My original plan for our house was to have a wood burning stove without boiler and rely on MHRV to move the warm air through the house. However, I'm concerned that the living room may still get too hot and I am therefore wondering about a stove with back boiler conected to the DHW and heating system. My question is:

Is it possible to connect a wood burning stove's boiler to a system where the hot water tank is on the ground floor (as is the stove) and the gas boiler is on the first floor? (The hot water tank will also have solar input).

Open vented, surely?

You can easily do that with a sealed system and mains pressure hot water, so long as you provide a gravity heat-leak circuit. The tricky bits are ensuring you don't get ant gravity circulation to the mains pressure hot water cylinder (which is easy in your case), finding a suitable stove, and finding a competent installer.

I'm having a similar system put in, designed to take an additional oil boiler if necessary. In my situation, the hot water cylinder is directly above the stove, so I'm having to use zone valves prevent gravity circulation.

T

So as long as I have a gravity heat-leak radiator (or would that be radiators?) upstairs, there is somewhere for excess heat to go. And since the hot water tank is on the same level as the stove there would be no problem with gravity circulation... What would such gravity circulation do to a mains pressure hot water tank?

What about the need for one of these H2 or Dunsley Neutraliser things? If we need one, could that be sited adjacent to the gas boiler or would it have to be by the DHW tank?
When we have sufficent output from the stove we'd need to pump that heat round all the radiators - what's the simplest way to control that?

Is no-one going to challenge the idea that the living room would get too hot? Would MHRV not move the air round the house sufficently? (I'm still hoping this would work since it is simplest! )

MarkH Have a look here,you could configure solar in too if you talk to them,they were very patient with me! http://www.dunsleyheat.co.uk/neutralizerlayout2.htm

Wow deja vu Mark H! We were discussing this same old link-up debate way back in the 'first' woodburning phase on the back of the Dutch Elm tragedy in the late 70s/early 80s. And not much has changed. Everyone's two penneth worth makes for some very 'interesting' plumbing that I or A N Other competent installer ends up ripping out in a few years time cos at best it doesn't work and often is plain dangerous. Great source of work, but not much fun for the homeowner. A little knowledge....

Basics first: Wood/solid fuel/bio mass in domestic installations in the UK still require an open-vented arrangement (header tank) for the primary system serving the boiler itself, AND cannot legally be connected to a secondary unvented cylinder to provide full gravity (thermo-syphon) function, meaning that you need either two loft tanks, or go the thermal store (vented) route with DHW capability for one loft tank. The continentals are more advanced than we are on this - though as their equipment needs regular servicing and maintenance, I would question the point of the advancement. Convenience of siting seems to be the major thing. Plus higher water pressure.

Link-up:

Yes, you can use a DB Neutralizer. Advantages are connectability. Period. Disadvantages - you HAVE to use the heat as you produce it - disadvantage!
Ditto the H2 panel which originated as 'Link-Up' in the 80s and was a Honeywell product. Advantage: convenience of connection and control. Same drawbacks as the DBN.

To me, long-time woodburner and pyromaniac, having a great fire in the evening is wonderful. But it's an awful lot better if I can get up next morning to a warm home using the heat from the woodburner from the night before. Meaning I don't have to light the fire early (!) or use the gas (!) (oil in my case). That's what a properly-designed Thermal Store can do for you. I design and install my own, and many are on the ground floor adjacent to the stove. Many advantages and merits, not least that you can connect solar, heat-pump, stirling engine, CHP, fuel-cell, (OK, I'm in hyperbole mode, but you get my drift) as the technology becomes available, or you can afford it. Future-proof heating, I call it.

Hope that gives some perspective.

Crusoe

Correct me if I'm wrong, I have always been taught that solid fuel systems must always be open vented.

If you heat water it will expand, with expansion comes increased pressure in the system, as pressure is increased so the boiling point of water is increased. At 3 bar water boils at around 144 degrees C, if it escaped to the atmosphere at this temperature (i.e. you turned on a tap) it would cause a steam explosion.

You have been mislead. Expansion vessels and pressure relief valves (among other things) ensure the safety of the system. An unvented cylinder typically holds water at about 60c - that's a big safety margin! When the water gets to 60c, you stop heating it. The primary system has to be able to dissipate the heat from a back boiler, which it can easily do. In a power cut, you rely on a gravity circuit to dissipate the heat, but if the stove itself is thermostatically controlled ,that's no problem.

The cylinder is protected by an expansion chamber and a pressure relief valve. It can't be heated in a power failure because it's also protected by a couple of zone valves that fail in the correct way. Furthermore you've got at least 35c safety margin in the tank which is heated by a primary circuit that is designed to fail first. The cylinder pressure relief valve might be set at 6bar, whereas the primary system will be set much lower, say 3bar. A working primary circuit cannot overheat the cylinder. So for the cylinder to become a problem a whole lot of reliable components would have to fail simultaneously, plus you'd need a power cut, plus you'd need the stove thermostat to inexplicably fail, plus the law of gravity would have to change, plus you would have to be out!

Dantenz Tom is right - you can have a woodburner with boiler on a pressurised system IF the boiler is designed to work under pressure (not many are).
Heat will leave by thermosyphoning to the heat leak rad and a cunning valve system is available that flushes excess heat down the drain and lets in colder water into the system thus getting rid of heat/pressure.
Plus the stove would be a thermostatically controlled one so it is not actually uncontrollable - the air supply to the stove is controlled by the water temp - if it gets too high the air supply shuts..
: )

Would someone please find and quote the specific regulations that require a boiler stove to be connected to a vented cylinder? I have looked for it, and it appears to be an urban myth propagated by plumbers.

