I think that I may be running out of suggestions Hood.
There seems to be 2 relevant factors and although seeming to be similar I am trying understand exactly why they are both happening. This is my thought process.
1. The flue temperaure is excessive.
2. The boiler gets up to temperature and cuts out eearly. ( It short cycles.)
Normally we wait for the boiler to come up to temperature before we take flue gas readings. (and I imagine your man with the test equipment did this)
I wonder, if he put a temperature probe in the flue just after start, what the temperature would be? Maybe much lower?
So perhaps the hot water is not being carried away allowing both the boiler jacket AND the flue gas temperature to rise!
Reasons for hot water not being carried away? Circulating pump failed or set to low speed or the system, including the pump, partially blocked with sludge? Check the circulating pump, Hood. Do you know about bleeding the pump by losening the centre screw (power off and wit han old towel and drip tray handy!) and if the pump is not turning remove this screw and put a screwdriver in the slot and spin the pump rotor? When you loosen the screw do you just get a dribble of water or a flow and what colour is the water? Let it bleed for a while becasue the water will probably be black at first anyway.
Hi again
I think things may be settling down but cannot give you latest analyser settings until engineer revisits.
I monitored the system from a cold house this morning at 7.20am with the outside temp 1c and inside 15c.
The boiler fired for 15mins continuously and then shut off for 3mins it then started up for 3 mins and shut down for 3mins. After 45mins(8.05am) the temperature had risen to 18c(our daytime temp) and the cycle started to be 2 mins on and 3mins off.
As the morning progressed the temperature had penetrated into the house
and we were seeing off times increasing to 30+ minutes and 2 mins firing.
The firing time is now constant at 2 mins on with excellent off times suggesting a good heat sink in the house
What do you think of the running times.
Will post the stack temp after the engineer visits(whenever that happens since we do have heating now)
Thanks again for your continued interest
Hood