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basics | how much current can AWG wire handle


There are 72 messages in this thread.

You are currently looking at messages 1 to 10.

how much current can AWG wire handle - panfilero - 2008-12-08 11:09:00

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

Re: how much current can AWG wire handle - Eeyore - 2008-12-08 11:13:00


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


Re: how much current can AWG wire handle - RST Engineering (jw) - 2008-12-08 11:31:00

>
> 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 



Re: how much current can AWG wire handle - Bob Eld - 2008-12-08 12:00:00

"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?



Re: how much current can AWG wire handle - Phil Hobbs - 2008-12-08 12:06:00

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

Re: how much current can AWG wire handle - BobG - 2008-12-08 12:17:00

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.

Re: how much current can AWG wire handle - Rich Grise - 2008-12-08 13:45:00

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





Re: how much current can AWG wire handle - Phil Allison - 2008-12-08 17:58:00

"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



Re: how much current can AWG wire handle - Spehro Pefhany - 2008-12-08 18:21:00

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. 


Re: how much current can AWG wire handle - Peter Hucker - 2008-12-09 13:40:00

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!

-- 
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