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**posted by** Stephane Boucher

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Optimizing Optoisolators, and Other Stories of Making Do With Less

Someday We’ll Find It, The Kelvin Connection

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Video: The PN Junction. How Diodes Work?

Two jobs

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Hello, Does anyone know where I can find out how much current specific gauges of wire can handle? I've looked up web pages on it, but can't figure out what they mean... for example at http://www.interfacebus.com/Copper_Wire_AWG_SIze.html There's a column that says: Current Carrying, and another that says Fusing Current I'm interested in figuring out if 20 AWG wire can handle steady DC of 7.25 Amps, for 20 AWG is says Current Carrying: 1.46 Fusing Current: 58.4 ? I don't get what they're saying.... other websites have been similarly confusing.. Much Thanks

```
panfilero wrote:
> Hello,
>
> Does anyone know where I can find out how much current specific gauges
> of wire can handle? I've looked up web pages on it, but can't figure
> out what they mean... for example at
>
> http://www.interfacebus.com/Copper_Wire_AWG_SIze.html
>
> There's a column that says: Current Carrying, and another that says
> Fusing Current
>
> I'm interested in figuring out if 20 AWG wire can handle steady DC of
> 7.25 Amps, for 20 AWG is says
> Current Carrying: 1.46
> Fusing Current: 58.4
>
> ? I don't get what they're saying.... other websites have been
> similarly confusing..
Fusing current is pretty obvious isn't it ?
Also beware of operation at elevated temperatures and derate when bundled
or run in trunking.
Graham
```

> > Does anyone know where I can find out how much current specific gauges > of wire can handle? www.rstengineering.com then Jim's Engineering Page, then Wire Table. > > There's a column that says: Current Carrying, and another that says > Fusing Current > > I'm interested in figuring out if 20 AWG wire can handle steady DC of > 7.25 Amps, for 20 AWG is says # 20 wire can carry any current you like, up to the fusing current. It is all a matter of how hot you are willing to let the wire get. The referenced table above will let you calculate the temperature rise of a wire over ambient for any arbitrary current and gauge. > Current Carrying: 1.46 > Fusing Current: 58.4 > > ? I don't get what they're saying.... other websites have been > similarly confusing.. The Current Carrying is how much current the wire can handle for a given rise in temperature over ambient. There should also be a note that the temperature rise will be more than calculated if the wires are in a bundle together. An unbundled #20 wire at 7.5 amps will rise about 30F (15C) over ambient, which is pretty warm. Your call. Fusing current is the current at which the wire will melt. Jim

```
"panfilero" <p...@gmail.com> wrote in message
news:d...@g38g2000yqn.googlegroups.com...
> Hello,
>
> Does anyone know where I can find out how much current specific gauges
> of wire can handle? I've looked up web pages on it, but can't figure
> out what they mean... for example at
>
> http://www.interfacebus.com/Copper_Wire_AWG_SIze.html
>
> There's a column that says: Current Carrying, and another that says
> Fusing Current
>
> I'm interested in figuring out if 20 AWG wire can handle steady DC of
> 7.25 Amps, for 20 AWG is says
> Current Carrying: 1.46
> Fusing Current: 58.4
>
> ? I don't get what they're saying.... other websites have been
> similarly confusing..
>
> Much Thanks
The current carrying capacity in the listed table is based on 700 circular
mills per amp, a very conservative number for wire wound inside a
transformer where heating is an issue.
The National electric code specifies current carrying capacity for open
wires or house wiring for example about twice that or 300 to 350 circular
mills per amp. This gives 20 AWG wire about a 3 Amp rating.
What is your application? What is the duty cycle? What is the thermal
environment, how hot can it get? Is it in a transformer or in open air and
how insulated? How much voltage drop can you tolerate?
```

```
panfilero wrote:
> Hello,
>
> Does anyone know where I can find out how much current specific gauges
> of wire can handle? I've looked up web pages on it, but can't figure
> out what they mean... for example at
>
> http://www.interfacebus.com/Copper_Wire_AWG_SIze.html
>
> There's a column that says: Current Carrying, and another that says
> Fusing Current
>
> I'm interested in figuring out if 20 AWG wire can handle steady DC of
> 7.25 Amps, for 20 AWG is says
> Current Carrying: 1.46
> Fusing Current: 58.4
>
> ? I don't get what they're saying.... other websites have been
> similarly confusing..
>
> Much Thanks
Back in the day, the usual rule of thumb for low-frequency power
transformers in continuous use was 1000 circular mils per amp, where a
'circular mil' is the square of the diameter in mils (thousandths of an
inch), i.e. 1 circular mil = (pi/4) square mil. The 1000 circular mils
per amp rule comes out to 5.07e-6 square metres per amp.
Cheers,
Phil Hobbs
```

