What would YOU do.

Having read the following remark repeatedly when "trawling" through the various threads- "the more you read the more confused you get" I`d like to clarify by asking the following-hopefully giving suffcient information to allow a constructive view.
I`m building a large four bed house with four shower ensuites one also with a bath. (Its not anticipated that more than two maybe three showers would be going in a an hour). Underfloor heating using Uponor. Four towel rails. Downstairs WC. A drying room/airing room has been catered for with a mix of underfloor and a radiator for high level. Obviously dishwasher/washing machine.
I`ve considered heat sources and discounted heat pumps, air conditioning units as air source heat, PV cells and solar. I have two major restrictions firstly the house is in an area of outstanding natural beauty so planning restrictions and secondly my personal dislike for solar on roofs and attached to buildings. My "green credentials " will extend to a pellet boiler but not immediately.
SO with no gas I`ve ended up with oil.
Further information is mains pressure is minimum of 10 bar ( already advised to fit a pressure reducing valve set at about 5 bar).
Want power flow showers so mains pressure.
Heat loss calculated at just over 12kw. - house obviously very well insulated and designed to get as much solar gain as possible.
Questions are
FIRSTLY make/manufacturer and type of oil boiler.
SECONDLY unvented or vented ( I would like to install myself if possible so pressurized system ill-advised and would be illegal)
THIRDLY whose thermal store.
FINALLY as an ageing sceptic I find it difficult to find it possible for the thermal stores to provide an adequate heat source for the number of showers required against the heat loss of the building. It seems logical that I`d have to over size the boiler to provide the flow rate compared to the underfloor heating requirement ( incidently there are 18 heating zones plus towel rails etc as stated).
One final point if important and that is that the underfloor heating is via wireless controls and includes an outdoor weather sensor.
I hope I have made my self clear in the above "book" and as stated given enough info.
Thanks in anticipation. JD

Sounds a beauty!
Only bit I can comment on is the thermal store, as we have one.
If you want multiple heat sources eg oil and pellet, and want to self-install, unvented isn't that much use. Vented and showers don't mix, so you're left with a store.

Water coming in needs to be checked for flowrate litres per minute - pressure will help, but is useless without a good flowrate. For either a thermal store or an unvented, what goes in is the same as what comes out - so in our case we fitted a 250l accumulator to help the flow during showers - and it seems to work, but for 2 to 3 showers at once, you'd need something big - 500l or more possibly. Needs sizing by a heating engineer - try asking dual/duo stream what they'd recommend sizewise.

If you are considering pellets, try the navitron woodburning section, and it may be worth approaching the pellet boiler supplier to see what they'd recommend for stores - 1000 litre stores combined with pellet boilers aren't unheard of. In your case having two cylinder/stores with the smaller one as a buffer may be if use, then you're not heating 1000 litres during the summer purely to get hot water.

There is a way to work out heat exchanger efficiency and therefore production of hot water and work it back to basically how many kwh you need stored to produce x litres if water at y degrees temp rise, eventually giving the store size for your showers.
You're right about space heating vs hot water energy, but if you go pellet burning, it does appear that the bigger the better, then the stored heat lasts for a few days rather than a few hours. Our 300l is little more than a buffer tank when the rads kick in, your requirements are biased more toward the hot water, so any store and associated waterheating should be sized to that rather than the minimal amount of space heating it appears you need.

So, if you do get a thermal store, go nuts with the hot water spec - we have an external plate heat exchanger, which on top of doing what it's designed to do, will also perform with the store cooled to well under it's design temp. Ideal for scale as it can be binned or flushed out, as it's not part of the store itsself.
DPS do plug'n'play design-your-own thermal stores with large hot water capabilities, ideal for DIY but they are mega £££ - whereas a lot of manufacturers will build what you want anyway for far less if you get the bolt-on bits yourself (pumps, stats etc) - just ensure hot water spec is OTT. I'd recommend getting loads of sensor tappings on the store as well - we have five I think and could do with more as we will have gas, solar and wood sources eventually.

UFH works at low temps, so can be tapped off low down on the store and still work fine - if you only need 12 kwh for 18 zones of heating I reckon a lightbulb would keep you warm enough as it sounds like you have shares in Kingspan. Our gas boiler just comes on a few times a day - if you have 18 zones, each independent, chances are a conventional direct to boiler setup would have the boiler on and off every five minutes. You'll even be able to run a separate pumped circuit for the towel rails from the store independently of the ufh - so a store has definite bonuses there.

Hardest bit is getting concrete advice and finding people who can sell you the right bits. I know nuheat (advance make their/our stores) use stores with their ufh - if uponor do the same may be worth asking them what they recommend. Note the nuheat store (and ours) is a sealed system design same as a combi boiler - runs at 1bar or so with an expansion vessel sized to cope with the whole store/rad system. Most stores are vented with an overflow tank and ballfloat etc in the loft.