What you _have_ to do is comply with the manufacturer's specifications, prevent gravity circulation to an unvented cylinder, and perform the building control notifications.

Just use a thermal store and get the unvented benefits without the risks.

Crusoe, I'm guessing your equine friend is a cross between a donkey and a bull. May I humbly suggest you take some of from riding around on your chimera to read the regs. I mean actually read them for once, because you clearly have not.

You are a classic example of why all these registration schemes are a scam!

I'll post pics of my sealed back boiler system when I get round to it.

Tom: This is beginning to sound less like a tirade and more of a crusade. Which is a shame as you sound like an innovative guy. Few points before I get into the technical grist:

1. I Don't understand the syntax in the 2nd sentence of your 1st paragraph. Please clarify.
2. I believe you are confusing chimera with hybrid. Chimera is by definition two genetically different animals, which wouldn't make it equine (Latin - equus). I would accept mule as it's nearer the mark (Lat. mulus).
3. You're shooting from cover. You can google me anytime you please, or go on the various bodies I mention to confirm that I am indeed a registered and qualified person to be offering advice on this subject. You haven't answered my point about offering unqualified and hence possibly dangerous or misleading advice, as opposed to suggestions. Please post your relevant qualifications. Because you can read or misread B Regs doesn't mean squat. Sorry.
4. What am I looking for when I read the B Regs? You already said they don't say it can't be done. I believe you. What's your point? They don't say lots of things can't be done, but rely on common sense and good practice and mfrs' advice. In this case two negatives doesn't mean a positive.

If you read my original post, I note that such continental systems are available, and biomass plant, commercial systems and now gassification plant likely would often be pressurised. But not an unvented cylinder. Nobody's saying it can't be done. B Regs don't say it can't be done. They also don't say you can't connect a heat-exchanger from a lorry's waste engine heat.

It's not what they DON'T say that is the issue here. The plain fact is that woodstoves and unvented cylinders are naturally incompatible due to the nature of their design. Yes, this can be engineered around - All things may be possible - not all things are desirable. You may have found one manufacturer who is willing to do this in the UK - bully for them. It doesn't make it technically correct or desirable for the majority as your posts are suggesting.

Thanks for the info re. the scam - Gosh, I never realised 'all these registration schemes are a scam' - and there was me forking out for what I considered good advice - so by definition all these plumbers are plain incompetent. Heck, I just realised all the manufacturers must be in on it too...

For anyone unclear on this subject despite (or because of) this bit of fun, don't take my word (or more especially Tom's) for it. It's actually a serious subject, with potentially disastrous implications of you get it wrong. Which is why long-standing, leading stove manufacturers DON'T RECOMMEND IT. Try calling them if in doubt: I have, and it's a no-no. The following are people I have personally dealt with over many years. Their advice can be trusted. Just talk to technical, not sales! Sales promise you the world... :)

Aga Rayburn 0845 2638178
Woodwarm stoves 01884 35806
Charnwood stoves 01983 35806
Clearview stoves 01588 650401

Also, talk to the unvented experts. There are many. I tried Tribune (Range Cylinders as they are known):
A BIG no-no here too. I wonder why. 08452 607260

Try the regulatory body for solid fuel/wood in the UK, HETAS. (rough equiv of CORGI for gas or OFTEC for oil) Their technical side is answered by the SFA, who state categorically that they do NOT recommend this. They are on 0845 2233033

Lastly, consider a non-technical matter close to the heart of every right thinking capitalist manufacturer: COMMERCIAL ADVANTAGE...yes please! IF it is so good and easy to do what is being suggested here - ie connect a woodstove to an unvented cylinder, WHY haven't all the above, and many more jumped on this new, profitable bandwagon? That's not to say they won't If and WHEN it becomes a widely accepted practice.

In the meantime, if you do the above contrary to mfrs' advice, be in no doubt, it is illegal and you will be liable for prosecution. Despite the fact that building regs does not say you cannot do it :)) Esp if you are one of those urban plumbers propagating myths.... (see Tom's prev posts). Though Bit difficult to be prosecuted if you are lying in a hospital bed with steam burns (fenlandhall, earlier post)

Logic says that, no matter how many gizmos we come up with to engineer around a solution, if there are basic scientific incompatabiity and safety issues attendant, we don't do it. But, even if we do, and all eventually accept it, it will always be a grey area because of the science. Heck, even with 'controlled' appliances like oil/gas boilers, you have to be specially trained to fit UV cylinders due to the higher level of risk associated with them (tho check with Tom as this may well be on his list of scams...) which is why manufacturers like Tribune recommend annual maintenance of their kit.

That spells expense. I'll pass and fit a thermal store...original models still going strong since 1983. Thanks. If you are unclear, like recent whispered comment from stove installer Roy (please re-post in forum Roy, as many have similar questions!) I read a very simple paper to CAT members' conference on the subject of 'future-proof heating'...projects I have completed over the years. The link is about 3 pages long, but google 'ben shirley cat members talk 2008' and it will appear. Similar papers are available on request about the differences between 'link-up' and 'thermal store'. And yes, having installed many of both, I am biased. Heavily. Cos I try not to let my training get in the way of my education.

Sorry about length of post. No further need to debate technical merits or de-merits as it's getting away from the useful side of giving advice.

Happy reading.

Crusoe

fenlandhall: They are OK - see original post. Put the original version in for likely half a dozen customers. And taken a few out. While control is enhanced and they are convenient, they are no different from neutralizer in one respect - that you need to USE the (space-heating) heat as you produce it (key point) which means re-lighting early next morning, or using automatic fuels. I would rather store some of that heat to use next day as I feel it is a. more user-convenient b. more eco-friendly and c. what woodburning to water is all about.

Try googling the CAT talk - might be interesting.

Regards

Crusoe