In the next couple of years we intend to remodel the back of the house, put
in a downstairs shower and toilet, and do various other things.
This will include replacing the current boiler and doing something with the
hopeless hot water system - at the moment you have to run the water for a
couple of minutes before anything approaching hot water comes through.
Obvious choice is a combi boiler situated close to the kitchen and bathroom
to give short pipe runs and on demand hot water.
However this is also an opportunity to 'go green' with for example a heat
store, solar water heating on the roof, a wood pellet boiler.
This also gives the option of adding other heat sources such as a solid fuel
stove with back boiler to heat water in the winter.
In this case the pipe runs are likely to be longer but good lagging and a
pump may help the 'instant hot water' requirement.
Is this a feasible option?
It looks expensive compared to a combi boiler - at least three major
components at least compared with one - and the financial (as opposed to
moral) payback may be unrealisitically long.
Has anyone gone down this route?
Is anyone contemplating it?
For us it will be a 'now or never' thing as once the house is done we have
no intention of mucking about with it for some considerable time.
We have solar heating (for hot water) and it's wonderful. We haven't
had the hot water heater on since about May. Our last four or five
gas bills have been refunds (compared to our neighbours, who are
paying upwards of £1000 pa.)
We have friends who installed a ground source heat pump and they
report very good results, but you need a big garden.
I've just done the solar panel thing (Navitron evacuated tubes) - still
need to burn gas as the weather recently hasn't been that good, but only
for 10 minutes each morning now rather than the hour or so before.
Biggest difference is probably the triple insulated tank - it's directly
heated from a conventional boiler (standard Y-Plan - not had a chance to
change that yet), and additionally heated by a back-boiler in the cooker
(Stanley range cooker - bit like a Rayburn), as well as indirectly heated
via a coil from the solar panel (which is the only pressurised bit in
the system) Internal coil/heat exchanger in the store to provide hot
water via a mixing valve to keep the exit temp to 50C
The cooker runs most of the winter, but only weekends in the summer,
(it's the only source of heat for that part of the house in winter)
so the store ought to be much more efficient at keeping the hot water
the cooker generates in a more usable state.
A future plan is to replace the conventional boiler with a log-burner,
but the issue then is how to heat the house when we're out for a day
in the winter ... I have half-baked plans to dump the store into the
radiators, but who knows yet.
If you've got a south facing roof, then go for it. Cost of all the bits
for me was just under £2K. (Panel/tubes, tank, pressure vessel, valves
and lots of copper pipe & fittings) I only wish now I'd gotten a larger
panel and tank!
Hard experience is always interesting. I assume this is your £2k total
Can you give any more information on your store (as it's easy to spend
£2k on one of those alone!) What is it? Did it have internal coils
already, did you add them yourself and were they designed specifically
for solar use? Are you monitoring tank temps in this system? Do you
see good stratification of hot & cold water, did you attempt to
encourage this, and do you think it's important in an efficient
I got the kit from Navitron and they made (or arranged to be made) the
tank for me. I had an idea what I wanted, and arranged the details on
the phone with them.
I started with this kit:
and made adjustments on the phone.
The tank is essentially one of these:
It has 2 internal coils - one for the solar loop to dump heat into the
tank, and one for the hot water extraction - this is a coil that enters
at the bottom, spirals up the full height of the tank and exits at the
top. I wish I'd taken some photos through the hole for the immersion
heater now (which I fitted with a blanking plug - might put in an
electrical immersion heater in the future)
It has 2 other pairs of connectors for direct heating - 22mm and 28mm
for the conventional boiler and cooker boiler respectively. These are
approx. 1/3 down for the entry and 2/3 down for the exit, just above
the inlet for the solar coil.
And finally, it's got a cold feed and expansion bottom and top,
respectively which is connected to a small conventional F&E tank in
So it's a thermal store as opposed to a heat bank. There is no external
heat exchanger and associated pump - it's all done via the internal coil
which is finned for maximum heat transfer. We live in a soft water area,
so I'm not concerned about anything scaling up. (8 years and the kettle
is still clean)
The cost from Navitron for the kit just was just over £1,700 - tank,
panel/tubes, pump, controller, expansion vessel and some pipe insulation
In addition, I bought 15mm and 22mm copper pipes, a few bags of elbows,
sleeves, etc. and other misc. items - everything's soldered where
possible. I upgraded some existing valves to full-bore levers, changed
some leaky pump isolators and so on. (Screwfix to the rescue!) I was able
to recycle a lot of old copper tubing from the old setup as I went though.
