Replacing wall stat with wireless?

[ericmark]

You seem to be assuming that everyone has TRVs. However, if the wide range of non-thermostatic valves still offered for sale is anything to go by, that assumption is probably significantly off the mark.

I must say that I've never really understood how TRVs can really do what they say on the tin, given that they are sensing temperature so close to the radiator.

Kind Regards, John

I think the idea is that the radiator is analogue controlled so will be at a set temperature as long as heating not turned on/off by thermostat so once set it will remain close to temperature set as not setting to a fixed temperature but a simple number on the dial, however the electronic heads measure water and air temperature and compensate air temperature reading using water temperature. And when my valve head reports 20°C for the room a independent thermostat placed on the fire (not running) opposite radiator does show 20°C also.

I also tried moving thermostat before fitting electronic TRV heads, I bought

this programmable thermostat however unlike the original thermostat

The new one did not have a fail safe, so anything that blocks the signal, or flat batteries leave the boiler doing what ever it was doing before, where the Honeywell wireless auto closes down if thermostat not seen in 30 minutes. So I returned to house to find living room at 27°C, I tried moving the thermostat a few times, but the results were random, I had moved the Honeywell to bedroom and set the programmer so Honeywell worked at night and Horstmann set low temperature at night and 21°C during the day, to start with it seemed to work, all upstairs TRV turned to frost as mother could not get up the stairs. However too many times I would visit to either cold or roasting house.
Not trusting thermostats I did not want to repeat same thing, so tried a pair of electronic TRV heads, they took time to settle in, but then I moved Honeywell thermostat back to hall, and the Horstmann put in kitchen on side of oven carcase and it was set to give morning boost then off rest of day and hall thermostat the Honeywell controlled boiler during the day, all was OK unless front door opened.
So then fitted a standard TRV to hall radiator and once set so at same temperature as wall thermostat it all then ran A1.
However then mother got worse so we moved in, one bedroom the smallest worked OK and kept warm, the other at rear would get too hot, and front bedroom too cold, so we bought another two electronic thermostats, however it seems the fault was the valves not turning off fully not the heads. However now they have been exercised a bit they are working quite well.

As can be seen except for living room all rooms within a degree of setting and living room has a large bay window which catches morning sun which is why that room is higher than set, originally the sockets were used to control the alarm for my mother, which is why I got energenie stuff, since my mother's death they have been reassigned and work my bedroom lights.
Hind sight, and hind sight is easy, I should have fitted EvoHome but at the time I thought I could latter fit Nest which works with energenie however do not intend to stop here long.
The Honeywell thermostat is not really suitable as it has built in anti hysteresis software which starts to cycle the boiler as it gets near to set temperature, however to use a thermostat without it with wireless also means no fail safe, and I am too lazy to hard wire a thermostat, unfortunately my boiler is bosch which does not support opentherm I would have to use a Wave thermostat which would only control one room to use a modulating thermostat.
Although we are told we should use modulating thermostats, as yet not walked into a single house where I have seen one fitted.

 

[Roger465]

Thanks – several thousand pounds’ worth of work was done in my house (insulating the attic, replacing 20-odd “blown” double glazing panels, etc) free under the terms of a grant available here in N Ireland. I do seem to find various examples of where corners have been cut – I think the problem is that the Housing Executive pays the contractors less than they would normally like, so they save money where they can

Looks like this is an example of that – I can see how a non-electrician like me might think “Hey, I have some 3-core cable, and I need 3 wires coming to this stat” without really thinking through any implications. Bit disappointing to see an electrician doing it though – seems so obvious now you’ve mentioned it. I mean, when I took the cover off the stat to photograph it for this thread, I immediately thought “Oh, that’s an earth – so I only have to figure out what the two other wires do.”

Anyway, thanks for the advice – I’ll see if I can get some brown sleeving in case I forget and grab hold of it years from now

 

[Roger465]

The new one did not have a fail safe, so anything that blocks the signal, or flat batteries leave the boiler doing what ever it was doing before

Thanks for all that

I'll try and find out if the cheapo one has a failsafe!

 

[Roger465]

No, don't think it has...

So many factors to take into consideration, including terrible reviews of different stats on various sites etc… I wonder if I could maybe extend the cable from the existing stat through the attic, then run a wire down the side of the chimney breast, and relocate the existing stat to the wall, say between the plant and the table lamp…?

The room’s rads are at the other side of the room, so wouldn't interfere with it I guess.

