Megaflow, oil and solar

We have decided to put in a Megaflow system. We are also considering solar heating. We have oil, how do you connect both up?
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Suz wrote:

With great difficulty and to very little effect I'd say.
Probably the most sane thing to do is to run the incoming mains pressure water via solar panels before it gets to the tank.
That way your £60 a year hot water bill will reduce to £55.
Until the solar panels freeze, of course..
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Not a fan of solar then? You have a bad personal experience?
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On Sat, 16 Dec 2006 15:58:32 +0000, Suz wrote:

Have you done the calculations on how much solar costs and how much energy it saves compared to spending the same £££ on other energy-saving measures such as draught-proofing, insulation, more efficient appliances and controls, and building improvements (such as porches to buffer external doors)? As TNP implies the amount of energy used for water heating - and thus the potential for saving through solar water heating - is typically dwarfed by the amount used for space heating. Solar is pretty expensive: the same investment put into reducing space heating demands can usually yield far greater benefits.
And you can always stick some glass-framed panels on your roof if that's what matters: nobody will know they're not real. ;-)
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Haven't done any calculations at all. The house is already double-glazed and there are no draughts apart from up the sitting room chimney. We have mostly all energy saving bulbs apart from the dimmers in the sitting room. When we do our renovations of course any extensions will be as energy efficient as possible. We plan to have all triple A applicances. I have already asked on this group about sensor lights etc. With a lot of hot water being used and thinking of adding a large whirlpool bath, I liked the idea of getting free (?) hot water for it. There is a portion new roof being added just right above where we hope to have a Megaflow, so I wanted to check it out. The direction of the roof isn't efficent enough for solar PV, but should be for solar heating.
Megaflow has a brother, Megatech solar, a new product designed specifically for solar, so I'm checking that out. There was some guff on it's site about direct and indirect. One was for adding to existing system and the other was for new installs. However the new install didn't seem to have oil backup so I'm a bit confused.

They are flaming ugly, wouldn't do it for for the look.
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wrote:

They will save you about £30-£50 per year. Look at the price increase on the "solar" tank and the price of fitting solar heating panels. If you shop around carefully and do it all yourself it can just about be cost effective in a couple of decades. If you have it done by "professionals" you and your children will die first.
--
Peter Parry.
http://www.wpp.ltd.uk/
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Suz wrote:

The short story with solarthermal is they can pay ok, but only if well designed. Commercial systems have almost no chance of paying back, and are not normally what I would class as well designed.
If you want to go with it, suggest talking to the news:alt.solar.thermal folk. Careful design is needed to get it to make sense moneywise. Theres nothing free about the energy.
Solarthermal space heating has much lower install costs and higher returns.
If youre putting solar flat panels onto a new roof, the sensible thing is to build it into the roof, displacing some tiling. It wont stick out like a sore thumb and it saves n tiles. Make sure the glass is toughened, wired or laminated.
NT
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The short story with solarthermal is they can pay ok, but only if well designed. Commercial systems have almost no chance of paying back, and are not normally what I would class as well designed.
If you want to go with it, suggest talking to the news:alt.solar.thermal folk. Careful design is needed to get it to make sense moneywise. Theres nothing free about the energy.
Solarthermal space heating has much lower install costs and higher returns.
If youre putting solar flat panels onto a new roof, the sensible thing is to build it into the roof, displacing some tiling. It wont stick out like a sore thumb and it saves n tiles. Make sure the glass is toughened, wired or laminated.
NT
Cheers NT
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I think it's only solar PV panels that can be built in. All the solar heating (thermal) jobbies look like they are added on top. Our roof is tiles and not slates, so I think the built in solar PV tiles aren't suitable anyway.
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Suz wrote:

Theres nothing to stop you building solar thermal panels into the roof. There are even commercial panels available specifically for this.
Forget pv, they make no sense at all.
NT
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On Sun, 17 Dec 2006 14:58:42 -0000 someone who may be "Suz"

http://www.imaginationsolar.com/solarp.htm is for solar water heating, though one can also have PV panels put in the same covers to produce a hybrid system. Note however that the underside of the PV panels must be kept clear, to allow adequate ventilation. This means one should duct the heat outside the building as PV output is highest in summer when heat is not wanted. Some of the heat could be recovered by a suitable heat recovery system.
Roof tiles are no problem with such systems.
--
David Hansen, Edinburgh
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wrote this:-

Ours are ridged tiles. Makes no difference is they are on top or slightly sunk in. They would just look very different to the roof.
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On Sun, 17 Dec 2006 18:33:48 -0000 someone who may be "Suz"

Indeed. However, one avoids the complications of penetrating the roof with fastenings, pipes and cables and making these holes waterproof.
Roof integration is generally marginal on existing roofs, but worthwhile on new roofs, when installation is easier and one does not need as many tiles.
--
David Hansen, Edinburgh
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On Sat, 16 Dec 2006 21:14:20 -0000 someone who may be "Suz"

There are roof integrated solar panels, which can be installed in place of tiles or whatever. One example of these is http://www.imaginationsolar.com/solarp.htm

Any good reasons for going for a mains pressure hot water cylinder? If there are then the solar panel is connected to an extra coil in the cylinder, which is below the coil fed by the boiler. There are some examples at http://www.navitron.org.uk/pricelist.htm , under the "Mains Pressure Hot Water Cylinders". Make sure the size of the cylinder is suitable for your application and the size of the solar collector is suitable for heating the cylinder contents completely in summer.
If you just want mains pressure hot water then there are many advantages to a thermal store, including the fact of avoiding an annual service. In this case the oil boiler and heating system are connected to the shell of the store, which acts as a buffer. The solar circuit is connected to a coil in the bottom of the store.
--
David Hansen, Edinburgh
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Question:
If the thermal store is hot ( heated by the boiler ), why does the solar panel not operate in reverse: loosing heat from the heat bank to the outside, acting as a giant radiator?
--
Ron



