Replacing Mechanical Thermostat with Digital

7 Apr 2011
Reaction score
United Kingdom
I have an ISTOR HE260 in my house which has a programming unit on the front of it.
The room thermostat is downstairs and its a honeywell mechanical one.

Can i replace this with :
a) a digital one?
b) a digital one that has a programmer on it?
(if i got a digital progammer on, would i need to somehow disable the built in one?

Sponsored Links
I'm not familiar with that built in programmer but it should be possible to set it to have the heating ON 24hrs.

Then the new digital timer/thermostat will be able to control the temp and the ON OFF periods. The new receiver (assuming you go for an RF unit) will have to be wired in to replace the old thermostat, and is usually best mounted near to the boiler.
Thanks for that, does it matter if its RF?

Was just going to take the existing off the wall and wire it into the new one?

What you plan to do eddie is fine, your replacing a dumb switch with another switch which has a bit of logic in it. As said earlier, as long as the programme function, whatever that may be, at the boiler end, allows you to have heating switched on 24HRs a day, then that powers your new switch/programmer 24HRs a day and it now has control. Did the same some years ago, simple and effective.
Sponsored Links
I have an ISTOR HE260 in my house which has a programming unit on the front of it. ...

a) ...
b) ...
c) ...

a, b and c - Yes you can!

As for 'c', is it the earlier or later version of the istore? The programmer on the later version is labelled 'itime'.

If you have the 'itime' version, all you need to do is press the button under the radiator symbol unit the 'on' on the left is illuminated.

But if you have the older version, it's a bit more complicated (as I found out when I changed my son's stat to a programmable one) as there is no facility to have the boiler permanently on. The solution is to delete all heating times, except the first and last, and the set the first to say 2am and the last about five minutes earlier, i,e so the 'OFF' period is when the boiler will never be required.

As for the programmable stat, this can be located where the existing stat is. Wiring will depend on which you have/get, but will not be complicated. Just post the stat info.

The Honeywell CM901 (24 hr) or CM907 (7 day) can be recommended.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local