boiler no longer responding to thermostat and programmer

[Delph79]

Hi all,

For the past 3 days my Viessmann Vitodens 100W has been overheating my house, regardless of the programmer and the thermostat telling it to or not. My wireless Honeywell stat was installed at the same time as my boiler, i.e. 4.5 years ago. They have always had trouble communicating but this year I was having no issues for the first winter since I have lived in my flat (5 years). The previous boiler failed aged 6 because the piping system is small and prone to build up. I have a Magnaclean filter and the system was flushed before the new boiler was installed. I was told my installer was a cowboy and had wired the system wrongly by the engineers who subsequently came to maintain the boiler every year and eventually fixed.

Can anybody please make suggestions as to what may be causing the problem and whether I hou call an engineer urgently? the only workaround I have found that works is to switch the system off (I have this switch that runs the programmer, boiler and probably feeds the valves to the water tank), which means I must switch off before the temperature gets out of hand and then switch on again an hour or two before I get up! Not good!

Thanks in advance

 

[Best]

Hello and Welcome. Looks like you have no choice but get an engineer out.
I am not gas qualified, but if your system has any motorised valves, one of them might be faulty. You could suggest this to the engineer when you phone. The valves often have a square white head (or can be silver metal) fixed onto a brass body, if you want to give details of actual make so the engineer has one.

 

[Howsie]

What is the make of your thermostat and where are you based?

 

[Delph79]

thanks both, there was a suspicion of one of the valves not working properly during a previous boiler maintenance session, and it was almost changed but in the end, the engineer managed to get it to work again. I had a play with it last night but nothing was happening (though it did the night before).
My thermostat is a wireless Honeywell CMT707 (would need to double check the model number once home but it looks exactly like this one)

I am based in London.

 

[Howsie]

Good boiler and decent thermostat. Should be no issues fault finding that. London is a big place.

 

[Chalked]

Might be, just be a matter of replacing the batteries in the thermostat.