Current Capacity of Standed Wire

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dwedem99

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My apologies for the uneducated nature of this question but not being an electrician or engineer I found your forum and it looks like you're the best resource for a correct answer.
My maintenance crew (non-electricians) are debating whether joining separately insulated stranded copper cables at the terminations at both ends (either by mechanical or soldering the conductors together) will carry the same current as a single multi-stranded insulated cable of the same cross sectional area. This is not for a building installation where safety is a concern. They are just looking at creating a 35 foot long set of jumper cables for use on jumping vehicles and equipment. Thanks, Dan.
 
dwedem99 said:
My apologies for the uneducated nature of this question but not being an electrician or engineer I found your forum and it looks like you're the best resource for a correct answer.
My maintenance crew (non-electricians) are debating whether joining separately insulated stranded copper cables at the terminations at both ends (either by mechanical or soldering the conductors together) will carry the same current as a single multi-stranded insulated cable of the same cross sectional area. This is not for a building installation where safety is a concern. They are just looking at creating a 35 foot long set of jumper cables for use on jumping vehicles and equipment. Thanks, Dan.
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If the same cross sectional area equals it would carry the same amperage when paralleled.
 
Old welder leads make awesome jumper cables. If you know any old welders that is.
35 feet are long jumper cables....... It would be easier to use a jump box or battery cart if there is no power available for a charger/booster.

The answer to your question is yes. You can parallel lamp cord if you want to for you application.
 
dwedem99 said:
My apologies for the uneducated nature of this question but not being an electrician or engineer I found your forum and it looks like you're the best resource for a correct answer.
My maintenance crew (non-electricians) are debating whether joining separately insulated stranded copper cables at the terminations at both ends (either by mechanical or soldering the conductors together) will carry the same current as a single multi-stranded insulated cable of the same cross sectional area. This is not for a building installation where safety is a concern. They are just looking at creating a 35 foot long set of jumper cables for use on jumping vehicles and equipment. Thanks, Dan.
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When used for any particular application, they will each carry very near half the current of a single wire with the same cross-sectional area... :p

I have a feeling you are asking about insulation performance, though. With two wires having the same cross-sectional area as one larger wire, and all having the same length and insulation Type, the single wire's insulation will begin degrading at a lower current level than the two paralleled wires.

PS: Welcome to the forum :thumbsup:
 
dwedem99 said:
My apologies for the uneducated nature of this question but not being an electrician or engineer I found your forum and it looks like you're the best resource for a correct answer.
My maintenance crew (non-electricians) are debating whether joining separately insulated stranded copper cables at the terminations at both ends (either by mechanical or soldering the conductors together) will carry the same current as a single multi-stranded insulated cable of the same cross sectional area. This is not for a building installation where safety is a concern. They are just looking at creating a 35 foot long set of jumper cables for use on jumping vehicles and equipment. Thanks, Dan.
Click to expand...

At the risk of seeming like a jerk, the very first sentence says, not being an electrician or engineer. Then my maintenance crew (non electrician). Is it not the policy of this forum not to give advise to those not related to the electrical industry? With this sue happy society all it takes is an issue to come up from the advise and someone says Mike Holt said this was the way to do it. Hate to be harsh. Just wondering and if i am off base just slap me. :happysad:
 
Daja7 said:
At the risk of seeming like a jerk, the very first sentence says, not being an electrician or engineer. Then my maintenance crew (non electrician). Is it not the policy of this forum not to give advise to those not related to the electrical industry? With this sue happy society all it takes is an issue to come up from the advise and someone says Mike Holt said this was the way to do it. Hate to be harsh. Just wondering and if i am off base just slap me. :happysad:
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I think the question is/should be allowable here as long as all we talk about is basic electricity theory, any "how to" information should be off limits though. For the most part all that has been discussed so far is the fact that same cross sectional area will have about the same current carrying capability, plus heat produced will have an impact on operating temp of any insulation. The other key thing here that is still pretty much theory and not "how to" is to look at potential voltage drop issues.
 
kwired said:
I think the question is/should be allowable here as long as all we talk about is basic electricity theory, any "how to" information should be off limits though. For the most part all that has been discussed so far is the fact that same cross sectional area will have about the same current carrying capability, plus heat produced will have an impact on operating temp of any insulation. The other key thing here that is still pretty much theory and not "how to" is to look at potential voltage drop issues.
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Consider me slapped. :ashamed1:
 
My answer to the question is that two identical wires in parallel will be able to carry more current than a single wire with the same insulation system and with the same total cross sectional area.

It is true that a wire?s ampacity is based in part on its cross sectional area. But the relationship between area and max current is not linear. You can double the area of a wire and not double its ability to carry current. That is because more of the current flows along the outer edge of the wire, and less current flows closer to the center of the wire. So if you double the overall area, you are not doubling the amount of area in which the bulk of the current will be flowing.

As further evidence, consider a pair of parallel #6 wires and a single #3 wire. Let?s disregard for the moment that a #6 is too small for us to be allowed to use parallel connections. The area of a #6 is 26,240 circular mils, so the total area of two of them would be 52,480 circular mils. The area of a #3 is 52, 620 circular mils. That is very close to the area of a pair of #6s. The ampacity of a #6 is 65 amps, so the ampacity of a pair of #6s would be 130 amps. However, the ampacity of a #3 is only 100 amps.

 
Per the OP : They are just looking at creating a 35 foot long set of jumper cables for use on jumping vehicles and equipment.


Sounds like DC to me, so current directly proportional to total cross sectional area for the time it takes to jump start a vehicle.

Yes, thermal convection, etc does start to play a role for long time periods which reduces the current capability, but negligible for jumper cables.


On a more practical note, a big solid single wire will carry far less current (e.g. zero!) than parallel small strands of wire after it gets flexed a few hundred times and breaks after being used as a jumper cable.
 
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