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I'm running a feeder to a 100A sub-panel. The total run is about 90 feet. 60 feet is in an attic, and I'm planning to use Aluminum SER 1-1-1-3, the other 30 feet is through a 1.5" PVC conduit on the outside of the house. I was planning to use THHN-2 or XHHW-2 Aluminum 1AWG conductors and a 6AWG Aluminum for ground. I'm planning to transition from SER in a large (10x10x4) box using Polaris lugs. Any issues with using a 6 AWG Aluminum ground?

Why does the Aluminum 1-1-1-3 SER have a 3AWG ground if 6AWG is sufficient?

I'm also running a Aluminum 2AWG bonding conductor through the same conduit, all the way from my main panel to where my main water pipe enters the house (within 3 feet of where it enters the house). My sub-panel is 10 ft away from where the water pipe will be bonded. Can I just run the 2AWG bonding conductor continuously from the main panel to the water pipe to the sub-panel and eliminate the Aluminum 6AWG ground conductor?

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    Any reason not to use THHN-2 or XHHW-2 all the way and save the cost of the polaris connectors and needing a splice?
    – crip659
    Commented Nov 25, 2023 at 17:35
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    That, or if you can't run conduit for the whole length, use a dual-rated (SER/TC-ER) cable instead of straight SER (Encore Wire makes the stuff)
    – ThreePhaseEel
    Commented Nov 25, 2023 at 18:41
  • @ThreePhaseEel Using tray cable is an interesting approach. Encore seems to only make a copper conductor version, not aluminum. Switching to copper would increase the cost a lot. The Polaris lugs+box add about $130 to the cost. Running PVC conduit in the attic would cost about $135 and a lot more work. I heard that some SER cables have markings on the individual wires, but it sounds like that is not guaranteed.
    – Christian K
    Commented Nov 26, 2023 at 1:24
  • @ChristianK -- look further -- Encore does make their TC-ER/SER combo in both copper and aluminum
    – ThreePhaseEel
    Commented Nov 26, 2023 at 4:21

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Note ThreePhaseEel's comment about SER/ TC-ER dual rated cable,good to run without conduit inside a house, and also inside a conduit outdoors.

Any issues with using a 6 AWG Aluminum ground?

That's fine.

Why does the Aluminum 1-1-1-3 SER have a 3AWG ground if 6AWG is sufficient?

Suppose you are running a circuit to a 50A RV stand. Normally you use #6 conductors and #8 ground. All aluminum. However, the run is 500’ so to avoid voltage drop, you bump the conductors -5 sizes to #1. You must also bump the ground -5 sizes to #3.

Can I just run the 2AWG bonding conductor continuously from the main panel to the water pipe to the sub-panel and eliminate the Aluminum 6AWG ground conductor?

Problem is, if you remove the subpanel, you sever the bond.

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  • Thanks for explanation about increased ground in case conductors are upsized. Since my sub-panel is downstream from the water-pipe bond, removing the sub-panel would not sever the bond between the main panel and water-pipe. Is it OK in that case?
    – Christian K
    Commented Nov 26, 2023 at 1:18
  • @ChristianK I'm not quite understanding your setup, but if it's like that then it's fine.
    – Harper - Reinstate Monica
    Commented Nov 26, 2023 at 20:31

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