I need to join a new 100A feed on #2 aluminum wire to an existing #2 wire running from the panel. So this is actually #2 alum triplex in both cases plus a #8 bare copper ground. The junction will take place in an access panel in the wall where the two PVC conduits meet. What size junction box do I need for this? Is a juntion like this done with wire nuts the way a Romex juntion is? Does it matter what material the J-box is made of?

Use either an 8"x8"x6" or a 12"x12"x6" PVC box. Metal is OK, just have to connect a ground wire to it.

Wirenuts are mot large enough for #2 wire. Need to use anything rated for #2 aluminum wire,such as split bolts with rubber and plastic tape. There are pre-insulated mechanical connectors available also. Be sure to use anti-oxidant compound on the wire connections.

Use either an 8"x8"x6" or a 12"x12"x6" PVC box. Metal is OK, just have to connect a ground wire to it.

Wirenuts are mot large enough for #2 wire. Need to use anything rated for #2 aluminum wire,such as split bolts with rubber and plastic tape. There are pre-insulated mechanical connectors available also. Be sure to use anti-oxidant compound on the wire connections.

I don't think I have enough room for a 12x12 box so I would go with the 8x8 if that's acceptable. I found one that is 8x8x4. Do I really need the 6" depth?

I was looking at PVC juction boxes last night in Lowe's and I notice that there are not pop-outs for access like there are for smaller metal J-boxes. Are you expected to drill an 1"1/4 hole into the side of these things? Does anyone have a recommendation on how to do this (hole saw bit for a drill?)?

Also for #2 wire (Triplex) can I use 1" conduit or do I need 1"1/4?

Thanks TK and others!

The 4" is fine, just keep the wires as long as possible without crowding them,leaving room for the actual splices.

You need a hole saw to cut knockouts out in a PVC box, if the conduit is 1-1/4" then need an actual 1-3/8" hole saw, or an electricians 1-1/4" .

Use the 1-1/4" for the triplex and equipment ground.