Hello, I am looking for with picking solution for my bi-passing of dumb thermostat. I my rented flat there is “dumb” thermostat with basic schelduling that with low temperature just connects two wires (dry contact if I am not mistaken in terminology) from gas heater which then starts to heat and pump water through radiators.
I was looking for solution but couldn´t quite figure it out. I was looking to get just temp sensor for each room (probably aqara) and something to actually operate the boiler. Any suggestion on device that can do that preferably battery powered?
I was looking on Sonoff, I know it isn´t battery powered, but I could live with that, but I dont like the fact that I would most likely have to modify it (to be drycontact ) and even flash new firmware. Any suggestions for simplier solutions are very welcome.
I have my instalation of openHab for a week so please excuse my mistakes.
Welcome.
Where are you located? Heating systems and some solutions vary depending where you are located.
What bindings are you currently using with openHAB?
Hello sorry I should have specified. I am located in Czech. Currently I am using deconz, hue and yeelight so just bog standard currently learning some basic rules fidling with openhab app for AlarmClock etc. The fact that it is supposed to be a dry contacts comes from fact my currecnt thermostat states so in it´s instalation manual (haven´t measured it) the thermostat is PT22 EN manual
You’ll need a dry contact relay such as https://en.cozify.fi/products/dry-contact-relay for your boiler.
Then you need in every room a radiator valve like this https://eurotronic.org/produkte/zigbee-heizkoerperthermostat/spirit-zigbee/ and a thermometer for measuring the room temperature.
That combined with a rule, such I’m developing and testing: Smart Virtual Thermostat (beta version) and you’ve got a smart thermostat.
Warning, it’s not a simple plug and play system. It involves a lot of time and effort 
Btw, I’ve giving examples of devices compatible with Zigbee, but with openHAB you can use any type of communication between your devices (even mixed).
Well, it’s basically ordinary system for like 90% of the houses out there 
99% of these works on relay basis, thermostat simply switch relay and tho shorten + - low-voltage (usually like 24v) so heater knows he should switch on.
what you are looking for as hardware? - well easiest is to grab Wemos mini D1 which you simply connect to the computer via USB a reflash with tasmota firmware. Then there are RELAY shields out there, which can be soldered to the board (or you can buy ready made one). Then simply connect wires to the relay and voala.
(indeed before just measure voltage on current thermostat wiring to be sure it’s operating on low-voltage)
Wemos can be easily powered by battery, but … idn I would recommend to wire it.
It’s very simple, anyway it indeed expects that you already have temperature sensors up and running so OH knows temperature of your flat/house
If you are not into small circuits boards you can grab Sonoff TH, which can switch and measure temperature at same time. But flashing it is HIGHLY recommended, just to be on the safe side and not in need to have chineese phone apps…
what you are looking for OH solution is summarized by me here:
Hello thanks for your write ups I really appreciate them. Just to address them and further continue the conversation. Just to clarify some facts. I live in small flat 55m2. Radiators with basic (manual) thermoheads are in both rooms and kitchen. Kitchen is dirrectly connected to the living room (without door) so the temperature is shared for the most part. Now the system feels just clunky beacouse if i set up the radiators wrong (set low temp) the thermostat (with higher temp) wont ever be able to reach it. Therefore some combination remotely operable heads with some temp measuring is probably the right solution yet on the not cheap side since the flat is rented. For the first part i was thinking more controlling the boiler since the schelduling (work hours/days) is different every week.
ljsquare : thanks for this solution, for some reason it feels too much into it, meaning that the investment would be as high as maybe some smart thermostat that can be controlled. But I see the point in using easier to use devices that are more foolproof. Haven´t looked up the thermoheads pricing look interesting. I have a big scare since i tried loosening the heads that are on the radiators right now but the water started dripping so I have no idea how are they actually connected :o.
kriznik I have to admit that I am totaly lost with the Wemos mini D1. I understand that the board itself is for connecting (the smart part), then i need some relay that will controll the boiler onto it smoething like this thing. Then solder it to the Wemos D1 mini. Feeling midly scared of my soldering to be an issue in the long run, maybe go a prebuild route of wemos with relay prepared?
Thaks to both of you loads of things to think about and especially sorry to ljsquare if it felt like you wasted your time on me with your solution. It just feels too detailed control for me.
if you dont feel like soldering search for some bundles
you need this
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwjrwfbR1ZbnAhXCJVAKHT2mB74Qjhx6BAgBEAI&url=https%3A%2F%2Fwww.ebay.com%2Fitm%2F1CH-Relay-Shield-V2-Version-2-for-WEMOS-D1-mini-ESP8266-WiFi-Module-Arduino-%2F282129779161&psig=AOvVaw0uj-8FVpIZPLZDmBFTDhcj&ust=1579763996805442
and wemos
or take a look on sonoff basic th, but again flash is recommended
for 55m2 you really dont need smart thermocouplers, they are mainly very bad anyways. your manual thermocouplers needs to be set on slightly higher temp than your thermostat trigger indeed
Given that you’re renting the apartment, you might want to consider not spending too much in case you need to move!
You may also need permission from the owner before you’d make changes to the heating system. Just my opinion.
No need to say sorry @Oky_Lister 
A more foolproof system can be the Honeywell evohome system. But it’s a pricey system.
Well I think I f-ed up 
Everything looked nice until the moment i realised what i ordered. I was led to believe that I was ordering wemos D1 mini but somehow ordered MH-ET LIVE ESP32 MiniKIT, Wemos D1 mini shield compatible. After some diging I couldn´t find way to flash tasmota onto this. Tried to diging other routesd but nothing straight forward process of just flash and go. Any advice?