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I need to join 4 wires together: a 6 gauge wire, two 10 gauge wires and a 22 gauge wire. The 6 gauge wire is the current source, the two 10 gauge wires will draw a continuous current of up to 30A and the 22 gauge wire about 20 mA. I need to do that twice - one for each leg of a 208/240v circuit. This is for an electric vehicle charging application.

I have been using a large size wire nut for this, but twice now it has failed due to overheating.

Left to my own devices, my next attempt would be with a split bolt, but then I'm going to need to wrap it all in a mile of electrical tape.

This is all going to be inside of a sealed chassis. The chassis will be portable, but all of the wires will have strain relief at the chassis entrance.

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Look for a "power distribution terminal block" or a "terminal bus bar." These are designed to land wires of various sizes and secure with a terminal screw, like the grounding terminals in your circuit breaker panel. Obviously you will need to ensure that the block or strip is insulated from other circuits as appropriate.

You may want to add crimp terminals/space lugs on the ends of your wires.

Terminal Bus Bar Example Spade Lug Example

Terminal bus bar, left; spade lug, right.

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  • \$\begingroup\$ I have been using QD crimp lugs on the other end of the #10 wires with some success. But are crimp terminals appropriate for the #6 wire that's expected to handle 60A? \$\endgroup\$ Commented Jan 21, 2014 at 18:40
  • \$\begingroup\$ Sure, there are terminals appropriate for heavy gauge wire. (For example.) Just be sure to check the rating of any that you use. You will probably need a special tool to crimp larger terminals. \$\endgroup\$ Commented Jan 21, 2014 at 19:12
  • \$\begingroup\$ There are crimp terminals which are fine for 60A, but you may wish to use high quality brazed barrel lugs and properly swage them with the recommended tool, as @JYelton suggests. \$\endgroup\$ Commented Jan 21, 2014 at 19:37
  • \$\begingroup\$ It looks like Cooper Bussmann has just the thing. Their 11725-2 has a screw terminal for a 2-14 AWG Cu line side, and 4xQD for load side. \$\endgroup\$ Commented Jan 21, 2014 at 19:59
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    \$\begingroup\$ Something to add to this is: if the connection is under cyclic electrical load, the parts will tend to loosen due to thermal expansion/contraction as the parts heat and cool. A good spring washer is recommended. See penwatch.net/cms/?p=386 for a cool picture of a big bolted connection, with a link to a document which talks about spring washers. \$\endgroup\$ Commented Jul 26, 2015 at 20:03
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Bus bars are good. If you want an even more positive connection, there are exothermic welding products that will melt the wires together. The result is similar to soldering in that the connection is electrically very good, but unlike solder, does not melt so easily. Unlike mechanical connections, the contacts don't corrode or come loose.

Examples of such products: Cadweld and Thermoweld. They frequently find application in lighting protection, especially where periodic inspection of a mechanical connection would not be feasible.

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  • \$\begingroup\$ Those sound excellent for commercial/industrial scale solutions, but I'm just a hobbyist. I don't think it's worth it for the volume I intend. \$\endgroup\$ Commented Jan 21, 2014 at 18:44
  • \$\begingroup\$ @nsayer Some of these things use single-use ceramic molds which are way cheaper than the graphite molds. Cadweld calls it "one shot". Should set you back about $10 to make a connection. \$\endgroup\$ Commented Jan 21, 2014 at 18:56
  • \$\begingroup\$ You can [make your own thermite](homescience.wordpress.com/how-to-make-thermite ) if you want. I already got flagged for Googling that, so go ahead and use the link. \$\endgroup\$ Commented Jan 21, 2014 at 20:45

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