What I was saying was that the contribution to fuel saving from upgrading a heating system is about 50:50 from boiler and the control upgrades.
Essentially, if you have the worst case system and go to current best practice you should save about 30%. If you already have a good control system then you should get about half of the improvement from just the boiler. Which is what you got.
If you don't have some sort of overall temperature control on the space heating then there is probably some more scope for saving.
IME the controls are more important than the type of boiler.
When I fitted my CH 28 years ago I put in one of the new fangled low water content boilers with a copper heat exchanger (22 mm pipe with fins) and zone valves with individual timers and stats. My gas bill has always been less than half of the other identical houses near me (the ones I know well enough to ask).
The insulation is so efficient that I turned the boiler output down to about
8kW and seldom need any extra heat (that doesn't stop the wife putting the gas fire on even though it uses twice as much gas for the same heat out!).
The system is "on" 24x7x365 even in the summer.
I did the maths once to see if I should change the boiler.. the answer is a definite no. The one I have has a claimed efficiency of 82% so if I went to a condensing one I would save about 12% which gives me a repayment period in excess of 10 years which appears to be longer than combies last..
You may like to know that the boiler is not modulating, it cycles quite frequently as there is not much water in the system and there is usually only one rad calling for heat when its on. It doesn't have much effect on the amount of gas used but I have worn a gas valve out once in 28 years.
There is almost nothing in the boiler, a few stats, the gas valve, heat exchanger and some pressed steel panels.
Where is the 82% claimed? I'd expect a non-fanned boiler with a standing pilot light to have considerably less efficiency than that measured seasonally (i.e. SEDBUK).
The message from "Dave Plowman (News)" contains these words:
How then do you maintain the desired temperature in the living room?
This is another repost so my apologies Dave if you saw the original and decided not to bother but the message I posted yesterday still hasn't appeared to me. Zetnet has gone to the dogs since they were taken over.
Your basic sealed compressor and sealed tubing reached astonishingly high levels of reliability, over 50 years ago. It's pretty impossible to add anything to that which doesn't rather dramaticly reduce the reliability.
And several sensors, which also seem to fail too often.
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