My air-con can have a temperature set and aim for it.
- It has a wide range of ± a few degrees which I don't like.
- It is not setting temperature by me, it is basing it on some sensor it has.
To fix this I have used an environmental sensor - on my desk, and for my bedroom, on my bed head. I then control the air-con - telling it I want it higher or lower than it thinks things are, so as to aim for the right temperature by me. It works well most of the time and keeps the temperature very close.
That is my bedroom, last night (cooling), units in ℃, so maybe ±0.2 ℃ at most. Good.
I also have radiators for the winter, and they have the same fun, driving the valve on the radiator with some prediction.
Which to use for heating? air-con (heat pump) or radiator... Bearing in mind some of the house does not have air-con, so has radiators anyway. I don't actually know which is most cost effective / efficient. But I can choose. Have systems in place to make sure they are never fighting each other :-)
Per room radiator control
One of the key things is per-room controls - this means a temperature sensor in the room, and a radiator control, and some way to tell the boiler that one of the rooms needs heat. We have two heating loops (up and down), my daughter has two (left and right!). But for each radiator there is one boiler control that is needed.
The hard way
So, the hard way, I have my fancy environmental monitors with a display. They have a config for temp targets throughout the day. I have systems to override for empty rooms. Using the light switch marks a room in use for the day :-)
They talk MQTT to a Shelly running Tasmota that controls the radiator. So needs an MQTT broker.
The Shelly talks MQTT to a FireBrick to say radiator is on/off.
The FireBrick has a set of profiles, and any one in each loop will cause a message to another Shelly running Tasmota to operate the heating loop valve.
This triggers the boiler as needed.
It is not cheap or simple - the env sensors cost, the FireBrick costs a lot.
The easy way - maybe
So I am working on an easy way - my daughter happens to have a FireBrick, but even so I am trying to make a really easy way to do this. Not all of my kids have one (?!).
The first step is the reference temperature. A sensor that can be placed sensibly, e.g. by a bed.
I had found some nice industrial (BlueCoinT) ones at €31, but now have found, thanks to a recommendation, some stupidly cheap ones on Amazon. They are only £9, and even cheaper on AliExpress. They can be refreshed with sensible code.this, £19.63
So yes, we are up to £45 per room. A few more £s for back box and fused spur box for the Shelly mini by the radiator. And one Shelly at the boiler.
The comms can all be BLE. Sensor to Shelly, and Shelly to boiler control Shelly. Just needs a bit of software.
Not ideal, but £50 per room for exact per room heating control is probably quickly worth it. Simple web interface (or maybe even HomeKit) for unoccupied rooms, and controls for times of day and target temperatures via a web page. This can quickly save on heating costs and make things more comfortable.
It always amazed me people ran their house with one thermostat on the wall in the hall.