?

Hi,

The question of current capacity for a wire is not just one about wire size and current alone, it's also about the application it is to be used in.  The application requirements include knowing a lot more than just the wire size and current capability.  That's because there are other factors involved sometimes like length, ambient temperature, temperature rise, wave shape of the signal, etc.  Sometimes an application is associated with a certain wire area per ampere to make the choice of wire size a little easier.
In the table attached, we can see wire size 24 and a current rating of 0.67 amps 'I' at 600cm per ampere.  That would be for a regular hook up wire that is not especially long.  If the wire was used inside a transformer though, we may have to increase the area to 1200cm per ampere which would mean wire size 24 would only be good for half that current around 0.33 amps.

There are a lot of other factors however.  In a transformer there is also skin effect, which raises the AC resistance of the wire.  That's an entirely different calculation that involves the frequency of the wire.

What this all means is that you don't really ask how much current a wire can carry you ask what an application requires.  So you are asking more about the application than the wire.  In real life you study different applications and that comes with the knowledge of what wire specs are to be observed.

A typical application is an extension cord for a home appliance (or similar device).  These days attention to wire length is also included in this application specification.  #16 is good for some lengths but #14 is chosen if the length of wire is longer.  The reason is that voltage drop becomes an issue because the voltage at the end of the wire is less than the voltage at the beginning of the wire where it plugs into the wall.

It does not make too much sense to talk about a billion ampere current through a #24 AWG wire because for one, the fusing time is inversely proportional to the square of the current, and the square of the current is a very large number.  This puts the fusing time somewhere around 0.0034 picoseconds, and as you know 1 picosecond is 1e-12 seconds, a very small amount of time.  Even a million amps will melt the wire in about 3.4 nanoseconds (25 degree C ambient).

Very often though we talk about "hook-up" wire, which is usually a short run.  The table in the attachment would be good for this application.

As mentioned above about applications, sometimes you have to think about the extremes too.  A wire in deep space will stay cooler than a wire inside a thermal container like a cooler used to keep things cool during the summer.
To show how extreme this can be, a wire that is completely thermally insulated will heat to the melting point every time even with a current of just 1 microampere.  That's because even the small amount of heat will build up over time because it has nowhere to dissipate.

[pcprogrammer]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Here we just use mm2, and for electrical house wiring it is 1.5mm2 for light circuits fused at 10A and 2.5mm2 for wall sockets fused at 16A. Simple, the bigger the number the more current it can carry. 

[MarkT]

You can pass 1000000000A through that wire. The only question is if the wire gets too hot while doing that, to the point of the insulation melting or catching fire.

No, that level of current is completely impossible, the magnetic forces alone would destroy it.

At 1GA flowing the power dissipation would be 10^18 times greater than at 1A, the only strategy to avoid vaporizing the wire is make the pulse less than a picosecond, which is completely impossible as light only travels 300µm in that time, much smaller than the wire diameter!!

There are at least two practical limits to max current, one is thermal, the other is the magnetic field being strong enough to explosively crush or snap the wire.

[TimFox]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Here we just use mm2, and for electrical house wiring it is 1.5mm2 for light circuits fused at 10A and 2.5mm2 for wall sockets fused at 16A. Simple, the bigger the number the more current it can carry. 

Similarly, the larger the AWG number, the smaller the diameter, and the lower current rating.
It's a logarithmic measure, similar to dB:  a change of 3 AWGs means a factor of two in cross-section area and roughly a factor of two in current rating.

[CatalinaWOW]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Here we just use mm2, and for electrical house wiring it is 1.5mm2 for light circuits fused at 10A and 2.5mm2 for wall sockets fused at 16A. Simple, the bigger the number the more current it can carry. 

Every system has its advantages.  Square millimeters can be expressed as a sensible number for wire sizes used in low power applications that aren't particularly tiny.  But need a change of units for very large sizes and very small sizes, or several characters of scientific notation.  The change of units is problematic.  Using square centimeters will trap the unwary because the conversion factor is not the kneejerk 10, but 100.

Right now the metric system wins.  Not for its intrinsic advantages, which are much smaller than proponents seem to think, but because standardization really is beneficial and at this point in time the metric world is much larger than the "English units" world.  And AWG isn't even a "English units" standard.  It could (an often is) square mils or circular mils which scales size with current as you prefer.

[golden_labels]

The one thing that stumped me at first with this AWG, not knowing about it and being a metrics born person, is that the larger the number the smaller the wire.   

Derives from the number of times a wire had to be drawn to obtain one that thin. Makes perfect sense, when you know the history of making strings for instruments!

