Thermostat to control other device

[slowmo]

I'm looking for a simple thermostat, which could be used to control my split air-conditioner/heatpump unit. Can I use HmIP-WTH-2 for that? Is it possible to read current temperature and setpoint from it using local API. And also is it possible to update setpoint by API if it is changed outside of WTH-2 (e.g. by using IR remote of A/C unit)? How will I be able to detect setpoint change? Polling of WTH-2 at a regular interval or will it fire an event?
I could buy one WTH-2 and CCU3 to do some experimenting, but I would rather hear first if achieving what I want is possible at all with this hardware.

[tomi_cc16]

Hi,

the WTH2 has no opening for any wires or so, it just sends the measured information to e.g. other devices or a central gateway like CCU3 - there you can create programs what should happen or be triggered. Also you can set a temperature and this information can be used for further devices to perform.

Not sure how your A/C can be triggered/get smart with just a WTH2??

[slowmo]

I don't need physical connection. A/C has a WiFi module and REST calls can be made to control it. So thermostat does not need to directly interface with A/C. When setpoint is changed at the WTH2, I need a way to know this and I will then forward new temperature to A/C through WiFi.
In other words, will I be able to configure everything so that I can connect to CCU3 using my own software, and read the set temperature, actual room temperature and humidity? Or maybe I don't need CCU3 at all? I see there are radio modules for RPi. Does it mean I can have functionality of CCU3 on my own hardware?

[tomi_cc16]

Hi,

It’s possible but there are cheaper ways than to use Homematic IP devices for example Wifi thermostats or a temperature measure e.g. from Shelly and a middleware/Mqtt Server to connect the thermostat and your A/C (like Home Assistant, ioBroker or OpenHab).

If you will read this (10 min) it will answer 80% of your general Homematic IP questions:
viewtopic.php?f=49&t=41325

But here my 5cents for Homematic IP scenarios:

Alternative A:
Anyway for Homematic IP I recommend you to get a WTH-2 and CCU3 (or build a RaspberryMatic as a CCU3).
On the CCU3 / RaspberryMatic install then the Addon Redmatic (Node-Red) here you can create rules/scenarios to control API‘s like your A/C.

Alternativ B:
Install Home Assistant on a Raspberry Pi, plug the HmIP RF USB Stick in it. Home Assistant has a Homematic IP Addon already preinstalled so with the USB Stick you can control the WTH-2.
Than create in Home Assistant scenarios to control the WTH-2 with your A/C API.

[slowmo]

It’s possible but their are cheaper ways than to use Homematic IP devices for example Wifi thermostats or a temperature measure e.g. from Shelly and a middleware/Mqtt Server to connect the thermostat and your A/C (like Home Assistant, ioBroker or OpenHab).

That's the problem. There are no cheap WiFi thermostats. At least I have not been able to find one. Most of them are expensive and do not even have local API. Some have cloud access, but I don't like that. Take for example Nest, who decided to retire their API. Closest I have been able to find is SML-5000 from China for around 50Eur. It supposedly has Modbus TCP, but I'm not sure if all the necessary registers are there to take full control of it. Might eventually order one for tests.

I will explore Homematic products as well, as I like, that there are many different devices, that could be useful around the house.

[tomi_cc16]

So what will you try Alternative A or B?