Unknown wiring question

This is the wiring in my existing controller (RainBird ESP-Me, non-wifi capable) that was installed when the house was built in 2014. I’m trying to figure out what the white wires in the lower right side of the photo (with the wire nut) are before I disconnect everything and take down the old controller. Maybe someone else has seen a similar original installation? Any ideas?

@BillQFL - my guess is there is a rain sensor that is wired into the common wire. The red wire on the Com terminal goes to the rain sensor, one of the white wires comes back and the other white wire is the real common wire.

One way to test this theory is with a volt/ohm meter (multi-meter). I’d take apart the white wires and see if there is continuity - zero/little resistance - between one of the white wires and the red wire on the common wire. The other white wire and any of the zone wires then should have around 25-30 Ohms resistance. Make sure the rain sensor isn’t triggered when doing this test as it will throw off the results - try a quick run to make sure the sprinklers run before doing the test.

Another way to test without a volt/ohm meter is to just take the white wires apart and see if the system runs - i.e. break the common wire. Again make sure the system works with a quick 1 minute run before doing this. If this method is used, then there is a 50% chance the right white wire will be hooked up to the common terminal when putting in the Rachio.

If there is a rain sensor, then I’d hook it up to the sensor terminals on the Rachio for better results.

Let me know if this works or if you have any other questions.


Thanks. I’ll see if that works.

It seems that most people set up the Rachio without the rain sensor. You can always add it later, but with the way the Rachio works, many do not use it. The rain sensor just senses water or not, but not much precipitated occurred. Of course, you need to figure out the valve common first as @DLane was suggesting.

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I’m not sure whether there is a rain sensor on the existing system, but I expect I’ll know more after this weekend, when we take a shot at installing the new Rachio controller. I’d taken the picture of the existing wiring to get an idea of what would be involved in setting it up, and those white wires with the wire nut didn’t seem to correlate to anything I could figure out. A rain sensor makes as much sense as anything, assuming I have one.

Agreed. Someone went through extra work to make all those curls in the wire. :wink:

Yes, the time spent curling those wires might have been better used to label them. :sunglasses:

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The curls create a little inductance which is good for suppressing electrical surges.

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Fortunately a neighbor with the same system saw my question posted on a local message board and responded. DLane’s suggestion that the wiring is related to a rain sensor (which apparently has never actually been connected to the irrigation system) is correct.

True that. I disabled my rain sensor when I replaced my old 2006 RainBird