"Andrew Gabriel" wrote in message
.. .
In article ,
Geoff Lane writes:
I've recently had an extension built with a new Glow Worm 30ci combi
boiler fitted.

There is a little old pipework remaining and one small rad otherwise
the system is new.

My previous gravity system gave no trouble, apart from the occasional
pump, it worked faultlessly but owing to a need for instant hot water
I went for a combi.

After 16 months the secondary heat exchanger failed, as I had not had
the apparently mandatory service this was not covered by warranty so I
had a very expensive repair.

The service engineer said this was due to the system not being flushed
as the heat exchanger was blocked.

Which side blocked? If you are in a hard water area, you can
expect the secondary side to scale up. I recently descalled
a friend's one in Baxi 105, but that took 4 years to block,
with a family of 5 including two babies.

Sounds like crud in the primary side.

I am now led to believe that system flushing appears to be a necessary
requirement for combis due to the design, how important is this
flushing, I would have thought any modern boiler should have some
filtering system to prevent fouling of the internals.

Desludging is needed in all systems not just combis. Also fit a Magaclean
filter on the CH return, as this will catch debris and iron.

There shouldn't be any new debris appearing in the heating
circuit in the first place (at least not within 16 months).

Depends on how much crud was already in the old system. The Glow Worms are
good boilers, and a failure like this is very rare.