What's the acceptable method of splicing 3awg aluminum wire inside a junction box?

I've got a 408V 3pole disconnect that's overheated from oxidized contacts. Wire insulation is burned off inside the switch and the plastic plate looks like a dali painting.

I would like to add a junction box at an existing conduit connector a few feet above this box and only pull new cable back to this box instead of pulling new cable all the way back to the mechanical room about a hundred feet away.

A split bolt connector and friction tape was suggested, This seems like sort of a home brewed remedy, are there any connectors made for this?

Thanks

We've used butt splices and heat shrink before on AL I believe the size was 4/0 it worked out alright.

M-guy,

You've got a few choices.

Split bolts and tape are perfectly good. I've torn apart split bolt splices that are 60 years old and are in great shape. They're not fancy, but they work.

Another option is a mechanical splice block where you insert the conductor in a hole and run a bolt down onto the wire to make the connection. Just make sure you use a torque wrench and follow the mfgrs specs. Those things have to be screwed down TIGHT.

Lastly, compression connectors. Cool. Catch is, you need a crimp tool that runs about a thou.

If the wire is aluminum, you MUST use no-ox compound. If it's copper, it wouldn't hurt.

Good luck.

Cliff

There are a variety of connectors available that offer lay-in lug design and set screw tightening. Most have snap on plastic covers. Check out Ideal Products "SL" & "GP" series connectors and "GIC" snap on covers.

Check with your local Hilti rep. They have a lot of stuff that can be helpful. Also, check out Square D, page 22-16 in my 2000 catalog for standard power distribution blocks. You can get plastic covers for them.
Why is your disconnect overheating? Is it ambient temperature too high? or is the load too heavy? If it were me, I would do some checking to know why too much heat!
Just an engineer-want-a-be's thoughts.

Thanks for all the suggestions, we ended up just cutting the conduit feeding the switch shorter and mounting an new switch alittle higher on the wall. Worked fine.

The overheating was because of oxidized terminals at the switch. Why the oxidized, I don't know but there are two 480V, 100A switches side by side, one for each of two boilers. And the other had the same problem last year and was replaced then. Wires were barely warm anywhere else, conduit nice and cool, and these things have been in service as is for 15 years.

Thanks again for the suggestions.