"Dave" wrote in message
ups.com...
Doctor Drivel wrote:
""Pet @ www.gymratz.co.uk ;¬)"" wrote in message
. uk...
I was contemplating a project for a long time in the future, and stumbled
upon an idea...
Our boiler MAN (ecohometec) can use pre-heated water to reduce/eliminate
required heat boiler input into DHW. Logical use of this is a Solar
heated
water bank thing before the boiler. That's the easy bit.
Next idea was on Wind power. Our home is in an ideal location to catch
the
SWesterly winds blowing up the Bristol channel see S.W. picture he
http://www.gymratz.co.uk/pete/sunset1.jpg
So, assuming I could get planning to erect a 2.5KW turbine, the ideal
scenario would be have the turbine feeding an immersion heater in the
heat
bank (something like the following:
http://www.eco-hometec.co.uk/solar_cylinders2.html
So Solar by summer and wind by winter, but with the magical bit
happening
when heatbank/store is satisfied....
Electricity being switched by tank thermostat and divered into ring main
as per usual method.
Can anyone see a possible flaw in my plan?
Currently we wouldn't be go the solar route as we only have East/West
sloping roof but that can be sorted with a future flat roof replacement
over the garage.
As it is, it's a "hmmmmm....." plan with much smaller things to be
sorted
first, I thought I needed to get some thought on the idea before I waste
more time on theoretical pipe runs and Mast locations etc.
:¬)
Your Eco-Hometec (rebadged German MAN) is a combi version (DHW and instant
CH in one box) I assume. Roland seemed to be showing a heat bank - a
thermal store using a plate heat exchanger and pump for DHW take off for
the
cylinder. Look at this web site for an explanation. http://www.heatweb.com
The Eco-Hometec cylinder is a normal unvented cylinder with a solar coil.
It
needs to be fitted by an approved installer and cost around £60 to £100
per
year for an annual service. Any gain via solar or wind is negated by the
service charge, so a no. no.
Try a vented heat bank (variant of a thermal store using a DHW plate heat
exchanger) heated directly by the boiler (no heating coil in the
cylinder).
Heat the cylinder via the CH section of the boiler. The wind turbine can
heat an electric immersion heater in the cylinder. Any solar can be via a
solar coil, or even directly into the cylinder using an auto drain down
system. This way any energy gained by wind or solar may be used for CH or
DHW, not just DHW. The CH circuit can be taken off the heat bank cylinder
using a Grundfoss Alpha auto variable speed pump.
The cold mains pipe goes through the DHW plate heat exchanger.
Now you have a redundant DHW instant section on the combi boiler. This
can
be used for backup if the DHW pump fails on the heat bank, by inserting
some
valves in the DHW cold mains supply by isolating the combi or the heat
bank.
This is the best approach for you.
You could make better use of the DHW
part of the combi by feeding the mains
input to the boiler with the output from
the plate heat exchanger. The combi
will boost the hot water temperature if the
thermal store is empty or not hot enough.
Firstly the combi, being an on-demand DHW heater, will be restricted down to
a lower flowrate than what the plate heat exchanger can deliver, so you will
get less DHW flows. The plate heat exchanger sized up properly will produce
all the hot water you need. So, best use the integral combi DHW section as a
backup using valve to bring in. With a blending valve fitted on the flow and
return pipes from the boiler to the heat bank cylinder, the boiler will be
pumping hot water up to temperature, say 75C, into the top of the cylinder.
This 75C water is then pumped out to the DHW plate heat exchanger. In
effect the boiler acts as an on-demand instant water heater when one of
these blending valves are fitted.
This means you can downsize the cylinder size and combine the stored water
energy with the energy produced by the boiler via the burning gas. Have a
larger boiler, and the effect is that you have a very large on-demand water
heater supplemented by a buffer of stored hot water. So you can have:
1. Large cylinder and small boiler (boiler supplements the cylinder)
2. Small cylinder and large boiler (cylinder supplements the boiler)
You can either store energy in large hot cylinders, or use all the energy
available down a gas service pipe and little hot water storage. You can
even have two small boilers connected directly to the heat bank and have
backup if one boiler drops out.