Home heating automation

I have my HW control showing on the Google Home app. My HW was still on my old 3 channel timer, but I recently bought a cheap complete starter kit in order to get the HW extension kit, and this gave me upgrade of my bridge to V3+ at the same time, and a spare CH stat sensor.

It's the scheduling and away mode that would be the most needed app functions. I've not tried any means of 3rd party scheduling (except IFTTT, which is now unsupported). It all works manually in the absence of Internet, and would now be controllable by Homekit, if I had an Apple cloud account I think, as my only Apple device, an Apple TV box, wouldn't allow me on its homekit app without this. I don't have an iPhone.

As an original V2 owner I had all features included on the old app, and years ago I stared down their offer to pay subscribe to the new app, until one day it just upgraded to it without any fuss, with no demand for sub, or loss of any features.

I've not received that new sub message either. I reckon they would like to remove the cloud dependency altogether, but how, without complete architecture changes. Are X adopters immune from this Sub? It X substantially locally programmed, and programmable offline, or if Tado servers are down? Wait and see I suppose.

As it's a system boiler, (no direct hw), and you have seperate CH and HW heating circuits, I would expect it is controlled by a switched live 220v signal, and not by Ebus. What are your current timer controller/CH room thermostat/HW control devices and arrangements. Have you two fully independent zones? Can you heat HW without CH? , and the opposite? It has an internal pump, so separation of heating circuits, HW and CH, could only be achieved by one or more motorised zone valves. A single valve will allow HW only heating during boiler firing, for either a HW or a CH timed event if you have a two channel controller.

An older arrangement is to have a single simple timer, often a mechanical segment or notch rotary timer, for all boiler calls, and a single zone valve controlled by a wall thermostat to open or close the CH circuit to the boiler flow.

Two zone valves in an Splan arrangement allows either or both CH and HW zones to call the boiler independently, and their 220v live independent SL (switched live) signals to the motorised valves are not connected directly to fire the boiler, rather the zone valves have relays which are combined to supply the 220v sent from the boiler's own live terminal and returned as SL to the boiler's RT terminal. See the image.

Live 220v is tapped at the power inlet and sent out of the boiler to the external thermostats/timers/controllers/valve relays and is returned to terminal RT to fire the boiler. Any of the smart thermostats on the market can operate your boiler in SL mode, and mosr like the Tado will use a type of modulation on the firing pattern to simulate digital control.

An ebus modulated CH flow which is also used to heat a HW cylinder simultaneously will not reach sufficient flow temperature for HW if the boiler is operated at low modulated heat maintenance temperature to aid condensing efficiency, as a CH only heat source. This is why two zone controllers ike Tado extension kit don't have digital outputs for OpenTherm or Ebus connection, and only have this if HW is direct from a combi boiler, but this controller doesn't have a HW relay for Splan, and generally will not actuate any relay when boiler control is via the digital terminals.

Describe how your current system is controlled, maybe post some images and take it from there. I won't confuse for the moment by commenting on possible dual calls to a digital boiler for 2 zone setups.

I should also add that firing the boiler in HW mode requires on off control with boiler flow having to reach sufficiently high temperature to prevent legionnalla in the HW cylinder, so boiler temperature of 60°+ would be needed. The ebus can't know which heating circuit is calling the boiler. HW or CH. Some boilers, ordinary SL controlled, have two SL inputs for either call, allowing a higher flow temperature on a HW call. With a smart thermostat controller with CH and HW relays to your S plan valves, the stat itself will not be involved in boiler modulation when the relay closes for a HW only boiler call, so this arrangement can achieve the best of both. The Evohome brand of thermostat controls has logic afaik to address a digital boiler for either call, while operating zone valves. They are expensive, but some here are very happy with their investment.

Diy install, goes straight in, in place of your 2 zone controller. Stat is wireless, takes over the timing and temperature control, so you just turn up the IMIT fully, or else remove and join it's in and out wires together, insulate, push back into the wall, and cover, with the new wireless stat if that location is best.

Apologies, I see your boiler zones are also controlled by warmup stats. These can be removed, with the zone hardwired on, or else turned up full.

I meant to throw in my two ha'pence worth on this, but @WildCardDoW is correct, the reason being your HW is from an immersion, not a boiler call, so the current requirement in amps of an immersion element is much greater than is required for boiler switching, and would exceed the capacity of the relay switches used in many of the popular smart thermostat wired and wireless devices. There are heavy duty Wifi 16a rated wall switches you can use to remotely time and control the HW immersion. These can be wired in place of its current mechanical timer. For the CH, I'd recommend any of the smart single channel wireless thermostats. Tado, Drayton Wiser, Nest, Hive. Their respective receivers are wired in place of your CH mechanical timer, and the thermostat is placed where it has the best read on your desired home temperature, either hall, or a living space. The only caveat to boiler switching current demand is when the boiler is an old, usually shed installed oil type without a permanent live connection in standby, meaning a boiler call demands a big jolt of current to start and run it, which can be detrimental to the relay contacts in wired or wireless smart thermostats or their receivers.