Combi Boiler to Nest , Please help!

[Captain Nemesis]

What would you tell a radiator to do?

You are looking at it the wrong way round.

Id tell it to go on/off/more/less.

I would not have it tell me (or another device) that I (or another device) needed to do something to make it go on/off/more/less.

Imagine starting with a blank sheet. Where would you think the best place would be for a thermostat measuring and responding to the temperature in the room - somewhere where it is best positioned to measure the temperature of the air in the room that is felt by the occupants, or right next to the device which is producing the heat?

If you had a water heater and you wanted water delivered at a particular temperature at the end of a pipe run, and that temperature might vary and the losses in the pipe might vary, where would you measure the temperature of the water to decide how to adjust the heater? At the outlet of the pipe or the inlet?

If you had an automated lighting system controlling floor uplighters which washed and reflected off the walls and the ceiling and your target was a given light level on a table in the middle of the room, where would you put the measuring device that would provide on/off/brighter/dimmer signals to the lighting apparatus? Next to the lights, or on the table?

Surely the air temperature you experience in the room is what you want to control so you measure it where you experience it, not a few inches off the floor close to the radiator.

TRVs are what we used to use before we had anything better.

If when looking at a new control system to go into an existing system you find yourself saying "I wouldnt start from here" then dont.

If you find that you have an existing control which will fight the new one, get rid of it, dont leave it but set it to be on all the time.

 

[Captain Nemesis]

Mothers house cure was two wall thermostats in parallel, one in hall and one in kitchen.

How about one in every room where there is a radiator?

 

[Captain Nemesis]

The Energenie still make their own wall thermometer so I would assume that still works with their TRV heads, I can see your point, you set the wall thermostat and that in turns tells the TRV what setting is required, and as long as the boiler does not switch off, that in theory should work. But once the boiler turns off, it does not matter what the setting is on the TRV, it can not heat the room.

So you have this View attachment 217586 from the TRV, and if the target is above current valve needs to open and boiler to run, and if target below current valve needs to close, but boiler may still need to run to supply another valve.

If you can have a radiator valve open and close itself and also signal a boiler to fire/go off/modulate based on the temperature it is detecting then you can have a device on the wall which can tell a valve to open and close and also signal a boiler to fire/go off/modulate based on the temperature it is detecting.

So if any of the TRV's View attachment 217590 show current under target then boiler should run, and only when all are satisfied should boiler stop. There is no need for the wall thermostat to be connected to internet, only the TRV heads need to be connected to internet, so you set each room, and they tell the hub/wall thermostat if boiler needs to run, and that tells boiler.

Im not sure any of it needs to be connected to the internet. Yes you set each room. Yes the hub/wall thermostat tells the boiler it needs to run. No the wall thermostat does not measure the air temperature down at skirting board level next to a radiator which (this is real life remember) might be partially behind furniture or near an open window or door or nowhere near an open window or door which is significantly affecting the room away from the sheltered TRV.

 

[ericmark]

If you can have a radiator valve open and close itself and also signal a boiler to fire/go off/modulate based on the temperature it is detecting then you can have a device on the wall which can tell a valve to open and close and also signal a boiler to fire/go off/modulate based on the temperature it is detecting.



Im not sure any of it needs to be connected to the internet. Yes you set each room. Yes the hub/wall thermostat tells the boiler it needs to run. No the wall thermostat does not measure the air temperature down at skirting board level next to a radiator which (this is real life remember) might be partially behind furniture or near an open window or door or nowhere near an open window or door which is significantly affecting the room away from the sheltered TRV.

Now you are cooking with charcoal, it is called IFTTT (if this then that) and is a protocol used by the Energenie TRV and many other devices, not sure I really like the idea as the script telling things what to do is embedded in the internet some where, so lose internet and you loose control.

I did use it to get a forth switching slot with my smart sockets, but never really worked out how it all worked, I simply used a script already written.

