First thing I’d say is that most TRVs are not suitable for use on a 1 pipe system.
Secondly just bite the bullet and repipe fully into a 2 pipe system.
Comfort levels and warmup times will be greatly improved so in the long run will be a more cost effective option
What everyone here seems to be forgetting is why smart meters were introduced in the 1st place.
It was some hairbrained scheme that made everyone believe that if people could see how much gas/electric they were using, then this would lead to them using less therefore reducing CO2 emissions.
Jesus talk about over complicate things it’s so clear you have a problem with your hot water creating short demands for heat from your boiler. Therefore you have to be losing hot water from your cylinder either through leaking PRV into tundish, dripping hot tap or leak on the dhw pipe work.
My guess from looking at things is that your air gap in your megaflo cylinder needs recharging. If your constantly losing hot water at a small rate through the tundish that is replaced by cold,the boiler will keep firing for small periods to bring your cylinder back up to temp.
Why are you blaming the engineer? SFH will clear after the boiler has run at the kw rating set on D0 after 10 mins. Personally IMO I think you have an oversized boiler with undersized pipe work and poor circulation so boiler short cycles
Due to the fact that the majority of your posts lack the clear technical knowledge as shown from other qualified engineers, then yes I do question your judgement on your fault that is so rare it only happened in less than 0.01% of boilers.
As in the words of Donald Trump your showboating old...
Awfully sorry old chap to try and rain on your parade but I rather believe you are talking your usual Drivel in my opinion. I will try and be as polite as possible and make sure there is no abuse, as we would not want to upset the mods.
Appreciated;). Mod Plod...