Question Multi zones with Nest thermostat

techno79

Active Member
I currently live in a property which has a combi boiler and a single heating zone for the whole house. I replaced the dumb thermostat for a Nest thermostat (3rd gen) when I moved in. I will be moving house in the coming few months and the new house will have a wet underfloor heating system (3 separate zones) for the ground floor, and radiators everywhere else.

My question is: Does my single Nest thermostat allow me to control all 4 zones (3xUFH zones + 1 radiator zone) or will I need to purchase a Nest thermostat for each zone?

I'd like to be able to control each of the 4 zones independently and remotely from my smartphone but I'd like a solution that is not going to be too expensive to achieve that. Should I stick with Nest or is there a better solution?

In case it makes a difference, I will be getting a Vaillant gas system boiler.
 

neilball

Well-known Member
If you want multi zone control with Nest then you need a Nest Stat & Heat Link for every zone.

And if you underfloor heating is a single manifold then also allow for a manifold wiring centre to make wiring the heat link to the thermal actuators plus dealing with the manifold pump & boiler demand signal easier - a Heatmiser UH4 would do the trick (assuming 230v thermal actuators) if there is not something suitable there already.
 

techno79

Active Member
If you want multi zone control with Nest then you need a Nest Stat & Heat Link for every zone.

And if you underfloor heating is a single manifold then also allow for a manifold wiring centre to make wiring the heat link to the thermal actuators plus dealing with the manifold pump & boiler demand signal easier - a Heatmiser UH4 would do the trick (assuming 230v thermal actuators) if there is not something suitable there already.

I'm not quite sure I understand all of that. Is it normal for an UFH system to use a single manifold? All I know is that I've asked for 3 separate zones for it. Not sure what a thermal actuator is either.
 

neilball

Well-known Member
How are you contracting to do the mechanical and electrical works. and are they co-ordinating with whoever is dealing with the controls? All three elements need close co-ordination and you will need to review their choices to make sure you are happy - location and mounting of room stat/sensor units (wall mounted with power from heat link, or wireless between stat and heatlink with local 5v power for stat) location and accessibility of the switching units (the heat links) and integration with the underfloor manifold valves/pumps, boiler, and any other zone valves & pumps as per of the wider system. Are you also wanting hot water control (if using a hot water cylinder)?

Nest is not the cheapest, but the stats do look really nice. However it does not easily wire to your underfloor heating manifold without using an additional wiring centre (hence why I suggested the Heatmiser unit).

If you want to go cheaper but with similar functionality then Heatmiser Neo may be worth a look. This gives you conventional looking room stats (wired or battery powered wireless), which can be used with all forms of heating, and includes timeclocks for hot water. Add a Neo Hib and it can all be linked up to the Neo App for smartphone control.
 

techno79

Active Member
How are you contracting to do the mechanical and electrical works. and are they co-ordinating with whoever is dealing with the controls? All three elements need close co-ordination and you will need to review their choices to make sure you are happy - location and mounting of room stat/sensor units (wall mounted with power from heat link, or wireless between stat and heatlink with local 5v power for stat) location and accessibility of the switching units (the heat links) and integration with the underfloor manifold valves/pumps, boiler, and any other zone valves & pumps as per of the wider system. Are you also wanting hot water control (if using a hot water cylinder)?

Nest is not the cheapest, but the stats do look really nice. However it does not easily wire to your underfloor heating manifold without using an additional wiring centre (hence why I suggested the Heatmiser unit).

If you want to go cheaper but with similar functionality then Heatmiser Neo may be worth a look. This gives you conventional looking room stats (wired or battery powered wireless), which can be used with all forms of heating, and includes timeclocks for hot water. Add a Neo Hib and it can all be linked up to the Neo App for smartphone control.

