Multiple TRVs in one room/zone

As a very early Tado adopter, been using it for years, but never been able to figure out some aspects of its operation - particularly when Tado representatives have supplied bizarre answers that simply do not match what is actually occurring (not the first time, as we all know).

We have several 'zones' that have multiple rads, each with a Tado TRV and some with also a tado room stat, although that makes no difference to the question:-

How do Tado zones with multiple TRVs operate?

A rather broad question, so I'll be more specific.

In the Tado app, you specify one measuring device to use for each 'zone'. Can be either a TRV or a room stat (again, makes no difference). But what does that mean? I initially thought this device was used to measure the temp for that zone and then all the TRVs would be controlled together to attain the set temp. However, this would mean the zone would likely have an uneven temperature (especially if segmented by doors), but Tado assured me this is how it works.

Fact is though, that in any zone with multiple rads (each with TRV), even when the zone is apparently calling for heat, it is possible for one rad within the zone to be full on hot and another cold. Tado just wanted me to believe it's the delay between TRVs being adjusted, but this is demonstrably nonsense as that situation can exist for an hour or more and it is patently obvious that the TRVs must be controlled independently within a single zone - despite 'what Tado says' (our new catchphrase 😀). All TRVs are NOT adjusted simultaneously (allowing for any understandable delay). So how are they controlled?

Has anyone actually determined how this all really works? I'm not sure Tado knows. 🤨



  • As I understand it, Tado trvs won’t call for heat unless they’re the master temperature sensor or they’re manually overridden. There’s a slim possibility that they still monitor temperature even when they’re not the master sensor and shut off when the target temperature is reached. That would explain why your trvs in smaller rooms (I’m assuming) in the same zone shut off first.

    Or you trvs could be low on battery power. Those are the only two explanations I can think of.
  • No, all batteries fine. It's not an isolated occurrence. In each room/zone that has multiple rads and TRVs, I can regularly find that the rads are at hugely different settings. Not always, but very often.

    If as you say each TRV limits the max for its rad, that makes a Room stat somewhat redundant as it is not truly controlling the room's temperature. Why use a room stat if each TRV is actually controlling its rad and then it comes back to my original question, if each TRV is not controlling its rad and it's all controlled by the room stat, then how can the situation possibly arise when one rad is full hot and another actually cold.

    It simply doesn't make sense and typically Tado are unable or unwilling to truthfully and accurately explain what is going on.

    To be clear, I am not someone bamboozled by technology and have spent time as a database developer and other coding activities, so I understand how stuff might work. But in the case of Tado, that's of no help unless they let on exactly what their 'code' is trying to achieve and how.

  • samd
    samd ✭✭✭

    I can only comment from my general experience in that in the early days with the system I had two areas in which rads were controlled by other TRVs rather than room stats and throughout that time experienced no difficulty in that the slave followed the master rad. Secondly since installing room stats in both locations, the situation remains the same.

    Have you tried doing a switch of master/slave where you can and how many settings for rads/room stats are you experiencing please - sounds horrendous!

  • I've tried using one of the TRVs as the one to use for temp or instead a room stat and it makes no difference. The rads in any of the rooms with multiple rads are often at different temperatures. Sometimes a small difference, but sometimes one full hot and another completely cold.

    It's not a horrendous problem. Those rooms are overall comfortable, but the behaviour is completely at odds with 'what Tado says', which is that (in the case of using a room stat) the temps reported by the TRVs play no part in controlling the temperature. The TRVs then merely turn the rads on and off according to the single stat. So all TRVs operate in sync (albeit with some built-in delay for which I still don't understand the requirement).

    However, for hours at a time, the rads in a single room can be very different, so 'what Tado says' cannot be true (surprise, surprise) and in which case, what IS the modus operandi of a single room with multiple rads?

  • The logical conclusion is that TRVs ask for heat only when needed, and only when the measuring device has not reached its set temperature.

    Suppose you have a thermostat as measuring device and two TRVs. You say you want the room to be 21 degrees. The thermostat measures 20 degrees, TRV-1 measures 20 degrees and TRV-2 measures 21 degrees. Then it would be logical to only heat TRV-1 and leave TRV-2 cold. Just giving all TRVs the same heat would result in possible uneven temperatures in the room, especially when there is a size difference in radiators or when the radiators are placed where the heat builds up easily.

    If this is how it really works can only Tado confirm (or deny). The algorithm can can also include other parameters like energy efficiency by keeping the return watertemperature as low as possible.

  • samd
    samd ✭✭✭

    You said: ...and in which case, what IS the modus operandi of a single room with multiple rads?

