Thanks everyone for the input.
Gene, you mention that the controllers shouldn’t run at the same time. I had planned that they wouldn’t and I figured that even if they did only valves connected to Controller A would work since Controller A’s common was the one being passed through the relay.
Then I started thinking about DLanes comments around phase. Now… if I had (2) 120v hots 180 degrees out of phase I can share a neutral/common without exceeding the capacity of the wire. With my limited knowledge this seems plausible with the 24AVC controllers too? So… instead of making sure the controllers were plugged in to the same phase, I would actually want to make sure they weren’t so as the common/neutral would be shared 180 degrees out of phase of one another. Maybe not, and if not can someone please explain why. If this does sound plausible, then I should be able to run both controllers at the same time.
I work for a utility company (computer department ) so I’ll try to find an electrical engineer tomorrow to get their thoughts (unless someone here has the answer first).
Oh… I’m only using the referenced relay because I had it on hand from a different failed experiment - lol