"Capitol" wrote in message
...

IMM wrote in message ...

"Capitol" wrote in message
...

I would disagree about the "ball park figure"
being adequate to start with,

Ballpark is fine. There are a few on-line calculators. It is best to
use
a
few. Ad 5 to 10 % extra if you like.

the odds are you will end up with a
boiler and radiators which are too
small.

The smallest of comi's will do the CH on a "very" large house. The
boiler
sizing is not a problem if it is not a big house.

Sadly not true, as our friend has found out the hard way!

Please read again. The smallest combi is approx 80,000 Btu/hr, which is big
enough for a largish 4/5 bedroomed house. Most houses in the Uk are a lot
smaller than that. The average sized combi is approx 95,000 btu/hr. They
must have a large house or one with no insulation.

Of more importance, where are the 10 year
maintenance and running costs factored in
on a combi system without soft water.

Always have a de-scaler on a combi, or on "any" system in hard water.

Combis with descalers in hard water areas, don't generally seem to give 10
years service. All my friends with new boilers are getting less than 10
years life from their modern boilers.

Why are they being scrapped? In many cases they are being replaced because
the replacement cost is so low compared to fixing. Also the newer combi's
work better, and give better flowrates, than a 10 year older. A combi can
be bought for approx £350 in trade places, and £400 off-the-shelf in B&Q. A
13 litre/min can be bought in Wickes with all the trimmings. Combi prices
have tumbled. They are so cost effective it is worth putting in two in a 2
bath house, with one doing upstairs heating and the other doing down.

Where are the manufacturers offering a 10year warranty?

Many give 5 years on the heat exchangers. I think Vaillant give 3 or 5
years on the whole combi. Many give 2 year guarantees.

I had a Potterton Neatheat for over 20 years. The boiler was very
reliable
in itself because there was not much in it. In that time I went through
3
pumps, a zone valve, a zone valve motor, a cylinder, cylinder stat, room
stat and a programmer. On the boiler a relay, flue fan and a pressure
differential switch. Overall the "system" was not that reliable. I am
certain a good Vaillant would have given far less trouble over 20 years.

I would regard that as being totally unreliable,

But average for a tank/cylinder setup over 20 years!!!

only one pump at most would
be necessary on a reliable system.

Over 20 years? I would say 2 pumps. I have seen few pumps go beyond 10
years.



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