3-wire (mains) 1-zone programmable room thermostat - why so expensive?

[David Robinson]

I bit the bullet and made my conservatory a separate heating zone.

I've got an S-plan system. I've added 3-core + earth running from the conservatory back to the heating junction box. I'm adding a 2 port normally closed valve to feed this.

I think I want a cheap, relatively simple 1-zone programmable room thermostat for the conservatory. 5/2 day, at least three on/offs per day. There seem to be plenty of cheap ones designed to replace a standard thermostat (i.e. 2-wire, mostly with batteries for power), but all the 3-wire versions seem to be far more expensive.

e.g. this does what I think I want...

I'd like it at this price! ... does it cost so much more to have one that runs from the mains?!

Alternatively, I could probably cope with separate timer + thermostat

• frost protection, though I'm not sure I want to mount all this on the conservatory wall!

Any suggestions?

Thanks in advance.

Cheers, David.

[ARWadsworth]

> ...but I'd like it at this price! ...

I want Amanda Holden to sleep with me. You cannot always have what you want.

Less demand/costs more to build/Dunno

It will not work out any cheaper by using seperate programmers and thermostats. Of course just because you have laid a 3 core and earth does not mean that you have to use all the cores, you can still use a battery operated unit.

Cheers

[David Robinson]

Yeah, it's all your fault too! ;-) It didn't work out that difficult in the end.

:-) as Les Dennis found.

I'll ask the boss. She'll be all for saving =A340, but (like me) will probably think that having part of the heating system running off batteries is silly.

Cheers, David.

[chris French]

In message , David Robinson writes

Are you wanting the conservatory to get heated more - such as when the rest of the system is not calling for heat, or to heat the conservatory at more controlled time?

Does it need to be wired into the system to call for heat from the boiler, or could you rely on the heating being on enough when you want the conservatory heated?

If the latter then maybe a programmable TRV head would do the job? Like this:

[Geo]

Do you want to have to reset the clock every time the power is interrupted?

[Colin Stamp]

It's a *lot* more awkward to make a mains powered one and once you've done it, you've considerably reduced the size of your potential market. The £10 manufacturers won't be interested in those economics, so you're left with the more expensive brands that can charge enough to make it worthwhile.

Battery power really isn't a problem anyway. They normally go for years between battery changes. The only advantage mains power might give, would be an always-on backlight, and I'm not sure any of them even have that.

I'd be wary of getting the cheapy one though. I've seen some truly dire user-interfaces on things like that. I'd reccommend a decent branded one regardless of power. I've just fitted a Honeywell CM907 and it's absolutely lovely :o)

Cheers,

Colin.

[John Rumm]

What is your objection to batteries? They last sooooo long as to be a non issue (e.g. our horstman centurstat is still on its first set after three years), and its rather nice not having the sodding thing forget all its programming when you get a power interruption. ;-)

[Tabby]

battery one plus wallwart

[David Robinson]

Thanks all. I've bought one with batteries!

Cheers, David.