How to handle 4 wires using 3-port AlumiConn connectors?

Question

I'm rewiring outlets and switches in our 1960's California home using AlumiConn connectors to connect the aluminum wiring to copper pigtails. Most cases are straightforward, but I've run into a case where a box (a double-sized box, thankfully) includes a joint of the neutrals of 4 aluminum wires (10 gauge each). AlumiConn's only come with a max of 3 ports.

What is the correct way to handle 4-wire connections? Is it correct to daisy chain the AlumiConns?

Lacking any other instructions, my instinct would be to wire them like this, but I don't know if this is acceptable, safe or correct:

  AL  AL      CU      AL     AL
  |    |   ,------.    |     |
  |    |   |      |    |     |
,--._,--._,--.   ,--._,--._,--.
|  AlumiConn |   |  AlumiConn |
`------------'   `------------'

Answer 1

You have two options here

You have two options here. Either you can daisy-chain AlumiConns as you describe, using 12AWG copper THHN for the jumper wire, or you can use a single Al/Cu rated mechanical tap connector (often called "Polaris connector") rated for the wire sizes in question (the smallest size you'll find can take anywhere from 14 to 4 AWG), provided the latter will fit into the box. An ILSCO PBTS-4-4, for instance, takes up about 2" by 1.3" by 1.4" (LxWxH) and requires a torque setting of 20 in-lbs for 14-10AWG wire. Either way, you'll need to torque these connections correctly, as you are already doing with your existing AlumiConns.

Or well, three now

While they weren't a thing at the time this answer was originally written, Ilsco has introduced their MAC-Block connectors, which'd accommodate a 4-port setup like yours (2 wires in each of the 2 ports) more compactly than either of the two approaches above. Their availability in retail channels may still be spotty, though; your best bet is to try an electrical supply house that stocks Ilsco products.