I have instructed a building renovation company to manage the whole project. The guy who owns the company is the PC (project co-ordinator) but he doesn't do any of the hands on work. He has a team of people and sub-contractors to do the various parts of the work. I haven't had a detailed discussion with the PC yet about the exact details of the heating system. I'm just trying to do a little bit of background understanding myself so I can go into that discussion in a more prepared fashion. The PC knows the high level details of what I require:
1. Gas system boiler with hot water storage tank
2. Wet underfloor heating system and for what area of the house.
3. Radiator system for rest of the house.
4. Fully smart controllable via phone/internet

While I have done some research already on what brand/model I want for some parts of the system (e.g. with the system boiler and storage tank). I do not know brands/models for other parts such as UFH system or what brand the smart control aspect is.

As long as it's a good system, then I'm okay. As I already had a single Nest Stat, I thought I might be able to save some cost by using that but sounds like it might be cheaper to go with another solution that to stay within the Nest Stat world.

At some point in the future, I'd like to setup Home Assistant for all my smart things, so as long as whatever is obtained integrates with Home Assistant, then I think I'll be okay.
 

mushii

Distinguished Member
I think that I would be looking at Honeywell EvoHome rather than Nest. It will give you the level of control that you are looking for. Nest does not really fit the bill well for multizone heating control, beyond 1 or 2 zones.
You would need the HCC80R to control multiple manifolds.
 

Seb Briggs

Well-known Member
As @neilball has mentioned getting a Heatmiser UH4 wiring centre can simplify a lot of the logic and doesnt necessarily mean you have to use heatmiser for every other part of the install.

We have used HeatMiser UH4 with Fibaro Zwave relays and no traditional zone stats but just temperature sensing in each zone however there are many other similar solutions

If its of any help here is one of our "famous" wiring diagrams that may give you a better understanding of what is going on. This is the 8 zone version of the Heatmiser UH4 the principle is the same.

In simple terms if any zone calls for heat whether triggered by a stat or a zwave relay then not only is the actuator for that zone opened, but also the boiler is enabled, the UFH pump and valve are also triggered. This is all automatic and needs no programming. Finally both the UH4 and UH8 have their last zone (4 or 8) able to be a radiator zone but works in a similar way but the rdiator valve is opened. If no zone is calling for heat then the boiler is switched off and valves and pumps are stopped.

They are not expensive and do help simplify all the logic.
1602156590712.png
 

Onlydiy

Novice Member
@Seb Briggs you have explained this very well and it clears a lot of my doubts. I have a question and maybe able to get help here. I have a combi boiler and currently have 2 heating zones. One is for the standard heating for the entire house and the other is for the manifold. My plumber created these 2 zones by splitting the water flow from the boiler into 2, one going to the entire house and the other going to the manifold for the underfloor that is for part of an extention. These two zones are controlled by a honeywell 2 port motorised valves. So when the underfloor temp is reached the motorised valve doesn't send water to the manifold. Now i am getting a new extension and would be getting underfloor heating laid there. The manifold has the option of creating 4 zones. My question s
1. With all the discussion above, it seems that instead of getting a motorised valve befote the manifold the plumber should have added an actuator head for the first zone. Is that correct?
2. Now to get a new zone, would i have to remove the motorised valve and change the manifolds first zone with an actuator?
3. For the new second zone in the manifold, i would have to add a second actuator, is that correct?
4. Going with what i see above, i can use a heatmiser UH4 wiring box for these 2 zones and if I want to use hive thermostat then I would have connect a receiver to the wriring box (one for each zone in the manifold) and then the thermostat would be able to control that actuator, is that correct?

Please advise.
 

neilball

Well-known Member
Hi can anyone help on my above quert?
Can you make it clearer as to what you are trying to do, from you description I’m unsure if you are expanding an existing manifold or adding a new one.

If it is a new manifold then is it having its own dedicated circuit from the boiler (with a new 2-port valve like the other circuits)?

I’d suggest keeping the main 2-port valves on each primary circuit so you can use the internal end-switch to trigger your boiler, which will also help make the wiring a bit easier to manage as you are not creating any dedicated wiring diagrams for installers to follow (or that they are creating to provide to you), and make tracing which part of the system is calling for heat easy to identify.

