Which new thermostat to fit? Radiators now, UFH soon as well

[tonetone]

Hi All

Apologies if this is answered elsewhere, I couldn't see an answer but I may have missed it

I have a crap combi boiler thermostat, I would like to replace it. (It's in the wrong place, hardwired and not very capable)

We are having an extension built this year, and will add wet underfloor heating to downstairs, new rad upstairs to join existing rads. I am expecting to use a JG room pack (30msq) or similar (suggestions welcome).

In my last two houses I've fitted CMT927 wireless stats, but I'm not sure they will support the UFH which comes with its own stat/controller.

Can anyone suggest what I might fit to support the new UFH to be installed in the summer? Willing to replace TRV heads with digital ones, etc, to make system work properly...

Ta very much, Tony

 

[ericmark]

Start at the TRV head and boiler, then get a thermostat which will work with them. I am told the Drayton Wiser TRV can have occupancy detection, not sure if this is true? And some boilers have dedicated ebus, some use opentherm, and some have only on/off controls.

UFH has a pump which circulates the water and adds hot water to the circulating water to maintain the temperature, there is normally a limit of 27°C on the floor so often the UFH is uncontrolled as far as room temperature goes, and the radiators control the room temperature, some systems can be rather complex, big problem is it takes so long to heat up and cool down. So any thermostat needs to work out time taken for changes, once heating over shoots it takes ages to cool down again, some thermostats have UFH option so it plans well in advance, think Nest has this. Sure many others also do.

So there is a reason why we refer to the guy who fits central heating as a heating and ventilation engineer, I am not one, I am an electrical engineer, but I realise how hard it can be to plan a system, the old way was select a room on ground floor which has no outside doors, and no alternative heating as a key room where the thermostat is fitted, the lock shield valve was trimmed so that room takes the longest to heat, so the TRV can adjust the heating in all other rooms. However once you start to have a sequence of heating, and each room is independent that does not work.

So in the morning in my house the living room kitchen and two bedrooms are heated, the bedroom heating stops by 9 am and the dinning room does not start heating until 4 pm. I still use the hall as key room, not ideal as outside door, and stair case, but what ever room I select there are problems, living room, dinning room and kitchen also have outside doors. So it is a compromise.

So fit EvoHome or the like and I am sure it will work, but at £60 each for programmable TRV heads that can connect to main thermostat it becomes expensive, so I am doing it on the cheap, using £15 programmable TRV heads, and it works near enough, but not perfect, and only you can balance between cost and performance, and you have not said what boiler.

With Bosch they don't have OpenTherm so your selection is limited, they may work as good or even better to OpenTherm enabled boilers, but unless you have two houses with families with identical life styles how would anyone know? There are loads of systems which will control the home spot on, however which will control spot on and use the least fuel is another question which likely you don't care about or you would not be installing UFH.

I like the idea of Hive, however also likely the idea of Nest with Energenie TRV heads but found the heads do not follow Nest as claimed, and heard Hive also has a problem with Heads loosing the wifi connection and not being powerful enough, hind sight and that is always easy, wish I had gone for EvoHome.

 

[muggles]

What make/model boiler do you have? Are you intending to keep it?

 

[tonetone]

What make/model boiler do you have? Are you intending to keep it?

It's an intercombi - we have to keep it for now, as a repalcement will go where the cooker currently is (one day). I figure the thermostat fitted this year will work with any combi...

 

[muggles]

Good boiler, keep it for as long as you can. It's still manufactured, with a few minor tweaks, as the Intergas Rapid. It's also OpenTherm compatible, so look at OpenTherm controls for best efficiency. EvoHome with the OpenTherm bridge would be a great fit if you want full zone control.