This one defeated me too, in my case a Worcester Bosch Group DT20RF Programmer with Digistat radio frequency controlled room thermostat – until I read the blogs and saw a lot of other people have been having the same problems as me. I am neither an electrician nor a heating engineer but I do handy work for a letting agent, so I am called to all sorts of central heating and hot water problems – all of which I can usually fix or diagnose for the experts
So, here’s the combined wisdom of 3-days searching blogs, reading manuals and system testing
1. the radio control on the thermostat seems to only have about a range of 2 meters. This is not mentioned anywhere in the manual. In fact, the manual talks about all sorts of potential places to put the thermostat but not that any of them should be within 2 meters ! a distance which frankly makes any other suggestion pointless. I have lived with mine positioned around 4 meters for a year, giving me a previously inexplicable, intermittent system. One blogger suggested a range of 2 meters is probably ‘about right’ so I did a test. I took the thermostat to the furthest point – the back bedroom and immediately the boiler couldn’t ‘see’ the thermostat – the green light flashed and the Mode was locked out; I then sat the thermostat on the cover of the boiler, and it all came back on within a few 10’s of seconds
2. When the boiler can’t ‘see‘ the thermostat, you get a flashing Central Heating Light the Worcester Bosch boiler. Their manual does not mention anywhere what this means. Added to this, the Central Heating Mode defaults to OFF at the same time, which you can’t change by pressing any button. The actual solution is to get the radio control thermostat close enough to the boiler so it can read the signal. You could spend a lifetime . . !
3. BTW Whilst we’re on the subject, the thermostat is counter intuitive:
a. you can see the room temperature on the thermostat but not the set temperature
b. to get the set temperature, you need to turn the dial – but then you’ve changed the set temperature [by ±1°C]
c. when you dial the temperature you want, whatever you do, don't press the obvious Set button, because that wont set the temperature you want, but instead it will reduce the setting to the default minimum of 15°C – you’re supposed to hit that when you go out. You could easily think though, that you’ve turned up the heat when in fact you turned it right down – remember, you can’t see the Set temperature
d. the thermostat reads in ½° increments but only sets in 1° increments
(what was wrong with a dial and pointer ! ? )
BTW I did speak to Bosch afterwards and eventually, after describing the problems to 3-people, Jez was able to say (a) just turn the thermostat to the desired temperature but don’t; press SET and (b) the remote thermostat has a 9-meter range but is affected by other things eg: mirrors, RSJ’s etc. If the central heating does flash red, just press the OK button
Shaun the Handyman, October 2013
