Heading into the home heating season, I am giving consideration to
installing a log burner. The existing fire opening and flue are
adequately sized for something up to 12kW and I think a flexible liner
should be easy to install. There is enough dead standing timber on the
farm to see me out, so security of supply is not a major issue.

However, although this is an open plan house including open stair well,
the most convenient location is in a room only 14' x 14'. I guess
anything over 6kW in such a small space will seriously overcook us.

Conversely, the ability to draw off useful hot water seems limited to 1
or 2 kW at most.

At the risk of awakening Drivel, how would one incorporate such an
intermittent source of heat into a gas fired fully pumped system? The
existing hot water cylinder, pump and controls are conveniently directly
above the preferred location: assuming the joists are adequate!

regards
--
Tim Lamb

Tim Lamb wrote:
Heading into the home heating season, I am giving consideration to
installing a log burner. The existing fire opening and flue are
adequately sized for something up to 12kW and I think a flexible liner
should be easy to install. There is enough dead standing timber on the
farm to see me out, so security of supply is not a major issue.

However, although this is an open plan house including open stair well,
the most convenient location is in a room only 14' x 14'. I guess
anything over 6kW in such a small space will seriously overcook us.


Open the doors Tim. It will at the least heat the room above, and some
adjacent ones, leading to a general reduction in CGH bills, and a
woodburner can be throttled way back, especially with good dried wood as
fuel.


Conversely, the ability to draw off useful hot water seems limited to 1
or 2 kW at most.

That is enough to fully heat a large insulated house for 3/4 of the year.

At the risk of awakening Drivel, how would one incorporate such an
intermittent source of heat into a gas fired fully pumped system? The
existing hot water cylinder, pump and controls are conveniently directly
above the preferred location: assuming the joists are adequate!


You probably need some sort of secondary pump and seection of morosed
valves that will circulate that hot water thruogh all primaries instead
of te boiler. I.e. some form of changeover switch so that when there is
enough heat being produced by the fire, it takes over as a 'boiler'


An alternative approach would be to run the CH/DHW return through the
woodburner to 'preheat' the water ..that would work very well indeed,
except that when the burner is on, and there is no call for heat I can
foresee the ruddy thing boiling. ISTR the usual approach here is a
gravity fed towel rail or whatever in the woodburner circuit.


MM. I think the latter approach offers the best way..just need a way of
dumping heat out of the burner backboiler when no call for heat exists.
Maybe you could couple in some kind of thermostat to turn the pump on
and the CH on whenever the boiler reaches critical temps. And use the
house CH as a heat dump. Simply wire that lot in parallel with your
normal timer and main stat..

Interestingly, this approach means the stove itself when not lit becomes
a rather cute radiator..



regards

You might find the Rayburn tech page on plumbing in solid fuel stoves
useful:

http://www.rayburn-web.co.uk/raytech/dhw3.htm

On Wed, 10 Sep 2008 12:47:45 +0100, The Natural Philosopher wrote:

You probably need some sort of secondary pump and seection of morosed
valves that will circulate that hot water thruogh all primaries instead
of te boiler. I.e. some form of changeover switch so that when there is
enough heat being produced by the fire, it takes over as a 'boiler'

No a solid fuel boiler must be able to dump it's heat without any
power(*). ie an open (as in no valves, other than isolating ones for
maintenance) gravity loop. You interface this to the existing system with
a "dunsley neutraliser".

It would be wise to have a radiator (more than a towel radiator as well)
on the wood burners gravity loop as a place to dump heat when the HW
cylinder is boiling (literally). This can be controlled with a thermosatic
valve, that is one with a wax sensor on the pipework which opens the valve
when it gets to hot.

(*) Partly so you don't run the risk of having a valve fail closed or a
power cut when you are not around with the fire burning and the thing
exploding or generating rather more hot water, steam and pressure than one
would like. And, probably more important so that you don't have to shut
down your independant source of heat when there is a power cut.

--
Cheers
Dave.

On 10 Sep, 15:07, " wrote:
You might find the Rayburn tech page on plumbing in solid fuel stoves
useful:

http://www.rayburn-web.co.uk/raytech/dhw3.htm

I'll confirm the use of the Dunsley Neutraliser, which is almost like
a miniature heat bank. The alternative is to go the heatbank route
and run the wood burner into a second coil. You most certainly, as DL
says, must run the wood burner in a gravity feed manner. You'll find
the DN's via Google.

My system runs both DHW and CH through the neutraliser so that the
wood burner can support the CH when it is running well. I've a
differential thermostat of home design to switch off the CH boiler
while the wood stove is hot enough to run the CH.
It may be that with the low HW output you have that the Neutraliser
should be on the DHW path only.

Rob

robgraham wrote:
On 10 Sep, 15:07, " wrote:
You might find the Rayburn tech page on plumbing in solid fuel stoves
useful:

http://www.rayburn-web.co.uk/raytech/dhw3.htm

I'll confirm the use of the Dunsley Neutraliser, which is almost like
a miniature heat bank. The alternative is to go the heatbank route
and run the wood burner into a second coil. You most certainly, as DL
says, must run the wood burner in a gravity feed manner. You'll find
the DN's via Google.


Not neceesarily. The woodburner here had a gravity rad as emergency heat
dump, bur was coupled into the pumped storage in normal operation.

I never figured it ourt completely though, and removed it all when the
house got demolished.

Perhaps that is teh answer: a gravity loop when a 2-way motorised valve
is 'off' and then simply in series with the boiler when 'call for heat'
is on.


My system runs both DHW and CH through the neutraliser so that the
wood burner can support the CH when it is running well. I've a
differential thermostat of home design to switch off the CH boiler
while the wood stove is hot enough to run the CH.
It may be that with the low HW output you have that the Neutraliser
should be on the DHW path only.

Rob