Using a Freeze Sensor with Iro2 Running Flex Daily


Yesterday I connected a ‘freeze sensor’ to my Iro2 that uses a Flex Daily schedule. I don’t have any limitations placed on the Flex Daily schedule - it’s set to start each day (that it determines watering is needed) at 10:15 AM. It covers all zones - there’s only one schedule.

My objective is to see if I can implement a freeze ‘turn off’ at 50 degrees without losing Crop Evapotranspiration accumulations. To do this I’ve guessed that the best way is to manage opening and closing Iro2’s sensor port. And to do this I’ll using my automation system to monitor outside temperature and open/close a relay connected to the Iro2’s sensor port. .

My second objective is to see what kind of watering pattern I get here for a Dallas climate. Trees and shrubs and grass don’t need much water. I’m curious if I’m going to get blasted with a lot of water during the days when temps are above 50 degrees (since Current Moisture Balances may be below Allowed Depletion).

Right now no zones are scheduled to water for a few days because it’s raining outside today.

I put ‘freeze sensor’ in quotes because my actual implementation at first is simply a piece of wire to simulate the freeze sensor. I’m assuming most freeze sensors that many cities require per ordinance are simply Normally Closed switches that open up at 32 degrees.

I connected my ‘freeze sensor’ to the S1 and SC terminals. I expected to see Iro2 activity afterwards, but nothing happened. Then I realized I needed to configure the Iro2 to tell it a ‘freeze sensor’ is connected.

My Iro2 shows to be ‘on line.’

Using the latest version of Chrome on a PC, I connected to and updated device settings such that ‘Rain Sensor’ is ‘on.’ I also went to user preferences and made sure everything was checked ‘on’ for emails and text messages.

Still nothing happened. Then I realized that freeze sensors are Normally Closed, and thus to simulate a ‘freeze situation’ I’ve got to open up the connection between S1 and SC.

I opened up the connection but nothing happened. Since I don’t know how Flex Daily is implemented, I decided to wait a day to see how scheduling proceeds today near my 10:15 daily schedule start.

Unfortunately (for the experiment) today I see at 8:15 AM in the Device Updates section: “Device status power cycle.” Indeed, upon checking, I did lose power for a minute (as reported by automation system and by NAS unit connected to a UPS).

Thus, the most recent entry: “Rain sensor activated” (also at 8:15 AM) is something that makes me wonder if I needed to have recycled power to the Iro2 after connecting the ‘freeze sensor’ last night. Or perhaps it wasn’t needed and today’s “Rain sensor activated” is simply a message will occur everytime there’s a power failure. I’ll figure this out eventually.

No other information at the moment. Nothing appeared in Schedule Updates this morning. This makes sense as it’s raining currently. No email or text messages either…

I’ll continue to update this posting as I learn more about how to install a freeze sensor set at 50 degrees when using a Flex Daily schedule.

Best regards,



I refined the above after learning I indeed had a real power failure. Bill


Thursday update:

Nothing has happened. The Iro2 remains configured to have a rain sensor on the S1/SC terminals. The wire connection between S1 and SC remains open circuit (I think simulating it’s freezing outside). No emails. No text messages. There’s no indication or confirmation that I’m correctly simulating that it’s freezing outside.

Flex Daily scheduling doesn’t have any zone planned for watering until Saturday.


@a0128958 Good work!

What did you do before the Iro2?!?! :grinning:


(Updated a little, on Mon., Nov. 13th).

Summary of observations when running one Flex Daily schedule:

  1. When you connect a freeze sensor to Iro terminals S1 and SC and then configure sensor 1 as a Rain sensor (no choice of choosing freeze), nothing’s going to happen. No real time messages, no text messages, etc. No implementation of actual freeze sensing either. The key point here is you must cycle power to the Iro2 afterwards. (Maybe Rachio designers assumed every owner would turn off power to the Iro2 before connecting something to S1 and SC. I didn’t - it’s only 24 VAC.) It’s only the first power cycle that produces any diagnostic info.

  2. Rachio cloud processing stops using remote weather station data (for freeze protection) when Sensor 1 is configured to be a Rain sensor.

  3. Current Moisture Balance is being appropriately maintained.

  4. The Iro2 checks at the time of start for every day’s FD schedule for a presence of a sensor and what mode it’s in. My open circuit simulation was picked up at the start of each day’s FD schedule.


  1. Absolute freeze protection does work if you’re willing to connect a freeze protection device to terminals S1 and SC. Some devices are set at 37 degrees, some at 39 degrees. (I’ll do this with my automation system, while monitoring outside temp). You must connect a freeze protection device (wired or wireless) to eliminate otherwise possible situations where you won’t have freeze protection but think you do.

  2. There is no other means of absolute freeze protection .

  3. Nothing works with respect to Iro2 options for emails, text messages. Status information via is kept up to date on existing / non-existence of freeze sensor after the power cycle (above) is done.

  4. Connection of a freeze sensor doesn’t get activated without going through a power cycle.

Let me repeat: All of this is for Flex Daily schedules only, and where only one exists.

Best regards,