I don't know if Nest Gen 3 is connected to IFTTT, however it does connect to Nest Mini and other things, so as you rightly say it is possible, but not sure if a good idea.

When we got the Nest Mini's they were to give us radio, as we don't have any VHF reception in this location in Wales, but they did work with the lights, however not quite as we wanted. A command hey google turn off music got the reply turning off 5 switches and all the lights went out, but hey google turn lights back on got a don't know how to do that yet. So lights were removed from the control of Nest Mini's.

My wife did try hey google turn up the living room heating and it did work, but the grand children think it's good fun to give google commands and then let us try to sort it out. Specially once they realised giving google a command took me out of the game I was playing on my tablet.

So yes you can do all sorts using IFTTT and voice commands with Nest Mini's, this

advert may be intended to take the Mick, but it is unfortunately what can happen.

 

[Captain Nemesis]

Oh I dont know - I must be missing something obvious that isnt obvious to me, because what seems to me to be the way to do it is to move the intelligence and decision making as far upstream as possible and for the elements to have less intellgence the further downstream they are.

So you have a controller/programmer/hub thing, and that knows what temperature each room is to be and when. Its programmed with its own interface or with an app. And if people want it, optionally with an app over an internet conection from a beach bar in Goa.

It receives room temperature information from a wall thing in each room. The wall thing may also usefully provide a way for the occupants to override the programmed temperature setting, via a knob or buttons or touchscreen if they dont want to use an app.

It therefore knows when to fire/modulate the boiler. It could do outside temperature compensation. It can learn how long each room takes to warm up/cooldown. It can open/close radiator valves either by talking to them directly or relaying through the wall things. It might usefully have an internet connection to do geofencing if people optionally want.

It would know that if someone had asked for their bedroom or other room(s) in the house to warm up earlier the next morning to preemptively close valves in other rooms to stop them warming up too early.

It can see the whole system, and make the best decisions on the combinations of boiler output and radiator valve settings to use.

The wall devices only know and care about their own room and may do as little as report temperature. Radiator valves just do what they are told. Internet connectivity is only needed if you want weather input, if you want geofencing or if you want to fiddle with things from a beach bar in Goa. And for remote control, including geofencing, "internet connectivity" is just comms link - no intrinsic need for any hosted services to be paid for.

 

[AngelaBrady]

Hi all
Thank you all for your help. I managed to hook it up as you guys advised:
ground to ground, neutral to neutral, live to live and 1 to 2 and 4 to 3.
The thermostat is always on but I can now control switch on with a simple " Alexa set temp to X"

thanks everyone for your help

 

[ericmark]

decision making as far upstream as possible.

Yes there is no point having a wall thermostat switch a boiler on if all the TRV's are closed.

I had a problem with my TRV heads in the hysteresis software was OTT. Clearly designed for a modulating boiler which rarely turns off, but set to 20°C at 7 am when been at 16°C over night, the raise to 18°C was fast, but from 18°C to 20°C rather slow, so cheated and set to 22°C for an hour then at 20°C and worked fine.

However if the boiler turns off before the TRV has reached target then clearly it never will reach target, to me the big question is why do we need a wall thermostat.

The TRV shows this on the PC, so we want some thing that says if any target below current then run boiler, there is no need for a wall thermostat, and in essence that is what evo home does and the cleaver bit where the algorithms say last time it over shot 1°C so this time start reducing the heating a degree earlier needs to be in the TRV head, which is the case with drayton.

But Nest can tell the TRV head what setting is required, although in practice only when manually changing through the app, it ignored it where schedule change or using dial, but it does not read the TRV to tell it when all the rooms are up to temperature, or allow an off-set to allow for fact wall thermostat mounted higher than TRV, so one is forced to remove the link, as it simply does not work, all you can do is program a schedule in the TRV and Nest wall thermostat which compliment each other.

