On Sat, 13 Dec 2008 12:02:55 +0000, MJA wrote:

On 2008-12-12, Doctor Drivel wrote:

"MJA" wrote in message
...

I am thinking about having my old, inefficient but reliable gas boiler
replaced next summer. I have been reading manuals and other web
resources, mainly looking at German and Dutch manufacturers.

some text trimmed

I prefer the look of the Quinta -- it seems more solidly built and
accepts an external 0-10v modulating input if I wanted to update the
system controls later. However, I am wary of the aluminium heat
exchanger.

Now that condensing boilers have been around for a few years, what are
people's experience with the relative life and cost of maintenance of
aluminium vs. stainless steel?

The Quinta is a commercail boiler, so more expensive. At this point
consider a system update. How about a quality high flow combi, giving
high pressure showers? The Broag 39C combi will do in most cases.

We've had a few water outages in my part of the Thames Valley, and I
also like having the backup immersion heater. Space for tanks is no
problem.

Have a Magnaclean on the return to the boiler. That will prevent any
blocking up of the tubes in the heat exchanger.

The Magnaclean is worth considering -- although the system seems fairly
clean and has had inhibitor in.

The Broag, has a 5 year guarantee. They use primarily industry standard
components and little plastic with Honeywell brass hydrobocks. The
Broags are better quality than Vaillant and much cheaper. They are a
well priced quality boilers having a superb control system with
integrated outside weather compensation and OpenTherm control protocal
control. http://www.avantaplus.co.uk

Yes, I have looked at the Avanta and Quinta instructions. I am wary of
OpenTherm because the interface specs are not published -- same problem
for Vaillant and eBus. A standard 0-10v input seems future proof --
that limits me to the Quinta 30, Keston Qudos or MHG with option module.

Now what is your system like? Cylinder? vented? how many showers?
Baths, etc. Then it can be whittled down to what you really need. It
is no good putting a modern boiler on an outdated DHW/CH system. Go
for gold.

Current system original when 3 bed bungalow built in mid 1970's. Gas
boiler Potterton C55 cast iron, floor standing, conventional flue,
55,000 Btu output, which is adequate given the insulation improvements
since the bungalow was built. Conventional hot water system -- indirect
tank in airing cupboard, primary gravity circulation, open vent with
Honeywell "C" system added by previous owner. One bathroom, bath with
gravity fed shower over. One-pipe pumped central heating circuit, hall
thermostat added by previous owner.

The economics of an upgrade are finely balanced. Current running costs
are about 700 pounds fuel, plus 60 pound annual boiler service. A new
boiler could be cost neutral over 10 years assuming a fuel saving of 250
pounds per year and 2500 for new boiler, installation and essential
system changes. Higher maintenance costs would put me off the change,
higher gas prices could make it worthwhile.

The old boiler is supremely reliable, and I would hate to find I had
swapped it for something as unreliable as the Worcester Firefly HD II my
father had years ago -- the flame sensor probe positioning was critical
so it regularly locked out leaving us to return to a cold house, and it
burnt through glow-plugs every few months.

I asked about stainless steel versus aluminium as the boiler choice FAQ
at www.makewrite.demon.co.uk/BoilerChoice.html views aluminium as
questionable, even though many manufacturers use it (Remeha Quinta,
Buderus, Worcester, etc.). The boiler choice FAQ mentions one incident
of aluminium corroding on the water side -- is this a problem nowadays
with correct inhibitors?


The silicon coated stuff /should/ be OK. I've put in a few and they seem
OK.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html