Normally, I wouldn't post a "me too" like this, but we have just been
through the same process and are still recovering from the by-products
of CH replacement, with the whole house still in chaos after moving
stuff to give access to pipework, radiators etc.

I have all the boiler paperwork, and have only had time to glance
through it, but could well have posted here to ask the original
question. As a long-term news-group junkie (although only recently
here), it's usually easy to sift the helpful and sensible answers from
the others, as it was in this case.

There is, of course the ancillary question about why, if it's a
condensing boiler, we see so much 'steam' from it. If it were condensing
fully, surely we should see no visible exhaust. Are we losing huge
amounts of latent heat here? Is a second stage condensing process worth
looking into?
--
Bill