Rachio 12 Zone and Rainbird ESP 12-LX (More wires than Zones)


I’m looking to convert to gen 2 controller. I currently have a Rainbird ESP 12-LX Plus that runs 12 zones. It’s roughly 10 years old and is well past its prime.

As I looked behind the cover, I have 16 wires. I was wondering if anyone has an idea how to wire that appropriately to a 16 zone controller. I’m uncertain why I have more wires than zones. Appreciate any help!!

@deannd - I don’t believe the wires connected to zones 13, 14, 15 and 16 are doing anything as there are no electrical components for those ports installed on the PC board.

I’d go monkey see, monkey do. In other words take the wire in terminal 1 on the Rainbird and move it to port 1 on the Rachio. The two white wires on the Common in the Rainbird go to C on the Rachio. I’m assuming there is a rain sensor in the Sensor port, so if that is being moved to the Rachio then the red and yellow wires will go to S1 (be sure to turn on the rain sensor option in the application) and SP. Finally, ignore the black and red wires in the 24 VAC terminals as Rachio has their own transformer - but do trace them back and unplug that vampire from the wall socket.

Welcome to the Rachio community and let us know if there are any more questions. I think the original installer was just making a neat install by hooking up the unused field wires to terminals.


Thanks DLane…really appreciate the help. Will give it a shot and will report back!

Dlane gave you the correct answer

I want to also ask about a similar rainbird. I have ESP-24lx plus. I only have 9 zones. I just bought the house and I’m not sure if we have a rain sensor. Here is what the current wiring looks like. I will do what you said about about the transformer and c wires. Any other advice based on this picture?

Hi Andrea, welcome to the community :slight_smile:

You have a relatively straight forward switch over ahead of you, so no worries :thumbsup:

As you’ve already mentioned, the thick orange wires going into the 24VAC terminals, as well as the thick green wire going into GND terminal, should be disconnected, you will no longer require any of them.
Don’t worry about the yellow jumper wire connected to SENSOR, that is just how your rainbird used to operate, it does not look like you have a rain sensor.
You have two white common wires, I’d recommend to connect them to separate C terminals of your new Rachio.
You also have two Master Valve wires (now sure why two, but it is what it is). Connect both of them to the M terminal of your rachio (I would twist them together if possible and connect them as one). Do not forget to enable master valve within the Rachio’s setup.
Finally just go down the line and move the zone wires from rainbird’s terminals 1 through 9 to Rachio’s terminals 1 through 9. Order should not be critical here, you will probably end up renaming the zones during the Rachio’s setup.

That is about it,


Thanks for the instruction! I was able to get it all wired up! Of course now it is going to rain for the next week, but it is nice to have my sprinkler system know it can skip watering.

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I am upgrading to a gen 2 from a Rainbird ESP 20-LX. I have questions about my wires. Thanks in advance for your help!!!

  1. The heavy gauge orange and green wires (top left), labelled VAC and GND, do they attach to Gen 2?
  2. Black and grey wires (top middle, labelled sensor), will plug into S1 and S2?
  3. Green wires (bottom left, labelled COM and TB6), do those go into a C terminal in gen 2? Does it matter which wire goes into which C terminal?
  4. The remainder will go into corresponding numbered terminal in Gen 2.

Thanks again!!!



@mkappus - Welcome to the community. I edited inside the quote as there are multiple green wires to avoid any confusion.

Enjoy and feel free to ask any additional questions.


Thanks for taking the time to walk me through this! I am excited to get this wired up!

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I had the exact Rainbird unit and purchased the Rachio Generation 2. I actually only have 10 zones and simply labeled the wires as I removed them from the Rainbird unit and inserted the zone wire in the appropriate slot on the new Rachio unit. Could not have been easier. I also printed a mailing label and sent my old Rainbird unit to Rachio so they could recycle it. Monitoring the Rachio unit from my iPhone could not be easier.

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Greetings. New to the community. Decided to share my input here. I saw useful information on this post, but to put a definitive answer to the number of wires is this: zone wiring comes in a range of wire sizes, the smallest being 2 (a common and a single zone wire). Whoever installed this system used a 16 strand zone wire. Some installers do not like to leave loose wires, so they will connect all loose ends even if they are not functional.

Hope this helps anyone that sees this in their controllers in the future.


Hello, I too have an existing ESP 20-LX and want to replace it with a 16 zone Rachio 3. Your answers above did clarify that it seems I don’t need, and should just cap the orange VAC wires, (shown circled, it seems I have 2). But I also have 2 yellow wires whose use I don’t know. Then I don’t seem to have a gnd, as my green wire© is one of 2 going to the sensor terminal along with the gray(B), (it has a Hunter rain sensor). Then there’s a green wire(A) with an unknown purpose that disappears behind the transformer. Other than those, it seems all of the other wires just map to zones along the bottom terminals 1-14, then another bank of 15-18, (I only use 16 of the 18). Unless I’m missing something else, I think I just need to know if and where the highlighted wires on the Rainbird go on the Rachio 3. Any advice would be appreciated. Thanks,

@hclmed - Here is my best guess:

When you remove the Rainbird the two orange and green wire behind the transformer will go with the old unit when it is removed.

The white wires (D), the green/blue wire © and the gray wire (E) appear to be in one bundle for the rain sensor. The rain sensor is optional for Rachio. The white wires would go in the Rachio 24 VAC + and - terminals and the other wires into the s1 and sensor common - should work.


Thanks for your help. As you correctly observed, there is a 2nd cable that is separate from all of the zone wires, and one of them is clearly to the water sensor, so it makes sense that all of them are to or from that sensor.

Since this is a risky time to disable my sprinklers, I’m thinking of starting by just connecting 16, (the Rachio max), of my 18 zone wires, along with the common, (of which I seem to have only 1), to the Rachio with external power. If that works, I’ll pull the Rainbird off the wall, and also explore reconnecting the Hunter sensor, if it has any possible advantage on top of the weather prediction service. Does that address all that would be needed to send the water?


@hclmed - the minimum to water is the common and one zone wire.

I’d run the existing Rainbird through every zone for a minute to make sure all zones work and that one knows where each zone number waters.

Next I would configure the Rachio without any wires connected. Get it connected to the WiFi and zones set up.

Then I’d start moving the zone wires over to the Rachio. After the zone wires (and common) are moved to the Rachio, then I’d do a quick one minute run on each zone to make sure they work and are in the right spot.

Welcome to the community and have fun!

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I appreciate your response. You’re very kind to help. The Rainbird has been in use for a few weeks this year, and a couple previous years for us, with all the zones confirmed, so the wires should be ok. We’ll label them all, and follow your advice to configure the Rachio without connections first, then start moving the zones.

I set up a simpler 12 zone Rachio up for my dad, and it’s been working great for him. I had to work out a plan to drop 2 zones and fully decipher, with your help, my 18 zone Rainbird, to work towards installing the 16 zone, (16ZULW-C), Rachio. Looking forward to its much more granular control.

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