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Wood fired Central Heating.


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I am sure there must be members of the forum here in France who have wood fired central heating.

Mrs PD has set her heart on a Rayburn 370SFW central heating cooker. I have no problems in agreeing.

However, the 370SFW is not (yet) available in France according to Rayburn France, but may well be later this year. ''IF'' we get one it will probably be by buying it in UK and bringing it ourselves.

Our main problem at the moment is designing an appropriate CH system. Technically this is/ was not difficult until the question of domestic hot water cylinder is addressed. As everyone knows (?) the standard French system is a sealed DHW cylinder with a GdS to vent any overpressure. Such a system does not seem to compute when it comes to solid fuel systems which, I am told by all and sundry, require an open vented cylinder with the necessary head tank, a la UK old style systems.

Such a system, I believe, contravenes French Normes, but does it really ?????

I can hack the feed & expansion tank requirements of the solid fuel boiler but I don't really want to go for a head tank driven hot & cold domestic system with the potential for low water pressure to the shower, even if it was ''legal'' to do so.

Another issue seems to be locating 28mm copper pipe in the Brico sheds, it doesn't seem to exist.

So basically, I am looking for feedback from anyone who has had, and overcome, these problems.

Any comments ?????????
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I might be able to help but from an off the wall direction i.e. narrowboats.

Most people who live on them have central heating. Before cheap diesel fired systems became available most used a coal fire with back boiler and radiators. Basically these system are designed to be gravity fed but of course that does not make the water flow very well so a pump is introduced. The pump is triggered by the outlet temperature of the boiler rather than traditional gas boilers where it is triggered when the boiler lights automatically. They also need bigger pipes because the flow rate is very low due to the low ability to keep the system temperature constant with regards to the water being heated by the back boiler which takes longer. Running these type of systems does require an expansion tank which is also where the system vents if it ever 'steams' up. As your wife will discover cooking with these type of ovens is quite different to 'normal' ones. Most manufactures do hold courses and there are books you can buy. Just like her concept of cooking this way is so different to 'normal' cooking so is the way the central heating system works.

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[quote user="powerdesal"] I am told by all and sundry, require an open vented cylinder with the necessary head tank, a la UK old style systems.

Such a system, I believe, contravenes French Normes, but does it really ????? [/quote]

Personally, when I (perhaps) address this question, PD, I have already decided on a Ballon for DHW, which enjoys Bi-Fuel or even Tri-Fuel inputs and thus heat exchangers. Why Bi or Tri? Since one can utilise Solar Evap collectors; the built in electric immersion and, potentially, sub-feed from the solid fuel boiler; pumped. In any case, the old concept of a gravity-fed, open vented system with an expansion tank for over-pressure/over heat, seems now to have been super-ceded by closed systems.

I must say, our neighbours (in France) have a sparkling newbuild, and he demanded wood-fired heating and DHW: it was very complicated (looking at the pipework when it was installing) and he is far from happy! The truck loads of wood he buys each Summer seem to vanish rather quickly: and they are forced to use electric random heating when it is really cold! And this, despite super-insulation: he carried out the second-fix on the built shell, since he's a plasterer (British) by trade. Not only were the walls hugely insulated, but also every ceiling downstairs as well as upstairs and the loft!

OK; your case is a tad different as you want a range plus CH+ DHW.

A wee bit like using an estate car instead of a van for work and a saloon for leisure, I fear......

My final choice is a gasifying wood burner and huge thermal store: but still retain the trusty old ballon, on cheap (or cheaper, these days!) rate.

With Solar input into a new ballon, eventually.

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We had radiators working from our wood burner in France, we needed a

pump with ours, and it was not a sealed system, there was an expansion

tank in the loft. We did not have domestic hot water from this fire.

The

problem for us was that when the electricity went off, which was fairly

frequently we had to dampen down and put the fire out as the system

started to 'boil'. I suppose if we had had domestic water, we could have

just run off the water.

At one point we had a secondary electricity system, via batteries, or some such thing.

I

always have alternative heating now, independent of electricity, so a

wood burner would sound like just the thing for you if you get the rayburn.

We use our wood burning stove more than the heating these days. And I have just come in after being out for lunch and for all I left plenty of wood on the fire, it was just about out.

