I cannot get my central heating to work although my hot water seems fine. The display is showing a d which does not appear in the manual? Does anyone know what this is and how to fix it? Many thanks

Sarah, January 2009

Mine has also started doing the same thing I can hear the fan and the temp is on 35 on the little display screen yet it still will not heat up my radiators :(

Laylah, May 2013

CH engineer explained d is a delay caused when system is returning water that is up to (or slightly above) set temp. The delay is a deliberate safety feature to allow boiler to cool sufficiently before restarting - more efficient than keep stopping and starting which would be very expensive and decrease life of your boiler.

Reason for my shut down = system appeared not to be balanced - hot water coming straight back too quickly without circulating through rads - causing the boiler to shut down.

I have a new property with a two year old CH system and when CH engineer checked, 3 of the MYSON thermostat's pin valves had stuck in the down position so 3 rads could never get enought heat (couldn't draw sufficient hot water so it was returning to the boiler without being cooled by the rad) which caused my boiler to think the system was overheating and my error d shutdowns.
Simple cure = we just removed my thermostat tops (easy, just unscrew knurled ring with large pliers - some may only be finger tight) then tap the centre pin to ensure it springs fully out of base and replace.
CH engineer said anyone can do this.
I'll be checking all of our thermostat pins annually from now on!!

If in doubt, always get a qualified CH engineer to check your system for you - like I did.
garryhq

garryhq, March 2009

Our boiler is also doing this - problem is, cold radiators while boiler makes up its mind what to do next. HAd F37 several times over last couple of years abd recentl F3- now noticed this d being displayed and cold rads - we must have some sort of fault. Will ring engineer tomorrow...

garryhq, February 2009

i've been told it means 'delay', no real fault with the boiler, other than it doesn't know what to do next. my guess its overheated, cooled a little and is now thinking what to do next.
will likely reset itself and start to fire up again, however, it'll probably repeat the symptoms.
Mine does!!!!

JIsaac, February 2009