"John Aston" wrote in message
...
"John Aston" wrote in message
...
I'll do a test to see how long it takes to fill
a large bucket from the main
supply stopcock where water comes in to
the house...
I did the test at 8.30 this morning.
My main stopcock in the house is a 32mm bore quarter-turn valve*. I
couldn't
take the water directly from the stopcock outlet. It had to first go
through
a straight 2m run of 15mm pipe before I could discharge it into a bucket.
(*Note: There is also a 25mm quarter-turn stopcock at the water meter end
of
the supply pipe.)
I comfortably filled two 15 litre buckets in one minute.
Your problems appear over. 30 litres/min is good enough. This should be
fine for 2 showers and one bath on a mains pressure system. Go for:
1. A heat bank
2. More cost effective:
View two combi boilers. One doing one zone of space heating (upstairs) the
other doing another (downstairs). Each boiler will have a programmer/stat
for each zone, preferably a Honeywell CM67, or equiv. Combine the DHW
outlets just before the bath using non-return valves and a small shock
arrestor expansion vessel, as per Worcester-Bosch Tech dept. It will fill a
bath pronto and give good power showers for two showers.
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 one 24kW
and one 28 kW. That is cheaper than the Worcester HighFlow 18 litres/min
floor mounted combi and can deliver about 21.5 litres/min @ 35 degree temp
rise and never run out of hot water. The highest flowrates of any
infinitely continuous combi is 22 litres/min @ 30 litre/min temp rise, 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. No complex and space
consuming zone valves used. 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.
If having two showers, have the shower split between the combi's to reduce
influence from one to the other.
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.
Do not exceed the gas meter flowrate of 212 cu foot per hour. To calulate,
e.g., a boiler is 100,000 BTU/hr "input". Divide by 1000 giving 100 cu foot
per hour. Add up all the appliances.
The Juniors are not condensing combi's, yet overall heating costs will be
equivalent to one condensing boiler as the upstairs will not be heated most
of the time.
A win, win, situation.
Its advantages a
- cheap to install.
- quick to install.
- 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 as two boioers are used.
- 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.
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