The problem for you is, that how do you keep the house hors gel if you are out or away. We have our gas heating on very low in some rooms, keeps the chill off, but getting something that burns wood takes quite some time to get heat in the home once one gets in.

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Idun,

I suppose it's all down to the individual lifestyle.

We ( only the two of us ) are retired, we do not go out to work and, apart from being out for a few hours on the odd occasion, we spend the vast majority of our time on the property. Hence keeping the stove stocked up is not a problem.

When we go away for holidays / short breaks ( caravan) we do not leave any heating on. Being that the CH would be for winter use and we don't tend to go on holiday in winter anyway it would not be a problem.

Our existing wood burner in the sitting room will stay lit for many hours, it stays in all night after being banked up at 10 PM until being 'flashed' back up at 6 AM. Going out for lunch / shopping / whatever for a few hours in the day is not an issue for us.

The Rayburn 370SFW is said to be capable of overnight burning when banked up, albeit at a 'tick-over' rate.

Gluey,

We are rapidly coming round to the decision to just have the Rayburn for CH ( and cooking ) on an open vented F & E tank and retaining the existing electric DHW system. Our hot water use is quite low due to there being only the two of us, using showers not baths ( Haven't had a bath for years and years !!!!!!! ) and having a cold fill washing machine.

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PD, you are now both elderly and getting less able and strong by the day, so you want a system that takes the minimum of effort to manage and maintain. Wood ain't it, frankly, nor anything where you have to lug bags or whatever about. So, go electric or oil or gas with maybe a few logs for winter pretty, pretty!
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[quote user="woolybanana"]PD, you are now both elderly and getting less able and strong by the day, so you want a system that takes the minimum of effort to manage and maintain. Wood ain't it, frankly, nor anything where you have to lug bags or whatever about. So, go electric or oil or gas with maybe a few logs for winter pretty, pretty![/quote]

Actually having asked about the price of running town gas central heating in another section thats the way to go. 350 Euros a year to keep nice and warm and get hot water, I think thats cheap and hasle free.

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Using an electric storage heater (Ballon) for DHW is, IMHO, the best option, PD.

[quote user="woolybanana"]PD, you are now both elderly and getting less able and strong by the day, so you want a system that takes the minimum of effort to manage and maintain. Wood ain't it, frankly, nor anything where you have to lug bags or whatever about. So, go electric or oil or gas with maybe a few logs for winter pretty, pretty![/quote]

I also much agree with Wooly's ethos, PD.

Best real solution is chips or pellets: since a hopper fed boiler is self-sustaining. Plus one can also enjoy remote ignition by telephone/internet.

Problem here is the fuel cost; and the space to store a year's supply: however same comment re wood, whether gasification, or combined boiler-cooker.

One putative solution which has not really been pushed thus far, is the concept of a large thermal store, heated primarily by off-peak electricity, plus solar evap arrays for when sufficient solar energy is available. A small number of UK manufacturers are producing basic electric power thermal stores and they are slowly being specified, mainly for new build blocks of apartments.

See Here:

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I did know somebody in The Midlands who bought a house 20 years ago that had a water thermal storage with about half a dozen tanks which had been placed in big wooden boxes with a shed load of compressed insulation around them.  This was because at the time thermal storage tanks were not being fabricated so you had to make your own. He had solar heating panels covering one complete side of a roof and they were backed up with immersion heaters in the winter. I had never seen anything like it before in my life (and nothing since) yet he said it worked very well and was incredibly cheap to run. The age of the system must be about 25 years now and as he sold ten years ago I have no idea if it still functions and how well it still function. I guess what I am saying is that this idea is not new, the principle has been around for years and the technology no doubt has advanced a massive amount as has probably their efficiency.
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Wooly and GS.

What is this ''elderly'' bit ??????

Stacking, cutting and moving logs keeps us fit. We also have a hydraulic log splitter and two chainsaws.

Should the day ever come when I can't move a barrowload of logs from the wood shed to the house we will 'possibly' convert to another method of heating, but by then this house will probably be too big to be manageable and we would move.

