How to adapt current system into modulation-capable weather compensation system

FuzzyDunlop

Hi everyone,

I am looking to migrate my current setup to the tado ecosystem but I'm not fully sure about how to best go about this.

Some background: I have topped up my loft insulation, had external PIR insulation installed, my radiators powerflushed before installation of an Ideal Vogue Max - 32Kw combi, in addition to a wireless Hive thermostat.
I am wanting to increase efficiency and the performance of my system to achieve lower flow temps, reduced cycling and a more constant and comfortable temperature.
After some rudimentary research I think that the use of the tado system, smart radiator valves, in addition to a weather compensation kit would be ideal for my needs. I'm a little out of my element in terms of determining the suitability of this so any advice would be greatly appreciated.

As I understand, the current tado thermostats available in the UK (V3+) have removed the ability for modulation which would be something that I would be wanting, as opposed to a basic on/off system. I understand that there are ways around this for example, with the wired receiver available in the extension kit or an EU version.

Would the following products be suitable for use in my current setup in order to achieve a weather compensation system that achieves modulation?

https://www.screwfix.com/p/tado-v3-black-edition-wireless-heating-hot-water-smart-thermostat-starter-kit/701kg

https://www.screwfix.com/p/ideal-heating-weather-compensation-kit/6563x

Thanks for any help

None

I’ve had Tado ext kit running on my Worcester with Worcester’s external weather comp sensor for a while. On my setup if I want to run Tado in BUS wiring mode (thereby getting the benefits of TADO’s load comp) I noticed TADO will override the weather comp. I found TADO would push boiler flow temps much higher that what my weather comp heat curve would have permitted and then adjust down through load comp as it got feedback on demand from the temp sensor (and perhaps the Tado TRVS?) in the rooms. In that setup my weather comp was redundant. In the end I rewired the Tado to on/off relay mode -allowing weather comp to be in charge of flow temp and TADO for geofencing, advanced scheduling and general geekiness . There’s a good article on Heatgeek re. Weather vs load comp which convinced me it was worth ditching the Tado modulation benefits to allow the weather comp. As far as I can tell, if you are seeking truly integrated weather and load compensation you may be best considering your boiler manufacturers own advanced programmer although I’ve no idea if there is one for the Vogue. Also, regarding smart TRVS: I am planning to sell most of mine because trying to have any significant variation in room temps around the house whilst seeking lowest flow temps = excessive boiler cycling (on my typical system anyway). Therefore, what I saw as the main purpose of smart TRVS is now redundant, for me. Once you have weather comp dialled in, and if you manage to get the rads finely balanced, you ought to find your TRVS (smart or analogue) never need to kick in anyway (perhaps with the exception of south facing rooms on a clear day). Hope this helps

johnnyp78

I haven’t wired it in myself, but on an ideal vogue you have a separate connection for weather compensation next to Opentherm. If you’re wiring the Tado in relay it shouldn’t clash with the weather compensation, because that will be modulating the output. I still think you really only need one or the other, except for cases mentioned above like geofencing, where you can use Tado to put the heating in away mode when you’re not in the house.

None

I would expect your Ideal weather sensor will come with installation instructions but assuming it will be similar to my Worcester it is not a tricky job: a single cable, two core, between sensor and a dedicated weather sensor port on boiler.

The Tado to a boiler in relay mode: if your boiler has a 240v live and neutral supply ‘out’ you should able to power your Tado ext kit directly from the boiler. Then a single connection between port no. 4 on the ext. kit to the heating live relay port in the combi boiler. If you have an existing basic timer controller you may find the wiring is essentially the same.

There is no interference this way because the weather sensor is just a passive thermoresister the boiler is reading and using to select and vary a flow temperature according to the values of your chosen heat curve. Whereas the Tado (when wired in relay), is neither sending or reading information to/from the boiler other than ‘turn on burner’ / ‘turn off burner’ so cannot take over control of the flow temperature or modulate the KW power output when wired that way.

Useful wiring instructions here:

https://www.tado.com/all-en/professional-manuals

You want: Extension_Kit_Manual_-_230V_Relay_Installations.pdf

johnnyp78

Do you want Tado to modulate the output from the boiler? If so, as you said, you’ll need an EU wireless receiver, a discontinued extension kit or the wired/wireless thermostat (not the temperature sensor).

I’m assuming you’re going to replace the hive with the Tado. I’m not sure why you want a weather compensation kit as well? They are both doing the same thing but from different ends. The weather kit will either override the Tado or be overridden.I don’t think you’ll be able to use trvs that call for heat with it either in different rooms. Weather compensation usually runs the boiler at low output to maintain a constant comfort temperature. Tado trvs vary each room temperature according to your schedule.