[Harrow]

Yeah. This underlines how important it is to be exact and include as much information as possible. What they failed to tell you, or you misunderstood, was this important piece: "without damage".

Haha, this is the true part. Just for fun, I tried to see if I could use some very light speaker wire with my arc welder. So pulling close to 200 amps through some very fine wire. To my surprise, it worked absolutely fine. Then I looked down and saw that the wire no longer had any insulation on it and was glowing red. 

[Picuino]

Take into account the voltage drop in the conductors, multiplying the current by the resistance per meter and by the length in meters doubled (for 2-wire cable).

[MrAl]

Hi,

In the old days they had to draw the wire through separate dies because the wire would break if they went through only one die with a large diameter rod.  The rod was drawn through the die and that reduced the diameter.  It was found that if they tried to go too small in diameter from the size of the rod, the wire would break, so they had to use one die to get down to a lower diameter, then another die to get to an even lower diameter, then another die, etc.  Each die would decrease the diameter by something like 10 or 11 percent.
From what I understand, Brown and Sharp produced the first dies, and the wire gauge number reflected the number of dies the wire had to be drawn through in order to get that initial (probably standard) rod size down to a certain size.  Thus, wire size AWG 24 had to be drawn through 24 dies.
I would think this made it easier for people actually making the wire since all they had to do was know how many dies to use to make a certain size wire.

Today we can convert that into a logarithmic system.  The ratio of the largest diameter wire to the smallest is 1 to 92, and that is part of the math used to calculate wire size today.

Is it dumb to have to use that system today?  Well, these old standards are hard to break because they have been used for so long and are known and understood by so many people today.  Changing them could result in errors which could result in dangerous situations coming up by some simple misunderstanding.  Many people who work in various industries know what a #22 AWG wire is, as well as a #10 AWG wire.  They may not even know what the actual diameter is, but they are familiar with that wire size by its AWG number and what it is usually used for.
For other applications though there are other standards such as SAE and ISO.
There's also SWG for wire sizes.

Today they may do the wire drawing a little differently with new techniques, and it depends what kind of wire it is too such as copper or harder metal.

I am sure there would be a lot to read on the web about all this.

[TimFox]

It is now common practice in the US to use “gauges” that are logarithmic in actual size or diameter.
This allows the user to find a gauge size that is within a certain ratio of the desired size, just as the standard choices of resistors in an E24 series (which are stated in actual value rather than sequence number).
Besides wire gauges (AWG = American Wire Gauge, slightly different than the British SWG Standard Wire Gauge), there are various sheet metal thickness gauges and “number drill” sets.
In practice, with either a gauge series or a metric arithmetic series, you still need to look up the wire resistance and rating in an engineering table.
Also, using a drill table you will find recommendations for “number drill” size for either  American UN screw threads or ISO metric threads so there is little need for both an arithmetic metric or logarithmic number set of drills.
Of course, since 1 inch is exactly 25.4 mm (by act of Congress), there is also a metric expression for the diameter of each drill size or wire gauge.

[radiolistener]

it depends on how many voltage drop and how many heating power you allow for the wire.

For example, for a copper wire AWG24 resistance is about 0.0841976Ω per meter.
So if you use 10 meters AWG24 wire it will have 0.841976Ω and at 7 Amps it will have voltage drop = 7 Amps * 0.841976 Ω = 5.9V. You will lose power 7 V * 5.9V = 41.3W, this power will going to a wire heating. Is it ok for you?

[soldar]

Q- How much current would a AWG 24 wire carry if a AWG 24 wire could carry current?

A- A AWG 24 wire would carry as much current as a AWG 24 wire could carry if a AWG 24 wire could carry current.

[CatalinaWOW]

Q- How much current would a AWG 24 wire carry if a AWG 24 wire could carry current?

A- A AWG 24 wire would carry as much current as a AWG 24 wire could carry if a AWG 24 wire could carry current.

Might want to add this to the engineering humor thread.

[golden_labels]

Wire drawing through dies dates back to at least medieval times.⁽¹⁾ Both the technique and parameters of the process. It was a huge industry centuries before Brown&Sharpe. They couldn’t be the first or even at the frontier.

However, Brown&Sharpe were well known. Visibility alone is enough to be perceived as the norm. They were also influential and abusing standardization process to get market advantage aren’t a modern invention. Though these are merely a plausible guesses made on the spot — I have no evidence for either.

⁽¹⁾ Stephen Birkett and Paul Poletti provide an overview in “Reproduction of Authentic Historical Soft Iron Wire for Musical Instruments”, along with some nice source pictures.