If mains gas was available we would jump at its use, but it's not. Oil is not going to get cheap in the long run ( forget the present 'blip' in oil prices ), LPG ( GPL ) ditto. Electricity would need an upgrade in supply. Pellets were seriously considered but a cost analysis showed they are not, at the moment, an option.
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I'm not having any of this we're fit and old, we only are, until we aren't.

ie husband's aunt and uncle moving to the top of a very long steep hill in their mid 70's, 10/12 years later...... and I frankly lose patience.... 'we never imagined that we wouldn't be able to manage it anymore[:(]'

I don't tell them that I think that they were short sighted and foolish, but that is what I think about it all. And she was a nurse. My Dad was running all over the world until a very few years ago and at the gym every day until three years ago, at 90 he can hardly walk and for all he has his marbles, he cannot do many things these days.

Plan ahead is my moto. And there are many ways of keeping fit.

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[quote user="powerdesal"]Wooly and GS.

What is this ''elderly'' bit ??????[/quote]

Wooley, not me, Mate! Just I have found (as has Mrs Gluey), after 12 years or so of cutting, stacking and carting logs, one becomes a wee bit fatigued by it!

And that's one reason why I like the gasification/thermal store route: one three hour burn  per day and job done for 24 hours!

[quote] Should the day ever come when I can't move a barrowload of logs from the wood shed to the house.........[/quote]

Ah ha: one of my planned investments for this year, is a nice towable trailer to go behind the lawn tractor!

[;-)]

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Another vote against PD - sorry.

My additional reason is that while cooking on a wood burning stove may seem very romantic - and as you have already done this in Wales - somewhat practical, I can assure you that in France in summer, it is anything but practical to fire up the stove to cook a pan of new potatoes, or to roast a chicken leg to go in tomorrow's salad when the outside temperature is 30 degrees plus.

When we bought our house the only cooking facility was a wood burning stove with back boiler. That is how I know just how impractical it is for 4-5 months of the year.
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Idun said: "The problem for us was that when the electricity went off, which was fairly frequently we had to dampen down and put the fire out as the system started to 'boil'. I suppose if we had had domestic water, we could have just run off the water. "

I fitted a coal fired c/h system in our home in the UK. It was normal practice with solid fuel to design the system so that one or more radiators, capable of handling the heat produced by the stove, worked by convection if the electricity failed.

We didn't opt for logs because a local farmer who had installed a wood system found that it used so much that he continually had a trailer of logs parked outside his kitchen window.

Steve
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If I have understood, convection, would mean that the water would rise into the radiators onto the floor above????

 We lived on the first floor and the only radiator that wasn't on the first floor was one in the downstairs hall, what ever, once the electricity went off it would sound like the expansion vessel above us, was full of boiling water and so the fire had to be put out gently.

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"If I have understood, convection, would mean that the water would rise into the radiators onto the floor above????"

It wouldn't need to if suitable radiators were on the same level as the stove, but yes. If you imagine two vertical pipes, joined at each end and completely full of water, if you heat one of them and cool the other, a convection current will flow round the loop.

"We lived on the first floor and the only radiator that wasn't on the first floor was one in the downstairs hall, what ever, once the electricity went off it would sound like the expansion vessel above us, was full of boiling water and so the fire had to be put out gently."

An out of control fire producing more heat than it can handle is a scary thing.......

Steve
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I have seen one steam up, well the aftermath to be exact, quite a mess. It blew most, if not all, the water out of the header tank. The problem is that after a few years the water becomes a horrible brown colour, probably from the radiators, and as tains just about everything it comes in to contact with and you can't get rid of it. The problem is the boiler, not so much on the heat side as the cooling down, can crack. If you have a ball valve on the header tank that lets cold water in and once the steaming up has finished the cold water goes back into the boiler thats when it cracks. I was told that you need to let the whole thing cool down naturally and the worse thing you can do is throw water on the fire. Not only because of the mess but also it can cool it down to quickly. Basically you get a metal bucket and remove the fire. Gas and oil are a lot better because if the power fails they won't light or stay alight and if the water out gets too hot (like if the pump mechanically fails) there is a thermocouple that turns off the boiler. My parents had an Aga which initially was coal fired but when my father added a back boiler to run radiators it was changed to oil fired primarily because of these problems.
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A few comments,

Summer cooking, we will have a summer-use cooker and will not be using the woodburner, that's what we did in Wales as well.

The runaway fire / overheating boiling issue is conventionally addressed by the installation of a ''heat leak'' radiator which should be sized at not less than 10% of the boiler output, our will be 17% as it happens. Some sources recommend 20%.

