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Home heating automation
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I'll have a look, but if the valves you're referring to are TRVs, not plumbed zone valves, then the situation changes. With multiple TRVs, modulation becomes complex, possibly redundant, as the hot flow is unpredictable. You could have ten radiator TRVs open, or just one. Flow rate becomes an issue, as one radiator would not be able to dissipate the fixed output of a firing boiler, so boiler max temperature is quickly reached, and the boiler will cycle. Setting the boiler heat exchanger to a low temperature will aid condensing efficiency, but this low setting may not be able to deliver sufficient heat when all radiators are open. What can help is a smart circulation pump, which will restrict flow when higher circuit resistance due to low load, i.e only one or two open rads, is present on the circuit. Reducing flow will help reduce the flow return temperature and encourage condensing. With a high flow pressure and low load, boiler return temperature will not be very different from hot flow output, reducing condensing.
Smarter boilers may have some say in this, if they're equipped with flow control pumps, pressure/flow sensors and flow return temperature sensor. This will assist the boiler in optimising condensing, even if just operating in relay on/off mode with no data from the stat.
There was some discussion of this here some months back, I linked a technical paper which discussed the setting and use of flow control pumping. It's a very professional heating system process, a bit beyond the generic setup in most single zone homes or dual CH zoned system S plan zoned valves.
It's worth saying that if you're referring to the Thermostat controlling plumbed zone valves, and not TRVs, the Zone valve 'passes on' the boiler firing live voltage via a built in relay to the boiler, so the thermostat is acting as if it directly calling the boiler, which it is.
Other interpretations of the "thermostat controlling the valve' might be where a stat is a temperture sensor for a TRV, rather than using the TRVs own built in temperature sensor. Such a sensor can wirelessly open the TRV valve, but the boiler still needs to be fired, so another thermostat or a wireless thermostat receiver must be configured as the 'zone controller', the actual device which switches the boiler on. In this arrangement, there are three physical devices enabling a single zone. In fact, I have this very arrangement just as of this year, where I doubled the size of the main living room radiator to get the room to temperature quicker, but I also installed a TRV on it to take it out of use until the evenings. Finally, I added another wireless thermostat to as a temperature sensor in the seating area, as the sensor in the TRV was too close to the concentration of heat in the radiators location on the most inner wall, and was closing the rad while the outer reaches of this almost 8 metre long room were still cool.
Does it work? Yes. The wireless stat is just a sensor, configured as the temperature measuring device for the TRV. The TRV is the zone device, and the main house wired thermostat is the, zone controller relay for the TRV, firing the boiler. Does it emulate modulation? The zone graph from last March showing the zone looking for heat at its first schedule call at six pm shows a fully on call to the boiler, dark grey, which then goes to medium grey,light grey, then white, so this looks like the software is reducing the heat flow, but more likely by squeezing the valve closed than by burst firing the boiler. During this period the main stat is acting as the general thermostat for most of the houses open radiators, with only one other TRV controlled zone. It's obviously a compromise when you have valves zones and unvalved zones. Mine is more complex as a stove with a boiler jacket is generally lit at this time also, adding a decent amount of kw to the water flow. If you want purist boiler modulation, just install a single digital connected main stat. Add TRVs for tighter temperature control, but add them passively, without assigning them a 'zone controller, where they willbact to limit overheating of their room, but can't call the boiler.
Here's my graph from the TRV zone with one thermostat acting as wireless temperature measuring sensor, and different thermostat acting as the wired relay to the boiler.
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I was referencing the one in this link that @WildCardDoW posted earlier. https://www.elektrobode.nl/products/bosch-ems-1-2-to-opentherm-converter-7736702317.
In the link it says its brand is Bosch, hence my comment. There's no image in the link, but I think it's not a bosch product, probably this Nefit one.
There's a discussion in reddit, available in the Netherlands mostly, where they like their OT and digital boiler controls, to save a few pence and the planet etc. The only time I've personally encountered an OT connected Tado was there, I later had to reconfigure it by manual instructions over the phone to my daughter in law when it lost connection after a boiler service. Hairy, but it worked
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Got my Wiser kit today. Just replaced the programmer and setup the thermostats and had the twi current thermostats set to max. The boiler didn't fire. Anyone any ideas? I've attached a few photos. The only one likely any help is the backplate photo with the wiring. It'll likely be something odd?
I've emailed Drayton as well.
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Oh ye of little faith. i posted the wiring connections for the Kit3. The Wiser should have came with a printed installation leaflet, which shows the wiring of the baseplate for the different Wiser controllers, 1, 2 and 3 zone. Your controller is 3 zone though you've no use for the HW timer. Here's a grab of the full page. I'll skip explaining the differences, just change your wiring to the 3 zone, which is achieved by moving the wire going to terminal 4 to terminal 1.
(Matthew, various chapters and verses for the opening comment, though I'm irreligious)
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