    In both my rooms with room stats and 2 TRVs, all I can say is that on telling the system to heat, the room stat will turn on both TRVs with 1/2 seconds of each other always but I have not measured or noticed the rate of decline in the heat pattern of each rad.

  • In answer to samd, yes when first starting to heat the room, they both come on, but later when simply maintaining the set temp. there can be a huge difference between the rads.

    To MichielTado, yes that would seem correct and it would make sense, but it's not 'what tado say', or at least, what they said when I asked this specific question.

    It is actually possible that behaviour varies depending on whether there is just one, or more rads with TRVs (SRVs in tado speak). So in the former case, maybe they are directly linked, whereas in the latter case there is some sharing of the measurement and control. Thing is, with a system as complex as this, in order to determine whether it is behaving correctly or not, it is crucial to know how it is supposed to behave and that has so far not been forthcoming from tado.

  • I can only echo samd. In my only room with two trvs and a master temp sensor, both the trvs turn on and off within 30 seconds of each other.
  • The Tado faq “How does tado° control radiator heating systems with a central thermostat?” is not 100% helping. It states that the thermostat measures for the TRV in the same room. But it is not stating how it uses multiple TRVs in the room to reach or keep the set temperature, individually or as one group.

    “3. tado° controls the boiler, and Smart Radiator Thermostats are installed in all commonly used rooms (recommended)

    All rooms are controlled individually. If there is a call for heat in any room tado° will turn on the boiler. The Smart Thermostat/Wireless Temperature Sensor measures the temperature for the Smart Radiator Thermostat in the same room.”

    if the TRVs do not use their own temperature sensor why even bother with buying Tado TRVs for rooms with a thermostat or temperature sensor? In that case dumb radiator knobs would perform (almost) the same. Thus it is logical to expect them to measure the temperature and use that info to selectively turn on/off the radiator (and/or control the flowrate).

  • The tado SRV is also required to turn the radiator on and off as required, not just supply a temperature measurement. If you replace that with a "dumb knob", you don't have any heating control at all.

    If you have a single rad with SRV, but use a room stat (as a lot of users seem to do as they find the SRV's temp. control to be poor), then you have one controlled valve (on the rad) with 2 temperature measuring devices in that room. If in the app you select the SRV as the device to use for measurement, then the room stat is doing nothing. If you instead elect to use the room stat (the whole point of installing it), then the obvious assumption is that the SRV is then NOT actually being used to measure the temperature. How otherwise could it utilise both measurements to control a single rad?

    If there is more than one rad with SRV plus a room stat, then there is an opportunity to look at all the measurements and try and adjust individual rads to create a more even temperature over the room, which, let's be honest, is better described as a zone since it is not necessarily restricted to a single room.

    Overall, I think the jury's still out on exactly how tado utilises more than one temperature measuring device in a single room/zone.

  • Agree, the SRV can turn off the heating and this is indeed more than a dumb knob.

    I am not sure what the usecase would be of using one thermostat over multiple rooms. If the temperature is reached in the room where the thermostat is, how would the other room reach it temperature, even if the TRV measures the temperature in said other room. I think there must be a thermostat or sensor per physical room. Combining multiple physical rooms in a “logical room” if all radiators have TRVs seems strange. But maybe I miss something.

  • Yes, I basically agree, one stat per physical room makes the most sense, but historically, there would be one stat for the entire house and I read on here that some users do try to segment the house into maybe just 2 zones/rooms, e.g. upstairs and downstairs which is far from ideal IMO. I want independent control in each physical room, but…

    When I first installed tado, quite a few years ago, there was a limit to the maximum number of possible rooms and so one had to combine them into zones. Maybe this limit has subsequently been increased, but it was a very real reason why several rooms had to be combined in that way.

    I must check what the current max. is as combining rooms into zones makes it hard, or impossible to correlate tado ‘rooms’ with HomeKit rooms. I know you can group the latter into zones, but apart from Apple’s dreadful UI in, their zones are just virtual groups and cannot have devices allocated to them, only to rooms within that zone, so back to the tado - HK correlation problem.

  • GrayDav4276
    GrayDav4276 ✭✭✭
    If you have more than 1 tado° Room in a "Zone" then logically you have more than 1 SRT in this "Zone"......however you can only select 1 device as the "measuring device" Therefore the tado° room that does not contain the "measuring device" cannot actually place a demand directly on the boiler. The "measuring device" is the only device in this multiroom "Zone" that can place a "heat demand" on the boiler. So the other tado° Room simply receives supplied "hot CH water" when the "measuring device" has requested a "heat demand" on the boiler. The tado° Room without the "measuring device" is not actually utilising it's internal temperature it doesn't/can't create an input which can be used to "average" out the temperature of this "multi room zone".
    It is more efficient and effective to have a "measuring device" per tado° Room and not a "multi room zone"......this obviously is dependent on the size of the house.
  • GrayDav4276 said "The tado° Room without the "measuring device" is not actually utilising it's internal temperature sensor.."