I'd also say I was, if not a sceptic, certainly very nervous between buying the store and firing it up. Also, and I know it's a personal thing, I'd be going ground source heat pump in your case, subject to space, as it's ideal for ufh.

Book #2 ends!

just to point out if going unvented, forget solid fuel being hooked up to it.think with thermal stores theres more of an advantage.

holty said:

just to point out if going unvented, forget solid fuel being hooked up to it.

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why?

one of the questions is simple to answer: unvented.
an old fashioned open tank is utterly disgusting.
why would you build a house in the 21st century and only be able to drink the water from the kitchen tap?

jddevel wrote

I`m building a large four bed house

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Heat loss calculated at just over 12kw. -

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How large in sq meters?
Are the bedrooms 6' x 6' with a heat loss that low?
Just working on a 4 bedder at the moment. 379sq meters of UF heating with 1 bathroom, 3 ensuites and downstairs shower. 210/L UV is being considered with solar being added later.
Grant Vortex will supply the heating coupled with a decent weather compensator controlling a single rotary shoe mixing valve.
Three heating zones (loft will have radiators at a later stage) using motorized valves with no actuaters on the manifolds and no room stats.

bengasman said:

one of the questions is simple to answer: unvented.

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I believe you can run water, through an unvented cylinder (via a coil), from a solid fuel burner.

bengasman said:

one of the questions is simple to answer: unvented.
an old fashioned open tank is utterly disgusting.
why would you build a house in the 21st century and only be able to drink the water from the kitchen tap?

Click to expand...

It's a southern problem Ben, the stupid practice of only supplying balanced cold to a bathroom. Up here we supply mains cold to bathroom and only put balanced cold in if there is a shower. And that just for the shower.

I was brought up in the south so I know how stupid they are.

Goldspoon said:

bengasman said:

one of the questions is simple to answer: unvented.

Click to expand...

I believe you can run water, through an unvented cylinder (via a coil), from a solid fuel burner.

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Its the way you cant effectively control the heat produced by a solid fuel burner that becomes a problem when trying to conform with G3

Whilst I must thank those who have taken the time to reply I must confess I question that those making both churlish and I believe unnecessary remarks should be listened to.
Regarding property. It has a total floor area of a fraction over 240 sq mtrs. Every consideration architecturally has been taken where possible regarding windows size,type and number. Solar gain from positioning and very high levels of insulation where practical.
From my research since DPS (DEDICATED PRESSURE SYSTEMS LTD) and ACV Ltd for example both, when told that I was considering a pressurized (unvented) system said that if I had the space why on earth was I doing that. They believed that they could and indeed (well DPS has- ACV said it was a standard tank- best to have hot water only) now have, designed such a system to run both the showers at mains pressure via a thermal store and in DPSs` case the underfloor to boot. They have made provision for the addition of solar should I or a later occupant decide to make this addition. Obviously I`m not that naive not to realise they want to sell me the equipment. But I have seen them recommended via other threads on this site. They were certainly very concerned about using unvented with solid fuel and its controlability.
So it just remains to find an oil boiler to go with it.
A Merry Xmas to All and a Prosperous but above all Healthy New Year. JDDevel

I understand what you say lcgs. Solar heating is also not controllable yet you can run a coil through an unvented cylinder.

I called the Solid Fuel Advisory Service and asked - they said you can pass a coil through an unvented cylinder (indirect) - you just cannot do anything "direct".

Sorry to have offended you jddevel.
The grant vortex is a very good boiler. (But don't take it from me)
You can see an example of an installation I did with a grant a while back on the following link.........
//www.diynot.com/forums/viewtopic.php?t=156525&postdays=0&postorder=asc&start=0
Prepare to be stood back in awe at the sight of supreme craftmanship at the zenith of perfection.
Perhaps I could give you a price.
BTW that property in the pic is also situated in an area of outstanding natural beauty so being aware of that I realised that the quality of the workmanship woud have to be top notch.

I've been staring at the 'zenith of perfection' for a while, and it's just dawned on me that it would actually work like that
Pffft, and there was me impressed with my guy using a spirit level on his pipework.

Well its been working 24/7 since late October Gordonpants. Had the boiler stat a little high at the start and over cooked the slab a wee bit but no harm done. The slab was laid early April. That little domestic circulator can manage 1/L min through 23 loops of UF pipework.
Joiners are not too impressed though as they cannot fit a few of the doors.
Happy Days.

back on to unvented, and solid fuel. most are missing the point. direct or indirect.solid fuel is a source of uncontrolable heat. as an unvented works on a set of safety controls to stop undue overheating, a solid fuel system will not work on unvented.unless a good designed system is done. but yet G3 does not permit this.as for solar it has its own design for overheat.being done be zone valves to the cylinder.