TH0472 Twin Channel Electronic Programmer

I've used this programmer in a multi-zone installation to control the upstairs heating and the hot water. I liked the look of its temperature control option for the heating, hoping it would save the need to install a separate thermostat. The programmer features are good; selectable 24hr, 5+2 7& 7day, three periods per day and you can choose to have it only use one or two of those, completely independent CH and DHW times, holiday mode and frost stat. However, when you set it to run in its temperature control mode it doesn't quite do what you'd hope. You set a single temperature which it will control to, so it's not quite a programmable room stat. Not an issue for the bedrooms.
But, say the program times are set to bring the heating on at 5pm and off again at 6. If the temperature at 6 is not higher than the set temp. then the programmer does not switch off the heating demand. It keeps calling for heat until the temperature is exceeded, even though the programmed times have passed. So if you only want the heating on for a short spell to warm the rads so you can put on warm socks when you get out of bed, you'll find the heating will remain on much longer till the temperature is exceeded.
The temperature deadband is also wide, 1C rather than 0.5C. So if you have set at temperature of 18C, the heating won't come on until the temp. is below 17C, then goes off when it climbs above 18. So if the temp doesn't fall below that 17C the heating won't come on, this time leaving you with cold socks!
I'm going to turn off the temperature control mode and just use it as a timer, then at least I'm guaranteed the heating will come on and go off when it should. If I find it's getting too warm after extended running I'll have to fit a separate thermostat.
(Posted on 27/11/2009)