Connecting Hydro-Rain HRC-100 Wireless Rain Sensor to Gen3

@emil Any thoughts about wiring the Hydro Rain HRC-100 for the Gen 3? Mine’s throwing rain alerts every few seconds…

Thanks :slight_smile:


I had a similar issue with my wired sensor. I didn’t notice the 24 VAC + and - terminals that are now used in place of the common for sensors.

Can you post some wiring photos? Thanks.


Hi @franz! Here it is. Don’t laugh, I’m not an electrician… :rofl:

Looks like you just need to move the thin white cable connected to the ‘C’ terminal next to zone 8 to the 24 - terminal next to S2.

While making adjustments, I would also move the second common thick white wire from the leftmost C terminal to newly available C terminal next to zone 8. This way you have less chance of connector fatigue in a long term. Idea is to have just one thick white cable connected to each individual C terminal.



Why do I even try…



Got to be quick to keep up with @DLane and I :wink:


I need to stay in my lanes.


Wow! Worked like a charm!!! Thanks @Gene, @franz. Appreciate the help :-):heart_eyes:


@Gene and his wiring skills.


@franz is still the master of a unique answer :+1:

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@Bobo1015, would you happen to have a picture of your working sensor’s wiring? I have the exact same setup and cannot make it work based on @Gene’s recommendations.

Out of town for a few days, sorry…

Can you post a picture of your setup? It is not just any white wire that belongs in the 24- terminal, but the one that is part of white, yellow and 2 red cable bundle.

@Gene, please see below. It’s a simple 4-zone setup. The sensor is not connected in the picture.

And this is how it was wired to the original Controller:

@ProjektR - at the risk of trampling @Gene 's great work here is what I’d try:

  1. Green - not connected
  2. Yellow - S1
  3. Red #1 24 VAC +
  4. Red #2 24 VAC - twisted together with the next wire
  5. White 24 VAC - again twisted together with the above Red wire.

I’m wondering if the White wire had a good connection as that is what I’m trying to accomplish by twisting them together.

Are any of the lights illuminated on the Hydro-Rain in this setup?

If the above didn’t work, then one could try putting the White wire in the C terminal by itself.

Thanks for the pictures! Helps tremendously.


@Dlane is right on the money, I do not think that it will come down to connecting the white cable to commons (it belongs to 24 vac- as correctly indicated by step #5).

P.S. Here is an official diagram on how to hook up this kind of sensor:

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Thank you @DLane. I will give this a try tonight. I had the sensor originally wired as such:
White -> C
Yellow - S1
Red 1 -> 24V1
Red 2 -> 24V+

It picked up the sensor, but I kept getting constant notifications about the sensor being Active/Inactive all within the same minute (the log is not granular enough for me to see if there was any delay). Safe to assume something was wrong :). I will report back.

@ProjektR - I think if the White wire is moved to 24 V- like @Gene commented on or in the directions it will be good to go. If not, @Gene and I will wrestle it to the ground - so far we are undefeated! (But who’s keeping score besided @Gene and me :slight_smile: !)


I am :wink:



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I continue to be amazed by the amazing troubleshooting and teamwork in this community! Thank you @DLane & @Gene for all of your help!