"John Aston" wrote in message
...
I have looked at this thread
http://tinyurl.com/3ef9x
and others on Google Groups to try and answer my questions, but found
nothing definitive.
I am renovating my house and plan to install a completely new gas-fired
central heating and hot water plumbing system. The renovation includes a
loft conversion, so I want to avoid a system that involves header tanks. I
am assuming that this means a sealed system for mains pressure hot water.
The heating system will be underfloor heating (typically 55 deg C), plus
supplementary heating (probably conventional radiators at 80 deg C flow)
for
when the weather turns really cold.
I would like to install a water softener (not a water conditioner) that is
compatible with a sealed system and a few on this newgroup have
recommended
an ion exchange type. Does anyone have a personal experience, successful
or
otherwise, with a water softener and sealed system that might influence my
choice of softener and boiler. What makes of these do you have?
The main supply water pressure at my property is 2.8 bar (measured one
February lunchtime). My wife and I have three small children, one bath,
two
showers and three toilets as well as a frequently-used washing machine and
dishwasher. With the old oil-fired vented system we used to have, our
water
bills show a consumption of about 200 cu.m. per year.
A difficult question I know, but can any expert out there recommend a
"dream" boiler-type/storage tank/heat exchanger so that I could start to
put
together a system specification that has a good chance of working? I would
rather err on the side of buying good quality equipment than a cheap
solution.
John,
Your title says combi, so..
With combi's the most important figure is the flowrate. 11 litres/min is
fine for showes and the odd slow filling bath. Here is a recent post of
mine...
For an even better flow rate and cheap too for what you get, assess using
two Worcester-Bosch Junior combi's.
For high flowrates it is cost effective to use two Juniors and combine the
DHW outlets. Worcester-Bosch will supply a drawing on how to do it, or ask
me here. Two Juniors are available for around £1000 to £1100 depending on
what sized units you buy. They have 24 and 28 kW models, you could use two
24kW or two 28 kW combi's or one of each. That is cheaper than the
Worcester HighFlow 18 litres/min floor mounted combi and can deliver about
21.5 litres/min and never run out of hot water. The highest flowrates of
any infinitely continuous combi is 22 litres/min, which is the ECO-Hometec
which costs near £2K.
Have one combi do the downstairs heating on its own programmer/timer
(Honeywell CM67 or equiv) and one do upstairs. Natural zoning, so you don't
have to heat upstairs when you are not up there saving fuel. The running
cost will be approx the same as a condensing boiler heating the whole house.
No external zone valves either, and simple wiring up too. The Juniors are
simple and don't even have internal 3-way valves.
Also if one goes down you will have another combi to give some heat in the
house and DHW too. Combine the outlets for the DHW bath pipes and all the
baths you want very quickly and no waiting. Best have the showers on
separate combi's. It will do two showers no problem at all.
The Juniors are not condensing combi's, yet overall heating costs will be
equivalent to a one condensing boiler as the upstairs will not be heated
most of the time.
A win, win, situation.
Its advantages a
- space saving (releases an airing cupboard). Both can go in the loft, or
at the back of the existing airing cupboard.
- never without heat in the house,
- high flowrates (will do two showers and fill a bath in few minutes,
- No waiting for a cylinder to re-heat
- Natural zoning, one does upstairs and one does down
- hardly any electrical control work (running a wire to a programmers/stat
and power to each,
- simple no brainer installation,
- minimal components used.
- less piping used
- cheap to run overall as upstairs would be off most of the time
- etc.