Home heating automation

My read on this is that the newer Bosch/Worcester boilers need a newer version of HT Bus or EMS. The Tado V3 has HT Bus which worked well, but failed with newer boilers. Tado need to address this for V3 as well as X. See here

https://community.tado.com/en-gb/discussion/9230/support-newer-version-of-worcester-ht-bus

You'd expect Bosch to have a setting to configure the digital terminals to the industry approved OpenTherm standard, open by name and nature, but manufacturers see proprietary interfaces as a cash cow, in every technology.

They are most likely pump speeds, based on pressure. If there is a system pressure sensor in the boiler, the pump can adjust speed to achieve a certain pressure, to compensate for radiator TRVs closing or opening, changing system resistance.

There may also be return temperature sensors in the boiler, which can be used to regulate circulation pressure so that the return flow temperature is at an ideal difference or Delta from the hot flow out, about 20-23° in a gas fired system. This I believe is 'DeltaT' control.

It's all about reducing boiler cycling and increasing efficiency. Too high a pressure, and the flow is returning at too high a temperature. Too little and distant radiators become slow to heat when all radiators are open. I think in your case DeltaP is just the pump pressure, if it has a sensor, or speed. Domestic Systems with basic external circulation pumps may have internal pressure differential sensors, but have no access to other data from the sytem. Your boiler internal pump is set at Proportional, which is probably the best option for balanced heating spread and boiler efficiency, especially if you have TRVs affecting the system flow resistance.

I guess this is the stuff of heating engineers planning commercial heating setups. I doubt your average plumber worries too much about it, but can perhaps twiddle with this setting, as you can, if you were getting high levels of cycling or individual slow radiator heatup, and the default Proportional setting wasn't cutting it. This is where hydraulic balancing also comes in, the use of the lockshield valves at the other end of the radiators to squeeze the nearest rads and direct more flow along the distant radiator branches.

Oddly enough, I have 4 sensor equipped circulation pumps in my pumped system (oil Boiler to blending/distribution manifold, Stove to same, pumped flow out to CH and pumped flow to HW cylinder. Theres also a direct gravity flow from the stove to the HW cylinder on a seperate coil). These pumps have a digital display and a bewildering number of fixed and sensor controlled speeds. At best I've set these to the lowest, then increased a notch or so until satisfactory spread is reached. There are no variable system resistances except two TRVs out of 15 radiators, no zone valves. I get a bit of boiler cycling when only HW demand is on, so less than perfect boiler efficiency, but I live with that. Lockshields valves let certain rooms get first dibs on the heat flow.

This is a good paper to read on the challenges of system circulation pressure, without getting all engineery. Hydraulic engineering is mental stuff.

https://www.xylem.com/en-ie/support/case-studies-white-papers/how-to-choose-the-correct-speed-control-for-heating-systems/

Post some pictures of the solo rads. Are these the convection type fan radiators which only push put heat when the fan activates. These have no flow control valve, the fan and the electrical control for that fan is the controlling element Check the model number of the solo and post that. It may have external actuation electric terminals. Post pictures of any other wall mounted controller or thermostats also, and the zone valves and their location.

So briefly, you could gain a lot of control by simply replacing the two zone valve wall switch with a two zone wireless receiver and two wireless wall stats. The HW coil in the HW cylinder is connected across the upstairs flow and return, and heats the cylinder whenever the upstairs zone is on. It would require close examination of the upstairs circuit to determine if this flow to the HW cylinder could be isolated out by a third zone valve closing the radiator loop, for this to work the HW cylinder coil would need to be the very first (or last) load on the upstairs loop, so that a single zone valve would shut off all radiators and leave hot flow to the cylinder for summer HW only heating.

If the existing plumbing makes this infeasible, an alternative is to have smart TRVs on all upstairs zone radiators, which will all be closed when a HW only call is made. I don't know if your standard upstairs radiators have manual TRV valve heads or just basic rotary tap like valves. The solo rads will have neither, but if you decide to add smart TRVs, then all radiators will need TRVs valve bodies with push pin valve actuation. It's not a particularly difficult task to replace the valve on a standard radiator with these, and it's also possible to fit them into the flow or return pipe of the solo rads, provided there is a few Inches of visible pipe upstand into the base of these.

An ideal kit fir your needs with optional smart TRV additions is the Drayton Wiser Kit 3. This has two wireless stats and a single receiver to replace the double valve switch. It also has a HW relay, which would give the option of converting upstairs into a two zone, HW and CH arrangement, if the plumbing permitted. You could also use a pair of Hive wireless stats and their receiver to achieve the same end, with or without a HW relay in one if them. Tado can also be used, but one of the CH zone valves would have to be wired directly to one of the walk stats. As the Tado is restricted to a single wireless wall statto the receiver equipped starter kit (which also has a HW relay). If the the existing wall valve light switch could have one of its switch wire pairs extended to a suitable location for a wired Tado stat, say in the front hall or living room, then a tado wireless starter kit plus and additional wired thermostat unit will work very well, and smart TRVs can also be added later.

Kit3 installation is a short diy job. In the rooms where you install the Wiser wall stats, make sure to turn fully up the l mechanical TRV, or the Solo radiator temperature, so that this room will heat to the temperature set in the Wiser stat's schedule, otherwise the local radiator thermostatic control may cap the room temperature below your Wiser app setting, and the boiler will continue to fire.

In the other rooms. the local TRVs/Solo temperature settings can be used to balance and cap those rooms from overheating before the control room with the Wiser stat closes the zone valve.

Folks, anybody have an interest in building their own three-zone heating controller with integrated thermostats and integrating it with Home Assistant?

https://github.com/RonnieLast/esphome-dual-zone-heating-controller

Would this include the briefly trained lads who were installing the 'free' heating controls for the utilitity companies when you switched your gas or electric?.