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Ask an Expert Forum Connect 2 different wire gauge; is the smaller gauge affecting the capacity of the bigger wire gauge?
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Connect 2 different wire gauge; is the smaller gauge affecting the capacity of the bigger wire gauge?

maolemieux
maolemieux over 6 years ago

Hello, I would like first to thank anyone taking the time to read this or help. I was wondering how to calculate how many amp I can use by connecting 2 different wire gauge. I am on a 12v dc circuit and would ie to connect a 12v led module to a battery for a long distance. The led modules come with a 22 awg gauge cable from the factory. I would like to run it for a long distance to the power source (battery or power supply) I plan to use awg 16 wire connected to the led module so I can make a big distance safely. I will solder the awg 16 to the awg 22 of the led module. I usually know how to calculate the max amp that I can run for a single wire gauge by looking at spec of wire. However I am not sure if the 22 awg wire gauge from the led will limit my 16 awg? Is the 16 awg maximum amp capacity is limited by the 22 awg or will the 16 awg be able to use it's full amp capacity?

 

So to calculate how far I can get with the awg 16 can I just calculate the 22 awg capacity and add to the 16 awg capacity or I need to calculate the 16 awg capacity as if it was a 22 awg?

 

 

I am sorry my english is not great I live in montreal and speak french

 

Thank again for any help

cheers

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  • Gough Lui
    Gough Lui over 6 years ago +5 suggested
    Your question is an interesting one can be solved by a little bit of thought - but the short answer is that each gauge and type of wire has its own maximum current capacity (ampacity) and connecting the…
  • jw0752
    jw0752 over 6 years ago +3 suggested
    Hi Mao, It sounds like you have an interesting project. Can you tell us what the current draw of the LED module is? Also how far is the long distance that you refer to? One thing that you can do is to…
  • jw0752
    jw0752 over 6 years ago in reply to maolemieux +2 suggested
    Hi Mao, You can always trust the voltage drop and the current to tell you what is happening. You said that you had a 7% voltage drop at the load end. If you began with 12 volts this would mean a drop of…
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  • maolemieux
    0 maolemieux over 6 years ago

    Hello Gough and John,

    Thank you for taking the time to help me with such a good explanation. I usually make a lot of search before posting and to be honest i’ve looked for a long time on google to find a similar post without success.

     

    Also the example of the home electrical distribution supply is a great example that helped me understand the concept.

     

     

    If you have any time to give me your toughs about my project it would help me a lot and would be so much appreciated. It would maybe help other fellow people.

     

     

     

    I am actually connecting Led module 12v dc 1.5w in series. They are already in serial from factory with a 5 cm wire between each module in 20 awg. I am going to connect 7 modules in parallel with another 7 modules (total 14 x 1.5w= 21 watt = about 2A) to a awg 18 wire. The awg 18 wire will be 10 meters until it get to the power supply that is also equipped with factory wire of awg 18.

     

    Concerning the drop voltage for my use I dont mind to lose up to 10% as my leds are very effecient and I have tested them with lower voltage.

     

    In my case I have checked the voltage drop as suggested by Mr. Gough on https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.599&voltage=12&phase=dc&noofconductor=1&distance=20&distanceunit=meters&amperes=5&x=39&y=30

    (thank you by the way very useful) I have checked it for 5 cm 1A awg 20 to see the voltage drop it will have from the first led module to the wire of awg 18 which gave me a drop of  0.0817%. (I checked with 1A because i have 2 lines of led in parallel)  Now I check the drop voltage for awg 18 on 10 meters with 2A = 7% which is ok for my use.

     

    I was wondering even with this drop do you think the circuit is overall safe please? It will be used many hours or even sometimes few days non-stop.

     

    I also had a question to Mr John about the drop voltage, is the drop voltage a good and reliable safety indicator? I often travel to china for work and buy parts there. Sometimes spec are not reliable. If I test a cisrcuit and see that the drop voltage at the end is only for example 5% does it 100% confirm me that it is out of a risk of cable breaking(burning)?

     

    Thank you again so much for your help, I wish you a great weekend Gough and John.

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  • jw0752
    0 jw0752 over 6 years ago in reply to maolemieux

    Hi Mao,

    You can always trust the voltage drop and the current to tell you what is happening.  You said that you had a 7% voltage drop at the load end. If you began with 12 volts this would mean a drop of 0.84 Volts. You said that the current in the wire was 2 amps. This means that the power loss in the wire would be Current times Voltage Drop or 2A times .84 Volts which equals 1.6 Watts. 1.6 Watts spread out over 10 meters of wire will not be even noticeable. Based on what you have described this would be a safe hookup with no danger. If you want it to be even safer you can put a 3 Amp fuse in the circuit so that if there was ever a short the fuse will blow before the circuit is subjected to high amperage.

    John

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  • jw0752
    0 jw0752 over 6 years ago in reply to maolemieux

    Hi Mao,

    You can always trust the voltage drop and the current to tell you what is happening.  You said that you had a 7% voltage drop at the load end. If you began with 12 volts this would mean a drop of 0.84 Volts. You said that the current in the wire was 2 amps. This means that the power loss in the wire would be Current times Voltage Drop or 2A times .84 Volts which equals 1.6 Watts. 1.6 Watts spread out over 10 meters of wire will not be even noticeable. Based on what you have described this would be a safe hookup with no danger. If you want it to be even safer you can put a 3 Amp fuse in the circuit so that if there was ever a short the fuse will blow before the circuit is subjected to high amperage.

    John

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