    That appears to not be the case. As I explained, in such a situation, one rad can be cold while another in that same room/zone is hot and that can only be due to each SRV still able to control its rad, independently of any others.

    However, what you say does make some sense. Perhaps, as you say, the elected 'measuring device' (let's call it the 'master') may be the only device that able to call for heat (or not) from the boiler, but the other SRTs ('slaves') perhaps do still have the ability to 'throttle' their rad. So these 'slave' SRTs can each reduce the temp of their rad, but not increase it above what the 'master' SRT has decided.

    I can see that being better than just all SRTs totally in sync as it provides some local control over the temperature in a largish zone and would fit with my observation that in such a zone the rads can be at very different temps. However, until tado themselves come clean on this, it is all mere speculation.

    Interesting test would be to see if any 'slave' rads are ever hotter than their 'master'. If they can be, then that refutes the above theory, but if it is observed that a 'slave' is NEVER hotter than its 'master', then that would support the theory as being largely correct.

    I must remember to test that this winter.

  • It is a good test to check all temperatures of both the measuring device and slave devices.

    Still it is possible that all Slave devices measure 22 degrees and the measuring device measures 20 degrees, and you want 21 degrees. In that case one or more TRVs would need to heat up even more. I would guess the effect of one radiator being hot and another one remains cool only happens when there is a difference in temperature between the slave devices, AND the measuring device has not reached its temperature.

    Indeed strange that Tado cannot explain here what the actual algorithm is…

  • samd
    samd ✭✭✭

    @UKenGB You said: Interesting test would be to see if any 'slave' rads are ever hotter than their 'master'. If they can be, then that refutes the above theory, but if it is observed that a 'slave' is NEVER hotter than its 'master', then that would support the theory as being largely correct.

    Surely, just as you might (should?) put a room stat in a location cooler than the rad's location, would you not wish to do so with the master TRV? I am sure that's what I did last winter when one of my Room stats went bust i.e. chose the cooler-located rad to be master. Unless I am thinking about previous systems I have used, do not some users deploy spare TRVs as room stats?

    If you put a 'Master' at the last port of call for heat in the pipe run and Slaves are never hotter.......!!!!!

    You are raising some very interesting questions - please continue - I would love to know the answers.

  • Order of rads in the pipeline cannot account for the effect I am seeing. It takes mere minutes for hot water to get around the entire system and my observation is that the difference between rads can last for hours.

    I've never seen the point of worrying about whether a stat is in a cooler or warmer part of a room. As long as the temp gradient is consistent, it will make no difference where the stat is as long as its temp is adjusted to suit.

    I also agree with tado that it doesn't make a huge difference whether temp is read from the SRV or a room/wall stat. The fact that the SRV is right beside the rad isn't the big deal many seem to think it is as the airflow will be upwards and not directly from the hot rad. There will be some effect due to heat conduction through the metalwork, but it makes less difference than often thought. I know some here claim they switched to a room stat and it made a big difference, but I have tried that and found it had little effect. It's just easier to read and adjust up on the wall rather than scrabbling around near the floor.

    Of greater importance is when tado decides to turn the rads on and off. Or somewhere in between which is another topic of debate and confusion obfuscated by incorrect info from tado. Also their 'early start' which sounds great, but when my bedroom began heating at 04h00 (about 3 hours early) when it actually takes about half an hour to get up to temperature, I had to disable it. Isn't it supposed to 'learn' how early it should switch on to ensure correct temperature at the set time and vary that depending on season, weather etc? I have no idea why it continued to be so utterly hopeless or whether they've improved it by now, which they should have managed after so many years, but I just don't trust them any more. Seems to be more important to add more 'bling' than get the heating working even as well as my old basic Honeywell programmer. Took tado years to realise they needed an overall/boiler on and off. Actually, come to think of it, they still haven't. The initial implementation of the 'All off' (heating off for summer) control also turned the hot water off. Brilliant. My pet chimpanzee could've figured out that was a dumb idea. If I had a pet chimpanzee that is. Which I don't. Regardless, do the tado developers actually use the system they are so (poorly) designing?

