"IMM" wrote in message
...
"sro" wrote in message
...
"Christian McArdle" wrote in message
t...
He also said that modern boilers used insulation to stop wasting heat
by
transfer into the surrounding space and that they do achieve lower
flue
temperatures which means they are extracting more heat from the gas.
Indeed, although it is the much larger, more efficient heat exchanger
which
does this, rather than insulation.
A well designed condensing boiler installation might have a flue
temperature
of 50C, compared to an old boiler with 300C. The flue temperature
being
considerably lower than 100C is the cause of all the pluming. Although
people worry about it, thinking it is a health hazard, the emissions
in
that
plume are much better than those in the invisible 300C one. But you
can't
see the 300C version, so no-one cares.
Thanks again - and now the real question,
are condensing boilers unreliable ?
No. They are same as a system boiler except they have a plastic drain
pipe
attached.
Here is an example of what I want from a boiler :
- Run for 18 years with minimal ( 3 or 4 thermocouples )
maintenance ( my old fashioned boiler )
That is possible, but you have to buy a top of the range boiler. As in
all
aspects of product prices, more expensive "generally" means better
quality.
Not always though.
- I find it amazing that modern combis seem to need new bits after a
couple
of years
Depends on what make and model again. Cheap units break down more. Poorly
installed units break down more too. A combi is just a system boiler with
a
water section. No reason for it to be unreliable at all. Some combi's
have
all the functions integrated to ensure no operating problems. The
Microgenus is one boiler with all integrated.
Am I being unrealistic
yes.
- are all modern devices complicated and unreliable ?
No. Depends on what you buy.
A fallacy is that combi's are unreliable. Some are, some are not, there are
the Ladas of the combi world as well as the Mercs. Some conventional
boilers are unreliable. A friends once had a Fuelsaver, much simpler than a
combi, and gave continuous trouble. He eventually replaced it after only 6
years with a "combi".
"All" the system except the rads is in the box. In a cylinder/tank setup, if
the ball-cock has trouble in the cold tank in the loft, no one blames that
on the boiler downstairs.
Compare a boiler/cylinder/cold tank system with a combi, you have to take
all of the servicing of the "system" (and that includes rads) and compare it
with servicing of a combi system (and that includes rads). Assuming the
rads and thermostat valves on each system are of equal quality.
You have to compare like-with-like. Comparing a combi "white box" with a
simple cast-iron boiler "white box" is ridiculous. You have to compare
total system vs total system.
All the old wives tales and fallacies about combis no longer exist. They can
do two bathrooms, they are high quality and reliable, they do have instant
hot water at the taps, they are cheap to install offsetting the high initial
"box" price, they are economical to run.
I had a Potterton Neatheat regular boiler for over 20 years. The boiler was
very reliable in itself because there was not much in it. In that time I
went through:
Outside the boiler:
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
combi would have given far less trouble over 20 years.
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