charles wrote:
In article 2,
DerbyBorn wrote:
After lots of checking a Heating Engineer has decided a mate's heating
system has a partly blocked boiler heat exchanger. Likely? 12 - 15 years
old. Has been pressure cleaned a couple of years ago.

I live in a hard water area and my boiler was installed in 1988!

Quite likely designed before boilers starting having low volume heat
exchangers. Keep it going, any theoretical inefficiency will be offset
by the cost and relatively short life of a modern boiler.