Rachio 3 Master/pump start relay with Bypass 3-way switch


In several conversations, including one that I initiated, the use of a 3-way switch is recommended to override the Rachio system and turn on a pump.

In my system, I have a well and a pump start relay. I have a 3-way switch mounted at my spigot so that I can locally turn on the well without having to pull out my phone every time. Previously, my Rachio 2 fed the 3-way with the M terminal and the SC terminal as an override. The common on the 3-way switch is wired to the 24V input on the pump start relay.

My question is:
On the Rachio 3, what is the best override signal? I could use S2, or 24V+. Will any of these work even though the pump start relay is fed with a common and not the 24V-?

I will eventually install the new Rachio flow meter (still waiting for the shipment), presumably to S1 and 24V-.



Instead of SC terminal, you would need to use 24 V -

The common line on the Rachio (Gen 1,2 and 3) is actually HOT (connected to 24 V +) and the zones (when active) are pulled to the 24 V- voltage rail.

It is confusing I know, but they do it in order to be able to sense active lines near the 24V - rail (same as they do for S1 and S2 inputs).

Safety wise it doesn’t make a difference since the voltages are AC and look identical to the any equipment connected.


Very helpful response; thanks!

I never did understand why I was using SC before. Everything is making a lot more sense now.