It’s still just a collection of switches either in series or parallel, so is electrically very straight forward, but it often quickly becomes overwhelming for non-technical uses or heating engineers without a reasonable level of experience in multi-zone systems. These installers are also easily put off by “smart” controls as they see them as unfathomable black boxes that do all kind of strange things rather than just treating them as the simple electrical switches that electrically are no different to the standard devices they replace.
 

Onlydiy

Novice Member
Hi, this is an existing manifold and I am adding a zone. So currently from the boiler there is a split, one goes to the regular radiators and one goes to the manifold that currently has one zone of underfloor heating. On each part of the split there is a motorised valve with its own thermostat receiver. The existing zone that underfloor manifold sends hot water doesn't have an actuator. I guess the new zone would need to add an actuator and a receiver for thermostat, but I also think i would need to do the same to the existing one as well. But i am not sure is what should i do about the motorised valve, would i still keep it? And connect that to the wiring center at the same place where the motor would be connected or remove it completely?
 

neilball

Well-known Member
You definitely need to add thermal actuators to the loops on the manifold, so that the rooms can be properly controlled independently. If the manifold has a mixer and manifold pump then you also need to run the manifold pump whenever either zone needs heat, plus ooen the 2-port zone valve (which I would keep if it were me), give the boiler a demand signal too.

I’d suggest you will find it much easier to use something like a Heatmiser UHF wiring centre to make wiring simple and straightforward otherwise you are going to need to use some relays to hook everything up and keep signals electrically isolated from each other.
 

Onlydiy

Novice Member
Thanks, I guess I have understood whatv you mean. I have attached a diagram of the existing setup. Point 1 on the manifold is being used but without am acctuator and point 2 is the zone being added. So if i add a heatmiser uh4, I add the 2 actuator for the 2 zones on the manifold and move the manifold pump and valve to the new wiring centre. Is that correct?
If yes, then 2 questions.
1. On the heatmiser wiring diagram i see it says connection for pump/valve, so should I connect both here?
2. Should i continue using the old wiring centre for the other valve used for radiators, or move that to the heatmiser as well and connect it to the zone 4 port as it states it can be connected to radiators?

Please advise.
SmartSelect_20210223-033126_Samsung Notes.jpg
 

neilball

Well-known Member
It does not really matter which way you go as either will work, but if you keep existing wiring centre just make sure that you clearly label if you have to isolate power from multiple points to make it all safe. I always ensure that all heating plant and controls that are inter-connected have a clearly labelled single point of power isolation in my installs rather than having to isolate at several points to remove all sources of power.
 

Onlydiy

Novice Member
It does not really matter which way you go as either will work, but if you keep existing wiring centre just make sure that you clearly label if you have to isolate power from multiple points to make it all safe. I always ensure that all heating plant and controls that are inter-connected have a clearly labelled single point of power isolation in my installs rather than having to isolate at several points to remove all sources of power.
Thanks Neilball, what would you say about my first question. Btw, ordered the heatmiser uh4 and 2x heatmiser actuators :)
 

neilball

Well-known Member
You would normally use the UH4 pump output for the manifold pump, and you could wire the existing 2-port valve there too. You would then need to use the boiler output on the UH4 to replace the end switch connections (orange & grey) from the two port calcs to fire the boiler if your UF calls for heat.
 

Onlydiy

Novice Member
You would normally use the UH4 pump output for the manifold pump, and you could wire the existing 2-port valve there too. You would then need to use the boiler output on the UH4 to replace the end switch connections (orange & grey) from the two port calcs to fire the boiler if your UF calls for heat.
Hi Neilball, I have all the UH4 wiring centre and the actuator, but am getting confused with the wiring. looking at the UH4 wiring diagram the wiring for actuator, the power and the thermostat included seems simple. Butthe bolier, how do i connect that to the UH4?

