Upgrading to smart heating… 4 zones

[BobbyDavro100]

Hi All

After some advice from people who may have encountered similar before. We’ve moved into a new property that has been developed over time. Part of the house is on modern Heatmiser UFH which works fine. The older part of the house is on traditional radiators, controlled by 4 thermostats and motorised valves, all operating through a Honeywell ST9400C programmer (also controlling HW).

3 of the stats are battery powered with two wires (live and I presume, live to boiler) - when the programmer is off, no power goes through the live to thermostat and then boiler. The 4th thermostat is wireless - when the house was renovated, there must have been an old stat where the UFH now sits so a wireless receiver was put in it’s place, controlled by a stat on the other side of the house.

I am looking for a simple replacement with smart system but the fact that one of the stats operates wirelessly when the others are wired is confusing me. I’ve experience with Tado in my last house which worked fine as do I with systems such as Hive. It seems pretty straight forward to replace the programmer with the central controller for one of these systems and the same for the 3 wired stats… but what about the 4th as it’s the wireless receiver thats needs replacing (and putting a stat on there would not work given it’s a completely different side of house)? I would presume Tado/Hive or similar would need the received installed too for this 4th stat but that would then end up running through the mail received (currently the ST9400C.

Any advice appreciated - am not tied to any specific system but trying to get all on one if possible (I would have gone all Heatmiser given that’s what UFH is currently on but these need permanent power rather than battery operated).

Thx

 

[Taylortwocities]

Step in @ericmark !!
@BobbyDavro100 get your popcorn out and settle in for an evening's tutorial!

 

[RandomGrinch]

Part of the house is on modern Heatmiser UFH which works fine.

What Heatmiser system do you have?
Some of the new WiFi systems have a zone, or two available for rads.
A battery powered neoAir stat would directly connect to the Heatmiser wiring centre.

The older part of the house is on traditional radiators, controlled by 4 thermostats and motorised valves,

Do you really require four zones?
This may depend on the size of the property, but some suggest that moving to a system like Wiser and their smart TRV's virtually makes zones redundant.

 

[ericmark]

As to UFH the normal is a wiring centre

which can have multi thermostats, and is basic a hub controlling all, as to how to automate that, not sure, there is normally a pump for the UFH independent to main central heating pump, which ensures water is circulated at around 30ºC and hotter water at around 70ºC is added to it to maintain the temperature, and that wiring centre is full of relays, and is well over my ken on how best set up.

Using radiators we also use motorised valves, this type is hard wired and has a micro switch inside to tell boiler when to run and is simple on/off, and this type has no micro switch and is analogue, so slowly turns the flow up/down, and the boiler uses the return water temperature to work out how much to modulate, (turn down) once the boiler has turned down to as low as it can go, then is starts to use a mark/space ratio, (turning on/off and adjusting the off time) but the boiler will not turn fully off.

So we can use a hub or wall thermostat to do that, and use higher quality motors on our valves (TRV) so typical to left wifi linked TRV heads, centre wall or free standing thermostat, and to right the hub. But since both this and this do basic the same thing, seems in the main a little pointless to use both. The TRV head is made by many manufacturers and is in the main the unit which is most important in the system. Each one seems to use a different hub, and often the hub also does other things as well, and not much good asking the person who fits them, it is the user who knows how well they work, and the aim is only to have one app to work all, so once we have selected one make, we tend to stick to it. However the likes of the google "Home" app can bring different makes together.

Likely you do not need expensive TRV's in every room, in 2019 (before brexit) I got 5 of these bluetooth heads for £15 each, they use degs C to set them, and can be set as to when to heat and can also be manually set, which is important as likely not everyone in your home will walk around with a phone glued to their fingers, these were more expensive, and little can be set without a phone or PC, one of the few which can be controlled with a PC without an emulator, were sold as being compatible with Nest, but are not, so wifi rather than bluetooth so multi people can control then wireless and can be set to geofence using IFTTT, Wiser also use IFTTT to work the geofencing, the Nest works direct, but is useless as can't set the distance.