    Don't get me started on battery consumption or their claims of how much they've saved me when they CANNOT possibly know either way since they have NO possible way to know what my consumption was before installing tado. It's just marketing BS and no savings could never possibly exceed the additional cost of all those batteries. Should last up to 2 years they said. 'Up to' being the important part of that statement. I monitor usage and record every change in every SRT and get about 3 months. So with 12 rads, that's about 100 batteries a year. Yay! Look how much we've saved. Yeah right.

    Anyway, back to HomeKit automations…

  • Just another thought unless it's already covered earlier. is it definitely that the two tado trv's definitely don't shift within seconds of each other. Mine react within seconds of each other to each change that the wall stat is controlling for the living room with two tado trv rads, mostly even closer together still.

    I am wondering if perhaps they are and you dont necessarily hear them?, but the cold one has a dodgy valve where the pin is moving but not actually opening the valve, so perhaps is it that the hot radiator is actively heating at say 15% for single squiggle request, but the cold radiator requires something major like 80% well above three squiggles before a trickle is allowed through thus slow to heat even at high request?

    Perhaps when both are cold try taking both trv off then turn heating on full, monitor and see if both heat quickly to the same extent or is the cold one slow to get heat due to low throughput before its fully hot?
  • Still can’t help with your radiator issue but I’ve read here before that early start is designed for under floor heating, not rads. That’s why it comes on so ridiculously early when you use it with radiators. Don’t think it learns not to over time either. Not sure why Tado doesn’t make this clear.
  • No Phillip_PAL all rad valves are working perfectly. I can take it off and see it is intended to be where it is. Nothing is sticking. We have 3 areas with more than one rad (each with SRV) and they are all the same. I must point out, this is not the entire time. Often, all rads are at the same temperature. But sometimes (and for a long time so not just some built-in delay) they are very different.

  • johnnyp78, that's an interesting point about it being for underfloor heating as that is indeed much slower to react. But as you say, tado do not make a point of this and in fact, this is the first time I've ever heard it mentioned as a reason.

    Surely tado knows if it's underfloor or just an SRV on a rad? Anyway, how many times does it reach temperature 3 hours early before the system learns and adjusts the start time. Seems to me once is all it needs and then after that it's just fine tuning.

  • samd
    samd ✭✭✭
    edited July 25

    @UKenGB Given that I do not see other users coming forward with significant differences in temperatures reported by yourself, could I ask whether these occur within the same room or within zones of more than one room please?

  • I’ve been following this thread with interest.

    My living room has a wall thermostat and two TRVs and I’ve always wondered how tado works here.

    I’ve never thought to check the radiator temperature differences before but am going to now although I’ve never really noticed the temperatures being off what I’ve set.

    Typically the system isn’t activating atm with the summer temperatures but I’ll be checking when it gets cooler.
  • samd both. Any zones that do comprise more than one room, the doors are always open, so in any case, all one connected space. Still, it's not something I would do if tado allowed unlimited rooms - or at least more than they do.

    Or have they increased the limit in the last 5 years?

  • samd
    samd ✭✭✭
    edited July 25

    @UKenGB Not sure whether it's changed:

    How many rooms can I have in my tado° Home?

    Written by tado

    Updated over a week ago

    Besides the Internet Bridge, you can have a maximum of 25 heating devices in your tado° Home.

    So, in theory, if you have one tado° heating device per room, you can have up to 25 heating rooms in your Home.

  • So that appears to mean that it doesn't matter how SRVs are grouped into rooms, there's a simply a limit to the number of devices. But what's a 'heating device'? Does a room stat on the wall constitute a 'heating device'?

    In any case, there is at least one room with 2 rads (one under each window) and there's no way I want to control those independently, so they are both in a single 'room'. However, for the purposes of the max. limitation mentioned above, is that 2 'heating devices' or since grouped into a single 'room', only a single 'heating device'?

  • @UKenGB you really don’t want to spend any time finding out questions yourself isn’t it? If you click the link in the response of samd you would find the answers to your questions…..

  • Well, you're at it again MichielTado making this a painful place to be.

    Clearly you didn't bother to follow that link or you would realise the same as I did that it doesn't answer the question(s) I asked, hence why I asked them. I have explained to you before the purpose of a forum and I cannot be bothered to do it again. If you are so apparently incapable of grasping that, please, as I have asked before, just don't bother to post.

    Your type are the reason why I have steered clear of this forum for so many years, despite being so unsatisfied with what tado have produced. Thank you for reinforcing my previous decision.

  • You clearly didn’t bother to follow the link because there you would find the link to the question about how many devices can be added to the room and what constitutes a heating device. And you’re welcome :-).

  • Don't mention it. Now go and pollute some other topic in which I am not involved.