The primary pipework is arranged to give a gravity circuit in the event of a pump failure (for whatever reason) with nothing interfering with the flow from the boiler output, through the heat leak and back to the boiler, all in 28mm copper with 'slow' bends to minimise restrictions. This is 'industry standard' installation. That's why heat leak rads are usually in a bathroom upstairs with the boiler on the ground floor.

Putting out the fire in a boiler. Never, ever, use water. As someone said, you will possibly / probably crack the unit. Sand is probably the best or ( I believe) salt can be used but I can't confirm that. Obviously totally shutting off the air supply will also reduce and eventually stop the burn. In the case of a CH cooker, opening the cooker top lids will dump heat via the hotplate, as will selecting heat to the oven.

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getting back to your system problem, You can still have a sealed, mains pressure hot water vessel connected to your taps. the vented hot water circuit can feed an inner coil and transfer heat from the boiler into the vessel without mixing of both waters and so can be connected using a low pressure vent and feed system through your solid fuel heater, you must fit a copper or steel expansion tank and ball valve as if it does over boil, they can distort or melt if in plastic.

Next problem is obtaining an indirect vessel in France, I haven't seen one but haven't had the need to look for one, readily available in England, the circuit from the heater will need to be connected to include a heat dump radiator, normally a towel rail fitted in bathroom and due to the new vessels pipe sizes a low speed running pump may need to be fitted to ensure circulation through vessel and back to heater, as to French rules, don't know the answer.
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Well according to Rayburn the 370 SWF is a vented pumped boiler.

Instalation Guide

It's a PDF file and there is a good picture of the way it all goes together, page 8. It also appears you need a cold water feed tank for the hot water cylinder.

On the website is does talk about the nessesity to keep the wood wood dry which means a wood shed. Working on the three pile circular use system thats a lot of wood you have to buy the first time round. The added cost, unless you don't mind cutting yourself, is that it needs to be in to no greater than 360mm lengths according to page 4 of the user guide. The ability to burn through the night will depend on quality of the wood you put in it.

User guide

There is an English run company in France that sells wood burning cookers "Stove Sellers" who sell amongs other brands Rayburns. Rather than rely on the 'guessing' of the forum I would start by contacting them as I am sure they may well be able to answer your questions about installing one in France and what the legislation is here with regards to their installation. Don't forget if you tax resident you can get some money back with regards to the installation.

Best of luck.

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Q,

Thanks for your comments, I have already downloaded the Rayburn files. I have spoken to Rayburn UK and am in contact with a Rayburn installation technician on a personal basis. The 370 SFW, as all the SFW Rayburn models does require an open vented Feed and expansion tank, together with a specific pipework arrangement to give a gravity circulation capability. The pump system is for driving CH radiators and an open vented indirect DHW cylinder. The gravity circuit in effect hinges on the incorporation of the injector tee shown on the rayburn piping layout together with 28mm piping and minimised flow restrictions. The heat leak is part of that circuit. The gravity circulation would only come into play if the CH pump failed to run for whatever reason. The pump is normally switched on by the built in high temp thermostat ( replaces the use of a 'pipe-stat' on the older models) even if the pump is selected off by a control system. The use of an open vented F & E tank is part of the safety requirements of all solid fuel fired water boilers. UK regs I know ( part G if I remember correctly ) but they are the regs I am familiar with.

Regarding wood, we already have a wood shed which generally has a stock level of 18 stere, with a minimum re-order stock level of 6 stere. Our existing logs are 330mm long to cater for the sitting room woodburner. We order wood yearly to ensure that it has additional drying time above that done in storage by the log supplier.

I am not relying on the guesswork of forum members but rather am asking for opinions and experiences. Knowledge gained by others and passed on can be a valuable feature.

I believe the tax refund system is dependent on having the installation totally installed by a registered plumber. Any work done outside of that professional work does not count. As all the radiators and piping have been / will be done by me means that cost is not counted.

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Have a look at http://www.gledhill.net/images/spec%20123%20renewable%20cylinders.pdf

The jury is out as to it being a good idea on an unvented cylinder as they are worried that if the pressure and temperature safety valves should fail the vessel overheats.

I am in the process of fitting an open vented solid fuel heating system to mine but without the connection for hot water, relying on elec only for the ballon

D.

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