I know price of eQ-3 has now rocketed since leaving EU, but my bluetooth version were £15 each compared with £30 for Energenie and the latter also needs a hub. So if the heads will not link to the wall thermostat may as well fit cheap Terrier i30 or similar, except that the Energenie on the program displays both target and current and the eQ-3 only shows target, and it has two sensors one air and one water so the latter should compensate for direct heat from radiator. But the cheap eQ-3 has window open shut down, and can be locally controlled, and tells you if pin stuck or travel to far or too little, so in many ways better than the more expensive model.

I have seen many reports on Hive, Nest, Wiser, Evo Home, tado, etc. But few reports on the TRV heads which is the main part of the system.

My Nest Gen 3 is wired off/on to an oil boiler, so I can tell you how it works with oil, but as to how well it works with OpenTherm with a gas boiler don't know. So it seemed Nest was not doing as I had told it to do.

It seems to have a mind of it's own, and clearly it only changed the Nest not the TRV heads so the changes resulted in no longer were the two lined up. I had some problems with the boiler locking out, so it thought boiler ran for long time with no temperature increase, I assume that is what caused the unit to alter and add to the schedule?

The 18, 18.5, 19 is because the wall thermostat is not that close to the hall radiator, so it tends to over shoot, so the stepped raise stops it over shooting, but go out and geofencing turns off heating, so still over shoots on return.

Hind sight maybe I would have been better with simple Hive, but hind sight is easy.

 

[Captain Nemesis]

to me the big question is why do we need a wall thermostat.

Because its a very good place to place a device which knows what the temperature of the air being experienced by the occupants is?

 

[Captain Nemesis]

Yes there is no point having a wall thermostat switch a boiler on if all the TRV's are closed.

But it never would switch it on, unless either the TRVs were on the fritz or they were not properly measuring the room temperature.

But Nest can tell the TRV head what setting is required, although in practice only when manually changing through the app, it ignored it where schedule change or using dial, but it does not read the TRV to tell it when all the rooms are up to temperature, or allow an off-set to allow for fact wall thermostat mounted higher than TRV, so one is forced to remove the link, as it simply does not work, all you can do is program a schedule in the TRV and Nest wall thermostat which compliment each other.

Is that another issue arising from trying to adapt/modify a control system by adding/replacing something into an existing system rather than starting with a clean sheet?

the cheap eQ-3 has window open shut down

Thanks for the warning.

Hind sight maybe I would have been better with simple Hive, but hind sight is easy.

But good for other people to use

 

[ericmark]

Because its a very good place to place a device which knows what the temperature of the air being experienced by the occupants is?

We have like most houses rooms with doors, and the radiators in each room naturally circulates air, so good place to monitor air temperature is the air returning to radiator, be it a fan assisted like a Myson or conventional with a TRV added, specially when the TRV has two sensors one which compensates for water temperature.

There is in theory nothing to stop one having a wall thermostat in every room, all wired in parallel, and a TRV in every room, the wall thermostat ensures the boiler runs when required, and the TRV stops any room over heating. However in practice I am sure one would find some rooms don't need a wall thermostat as the boiler would be running anyway. So in real terms likely more than one room with wall thermostat but not every room, and we know there are wall thermostats designed to run and master/slave configuration, so can even do that with OpenTherm.

My last house was designed open plan, and one thermostat between the living and dinning room next to archway could control the whole house, with some TRV's upstairs to stop bedrooms over heating if doors left open, not needed if bedroom doors kept closed, so yes a house can be controlled with one thermostat, but most houses do have doors, and the old idea was a thermostat in a room kept cool, so thermostat can be set low, so will not run central heating on warm days, on the ground floor as heat raises, with no outside doors, or alternative heating, but the problem is often such a room does not exist.

So we hunt for a compromise, and the more adaptable the thermostat/hub is the more homes it can be successfully used in, but we can control heating rates (lock shield valve) and stop over heating (basic TRV) but we can't control cooling rates. Also we tend to use rooms as certain times of the day, for example bedrooms at night and living room in the day, so we have all these programmable TRV heads so rooms only heated when required, then try to control the boiler with a single non linked thermostat, and it does not take rocket science to see the flaw.

