Multiple Rachio Controllers with Shared Command and Master Valve

I have about 26 zones so I need 2 controllers. I will have a shared common between the controllers because I don’t want to spend hours/days re-wiring boxes to isolate the commons. Finally, I have a master valve to add a little more in the mix :slight_smile:

I saw the Rachio article on using the Isolator devices, but that would cost me over $100. For $10 I think I can do the same: KUP-14A15-24 relay and base.

Please see the wiring diagram and let me know if you think I’m crazy.



IANAE (I am not an electrician) but I slept at Holiday Inn Express last night! (joking)

To my untrained eye, the logic flows correctly and this will limit so that only one valve can be open at a time. I give it a thumbs up.

1 Like

@janderson - what about the situation where both controllers are running at the same time? I think that the common would be returning through Controller A for valves from Controller B.

I’d also make sure the power supplies for both controllers are coming from the same electrical phase so the sine waves won’t be out of sync (e.g. same outlet with a multiple tap) with each other.


I can be of no assistance other than saying I personally love the above diagram including screenshots of our generation 1 controller :wink:


1 Like

What you have against the Gen1’s @franz?!?!? :rofl::joy: #OGGen1


@janderson, I see no problem with your plan (as long as your properly schedule your controllers to never be active at the same time), good job. My only feedback is that you could accomplish a similar setup using a single SPDT relay, more on this can be found in an old post (link). Only difference is that you would use R1 terminal on your Gen 1 controller, instead of SC terminal shown on the original wire diagram.

The fact that above post discusses a hunter controller does not matter (it is simply a second controller), pump relay is essentially the same as the master valve for the purposes of this discussion and using SPDT setup has an additional advantage of not having one of your rachio’s potentially driving three loads (two valves & one relay) at the same time.

P.S. @DLane is right, ideally the commons for the valves driven by a particular rachio would be separate from the other valves and connected directly to the corresponding controller. If this is not possible, sharing only one line between controllers (such as your commons) can work without creating a potentially hazardous circuit.


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 :confused:) 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

As long as only one line is shared between the controllers, such as your commons, the phases should not matter as the transformers within the power-supplies would provide a voltage isolation. This should hold true for any AC supply that only uses two power terminals (without a third GND terminal).

Phases come into play if/when a second line is shared, such as connecting both Master valve lines using a wire nut, instead of a relay. In case the controllers are on different phases, the voltage on the pins may go as high as 48 volts, in other words 200% of a nominal rating, killing the supply and/or controller(s).

1 Like

Thanks Gene for all the great info! I think your comment around voltage isolation is helping me better understand what is happening and why the common from controller A can’t be used with the hot from Controller B like I’m used to with 120v house wiring (assuming out of phase hots so the neutral/common isn’t carrying more current than it is rated for).

The master valve comment makes complete sense.