Wiser and Nest can use OpenTherm, but Hive can't since my boiler does not support OpenTherm rather pointless, the Wiser and Kasa both show performance, so I can see the response time, but this is also controlled by the insulation in the home, size of radiators, and size of boiler, so for me to use geofencing does not work, as radiators and boiler are too small, for me simple time works better, and a sequence of heating rooms in the order they will be used in, but my boiler is oil, and does not modulate, it is either on or off. mother house had a Bosch boiler with no way to control modulation other than the return water temperature, and the first of the smart TRV heads worked well the radiators would in the main stay just warm enough to maintain the room temperature, so next to no hysteresis, however the anti-hysteresis software in the heads was OTT, so would set to 22ºC at 7 am and 20ºC at 8 am to defeat the OTT anti-hysteresis software, this mean the geofencing would not work.

Wiser claim their TRV heads work out how long it takes to heat a room, so you set temp and time you want to use the room and it works out when to start heating the room. A TRV motorised valve turns up/down which suits a modulating boiler, the old motorised valve turns on/off and not really suitable for use with a modulating boiler, however EPH make a thermostat designed to work with the old valves, up to 10 valves, and still use OpenTherm, but what I don't know is how OpenTherm will work with the UFH.

There is a reason they call themselves heating and ventilation engineers, I consider an engineer is some one with a degree, i.e. trained over level 3, yes I am an engineer but electrical not heating and ventilation, you pay them a lot of money, but they can save you money by working out cheapest way to get what you want.

Without the UFH I would say Wiser, Tado, or EvoHome was the way forward, they all use TRV heads linked to a hub or thermostat and have OpenTherm. But with UFH the whole idea is to never turn it off, but with radiators we are looking at recovery times, the two systems are so different can't see how they can work together.

 

[BobbyDavro100]

Wow, very detailed explanation - thanks! To answer some of the questions

Heatmiser system is the NeoStat v3 and are all connected to the NeoStat hub - this works fine and is independent from the older (radiator) system - it is linked directly to boiler so bypasses the old programmer and system. Whilst ideal to have this on the same thermostat system as the radiators, it’s not 100% necessary.

Do we need 4 zones - probably not but I wasn’t planning on changing all of this at this stage. The system does work so I was hoping just to make changes at the thermostat side if possible.

On TRVs, most of the radiators are boxed in (not ideal but we are not going to rip these out) so TRV will read incorrect temp. Looking at most of these systems, you can pair these to a room thermostat so the stat becomes the controlling device but it starts to get pretty expensive!

Hence, looking at the options of just replacing 4 stats with smart stats, programmer with smart programmer but that leaves the issue of the 4th stat which is wireless and how do we connect this… Can you hvae one receiver feeding another receiver on these systems?

 

[RandomGrinch]

Hence, looking at the options of just replacing 4 stats with smart stats, programmer with smart programmer but that leaves the issue of the 4th stat which is wireless and how do we connect this… Can you hvae one receiver feeding another receiver on these systems?

There are many options for how you could proceed.

It's possible that there is a hidden wire behind the existing stat (we often see that on this forum), that could be utilised to supply mains powered stats.
What are your existing stats, could you post a picture of the wiring behind them?

Also, are your wall mounted stats in a decent position? - if not, they could be replaced with WiFi stats; the wiring could be ripped out back to the zone valves and the receivers installed there.

You say you don't want to mess with the zones now, but it's worth having a think - combining zones would be simple to achieve, and could save you the cost of replacing an extra thermostat, or two.

If you do decide to stick to the four separate thermostats - have a look at Tado.
They support multi zone heating via the app and come in a 'Wired" version - battery powered to replace your twin wired stats, or the Wireless version, that would replace the wireless receiver and can also control hot water.
They are also compatible with Tado smart TRVs.
This is good for keeping all your controls (apart from UFH), under the same ecosystem.

 

[BobbyDavro100]

Thanks RandomGrinch.