FuzzyDunlop

Hi Johnny, thanks for your reply. I was aiming to use the weather compensation kit to modulate the boiler output, utilising the Tado for further features like geofencing, scheduling and radiator valves.
You're correct in that I'm getting confused! I thought that I would possibly be able to use both systems in a way that allows me to incorporate both of their features; the weather compensation kit as the boiler modulator and Tado receiver as a way of further adapting the system to my requirements. I wasn't sure if they would both conflict like you have mentioned.

Is there a way that you know of to gain additional features with a weather compensation kit such as geolocation and scheduling, or would I be best just utilising the Tado system on its own and its internal thermostat.

Thanks

johnnyp78

I think it’s either or. Tado uses its own form of weather compensation (from a weather forecaster, rather than a sensor) to adjust the boiler output, so you get some element of weather compensation with it anyway.

You could use Tado trvs without a zone controller and a weather compensation kit, but I suspect you’d get very low output to the rads so it would be difficult to set a heating schedule.

FuzzyDunlop

Thanks 'None', that's a great answer and what I was wondering as to the feasibility of achieving. That's good to hear that you have managed to get a your system running the way which you want it to in which it can allow weather compensation to regulate flow temp and tado to do the smart features. That's what I'm hoping for too!

I think I will have to do the same as you, in obtaining the weather compensation kit from Ideal (it looks like they provide one that is compatible with my boiler although I will double check) and then using a wired extension kit in a simar way to you.

Out of curiosity, how have you now wired the 2 systems into your boiler? Does the weather compensation kit have it's own connection and then how have you wired the Tado for On/Off relay mode and preventing it override the weather comp?

Thanks

FuzzyDunlop

Hi Johnny, thanks again for your reply. That's interesting to hear, I think I will order the weather compensation kit and then look into how to wire the Tado in relay.
After some thought and your suggestions I think I'll leave the radiator valves as they won't provide much benefit (if any) if used in conjunction with the setup I'm aiming for. I'd really like the Tado for the additional features, as you say like geofencing. I work 24/7 shifts and they don't fit a regular pattern unfortunately which makes setting any heating schedule redundant. I think for my circumstances geofencing would be more beneficial

johnnyp78

That sounds like a good idea to me. If you decide it isn’t to your liking you can always order trvs further down the line.

FuzzyDunlop

Many thanks again None for the information, it is a great help and sounds like you've got exactly the setup I'm after! Have you found it meets all your requirements and has there been any teething problems?

Just to confirm, you only have the wireless extension kit and your own Worcester weather compensation kit, no tado bridge or anything else? I'm just checking what I need to obtain before sourcing one of the extension kits.

Thanks!

johnnyp78

If you don’t have a Tado bridge then the Tado devices won’t work.

None

As per Johnnyp78:

Without a bridge your devices are not connected to the internet (I.e you need one)

I have:

- 1 temp sensor (acting as a thermostat in a reference room and, in my set up, the only device enabled with being able to call for heat). If I had wanted to put this in reasonable proximity to boiler I believe I could’ve wired this in to boiler instead of an ext kit and saved some money

-ext. kit wired to boiler

-bridge

xfield

Just to add to earlier comments, I have a Baxi boiler with weather compensation. When I wired Tado via opentherm I also observed it overrode the weather compensation. It would throw flow temps high when heat was first demanded, then ramp down. I was uncomfortable with this and chose to put tado back to on/off.

It's certainly disappointing tado can't read in the external temp from the boiler and take it into account, I'm sure the opentherm must give the insight. When I tested tado with opentherm I'd see flow temps of 80 degrees on a mild day in May, which felt excessive. The flow temp control on the boiler had no bearing on this.

I'm rolling into my first winter with this setup, and following six months of renovations on the house. I'll be tuning my programmes and monitoring the usage!

FuzzyDunlop

Apologies for my late reply, work and life have gotten in the way!

Johnny: Great, I thought as much but just wanted to confirm. Thank you for that.

None: Thanks for your reply. So your extension kit allows the use of the Worcester weather comp kit, can I ask then what the purpose of the internal temperature sensor is then? Is this as a fail-safe where you can ensure the room is at your desired temperature and request heat from the boiler if required?

I already have the weather compensation kit for my boiler; do you think if I were to purchase the V3+ Wired starter kit (https://www.amazon.co.uk/dp/B098B2W5GP?smid=A3P5ROKL5A1OLE&tag=pepperugc03-21&ascsubtag=2431582827) and wired it to the boiler in relay it would mean I could avoid purchasing the extension kit?

xfield: That's interesting to hear, yes I agree that it is disappointing that they have removed the features that allow for full modulation. Hopefully this will be something that they reintroduce for the UK market. The rest of the kit sounds great and they provide it elsewhere so it seems like a no-brainer to me!

How have you found your setup performing in the recent cold weather we have had? I would be interested to hear how the smart features have been for you both too with the weather comp.

Thanks again for your help. You've all been a great help answering my many questions!

DM932187

Just to reinforce the excellent replies from others, I have been running Tado with Viessmann weather compensation for almost 10 years (on a V1 (beta) set up).