I see the boiler has 5 wires coming out of it and on the old wiring center it has 2 wires(black and brown) connected to the Line, blue connected to Neutral, green to Earth and then there is a greyish one connected to a port that has one of each connected to the two 2 port honeywell value (one valve for the radiator and one for the UFH) on the UH4 it shows 3 ports (LS, E & LR), so which of the 3 bolier wire go on it and what do I do with the remaining 2. also says volt free on the UHF what is that. so confused.

Again the 2 port honeywell Value has 5 wires, if I connect it at the same place as the UFH pump I would be left with 2 spare wires, what do I do with that?
 

neilball

Well-known Member
Are you now using just the UH4 to replace you original wiring centre for all heating wiring, or just to control the UFH?
 

neilball

Well-known Member
Well if you are only using it for UFH then just leave the grey and orange wires on the 2-port zone valve as they are because presumably they already call on the boiler when the valve opens just now...
 

Onlydiy

Novice Member
Well if you are only using it for UFH then just leave the grey and orange wires on the 2-port zone valve as they are because presumably they already call on the boiler when the valve opens just now...
Yes, but it calls the boiler when the thermostat triggers the request and that too because the UFH as a whole currently works as a separate zone. And when i open the new zone within the UFH manifold, i would need to operate as 2 zones and that was the whole idea of getting this heatmiser uh4 so that i can plug in an actuator in the first zone and connect that to the existing thermostat and then connect another actuator to the new zone and connect a new thermostat. So when either of them call for heating, the existing valve opens up and the pump kicks in.
 

neilball

Well-known Member
You sound like you are getting confused - the original 2-port valve feeds the manifold, and with the UH4 wired correctly will no longer triggered by any thermostat directly.

You should have two thermostats for the UFH, wired to Zines 1 & 2, and new thermal actuators wired to the zone 1 & 2 zone outputs. none of this has anything to do yet with the manifold pump nor the original 2-port valve.

When either of your stats call for heat and trigger their respective thermal actuator you will also see the pump output on the UH4 trigger, and it is the switches pump output that you connect to both your manifold pump and the switched live/neutral/earth of the original 2-port valve that feeds the manifold.

The original 2-port valve has a mechanical switch within it that operates across the orange and grey wires, with turns on when the vance is fully open, and if you’ve not disconnected these wires they should already be wired to operate the boiler. So now when the manifold pump runs and the original 2-port valve opens you should see your boiler run, and when Zone 1 and Zone 2 switch off the manifold pump will stop and the original 2-port valve will close, and if none of your her heating and hot water zones are calling the boiler should also shut down too.
 

Onlydiy

Novice Member
So what you mean is keep the valve connected on the old wiring center as it is? but then how do I connect the bolier to the new UH4, it can either be connected to the old wiring center or the new, or can it be connected to both? :(

BOILER WIRING that I have is:

I see the boiler has 5 wires coming out of it and on the old wiring center it has 2 wires(black and brown) connected to the Line, blue connected to Neutral, green to Earth and then there is a greyish one connected to a port that has one of each connected to the two 2 port honeywell value (one valve for the radiator and one for the UFH). On the heatmiser UH4 it has 3 ports (LS, E & LR), so which of the 3 bolier wire go on it and what do I do with the remaining 2. also says volt free on the UHF what is that. so confused.

I am extremely sorry if I am making anyone feel frustrated with my questions. :(
 

neilball

Well-known Member
As long as the power for both the old and new wiring centres are from the same supply (so that both are powered off together from the same isolator) then it’s not a problem that the 2-port valve live/neutral and earth are on the UH4 but the hey/orange of the valve end switch go to the old wiring centre. If you prefer you can remove the orange and grey wires for the valve and replace those connections to the old wiring centre with a new two-core cable connected to the boiler volt-free output instead. Either way will see the boiler fire when either of the new UH4 zones call for heat.
 

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