CH thermostat replacement with combined timer/thermostat

[pemba]

Hello i've a valiant combi boiler feeding both central heating and hot water system. The CH system On/Off is controlled by selecting the thermostat temp. Obviously this is less than good in that we have to get out of bed to get the heating on - no fun with this cold snap!

I'd like to replace the current thermostat, an old Honeywell device fed with 3 cores plus earth, with a combined timer/thermostat. So can anyone advise me on:
is this a relatively simple task?
what device should I buy? (cheapest and simplest possible please - unless this would be a bad approach?)
are there any gotchas to watchout for?

Many thanks Pemba

 

[YELLERBELLY]

what's wrong with using the timer on your combi?

 

[pemba]

Ahh good question and one that I did think about covering in my initial question.

Where my boiler is sited is in a cupbord that also houses a washing machine and tumble drier with the tumble drier being mounted directly in front of the boiler - so access is limited (I have to remove the tumble drier if I need to service the boiler).

Hope this clarifies.

 

[mikely]

It is a relatively simple task, but it does involve working with mains wiring. I’d recommend a Honeywell CM907 programmable thermostat. It’s not the cheapest or probably the simplest, but it is an excellent controller (about £60). I initially fitted a cheaper unit but ended up replacing it with the 907. Set the Optimisation function on and it will have the house nice and warm at the times you set, which you can vary for any day of the week.

 

[pemba]

OK sounds like i've a job for the weekend. Will let you know how I get on with it.

Pemba.

 

[pemba]

Ahh just had a read of the spec for this item and it states it is fed by 2 wires - which 2 of my 3 (discounting the earth presumably!) would I use?

Pemba

 

[mikely]

It will connect (on terminals A & B) to the two wires in your current thermostat that are connected to the thermostat’s switch contacts. It doesn’t matter which way round they go. The other wire will be a neutral which is not needed and nor is the earth. These you should stow in a two terminal choc block. If not actually marked on the old stat, you should be able to download a data sheet for it from which to distinguish which wire is which.

 

[pemba]

Thanks Mikely - i'll let you know how it goes.

 

[bengasman]

...what device should I buy? (cheapest and simplest possible please - unless this would be a bad approach?)

It may have changed recently, but for a long time it was a matter of: buy cheap, get cheap