Home heating automation

Only a device with an electrical relay can actually switch the boiler on. The tado wall stat has such a relay. The Tado ext kit has two, one for HW and one for CH. These can't just be joined together at the boiler, otherwise HW timimg would heat the rads and vice versa. With two relays and two zones to heat you need zone valves to switch the hot flow to either, so the HW live output from the HW timed schedule in the App (or manual override on the app) will open the HW zone valve. Similarly, the CH live output from the CH timed schedule in the app, ( or manual override on the app or by pressing the wall stat buttons) , will open the CH zone valve. When either or both valves are open, we need to fire the boiler, but, (and this is the bit that many sparks and plumbers can't grasp initially), we can't just use the CH and HW lives and connect together so either or both fire the boiler. Why? Because if we join them any one will open the others zone valve, yes? They have to be isolated from each other, so instead, the zone valves are fitted with a relay, supplied by permanent live from the mains. Each zone valve will close its relay when activated, and these switched zone lives can all be happily joined into the one wire and sent to the boiler SL (switched live) input. As many zone valves as you care.

Mechanical TRVs exist to cap the temperature in a room by closing the flow as the set room temperature is reached. If the room cools, they will open. But they are not equipped to fire the boiler, that is the function of the general wall stats and zone valves, upstairs and downstairs being the most common S plan, with a third zone valve for HW.

Smart TRVs can enhance trv operation, by having a wireless link to the wired thermostat relay or receiver relay, in order to call the boiler EVEN WHEN this thermostat is 'satisfied', off and not calling the boiler. The anomaly that arises is when only some radiators have smart thermostats, so any boiler call, including those initiated by a TRV through the zone stats relay, will cause all open radiators to heat, not just the one with the calling TRV. The ideal solution is that every radiator has a TRV, and the main stat only acts like a timer, firing the boiler at the TRVs' behest. A radiator in the same room as the wall stat can have a smart TRV, but can use the temperature sensor in the wall stat as it's reference, so that this rad is not being controlled by two different temperature measuring devices.

Thus, the Settings in the App determine if a TRV uses its own stat, or is just a slave to the temperature read of the main wall stat. If you have more than one CH zone with it's own wall stat and zone valve, the app needs to know which stat relay to close for a boiler call from a TRV. Upstairs TRVs will reference the upstairs wall stat and its relay, opening the correct zone valve, and so on. This appears in the app as the 'Zone Controller' for a TRV, the number in the field being the device no. of the wired switching device. There's only one with a single stat with extension kit, the CH relay. With Tado, extra CH zones after the wireless CH and HW kit can only be wired stats, and will be physically wired back to their respective zone valve. The TR1/TR2 link has no function in any of this, it acts as a virtual pair of wires to link the combined boiler call lives from all zone relays, HW, CH1, CH2, etc, to the single boiler SL input.

You'll need to test each TRV as you install it. They can be in their own room, with their own schedule, or can be in the same room, physically and virtually, as other TRVs, sharing the same schedule, opening simultaneously, and using the assigned Zone device as the source of temperature measurement. This can get messy to understand, if you have say three or more radiators in an open plan home, it's best to have them all activated by a single schedule, with just one if them acting as the master device to determine boiler call, while the others are just slaved valves. Plenty here to chew on for a while. Get your two zones firing and their zone valves opening as your first priority, then add in the smart TRV heads one at a time, giving them their own schedule or adding them to an existing room with a schedule. Good luck! Midnight, better go before I turn into a pumpkin.

I think you mentioned a few posts back about being stuck on 'Yellow'. I dug out the configuration sheet for the wireless stat/ext kit eventually. As you can see, the configuration signal for S plan two zone is a green lamp, and this is the default, hence it works out of the box. If you were seeing a yellow lamp, it seems you've configured your receiver for a Combi boiler, where the plumbing will not have a HW cylinder and thus the HW relay is redundant. This may not be your fault, if you went through a process of listing your system and entered combi boiler, your App may have preprogrammed for this. A combi boiler can have still have a HW tab though if the ext kit is digitally connected via OpenTherm, but this extension kit version does not have a HW relay, it has Digital/OT terminals instead, and is sold on the EU market. The HW tab on these units can control boiler direct HW temperature and pre heat status, but no schedules as HW is on demand and is not stored in a cylinder.

Follow the configuration instructions on this sheet which you must have. This should restore your App to S plan switching.

It's set and forget. I don't change schedules over the year, or touch a stat. When the weather is fine, it just stays off hy itself as stat thresholds are never reached. As winter approaches, it will kick in earlier and for longer.

It's a bit like automatic washing machines when they first appeared. My long departed mum in law would sit and watch the steps of a cycle, getting frustrated it wasn't moving to a rinse, orva spin, while we laughed and advised her to ignore it till it stopped. She eventually settled for manually crashing the rotary programme knob forward when she couldn't bear it any longer. There are people on here who don't trust stats, preferring to act as human stats, leaping out of the chair and pushing the stat up, then down, trying to beat it for efficiency. The smart stat will know the rate of cooling or heating, even allowing for outside temperatures, and will be slow to push sudden surges into the system, rather using modulated bursts.

These are the option choices to determine the duration of manually override the temperature settings on the main stat of a TRV, either by adjusting them on the app or by manually twisting the TRV knob or pressing the buttons on the main stat.

If for example, your kitchen TRV schedule is set to 18° from 2pm until 5pm, then 21° from 5pm until 7.30 pm,, and do on. Say You manually turn it up at 2.30 pm to 22° by twisting the knob, or by swiping the room indicator bar in the app upwards. (Not by editing the actual schedule though).

In our example, the first choice will leave the setting at 22° until the timer sets it back to 21° at 5.pm.

The second choice allows you to boost for a specific time period. Once set this becomes the default, so a short period of say 10 minutes will prevent long periods of boost.

In the last choice the boost remains in indefinitely until you turn it back to timer at the app or at the control.

I'd expect the effect on HW to be just 'ON', as there is no app control of HW temperature, but if you have a cylinder stat, this will break the boost if cylinder set temperature is reached by turning off the HW zone valve.

Finally, note that the settings made in the app configuration page you posted are the default for manual adjustment, but when overriding on the app, you can change this at the bottom by tapping the edit 'pen', and this choice then becomes the default for this stat. So go round them all in the app and give them a time limit. This is useful if you have 'someone' in the habit of just whacking up stats when they enter a room for 5 minutes.

Yes, Tado is out because of no wired wall star locations. Drayton are advising two CH heating zones maximum, it's not completely clear how an extra Drayton thermostat/receiver will integrate on the app. Hive will work though, the Hive active CH plus HW kit has the thermostat, CH and HW receiver and hub, which covers the first CH zone. You can then add 'multizone' add ons, which are just the Hive CH thermostat and CH only receiver, without the hub. The hub on the primary kit covers all the extra receivers' connections to d'internet. It's explained, rather awkwardly it has to be said. here;

Hive also have TRV products for optional room zoning.

That confirms its not a heat pump, so you can benefit from the installation of a smart thermostat. What is the current method of control. Is there a wall stat in the living area with the uh, or more than one. Is there a timer there or elsewhere?

Post an image of the wall stat and hub.