[Shop-talk] Extension cord length vs. wire gauge

[Neil Sherry]

Comes back to ‘will it work’ which will depend on the device. In some places the utility companies are reducing line voltages to save energy – and stuff still works.

Only issue with the 40W dissipation would be if the cable was still coiled up – then it would build up, melt the insulation and be a hazard. Over 300 feet the heat per foot would be negligible – in fact more or less the same as it would be whatever the length of cable (actually a bit less, as the current is less due to the combined resistance).

Neil

 

From: Shop-talk <shop-talk-bounces at autox.team.net> On Behalf Of Jimmie Mayfield
Sent: 31 October 2018 02:56
To: shop-talk at autox.team.net
Subject: Re: [Shop-talk] Extension cord length vs. wire gauge

 

It comes down to voltage drop.  You generally don't want voltage drop of more than around 5%.

 

At 4 amps, a 100ft 16ga cord is going to have a voltage drop of about 3.5V.  This is okay.  At 300ft, the voltage drop will be about 9.5V.  That's unacceptable.  Assuming your equipment still functions, your cord would be dissipating around 40W of heat due to internal resistance.

300ft of 14ga cord will have a drop of around 6V.  That's marginal.

12ga cord will have a drop of about 3.75V.  That's okay.

So go with 12ga cord. 

 

J

 

 

On 10/30/18 15:54, Scott Hall wrote:

Guys, 

 

I need about 300 get of extension cord. 16 AWG was fine at 100 ft. Can I string 3 of those together without a problem, or should I go up a size? Draw is 4 amps.

 

Thanks, 

 

Scott





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