UK dumb heating controller

I recently had a power cut which means I need to fight with the terrible interface on my heating controller to set up what times the heating and hot water will be on.

I currenly have a heating controller like this

What I would really like is something with a nice web based interface so I can set this up easily and allow me to override the timings using MQTT/Home assistant. I could implement this myself on an ESP32, however I would need to connect it up to my current heading system, and I’m not that confident playing about with the wiring of the heating system.

All I really want is a “Dumb” heating controller that just exposes the water on and heating on state as switches that I can then replace with relays. If I could get the thermostat value that would be interesting but TBH I could add my own sensors in each of my rooms to get a better indication of the temperature than the built in thermostat which is at the top of the stairs.

I know I could go the Nest/Hive route, but I’m not sure if they would let me do my own thing with a local API, or impose the “we know best” approch of trying to set everything up for me, not to mention requiring a cloud connection.

Does anyone know of a simple drop in replacement that will give me what I want?


Can I suggest listing out your key features, and then putting them in priority order? Start with the engineering trilemma of Quality, cost, delivery (QCD) and add the things you see as important.

As it stands your requirements seem to be:

  • local LAN API control (e.g. not cloud - rules out many commercial products)
  • MQTT / HASS integration
  • Works with UK based systems with two zones - thermostatic heating and domestic hot water.
  • Unknown - suggests a hot water cylider with a thermostat, rather than a combi with instant water heating
  • Unknown - Y-Plan (3-port AB valve) or S-Plan (2-port valves)?
  • Unknown - CH timer + separate thermostat or combined?
  • Unknown - location of key components (impacts wiring - many have a ‘wiring centre’ next to the HW tank, but some control signals are at the boiler)
  • Low electronic / electrical self-build

On that basis, the closest that comes to mind is a Sonoff TH16 or Dual running Tasmota/ ESPhome plus a room temperature sensor.

  • HW - likely needs only ON / OFF relay control assuming a cylinder with a mechanical thermostat.
  • CH - Programmable temperature set point with ON /OFF relay control (e.g. no OpenTherm modulation)

If you add a DS18B20 to a Sonoff Dual R2 (see the Tasmota Wiki), and rewire the boiler, a single device could achieve this, BUT the temp sensor may be be located remotely next to the boiler (where the existing timer is), or next to the cylinder (where the wiring center may be).

If your boiler has separate mains level HW / CH inputs, and controls the pump itself, then a Sonoff would give you pre-packaged hardware with the option to customise the software.

Another option is to turn the existing CH mechanical thermostat down to frost (a useful backup), and use a relay in parallel as a room stat. Just set the desired temp low when you don’t need heat. A Shely One can do this, but a Sonoff would need modification to separate the relay from mains (‘dry contact’).

Sadly, most UK heating systems are wired in a more complex way to save pennies… (which also can cause issues for non-UK ‘smart’ controls). There’s lots of variation with significant differences (3-port valve, 2-port valves, separate HW, multi-zone, combined timer + thermostat, combi with integrated HW tank etc) and a picture of a generic timer sadly just isn’t enough to offer any useful advice! :frowning:

I suggest researching how the traditional Honeywell Sundial 2 or 3 (AKA Y-Plan) system skimps on components to drive water valves as usually the CH needs a change-over relay (SPCO), and all but the Sonoff 4CH Pro have only single contract relays.

There’s lots of places to start - check your existing boiler controls out, and then watch John Ward’s series on UK heating controls.

Even if you were to go out and buy a ‘simple to fit’ commercial cloud-based unit, you’ll still need to know how your existing system works - unless you pay a plumber or sparky (and they tend to know much less about the automation side, giving different issues).


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I just installed one of these:

Has its own app which runs in the cloud, but there is also a HA component that lets you control locally.

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My heater’s control panel has a simple “1 hour” button that turns on and off the heater. I’ve just added a ESP32 controlling a servo motor to push the button whenever the house needs more heat. This is by far the less intrusive and simple system you can build.

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Cheers everyone, especially @FloatingBoater for his detailed suggestions, I have much to read :slight_smile:.

Technically I have a degree in Electrical Engineering but I concentrated on the electronics, and software side before getting a job as a software engineer so my knowledge of home wiring systems has atrophied over the years, which is why this is frustrating since I know how simple what I want to do is, but just outside my experience. Hopefully those video links will help explain the systems to me.

(Also I looked at the wiring center when I had to replace the motorized valve a few years ago and found it to be a complete rats nest so I just replaced the cover and walked away)

Hi Dave,

Coincidentally, I’m also an elec M.Eng who moved into software and telecoms professionally but kept up some of the practical side with IET on-site guides.

A failed A/B valve over Christmas in a previous house forced me to trace out the system, and fix the heating by replacing the synchronous motor for a mere £7 from Screwfix! As you say, the rats nest wiring centre is truly 'orrible with little standardisation.

To start somewhere, you could get a Sonoff TH16 with Tasmota and a DS18B20 sensor and only connect a permanent mains supply to send MQTT tank water temperature to HASS, or add a second to measure radiator temp. The resulting graphs will show when the boiler is running with details like usage, time taken to warm up (“optimum start”), hysteresis, and boiler cycling time.

One extra switched live wire may give HASS CH control (hint: trace the AB valve White wire back through the room stat to programmer terminal 4), with HW more complex (as it typically uses a SPCO in the timer). You system may be different, hence the thought to start with read-only access!



Hi, I am looking to buy this too, you say there is a HA component to control it, what is the component / integration? cheers. James

This one here, recommend installing HACS then installing