There are neutral wires present (disconnected) behind the stat but my electrician/plumber is not being particularly helpful in tracing where they go (I presume behind the programmer but it’s beyond my skill level). I have been thinking Tado (have prior experience in a much simpler setup) and looking at Tado X when it becomes available. But, it leaves the issue of what do i do with the existing wireless thermostat today… If i understand my setup correctly, 3 stats are connected to the programmer (if i turn programmer off, the live input for all stops). The 4th one is wirelessly connected to a wireless receiver box which in turn is also connected to the programmer. The Tado receiver unit will replace the main programmer but what would i then replace the wireless receiver with for the 4th stat? Can you stack two Tado receivers on top of each other, one connected to the other? Simple diagram from my understanding of current setup below!

 

[RandomGrinch]

The Tado receiver unit will replace the main programmer but what would i then replace the wireless receiver with for the 4th stat?

You're over thinking this.
The Tado wireless receiver would replace the existing programmer.
This would control the Hot water.
The existing heating connection from the ST9400C would be 'linked out', i.e. all the 'wired' Tados, would be live, ready to turn the heating on whenever - there is no need for a separate programmer.
The C/H controls from the Tado wireless receiver, would link to the zone valve of your existing wireless receiver.

 

[BobbyDavro100]

Ah, OK - this makes sense (I think!). So I hardwire the existing wired stats so they bypass the programmer all together - these are permanently live on one side. The wireless Tado system (plus receiver) would then replace the existing WiFi receiver and have HW connect to this too… corresponding WiFi receiver can then go anywhere…

To remove the existing programmer, I assume simply bridge the existing live into the STC9400 with the output to the stat (HW ON) and this then sits behind the new receiver (possibly a job for the electrician).

 

[RandomGrinch]

The wireless Tado system (plus receiver) would then replace the existing WiFi receiver and have HW connect to this too… corresponding WiFi receiver can then go anywhere…

Basically yes, but 'anywhere' will mean a location between the ST9400C and the existing wireless receiver/zone valve/wiring centre (depending on what you have).
There is usually a mass of wiring behind the programmer, so it is normal for the new receiver to go there, but it really does depend on the layout.

To remove the existing programmer, I assume simply bridge the existing live into the STC9400 with the output to the stat (HW ON) and this then sits behind the new receiver (possibly a job for the electrician).

If you would like to post a couple of pics of the location of the zone valves, receiver etc. and the wiring behind the ST9400C, we may be able to advise further on the wiring.

 

[ericmark]

You can get TRV heads with remote sensors

not used, so no idea how well they work, the idea is to put the TRV in the natural flow, so mounting upside down may help it sense the return air, or even a simple baffle.

@RandomGrinch is right (as usual for him) you can over think it all. I have many times, with a TRV you stop the room over heating, even with a simple one, so the aim is two fold, one stop boiler running when there is no where needing heat, and make it run when some where needs heat. Putting in multi wall thermostats in parallel and ensure the latter.

I have a thermostat in the hall, and one in living room, hall ensure rest of house kept warm when sun hits the living room windows, living room one keeps living room warm when hall takes too long to cool.

My cheap TRV head, cost me £15 each in 2019, allows me to turn off rooms when not in use, can set to 10ºC and 30ºC if you want, but it means you can set times, so bedroom not heated during the day, and dinning room not heated during the night.

I find the thermostats rarely agree with each other. This is from Google Home, showing my hall TRV, and hall wall thermostat, 2.5ºC difference, so I have set them 2ºC apart, living room is the same, two TRV's and a free standing thermostat, well it is at the moment, trying different locations, be the TRV in a box, or behind a settee, or under the dinning table, often they are not in the ideal place, so you just set them higher or lower to compensate. 9.2ºC outside now, my central heating is not that good, so have to try making a silk purse out of a sows ear, only had second thermostat for a week, so still experimenting.

But yesterdays report from my thermostat helps unfortunately only the wiser wall thermostat and the Kasa TRV show a graph like this, the Nest Gen 3 is rather useless. Only shows how long it was switched on each day.