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#43945 10/25/04 10:28 PM
Joined: Apr 2004
Posts: 811
Hey guys, I'm working on a low-voltage project, nd I forget how many amps 20-24AWG wire can carry. Can you fill me in here? Thank you.

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#43946 11/09/04 07:32 AM
Joined: Sep 2002
Posts: 1,498
C-H Offline
I didn't want to jump in on this one, but now your post has been here for two weeks without a single response. I can just as well give and answer and hope for the more knowledgeable guys to correct me. [Linked Image] [Linked Image]

Without any warranty, no assumed liability and everything else you can think up for a disclaimer: Here is a formula I made up:

I =10^(3/50 x (35-AWG))

I could explain how I arrived at it, but I don't think anyone is interested nor do I have the time at the moment.

#43947 11/10/04 02:20 AM
Joined: Dec 2003
Posts: 886
Never saw the post!

Anyway, it's not that simple. Much depends on the insulation and the cable construction just like the larger stuff. Unless you are running uninsulated wire in free air the correct source of information will be the manufacturer.


#43948 11/10/04 09:46 AM
Joined: Aug 2001
Posts: 7,520
Sorry, I missed this first time round as well.

There are variations in the allowable ampacity depending upon specific conditions, just as the NEC restricts currents for bundling, ambient temperature, etc.

The low-voltage cabling used in marine/automotive applications, for example, often has somewhat higher ratings than for house wiring. Compare the NEC with this table of marine use, for example:

Here's one table of ratings for general equipment use:

#43949 11/10/04 09:04 PM
Joined: Feb 2004
Posts: 133
20 AWG -> 3.3 Amps
22 AWG -> 2.1 Amps
24 AWG -> 1.3 Amps

#43950 11/10/04 09:12 PM
Joined: Feb 2004
Posts: 133
Oh ya, almost forgot:

NOTE: This information is provided as is without any express or implied warranties. While effort has been taken to ensure the accuracy of the information contained in this text, the author assumes no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The ampacities listed might be totally inaccurate, inappropriate, or misguided. There is no guarantee as to the suitability of said circuits and information for any purpose.

Jim Sokaloff

#43951 11/11/04 04:25 AM
Joined: Sep 2002
Posts: 1,498
C-H Offline
Now we have at least four different answers, with a huge spread. There is a reason for this: It makes a difference if it is a network cable with 8 wires or a single wire inside a computer case. You need to derate for bundling, as you can see in Paul's first link. If you have one of those phone cables with dozens of pairs, it must be quite severe.

My little formula above simply approximates 310.16.

[This message has been edited by C-H (edited 11-11-2004).]

#43952 11/11/04 11:17 AM
Joined: Jul 2001
Posts: 599
JBD Offline
According to table 13.5.1 in NFPA79 Electrical Standard for Industrial Machinery.

#24 = 2A
#22 = 3A
#20 = 5A
#18 = 7A

These values apply to both 60 and 75C insulations in ambient 30C.

[This message has been edited by JBD (edited 11-11-2004).]

#43953 11/28/04 08:46 PM
Joined: Apr 2004
Posts: 811
Thank you guys very much! I ws starting to get worried, but if you missed it, don't worry about it! Thanks again.

[This message has been edited by Theelectrikid (edited 04-23-2005).]

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