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 |
`------------'   `------------'
  • Are there devices in this box, or is it merely serving as a splice point? Also, how deep is the box? Dec 11, 2018 at 4:52
  • It's the box for a switch operating a switched outlet in the room. The box is extra wide behind the opening, so there is space for all the wiring. One of the wires must be incoming power, one must be going to the outlet, and the remaining two presumably go to another room.
    – mhucka
    Dec 11, 2018 at 4:57
  • 1
    You are using a torque screwdriver on your AlumiConns so far, right? Dec 11, 2018 at 5:20
  • 1
    Yes, absolutely, using a torque screw driver.
    – mhucka
    Dec 11, 2018 at 5:22
  • 1
    @Harper I see no reason to use aluminum to connect the two connectors. All over the house there will be copper pigtails in AlumiConns so what is two more? A copper wire is more resistant to stress. Jul 12, 2021 at 19:07

1 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.

  • 1
    2" x 1.4"? Holy cow. Now I understand that depth really is a concern :-).
    – mhucka
    Dec 11, 2018 at 5:38
  • How about MAC Block connectors here? Jul 12, 2021 at 20:51
  • @Harper-ReinstateMonica -- updated Jul 14, 2021 at 15:06
  • Yep, and I had an aluminum MWBC homerun with 2 12-2 aluminum and 2 14-2 copper wires packed into a single-gang switch box. Try roughing in and packing five(5) of those 3-port Alumiconn inside. Used the tandem extension to tie 5-wire neutrals together. Lots of fun! Not sure if an Ilsco 5-port block is smaller than two Alumiconn 3-port. Feb 28, 2023 at 1:49
  • 1
    @JohnGreene -- the ILSCO blocks are 2-port but can handle more than one wire in each port in some cases Feb 28, 2023 at 3:01

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