I have 2 temp sensors in the tank - it came with 10mm tubes fitted to
put the sensor into the middle of the tank (they're sealed at the
far-end!) The bottom one is in-between the entry & exit of the solar
coil, (which in in the bottom quarter of the tank) the top one just
under the hot-water exit. There is a 3rd sensor at the solar panel, and
that plus the tank bottom sensor is used by the controller to turn the
solar loop pump on. (Simple difference which is all programmable in the
controler) The 3rd sensor goes into the controller too, but isn't used
for anything right now, other than to display it.
I plan to use the top sensor to turn on a heat-dump pump during the summer
when the tank temp exceeds 90C to stop it boiling. (The controller can
The tank does seem to naturally stratify and I think this is good. When
it's low on heat, reducing the hot water flow makes the most of what's
left in it - the cold entering the bottom through the coil does take what
little heat is left in the bottom of the tank while leaving the top as
hot as possible. I've seen the bottom at 25C and the top at 50C when
looking. (I got the cheap controller TDC3, so I can't put it on the
house LAN to remotely check it)
Other than convection from the solar coil, water in the tank only gets
agitated by the boiler pump - so 10 minutes in the morning, and even
then, the bottom of the tank doesn't see much of an increase. (I have
the pump set to slowest speed) I've yet to see how the cooker boiler is
going to affect it though - I've only done one trial run of it so-far,
but we'll be cooking this weekend, so will find out more.
It's still very early days for this yet, so still getting "used" to it
and working out how to make maximum savings. E.g. the run to the bathroom
takes 20 seconds and it's in 22mm pipe which I can't practically change,
so we've decided that we'll wash hands in cold water rather than waste a
long 22mm pipe of hot, but we're not afraid to take hot when we need it -
the kitchen is much closer and piped in 15mm from the tank, so minimal
lag to get hot water.
Not tried filling the bath up yet - I suspect it may require a gas burn
if it's not been sunny...
On Wed, 9 Sep 2009 11:04:40 +0100 someone who may be "David WE
Make sure the thermal store has enough tappings/coils for the
sources of heat you might use. Solar needs a coil, assuming you want
it to be on a separate circuit filled with antifreeze and
pressurised to better resist flashing to steam under stagnation.
Other sources of heat and radiators can just be on tappings.
If you are considering underfloor heating this is in many ways best
fed by a coil fairly low down the store, to get a better temperature
for it, though it is possible to mix down hotter water.
You may want a separate shower coil for mains pressure showers,
while having the rest of the hot water system as the better gravity
fed system via a separate hot water coil.
If in a hard water area plate heat exchangers are the thing to do
for, though they are more expensive.
Is there a problem locating the store near the kitchen and bathroom?
The pipes from solar and other heat sources can be well insulated to
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
Solar HW usually fails to ever pay its costs off, but its not
impossible to make it work financially. Have fun designing a system
that will do so. Needles to say professional systems are the least
likely to pay their way.
I agree that if a system is "professionally" installed then the payback
time can be very long indeed - mostly due to the so-called professional
installers ripping the customers off... (IMO - e.g. a relative paid 4
times what I paid for my system, but she got a 15% grant so that was
However a DIY install, which is what I've just done ...
The capital outlay for me was just under £2K and it's already saving me
money - a mere 10 minutes of gas burn a day rather than the 1-1.5 hours
it would normally take to heat the old tank up in the morning. Today
the suns been shining all day and the bottom of the tank has gone from
27C to currently 58C and there's another 3-4 hours of usable sunlight
to go. At this rate I won't burn any gas tomorow at all.
Now, it can probably be argued that part of my savings has come from
having a much more efficient water storage system, but even so - I'm
getting free hot water today, and enough for tomorow too!