My advice would also be to use either weather compensation at the boiler (WC), or load compensation (LC) from Tado, but not both, and which one you choose depends on the characteristics of your property (see Heat Geek).

Our house is about 2200 ft2, old and has moderate insulation (e.g. roof and majority double glazed windows, but not walls or floors). We also have maybe 60% radiators that are older (smaller), and some that are newer (and larger), which is relevant to effective flow temperatures from the boiler.

I find that WC works well with Tado in relay mode in our set up, but that features such as Early Start aren't particularly effective. For example, on a colder day, Tado starts earlier, but the boiler also runs at a higher flow temperature - i.e. both 'know' it's colder. You also can't be too aggressive on the away mode temperature set back, or the tight WC curve won't get you back up to a comfortable temperature. You have to take these things into consideration, and bear in mind that as with almost all thermostats, Tado is designed to improve efficiency on standard, fixed flow temperature boilers and not those with WC. In fact if you have 'full' (advanced) weather compensation (we have basic), then you don't want (or need) a thermostat at all because you can exactly match the boiler output to the heat load of the property and it will just sit there, 24/7. In this case, you do any set back with a temporarily reduced boiler flow temperature, not by a room stat target temperature.

I've not tried Tado load compensation (Opentherm). It's not available on V1 anyway, but I'm pretty sure it would override the Viessmann WC, making it redundant. In our case, that would be counter-productive as WC, rather than LC, is best suited to an older, less insulated and higher thermal mass house such as ours.

LC is also localised, in that it reads the load wherever the sensor is located in the property (think solar gain or secondary heat source), whereas WC takes its reference from the outdoor temperature at the property location. LC can therefore cause the property to under/overheat if the reference location does not reflect the whole property temperature.

However, you mention you've been busy upgrading your insulation. Unfortunately, this has never been cost-effective for us (so will have to wait until the next house). In your case, you may find Tado LC more suitable.

If you were to go with boiler WC though, assuming it's not advanced WC (where you can fully adjust the WC curve by slope gradient to reflect the property, not just by moving a fixed slope gradient up and down), and pair that with Tado, then my advice would be:

• Just have the Tado replace your room stat, and use this as a central 'high limiter' in the house - i.e. a switch for when the heating is needed. Don't go with the TRVs as I believe they do not modulate, but are rather on/off, which will leave you with a reduced emitter area and likely actually REDUCE your system efficiency, as with WC, you'll need to raise the curve to increase the boiler flow temperature to meet the heat load - see Heat Geek.
• Set the Tado temperature slightly higher than you want it, to keep the boiler modulating for as long as possible rather than cycling.
• Use only a small temperature set back when out and at night. If you go too low, you'll need to raise your WC curve on the boiler for recovery, and you'll then lose your savings from running WC.
• Don't expect Early Start to work very well.

If you're able to go with advanced WC AND your boiler has a wide modulation ratio, you probably don't need Tado (or any stat for that matter) at all if your house is very well insulated. Dial in a tight curve with boiler flow temp set back at night. Ensure your system is properly balanced. Set it and forget it.

Bottom line - most of the Tado features are not that useful if you have even basic WC, but as Tado is currently comparatively priced with any other reasonable quality room stat then you may as well get it for the geolocation (although bear in mind that's chargeable if you want it fully automated) and the ability to remote control, which is very useful with WC as you'll need to switch the heating back on quite early if you've set back whilst you've been away - 24H in advance is not uncommon in our house, but it depends on your interim heat loss.

Final point to note - with WC and Tado, we are running around 26,000 KwH annual gas consumption, which is a lot more than I'd like, but when you put it in the context of typical usage being 13,000 KwH, our property being on the lower end of insulation, and being about 2.5 times the size of a typical UK home (as I understand it), its actually reasonably efficient, albeit that it could definitely be better. Certainly no regrets going with our set up though.

Hope this helps.

Zamzoo

DM932187, or anyone else, what do you think would happen if your boiler (such as my Greenstar 30i) only range rates down to 8kW or so, while the whole house heat loss at -2.2 outside is 4.5kW?

Will weather comp struggle to match the output to the heatloss, meaning it will cycle anyway and lose the advantage of WC?

Zamzoo

Does the tado relay override the WC system call for heat? e.g. with Bosch Sense ii will it only function if the Tado system is attempting to heat the system, or will the WC controller also be able to fire the boiler? Perhaps this is a configuration option..

johnnyp78

I would think it depends on how your boiler prioritises calls for heat. On some boilers relay takes precedence over WC.

Zamzoo

So if the relay is off... the WC controller wont be able to do anything. I think that makes sense as to why other users have given tado a wide temp range in which to be "on" then.

johnnyp78

Yup, exactly. As far as I can tell the only benefit of having Tado with weather compensation is that you can use geolocation to turn off the heating when you’re not at home.