Which Central Heating System?


Hi all
I'm starting from scratch. House previously had storage heaters and open fires.
I am intending to put in gas central heating. The house is detached and will end up with four bedrooms.
I am aware that there is a choice of systems. However I don't know the pros and cons of each. My plumber is talking about a 'Megaflow' and informs me that tanks in the attic are old hat.
I want to choose a ststem that is best for the job not necessarily best for the plumber( me cynical?).
Advice sought.
mark
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have learned is that if you get rid of your storage and so forth, you have immediadly removed the solar hot water option in the future. If energy prices continue to rie at the expected rate i think that might be more important than mot people think at the moment. Plus all the modern ystems are becoming comlex.
So for my two pennyworth i wouldnt get rid of the tanks in the attic!
Cheers
John
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"Mark" wrote:

Depends which Megaflow he is recommending. Direct Megaflows are powered by entirely by electricity, normally taking advantage of cheaper night-time economy 7 tariff. Indirect Megaflows also have a built-in immersion heater and can also be connected to a gas boiler. Modern electric and gas HW and CH systems are usually pressurised and fed directly from the cold water mains supply so there is no use or need for cold water storage tanks except for toilet cisterns. If you want conventional gas HW and CH in a detached house then you would normally be looking at a wall-mounted condensing combination boiler, something like a Worcester Bosch 24i junior combi. Again, fed directly from the water main, definitely no cold or hot water storage tank.
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Thanks for this. I definately don't want Economy 7, having just come through the saga of getting the dual tariff meter changed to a single tariff meter. I'm adverse to combi boilers too as my experience is that of taking ages to run a bath. So Megaflow is not actually a boiler?
mark
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You should have a look at the DIY wiki: http://wiki.diyfaq.org.uk/index.php?title tegory:Heating Especially the sections on "Unvented DHW" (e.g. Megaflow) and "Thermal Stores & Heat Banks". Both of these systems (as well as old-style gravity fed cylinders) can take multiple sources of heat e.g. boilers, solar, electric immersion, Aga, etc. But this usually needs to be designed in from the start and is difficult to retro-fit.
Personally speaking, I replaced my old Economy7 immersion heated gravity cylinder with an Albion Mainsflow thermal store. It works really well, and I recommend it. I heat it using a small gas boiler with a backup electric element. In my case, the store also feeds the radiators. I'm considering adding solar at some point, but I think I'd do this by adding a second thermal store to pre-warm the incoming cold water, rather than try to retrofit (there are other reasons around stratification and heat transfer efficiency).
You should first check you have a sufficient water supply (both pressure and flow), and with the current problems in mind, a reliable water supply. If this isn't good enough, you could keep the existing water tank and add a booster pump between it and the Megaflow/thermal store. Or you could go for an accumulator (like a giant expansion vessel. This all adds to cost and complexity, and may be beyond the comfort zone and experience of your plumber.
-Antony
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"Mark" wrote:

Combi boilers need a mains water supply of high enough pressure. It doesn't help if there is a long run between the boiler and the bathroom hot tap, and if anyone runs another hot or cold water tap in the building then the pressure drops right down. A Megaflow is a boiler in the sense that it has an immersion heater inside, but that is an expensive way to have HW and CH if the Magaflow isn't being fed hot water from a gas boiler or other cheaper source of heated water.
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Thanks for the feed back guys. Looks like I need an indirect Megaflo. I'm still not sure how a Megaflo is different to a conventional copper cylinder with a immersion heater and an indirect coil.
Next question is what sort of gas boiler do I go for to be compatible with the Megaflow. Is it just a case of any one with the required output?
Thanks
mark
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"Mark" wrote:

Regarding the sort of gas boiler, building regulations now mean that it is virtually impossible to have anything other than a wall-hung gas combination boiler. I can understand having a gas boiler and an indirect Megaflow if you intend adding another system in the future that needs a hot water storage facility, such as solar panels on the roof, otherwise I am not sure why you would want to have the additional expense. There are over 200 combination boilers on the market. You need one that is SEDBUK A rated (90% and above efficient), such as a Worcester Bosch 24i junior. I don't understand why the plumber who recommended the Megaflow hasn't quoted for a complete system including boiler unless he assumes that you will have a direct Megaflow that is powered by entirely by electricity.
You may find the following websites helpful: http://www.sda.co.uk/qsedbuk.htm http://www.gasman.fsbusiness.co.uk/index.htm http://www.makewrite.demon.co.uk/BoilerChoice.html http://www.bhl.co.uk/home.php?cat 49
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There is no such reg. There is a reg (part L) that means you have to have a condensing boiler in most cases.
Adam
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"ARWadsworth" pointed out that:

I sit corrected.
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Not a problem, it is a mistake I once made myself :-) A lot of flues can go through the roof but the maximum length of the flue (on most models) stops the boiler sitting in an old fireplace etc like the good old backboilers. Adam
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I'm no expert on how these things work, but we've just had our old conventional boiler & HW cylinder replaced - with wall-hung boiler (Vaillent) and a Megaflow (Sunrae). I confess we had a plumber do it (way beyond my capabilities) but the outcome is brilliant. High pressure HW - great for showering after the slow drip of traditional UK showers. AIUI (but I may be completely wrong) (1) all boilers these days are "condensing", (2) "combi" boilers don't [yet] have the capability of supplying enough hot water for a larger house. Since you'll end up with 4 beds, I assume you'll therefore need to avoid a combi - for the next occupants' benefit if your own HW demand isn't that high.
Another suggestion (and, IIRC, this was a thread a week or two ago) - have plenty of "controls". We've split up and downstairs rads into 2 separate circuits ["zones"] with "radio" room-stats. These stats are good - and we'll be moving them around for a while, while we experiment to find optimum position. You can't do that with hard-wired stuff.
You're only likely to install this lot once, and have to live with the results. So I suggest not skimping. The total cost dwarfs the cost of the "little" things - such as the radio room-stats, good quality thermostatic showers, TRVs etc.
FWIW, we didn't skimp on the plumber either. But the service, punctuality etc. was faultless - and we didn't get ripped off for extras...!!
HTH
--
Martin
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Thanks for all the feedback. The penny is starting to drop!
As I understand it Megaflo is Heatrae Sadia's brand name and has become the generic name for any unvented hot water cylinder.
I've just spent over half an hour online finding out to whom I apply to to get a gas supply in from the road.Used to be straight forward. Isn't progress wonderful!
mark
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http://wiki.diyfaq.org.uk/index.php?title tegory:Heating
Don't know if you've had a look at the uk.d-i-y group, there's a mine of information there too and in the original uk.d-i-y faq pages: http://www.diyfaq.org.uk/contents.html
You can also search that group on google groups: http://tinyurl.com/65kwq (tiny'd to avoid a wrapped link).
I'm a fan of stored hot water (as you appear to be) but I chose to keep the loft tank, it's a less complicated and cheaper system as the bits don't need to be proof to mains pressures. Technically you're not allowed to DIY a mains pressure water system so there is a further cost implication there. If you're planning to go direct from the mains, do check that you have sufficient flow. The mechanism for checking mains flow should be in the faqs but it basically involves timing how long it takes to fill a bucket of water at full flow (in the bathroom) and doing a bit of arithmetic to get a flow rate in litres/min, if you can't get enough then stored water (header tank) will be required (but may need to be pumped). Be sure to check this at the times that others in your street are using lots of water, morning for showers, evenings for kids baths etc.
Good luck
--
fred
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