I have to say, one of the reasons I wanted it wasn't to just save money,
but to get-back at the greedy energy company shareholders.. Even so, I
appear to be doing both. It will take some time (and a winter) to fully
work out the payback time, but I don't care - I can see savings already,
so I'm happy.
(OK, still cavorting about like an evangelical maniac, but I think it's
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Gordon Henderson
It's no use trying to talk sense to him about diy solar - I would 't be
at all suprised if he's in the pay of BNFL to promote nuke power and he
certainly has a severe wasp up his arse every time someone mentions
Funny, last time I pointed out this was a diy group and I was diy-ing
solar, he shut up.
Glad to see someone else doing it and putting the nay-sayers' gas at a
Heh... Intersting to read the other comments while shutting up for the
past few days... I find it intersting that no-one actually asked me
what I think about it all, nor why I was doing it, but rather assumed
I'd been conned by the greenies, or hype surrounding it all. Ah well.
All I'll say is that I'm a Geek, Engineer and Scientist in that order,
and leave it at that.
Now, anyone replaced central heating system with a home-made controller
based round e.g. Arduino? I've only recently realised how crude central
heating systems really are regarding their controllers and choices made
in them. Must have been a genious of a madman that invented the 3-port
valve! MOMO valves would appear to be the way forward, but I guess 30
years ago were quite expensive...
And now to have a free hot bath, heated by the sun and by-product of the
cooker. Spent the day with the chainsaw filling the wood store (we have
2 wood stoves, thinking of a 3rd)
Someone asked on Any Questions 'what are you doing about climate change,
For anyones information, THIS is what I am doing about climate change,
personally, telling the facts.
If solar hot water made the slightest sense economically in this
country, or saved any significant fraction of CO2 emissions, I'd be for
it, even if it was not completely and utterly misleadingly missold.
I am PISSED as hell because some smart talking salesman sold my father
in law 2 grands worth of kit, on the promise it would save 'up to half
his heating costs' (which run about £2500 a year) when the brochure
itself and the figures it quoted showed it would save at most £150 a
year, and moreiussu overhauling either.
I am PISSED as hell because it does NOT have an energy meter on it. Just
a temperature gauge. He still thinks that because he is 'getting 70C' on
the roof, it actually means something. It is a carefully crafted CON
trick and he has been ripped off of savings that he really cannot afford
So yes I DO have a wasp up my ass.
Ad far as nuclear power goes, I am for it because my training as an
engineer, my ability to actually do sums and also my time managing
financial affairs for businesses show that it is actually the ONLY power
generation technology of sufficiently low carbon cost, low actual cost,
scalability and energy density to actually SOLVE the problem of the
countries energsy needs without wrecking the planet completely.
All other technologies, apart from heat pumps, are simply incapable of
supplyinmg more than a very small fraction, and in most cases, at vastly
higher costs, and in the case of the so called renewables, at such low
energy density that literally MILLIONS of square miles of the country
would be needed to be completely covered with them in order to get
anywhere near the output thats few nuclear sets could give.
I didn't write it, but I was instrumental in getting it published,
because it is the first book that actuality tells the facts:-
Do yourself a favour, in your smug self righteous selfishness, that you
have stuck two radiators on your roof and saved yourself £50 a year, and
actually start taking an interest in the real issue: whether or not you
or your descendants will be alive in 50 years time.
The FACTS say that without massive nuclear power, you or they will *not* be.
On Sun, 13 Sep 2009 22:56:44 +0100, The Natural Philosopher wrote:
And I see the author is just about to take up a government post as an
advisor in the Department of Energy. I just hope he has the guts and
strength of will to kick the politicians into actually doing
something that will produce real results instead of just pandering to
the media and lining their own nests.
And I suspect Miliband may well regret making this statement "There's
no danger of power cuts in the next decade."
well if you hadn't spent the money on it, you would still have the
money, no matter what the greenycons shout.
The dangerous thing is that the greenycons DO influence a LOT of people.
It wouldn't be so bad if
(a) the world could afford it
(b) it actually solved the CO2 problem
Not only does it do neither, it also prevents attention being directed
at real solutions.
Greenpeace are, by and large, traitors to the human race.
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