I have received so much help in this group over time that it may well
be time for a bit of pay back. Because I feel less competent than many
to comment on specific questions, I think I could contribute an
experience report on my recent fitting of a new combi system. Some of
you looking at a similar job may find it helpful, others may have a
laugh on me for the mistakes that I made. Here we go:

The situation: bought a victorian 4-bed terrace in Yorkshire with a
really old gas boiler (estimates put it at between 20 and 30 years)
serving a hot water tank in a bedroom (!). No roomstat led to the
boiler being on all the time. Plus, the attic bedroom did not have a
radiator, arguably because the ch pump was so weak that it would have
had a hard time serving it. The shower is one of those victorian retro
showers.

We wanted a combi as we have seen combis work efficiently in other
houses here and abroad. We realised the potential problems with the
flow rate @35 but since we prefer showers over baths, the specific
advantages of a tank system were a bit lost on us. Also, we really
needed this bedroom to be free of the tank, so a major replumbing job
was kind of unavoidable.

We asked for three different quotes: local small plumber (quote for
3200), local large plumber (quote for 4000), British Gas (quote for
6000). We let the plumbers decide on how many radiators needed
replacing as some of the radiators are indeed very old. Needless to
say, they all differed as to which radiators needed swapping, but they
all arrived at between three or four radiators had to go, whilst also
offering to fit the attic bedroom radiator.

Small plumber advised on Worcester Bosch 30 Greenstar plus (with the
control in the boiler), large local plumber said WB 30 Greenstar old
(with separate digi controls), whilst British Gas recommended an 28kw
boiler of their own range - apparantly manufactured by WB all the
same. As for the shower, local small said shower works well with a
combi, local large said shower might or might not work with a combi,
British gas said you need a new shower as this one does not work.

We went with the cheapest quote, having a hunch that the shower would
probably work and that his information on radiators was the most
convincing one. Also, we thought, if all recommend the same boiler
firm, then why not go with the cheapest quote. Ok. So far so good. Our
biggest concern was the hot water flow rate of the boiler, as we often
shower whilst having the washer on and maybe someone doing the dishes.
Amateurs that we are, we were totally focused on the boilers
abilities, hence we asked the quote to be upgraded to the Worcester
Bosch 40 HE Greenstar plus, a difference of about 300 pounds - we have
yet to see the final invoice. We did estimates of the mains flow rate
but never measured it when all the other households use cold water as
well ;-)

The whole job took almost five days to complete, two nights without
heating or hot water was a bit of a hassle for a family with two young
children. The plumbers first came with a WB 40 HE Greenstar
convential. It took me to repeatedly point it out to them that the
whole purpose of the excercise was to fit a combi and their boiler was
not a combi (praise the web - makes it easy to double check), and
after a brief exchange they realised the mistake - blamed it on
suppliers mind you but who would not double check before unpacking
that sort of equipment? The right boiler came next day and was then
fitted to the outbuilding directly adjacent to the kitchen. Reason
being that it's fairly large and the condensation flue needed to be
somewhere where it does not blow into a neighbour's garden or window.
Could not be connected that evening because the electrician was off
sick.

During the installation, most of the job went smoothly. The shower
works no problem (British Gas overlooked this and quoted an additional
300 pounds for the replacement shower). We did not swap any of the
radiators as we thought better to check out the heating with the new
boiler on, had only the radiator in the attic fitted. They used
plastic pipes for the attic radiator, which had to be moved as we
wanted the wall where the original tank was to be freed up in order to
place some wardrobes there. We made this clear to the plumbers, but
they only moved the radiator pipes. For whatever reason they left the
shower pipes in place. When I pointed this out to them, they said that
they did not expect the shower to be fed from pipes running through
the attic. I of course in my naivity had seen this first think as the
shower pipes go to the ceiling... Never mind, they agreed to move the
shower pipes for another 150 quid. What do you do then? You just say
ok, because you want to get the job bloody finished. Personally, I
consider this borderline ripoff as we made it clear that the purpose
of moving the radiator pipes was to get the corner free for the
wardrobes. They are the experts to tell me that these could be shower
pipes as well...

