Doctor Drivel wrote:

I spent some time trying to steer a
relative away from a combi. They're
more complex than the equivalent
system boiler and just have more parts
to go wrong. The relative lives in a hard water area.

You don't know much about boilers then.
Oh dear.
I know enough to know that they didn't want a combi. 1.5 bar max mains
pressure, very hard water, large house; only an idiot would install a
combi.

A combi is a system boiler with a
water section added.

A combi is a combi and is not a system boiler.

Some are clearly not complex at all. Look at the link
for the Atmos I gave.

Yeah, thank s for that recommendation, Dr. Drivel.
(Makes mental note, avoid recommended boiler like a very virulent &
incurable plague).