Home heating automation

Nevermind the heating - I'm lovin' the retro/stock-trader's mechanical keyboard! 😁 🤓

Any wall stats with the two controller CH zones?

Sorry, should have quoted. Are there radiators downstairs as well as kitchen UFH? Is the downstairs stat in the kitchen? Generally zoned heating is a compromise, the measuring stat is often in the hallway, well in from the front door, and it acts as the sensor for all downstairs rooms, though most heavily influenced by its location heating devices, rads or UFH. It's good practice to have at least passive mechanical trvs on the rads in the areas that don't directly heat the thermostat. Normally open doors tend to circulate the heat from all rooms in a zone, evening up any imbalance.

The warmup thermostats can be used as a simple air temperature measuring device, and in this capacity, can be easily replaced with a wired or wireless smart stat. When used for UFH, there may be a complication. The stats have provision for an underfloor temperature sensor in addition to the normal air temperature sensor, to better gauge the output of the UFH. Replacing with a stat that relies solely on air temperature could risk excessive output or slow response of the UFH , but plumbed UFH will have temperature controlled valve limits on the hot flow into the UFH tubing. That's assuming your UFH is hydronic, hot water based. This particular stat is also designed for electrical mat UFH. If this is what the stat is controlling, the underfloor sensor is probably more critical as a means to limit overheating. The mats are directly powered by the mains switched by the stat, with the capacity to switch a hefty 16 Amps or approximately 4Kw of UFH mat elements. If your UFH is electrical, I would not advise switching this directly with a normal smart stat, without the use of an in-between 16a relay, and would still be inclined to leave the warmup stat in circuit to act as a controller.

This would not be an issue if the stats are controlling boiler flow to rads or UFH tubing, in that case they could be replaced by wired smart stats or by the receivers of wireless stats. Have a look to see if the kitchen is electrally heated or by boiler, and it will be clearer what your options are.

https://www.warmup.co.uk/wp-content/uploads/Warmup-OM-Tempo-V1.3.pdf

The receiver for the wireless Tado CH thermostat also has a relay for HW timing, so you can remove the old controller altogether. Option 1 was a very simple DIY job to smart automate your CH zones, while leaving HW timing to the original controller. Removing and replacing the controller is often a task too far for some, so you need to hire an electrician.

You can still replace that three zone controller with smart system such as the Drayton Wiser Kit 3. This is a drop in replacement and will give you two smart wireless thermostats for the radiator CH zones, HW control, and the option of Smart TRVs. If the Kitchen UFH is electrical, it can be left on the Warmup, and any link to the plumbed zone removed if present. It could be that the 3 zone timer receives its downstairs zone switched live in from the output of the Kitchen Warmup. On the other hand, if the UFH is plumbed, then it may just be acting as a low current thermostat for just the kitchen UFH, or the entire zone. You won't know until... you know. A few electrical tests will figure it out.

does the second warmup stat control any UFH? It may have been used just as normal zone stat for upstairs plumbed. Next thing to test is your three zone controller. I can't make out the brand in the image, but I'm assuming there are boost buttons. Press the boost for downstairs and see does it bring on the downstairs radiators without the kitchen UFH being on. This will provide a clue to the wiring.

With a very light load of on one or two rads, the boiler will inevitably cycle, that is, it will halt firing at its set internal temperature but will continue to move the heated flow around, to be consumed and cooled by any open zone TRV equipped rad. If you have large numbers of smart TRV's, then you will have conditions for this.

The only inefficiency that can occur is a reduction in the condensing efficiency of the boiler as the flow temperature rises to boiler se max. The smart stat only has knowledge of the room temperature responses, not the boiler jacket temperature, but notwithstanding this it should know the rate of rise of room temperature is rapid when there's only one or two rads pulling heat from the flow, so it will likely modulate firing bursts to keep the rate of change under control.

All smart stats use a number of techniques to exercise fine control, including a method called PID mentioned a few posts back by @10-10-20 in a discussion with @ecomental using basic Shelly switches and temperature sensors. PID or Proportional Integral Differential applies those derivatives of the actiual and target temperature differences to the boiler response, along with other tricks like modulation and learning. Very interesting stuff, the maths is hairy as I remember well from my college days, but I leave that up to Tado and the rest of them.

That's probably where the learning element comes in. You can calculate the PID to warm a given volume to a given temperature with a classic response curve provided you have Proportional control of the heating souce. Boilers are full on or off, not variable, so that's where modulation comes in. The load can vary significantly too, depending on the number of open rad/zone valves, and variation in cooling due to outside temperature. Smart stats are constantly doing the sums on this, including using online local temperature and weather data. There's no one size fixed Pid value that can turn a basic on/off temperature switch into a smart one, but you can probably get a decent compromise, otherwise it's no better than a mechanical stat. The issue of condensing flow temperatures further overeggs the pudding though, most homes' radiators wouldn't heat the rooms comfortably in the really cold days we've had recently if the flow temperature was restricted to ideal condensing temperatures, so again its a compromise.

I wonder could @ECO_Mental have left his 12 thermostats in situ, on the basis that they probably had some level of pid built into them, and just used the shelly as timers to activate switched power to the stats relay commons when heating was needed in specific zones. the Shelly could bring the stats in and out of service on a timed and also secondary limiting temperature basis. This would give some remote control of the zones while retaining the thermostats' response profile for comfort level heating, assuming they weren't just dumb cliff edge thermostat switches. I haven't looked them up to see their spec.

Yes, that's why I was suggesting to him to use room sensors over ZigBee and then putting the Shelly's as the control device as some of the PID controllers have an autotune mode which can help to discover the basic inputs to P, I and D and then allow for an easier setup after that.

https://github.com/ScratMan/HASmartThermostat/tree/master