But now to the biggest thing if you like concern: the end result.
Heating works marvellous, a warm house with single glazing and exposed
floor boards and what not. It comes on quickly and the control on the
boiler are fairly sophisticated to allow for all sorts of heating
scenarios. The hot water is another story though. It takes for ages to
actually come through. Maybe not much longer than with the tank,
especially in the kitchen, but regardless: you turn on the shower,
then take off clothes and then carefully step in as it may still not
be hot enough. Thank God we are not a water meter. But the real issue
is the flow rate: the shower is certainly no better than it was
before. Maybe about equal. And that is not so much due to the boiler
but the mains flow rate in the first place. Also, I can get the shower
to die instantly if I turn on the bathroom sink ho****er tap. I knew I
would see less flow rate, I did not expect not to see any water at all
with another tap open.

Plumber says this is partly due to the shower being piped through the
attic which is probably true. But generally speaking, we have to tell
people not to turn on any water either hot or cold when someone is in
the shower. Now that is a major bummer I have to say. We spent the
best part of three thousand pounds to *downgrade* the comfort level of
our ho****er. The thing is, the boiler itself is capable enough with
its 16l/35 degrees. The main culprit, imho which may be wrong, is the
mains flow rate. British Gas was the only one to have concerns over
this - so all credit to them for being more if you like theoretical by
actually measuring flow rate. The others turn on the taps and said oh
yes that will work well. The next issue is the way the house is piped
is made for the tank system. You can tell that not all taps or water
outlets have the same effect on the boiler. You can indeed survive the
washer or washing machine coming on in the shower, but less so the
bathroom or kitchen sink taps.

Another area of comfort loss is the hot water in the kitchen. The pipe
is very narrow in order to give the most pressure - due to the tank
system I would have thought. With a tank you then only turn on the tap
a tiny bit to get enough hot water without the pressure really. But
with a combi this does not work anymore as the combi basically
requires us to open the tap fully in order to get the combi fire up.
You can live with this sort of thing by changing your habits - always
wear an apron for starters and fill the sink with hot water before
washing up. But do you really want to be forced to change your habits
for a new boiler? Final issue is the condensation flue. It was
installed vertically, but we did not expect the amount vapour that
would come out there on cold days - nor did we expect all the noise.
The boiler is sound insulated except for the condensing flue which
means that our vertical flue works like a loud speaker. I am sure our
neighbours will hear it in their kitchen. Nobody pointed this out to
us at all - we knew about condensation, but certainly not about sound.

Would we do the job again? The premise was to get the bedroom free
from the tank. That much we have accomplished. By getting rid of the
old system we did something for our comfort due to less worry about a
breakdown, lower energy bills and for the environment by buying a
A-class boiler as opposed the about z that we had installed
beforehand. But ho****er comfort is crap. We are, in that sense,
totally disappointed by the system. We would certainly have asked for
quotes for tank systems and then encouraged the plumbers to find
better places for a tank. Maybe we would still have fitted the combi,
but next time round, we would be even more careful to think about the
possible implications of the pipework (e.g. shower through the attic -
no way!). As it stands, I can only warn people to think it through
properly before fitting a combi. We find plumbers in particular to be
working as empiricists, they solve problems as and when they come
along, but they don't seem to be able to think the whole process
through beforehand. My impression now is that we should have discussed
a number of factors in more detail, the boiler specs are probably the
least concern. I mean based on our experience, the Worcester Bosch
website is a joke: they claim that this boiler can serve two showers
at the same time - maybe in the summer with a water preheater and a
second mains pipe. We cannot even open another cold water outlet in
the house, so treat manufacturers claims with care. The reality
probably depends more on your setup.

I hope this helps other people in their decision making. I am trashing
combis, but their success depends on variables that we did not
properly understand before agreeing to the job.

Fred