My hall connects to 4 rooms, and is on the ground floor well OK middle floor but we don't use rooms under main house, but where the wall thermostat is could not really be more central, and it is affected by all the adjoining rooms, so would seem the ideal place, but the hall cools too slowly. Outside door in hall never used, so it ticks all the boxes, except it cools too slowly.

And in all but that open plan house, I have had a problem with the thermostat not turning on the boiler when required, be it sun in a bay window, wind direction, alternative heating like gas fires, only the open plan worked, we would come home, turn the thermostat up, switch on the 4.5 kW gas fire, and the main room was toasty warm within 15 minutes and we would within 30 minutes hear the Myson fan assisted radiator turn off. The house was designed to be heated by that single gas fire, but the gas fire was not thermostatic controlled, so as soon as warm would turn it off, and central heating maintained the heat in the house. No need for geofencing, or other clever thermostats, it was simply down to house design, but was a draw back, could not stop sound travelling, so not a perfect house.

However when I lived there I could not understand why anyone had a problem, it worked, only when I went to a house with doors did I realise there was a problem with some homes. The home before that one used gas hot air heating, and there were vents in every door for air to return to boiler, well suppose not a boiler when no water to boil, expensive to run, but again one thermostat controlled all.

So there is no one heating system suits all, but it is very limited as to which homes can be controlled with a single thermostat.

Oh and the open window on eQ-3 can be configured to what you want, it does not have to be used.

 

[Captain Nemesis]

There is in theory nothing to stop one having a wall thermostat in every room, all wired in parallel

Or all reporting back to a higher authority.

and a TRV in every room, the wall thermostat ensures the boiler runs when required, and the TRV stops any room over heating.

Any reason a wall thermostat cant stop a room overheating, or why an intelligent device reading the temperature from a wall sensor cant?

However in practice I am sure one would find some rooms don't need a wall thermostat as the boiler would be running anyway.

Id suggest that every room with a need to have its temperature controlled should have its temperature monitored.

so yes a house can be controlled with one thermostat, but most houses do have doors, and the old idea was a thermostat in a room kept cool, so thermostat can be set low, so will not run central heating on warm days, on the ground floor as heat raises, with no outside doors, or alternative heating, but the problem is often such a room does not exist.

As I keep saying - one thermostat per room.

So we hunt for a compromise, and the more adaptable the thermostat/hub is the more homes it can be successfully used in, but we can control heating rates (lock shield valve) and stop over heating (basic TRV) but we can't control cooling rates. Also we tend to use rooms as certain times of the day, for example bedrooms at night and living room in the day, so we have all these programmable TRV heads so rooms only heated when required, then try to control the boiler with a single non linked thermostat, and it does not take rocket science to see the flaw.

I didnt think it was rocket science to see the flaw in trying to control a boiler by only measuring the temperature in one place, i.e. trying to put an "intelligent" thermostat in one place to replace the traditional dumb one in one place, a design whose drawbacks led to the need for TRVs in the first place.

be it sun in a bay window, wind direction, alternative heating like gas fires,

If a room has been warmed by the sun or anything else, don't have the control system tell the radiator valves to open, or to tell the boiler to fire up, if no other rooms as measured by the sensors in those other rooms and guided by the schedule for those other rooms need heat input. Let the system get on with its job of controlling the boiler and the output of the radiators in order to keep each room at the right temperature.

but it is very limited as to which homes can be controlled with a single thermostat.

As I keep saying thats the very last thing I think is a good idea.

Ive got a 3 bedroom house, and as it currently is I can easily envisage an absolute minimum of 6 "wall thermostats", quite easily 8 as it currently is and quite easily a dozen after extending.

Oh and the open window on eQ-3 can be configured to what you want, it does not have to be used.