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On Sun, 17 Dec 2006 10:27:03 -0000 someone who may be "Ron Lowe"

The answer is, it depends.
Firstly, one has got the controls very wrong if one ends up in this sort of situation.
Secondly, with the more advanced controllers the controller will not operate the pump in these circumstances.
Thirdly, even with simple controls the fact is that the sun is still heating water in the panel. As one manufacturer states http://www.solartwin.com/technical_faq.htm
"Q: During the winter months when most of the hot water will be generated by the boiler, what happens if there is enough sun to set the pump in action. At which time there is not enough thermal energy to heat up the water sufficiently so that when it is returned to the hot water tank it reduces the temperature there?
"A: The pump runs only on solar energy in the form of electricity. It has no temperature sensor, only a high pressure bypass in case the panel or its pipes are frozen. In response to your question: First - best not to have the hot water system on all day since this is wasteful anyway and does not allow for optimum solar performance. Most boilers have separate timers for this, but not all. Ideally time the boiler to add heat to the domestic hot water after 4pm. Second, even in winter some hot water is made by Solartwin, not all by the boiler as you say. Third - the panel is well insulated and so will still raise the temperature of water going into it since it collects heat from the sun and not the air. Fourth - at 100% sun and a water input temperature of 50C and air temperature of freezing our mathematical model (based on extensive tests at Napier University) suggests that the water will still leave the panel at least 10C hotter than when it went in. Fifth - if they really want to put cold water in under these circumstances they can connect a second cylinder behind the first and draw water off it! This will also allow for more summer hot storage and is a neat solution for people with AGAs and Rayburns."
Some of the advanced controllers do use the panel as a radiator, but this is in the summer, at night, when it us used to cool the store if it is too hot. An example of such a controller is below, the "mounting instruction" link has details of the control scheme http://www.resol.com/en/Produkte/Solarregler/DeltaSolBS.shtml
--
David Hansen, Edinburgh
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A temperature differential controller stops that.
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Please do not. Fit a heat bank (thermal store) http://www.waterheaterblast.com

Via a heat bank (thermal store), which will give main pressure hot water, no potential bomb in the house and incorporates DHW, solar and CH all in one and giving great boiler and CH buffer.
The only way to go.
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I'm finding the options out there a bit confusing. Isn't a Megaflow cylinder for storing hot water? Can you give me a link to heat bank products so I can have a nosey?
Thanks Suzanne
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Try looking at http://www.heatweb.com/products/cylinders/heatbank/heatbank.htm
{There are other manufacturers.}
There's a bit of 'getting your head around' heatbanks involved. AIUI, fundamentally there's owt for nowt. You must obtain Heat from somewhere and you'll consume Heat whether its source is oil, gas (boilers) or electric (immersion heater) or solar. A Heat-bank will make better use of the Heat you stick into it; but _won't_ magically 'make' heat. A 'normal stored Domestic Hot Water (DHW) cylinder takes in cold water which is heated by 'extracting' heat off a coil [through which a 'transfer-fluid' (actually itself water) heated by the boiler is passed]. The was-cold water is taken off the top of the cylinder where it is now 'hot water' and feeds the taps.
In this 'normal' set up the 'transfer fluid' is confined to the boiler jacket - I'm ignoring CH - and the coil and associated pipery. Essentially the boiler is heating up a small amount of 'transfer fluid' which then warms up a much larger cylinder of cold water.
A Heatbank on the other hand actually has all the 'transfer fluid' inside it and is connected to the boiler jacket. The boiler heats up a much larger volume of 'transfer fluid'. [I did say there's owt for nowt.] Then - as and when required - this ;Bank' of 'Heat' is used to heat up the by means of a heat-exchanger the tiny amount of water flowing out of the tap. It's the 'as and when required' bit that gives the results.
There are lots of advantages , explained on the referenced URL, which I won't bore you with.
Heatbanks store heat (IMHO if the transfer fluid wasn't water they'd be easier to 'get your head around'). Heatbanks can accept heat from many sources; electric, off boilers and solar panels by the number of connections that are tapped into the cylinder. Heatbanks can deliver heat to DHW and CH circuits, once again, by the number of connections they offer.
Most heatbank manufacturers ,AIUI, affect the heating of cold (mains) water to DHW (mains pressure) by means of a plate-heat-exchanger (somewhat like a car's radiator). The Heatbank I've installed cites it's heat exchanger as 160Kw (equivalent). Practically, this means it'll supply simultaneously three baths. We never run three simultaneous baths! but it has that capacity. Once again, there's owt for nowt and the heat has been input from a boiler which is rated at 16Kw. The boiler is buffered (de-coupled) from the DHW and CH circuits by the Heatbank.
AIUI, 'Megaflow' cylinders utilise a coil, inside the cylinder, to transfer heat from the 'transfer fluid' to the DHW. I'm unsure what the heat transfer rate might be with these systems.
IMHO, the choice of 'system' is somewhat like choosing a Religion! There's big-Combi fanatics; there's multi-point fanatics etc. etc. You have to study the competing claims and make a decision which 'religion' you'll follow!
I, too, found the options confusing but I frequented the FAQ and studied the competing postings in this newsgroup than joined the Heatbank coterie .... as the previous poster said; - "It's the only way to go!" ... IMHO .... :)
HTH
--

Brian






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