But before the wire gets too hot, there will probably be so much voltage drop that the voltage at the load is too low, so that might be the more important criterion.

```
On Mon, 08 Dec 2008 08:09:02 -0800, panfilero wrote:
>
> Does anyone know where I can find out how much current specific gauges of
> wire can handle? I've looked up web pages on it, but can't figure out
> what they mean... for example at
>
> http://www.interfacebus.com/Copper_Wire_AWG_SIze.html
>
> There's a column that says: Current Carrying, and another that says Fusing
> Current
>
> I'm interested in figuring out if 20 AWG wire can handle steady DC of 7.25
> Amps, for 20 AWG is says
> Current Carrying: 1.46
> Fusing Current: 58.4
>
> ? I don't get what they're saying.... other websites have been similarly
> confusing..
>
> Much Thanks
You didn't read the rest of the page:
"Current Notes:
The current shown per wire size listed above is based on 1 amp/ 700
Circular mils, other tables provide different current per wire size, and
different current for open air ~ check your local electrical code for the
correct current capacity [Ampacity]. The 1 amp/ 700 Circular mils seems
to be the most conservative, other sites provide/allow for 1 amp per 200
or 300 Circular mil. For shot wire lengths use 1A/200 Circular mil, for
longer wire runs use 300 Circular mil, and for very long wire runs use
the table above, 1 amp / 700 Circular mil.
The current rating is listed based on permissible voltage drop and not
conductor heating.
The ability of a wire to carry a given amount of current is affected by a
number of additional factors, which are not accounted for in the AWG
table above. The ambient temperature of the surrounding air, wire
insulation, and number of other wires bundled together [provided below].
Ampacity relates to the ability of the conductor to carry current [amps]
before the cable over heats. I understand there are hundreds of Ampacity
tables for many different conditions. The numbers above are but one
example. Ampacity Tables for many conditions:"
Hope This Helps!
Rich
```

"panfilero" > > I'm interested in figuring out if 20 AWG wire can handle steady DC of > 7.25 Amps, for 20 AWG ** This page say 20AWG is good for 11 amps when used for "chassis wiring" or wires mounted in mid air. http://www.powerstream.com/Wire_Size.htm Tallies with my experience. 1 metre of 20AWG will dissipate about 6 watts at 11 amps when used this way. ..... Phil

```
On Tue, 9 Dec 2008 09:58:11 +1100, "Phil Allison"
<p...@tpg.com.au> wrote:
>
>"panfilero"
>
>>
>> I'm interested in figuring out if 20 AWG wire can handle steady DC of
>> 7.25 Amps, for 20 AWG
>
>
>** This page say 20AWG is good for 11 amps when used for "chassis wiring" or
>wires mounted in mid air.
>
>http://www.powerstream.com/Wire_Size.htm
>
>Tallies with my experience.
>
>1 metre of 20AWG will dissipate about 6 watts at 11 amps when used this way.
>
>
>
>..... Phil
>
AC 43.13-1B shows AWG 20 okay for about 16.5A if you don't mind 80°C
rise (eg. very high temperature rated insulation in moderate ambient).
That's for *one wire in free air*, deratings for bundles (two wires
are a bundle), and altitude, of course, and the detailed calculations
are shown for various situations. May be available on the FAA dot GOV
website.
Mostly you'll not want to get anywhere near those current levels or
voltage drop will kill you.
```

On Mon, 08 Dec 2008 23:21:44 -0000, Spehro Pefhany <s...@interlogdotyou.knowwhat> wrote: > On Tue, 9 Dec 2008 09:58:11 +1100, "Phil Allison" > <p...@tpg.com.au> wrote: > >> >>"panfilero" >> >>> >>> I'm interested in figuring out if 20 AWG wire can handle steady DC of >>> 7.25 Amps, for 20 AWG >> >> >>** This page say 20AWG is good for 11 amps when used for "chassis wiring" or >>wires mounted in mid air. >> >>http://www.powerstream.com/Wire_Size.htm >> >>Tallies with my experience. >> >>1 metre of 20AWG will dissipate about 6 watts at 11 amps when used this way. >> >> >> >>..... Phil >> > AC 43.13-1B shows AWG 20 okay for about 16.5A if you don't mind 80°C > rise (eg. very high temperature rated insulation in moderate ambient). > > That's for *one wire in free air*, deratings for bundles (two wires > are a bundle), and altitude, of course, and the detailed calculations > are shown for various situations. May be available on the FAA dot GOV > website. > > Mostly you'll not want to get anywhere near those current levels or > voltage drop will kill you. How can a voltage drop kill someone? The lower the voltage at the outlet, the safer it is! -- http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com Your cancellation is being cancelled. Please press ok to continue cancelling the cancellation or cancel to cancel cancelling the cancellation.