I have a “drip pan” underneath my air handler that has a shutoff “float” switch in it. If the drip pan starts to fill with water, the float switch kills power to the air handler so that it stops running and doesn’t cause a flood. The switch just has two wires coming in/out…
I’m looking for a simple device to add into the mix that I can use in HA to monitor things. (Realistically, I’ll want to get a notification if the float valve “floats” and kills power - that way I’ll know that water is collecting in the pan and I need to investigate.)
My HA skills are moderate, but my DIY skills are lacking and I’m hoping not to have to learn about ESP/Arduino boards, etc. Ideally there is a “smart” device of some sort that I can wire into that configuration and will integrate with HA. (I do have HubZ integrated with HA if that leads to a potential solution).
Thanks, both. I have considered a water sensor, but it seemed to make more sense to try and tie a sensor into the existing mechanism that I know works correctly. The float valve allows for some water to collect in the pan before it rises high enough to shut things off. If I add a water sensor it will probably be impossible to get it to the exact right level where the float valve kicks in, and so my goal - if easily achieved - is to monitor the float valve (or more accurately the current passing through it and when it shuts off that current) rather than the mere presence of water in the drip pan.
I think I figured it out (well, almost - just waiting on a part for the last piece of the puzzle). I’ll write it out here in case this ever helps anyone. The first part should solve basically any situation where you want to monitor a “dumb” switch with a smart device. This works in my application because the float valve is, in essence, just a switch. It’s got power coming in and power going out, and it’s either open or closed based on the float valve.
So I got a Shelly 1 and wired it to the switch like this:
and I configured the Shelly to be an ‘edge’ switch. In this configuration, if the dumb switch is turned on or off, the Shelly will update itself to be either on or off to match. So if the drip pan collects water and the float floats and thus the switch opens, the Shelly will toggle to be ‘off’ and I can use that as a trigger in Power Home to let me know it’s off.
The good thing about this is that the float switch will work as designed even if there’s a problem with the Shelly - if the Shelly craps out on me the float valve will still turn things off if the float valve floats. (In this setup I also had to remember to set the Shelly to default to ‘on’ - while I won’t ever use the Shelly to turn my air handler on/off, I need it to default to ‘on’ in case I ever lose power or turn off the circuit breaker so that everything is on when power comes back.)
The part that remains - after heading up to actually put this in place I realized, stupidly, that the float valve is not actually controlling mains power, it’s controlling the 12v low voltage wiring to my thermostat - it’s in the ‘Power’ line to the thermostat. So if it floats what it’s actually doing is turning off my thermostat (thus effectively turning off my HVAC) - it’s not turning off the air handler itself.
After realizing this I was delighted to find out that the Shelly can run on 12v DC. I’ve now ordered a relatively inexpensive AC->DC converter (https://www.amazon.com/dp/B08JCRGVRY?psc=1&ref=ppx_yo2ov_dt_b_product_details). But my expectation is that I’ll be able to wire that into my thermostat wiring using the float valve line (power) and the Common from my thermostat, and then everything should just work.
If I don’t write back to say it failed, you can assume it all worked! (Or assume that my house flooded and my HA system, and all smart configurations, are kaput and I’m now living in a tent.)
The Shelly UNI I suggested would be a cleaner solution. Power it from the 12v in the A/C and then use one of its inputs to monitor the switch. You are not replacing the switch but instead monitoring when it activates from the internal voltage. So arguably more reliable to keep you out of that tent!
Oh, wow, I somehow missed that idea in your original post. Thanks for highlighting it - now that I’ve dipped my toes into the Shelly world I’ll grab one of those and check it out. Thanks!
jtf
So I got a Shelly Uni and I have it wired and “working” properly, but something is curious and my limited skills in this area are proving insufficient to figure it out. First, it turns out I was wrong about this being DC. The thermostat us running on 27v AC (as most people here probably already knew). That is sufficient to power the Uni, and so that part works great. But when I wire the white ADC input wire on the Shelly into the line the voltage fluctuates … very consistently it rises to 27v then it slowly drops down to 0, then slowly rises back up again.
Yes, I didn’t do what you suggested, to use one of the inputs to monitor the switch. I thought simply monitoring the voltage would make sense. Any idea why the ADC sensor rises and falls?
The ADC requires DC voltage. You may be able to use a rectifier (or 4 diodes) to convert to DC. There will be a fair bit of ripple in the DC signal so you’ll need a smoothing capacitor. That might give a fair bit of lag between on and off but I am not an electronics guru. Hopefully you can set the ADC voltage level to compensate.
Thanks once again. With that understanding, and a bit more playing with the Uni to understand what it does and how it works, I switched over to monitoring the switch via one of the Shelly inputs. Works like a charm! Thanks for all the support,
jtf
