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Wood burners with back boilers.


f1steveuk

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Just because it's a sealed system does it need to be pressurised to about 1bar or so? As long as its got an expansion vessel would that not be enough to displace any water expansion, and of course a relief valve. We run a wood/coal boiler in France and the gauge has never gone up to one bar even when its hot.

Just a thought.

Steve

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Depends on the volume of the system, the surface area of the heat exchanger and the ability to move heat around the system. A 16 kw back boiler at full chat can be an effective steam generator if circulation is not good. Steam in an enclosed system needs to be respected ....a plug of boiling water issuing from a failed pipe or fitting does not bear thinking about hence my slightly OTT comments to urge others of a DIY bent to consider their design.

The Quebb has a PRV on the boiler but I will replace it as a matter of course

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We've had a Villager for 19 years in Britain and I'm pretty sure they are imported into France.

The last two winters it's come into its own as the oil price has become uneconomic for heating (1991 - 11 p per litre,   2011 -  75 p per litre).    We've another half ton of coal coming tomorrow.    It struggles to run our full twelve radiators but is fine on six,  which is all we need.

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Can I suggest that anyone considering this heed the warning so far posted and add another.

To make fire any Pompier will tell you that you need 3 things; Fuel, oxygen and heat; (self evident isn’t it!!)

But if you remove one of them then you don’t have a fire. So in this case if you are getting a nice fire going and then you start to circulate through the back boiler with a forced pressurised system then you will soon strip out the heat of the fire it will labour producing masses of soot and eventually go out.

The results are many including: cold house; wife on the warpath; p$ssed off husband, chimney nicely sooted up in preparation for the next raging burn which might result in a chimney fire, and so on and so on.

There are several clever remedies to this as the problem is by no means new. The first clever devise is a laddomat to control the circulation of the water though the radiators based on a critical temperature base line over which the pump is turning under which it stops to let the fire recover.

that this thing..

[IMG]http://i584.photobucket.com/albums/ss285/andrewhenderson/Solar/LADDOMAT21-100ISOLERAD_Mindre.jpg[/IMG]

The second clever thing is a Accumulator, to store heat produced by the stove when its burning to be re-circulated when its not. I think the use of this storage is pretty self-explanatory, but it surprising the number of installations, which don't have one. Its making the most use of the energy the so rooms don't get too hot and still the fire can burn efficiently and still the excess heat can be used later. It’s really a no brainer.

that would be one of these...

[IMG]http://i584.photobucket.com/albums/ss285/andrewhenderson/Solar/AKVAir2000Connected-1.jpg[/IMG]

Anyone who is interested to see a schematic of how that works, send me a PM

Andrew

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A no-brainer until one looks at the costs of Andrew's suggestions I daresay.

Careful supervision of a fire largely obviates all of these problems in our case,   and we have a pumice-lined chimney which is designed to clean itself.   Yes we have to close four valves when we want to go back to oil but that's not exactly difficult,   and motorised valves (for example) have a nasty habit of failing,   expensively.

The two people we know who have gone for Rolls Royce solutions to their heating requirements in Britain (one a Kidd oil boiler,    the other some sort of wood pellet burning boiler) have had nothing but problems (the pellet burner has left them in the cold two Christmas's running) and HUGE service costs on top,   which have more than wiped out the promised energy savings.

I'm sure Andrew's suggestions are fine if one has the up front capital.  But like all things if you are prepared to do a bit of supervision "simple" can work just as well.

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There are much simpler and cheaper solutions to the problems of condensation etc. with wood fired boilers than the ones described above.

It is essential that any solid fuel system is open, not sealed, and ideally there should be a gravity circuit as well as a pumped circuit.

Many people don't realise that if you are using a back boiler most of the energy will be absorbed by the water circuit and this may mean that there is insufficient radiated energy from the stove to heat the room in which it is located.

All these issues can be overcome with careful design and installation.

PS. I'm curious about the Turbo Fonte as I can't find any reference to water back boilers on their site.
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