I REALLY don’t want to have wires through the ceiling and things, but…

 

[JohnW2]

I think the idea is that the radiator is analogue controlled so will be at a set temperature as long as heating not turned on/off by thermostat so once set it will remain close to temperature set as not setting to a fixed temperature but a simple number on the dial, however the electronic heads measure water and air temperature and compensate air temperature reading using water temperature. And when my valve head reports 20°C for the room a independent thermostat placed on the fire (not running) opposite radiator does show 20°C also.

I wasn't really thinking about electronic ones (which, in terms of the big picture, are rare), but I'm still amazed that any of them (traditional or electronic) are able to do the job particularly well.

I wasn't really thinking about 'erroneous' temperature sensing (which could perhaps be 'compensated for', to some extent, by also looking at water temp) but, rather about the fact that the air temp very close to a radiator may be genuinely a lot higher than the temp of the room as a whole, particularly when the heating is first switched on in a cold room. ...

.... you say that your 'independent thermostat' some distance from the radiator reported the same temp as did the electronic TRV, but what do you think an 'independent thermostat' (or thermometer) would say if you placed it an inch or two from the radiator (even if it was shielded from radiant heat), particularly in a room that you had just started heating from cold?

Kind Regards, John

 

[bernardgreen]

An ELV ( Extra Low Voltage ) thermostat operating on 12 or 24 volts could be wired using alarm type cable which could be concealed in the corner, far easier than trying the conceal mains voltage cable.

Some boilers will operate with ELV thermostats, if yours doesn't then a bit of interfacing would be needed, a small power supply and a relay near to the boiler.

 

[ericmark]

The Horstmann thermostat could be used free standing and I did try in different positions. It would seem heat goes up from radiator along ceiling down the far wall and along floor back to radiator, so opposite wall works well, on a table in front of radiator also worked well, but had to reduce setting by a degree, however on a chest of draws 90° to radiator produced a massive hysteresis. This fits with diagrams given with thermostats.

So reasonably low down as side of radiator likely has both return air travelling along the floor to compensate for radiated heat from the radiator.

I have to admit some of the TRV's will not fully turn off, so does not matter how good the heads are, if the valve will not turn off, then the room will over heat. However the Terrier i30 I have found advertised as low as £15 although so are listed at £50 but the question must be, go to all the work wiring a wall thermostat or simply swap to electronic head?

I will not pretend using a non linked electronic TRV head is perfect, but I don't think we are prepared to pay for perfect, so I feel what I have is near enough. EvoHome for four rooms will likely cost £400 to £500 it will do the job, no question about that, but do you want to spend that much?

Energenie plus Nest will likely cost the same, however you can do that one in stages, but not likely as good as EvoHome.

 

[EFLImpudence]

I thought thermostats should ideally be placed at a height of five feet on an empty(ish) wall away from direct sources of heat.

Obviously they won't work as well if put in a drawer.

 

[Roger465]

Thanks well, as none of this is life-changing, and the total risk is only £20, I've ordered one of the cheapo Tower ones.

I'll connect it up, experiment with it, and post the results here in a couple of weeks or so.

If it doesn't work properly, I think maybe I'll run the stat wires through the attic, out under the eaves, down the wall, then drill right through the wall where I want to mount the original stat, and do it that way.

Bearing in mind the previous cable howler, and the fact it'll have to go outside for a bit, do I have to use twin and earth, or is there any kind of round cable which is waterproof and reasonably flexible?

Thanks again chaps

 

[flameport]

or is there any kind of round cable which is waterproof and reasonably flexible

4 core black flex is available.

3 core & earth and some black or white round plastic conduit for the outside part would be a more likely solution.

 

[Roger465]

4 core black flex is available.

3 core & earth and some black or white round plastic conduit for the outside part would be a more likely solution.

I was thinking something easier to work with than T&E, just to get it through and into the back of the stat etc - would this be any good?

 

[flameport]

would this be any good?

No - only 3 cores.

 

[Roger465]

No - only 3 cores.

Right... now I know I know notheeng (like Manuel on Fawlty Towers) - that's why I come here after all - but the existing one is 3 cores?

That's the one where the earth has been used as the switched live. Now, while I know that's wrong, as you've explained, does the wall stat actually need to be earthed, bearing in mind anything you can touch is plastic?

Sorry if I'm being dense...

 

[flameport]

Wiring regulations require that green/yellow is only used to identify the earth, and that an earth is provided at every point, regardless of whether a particular device needs it.

 

[Roger465]

Gotcha, thanks for that