Heat recovery on a stove with wood (optimization)

[the middle]

patkersule, mmoi my heating regulation is:
the boiler always maintains a setpoint of 60 ° C and always turns (just to regulate) as well as the regulator.

my thermostat controls a 4-way mixing valve, which mixes the cold return from the heating loop with the boiler's own loop. the thermostat must have 3 wires (common, normal open, and 1 normal closed for the 4-way valve).
yes 2 loops, a boiler hot circuit and a radiator heating circuit!
this is the best "I presume" principle ...

This system has the advantage of avoiding thermal shocks on the boiler. Going from 15 to 60 ° C several times a day is not the best (some boilers do not take these constraints)

[jonule]

ok I make you a diagram!

[patkersule]

woaw !! thank you !!!

I leave on the idea to experiment with the capture of calories
by coil around the stove pipe.

about 20ml in diameter 16, what spacing advise me
you between two turns? knowing that I am inserting a sheet
copper between the conduit (pipe) and the coil.

the tube will be welded at several points see cords if I
do not have deformations .. to improve the transfer ..

all circulating in a steel radiator, placed 1 m above
of the coil ... I start to collect the stuff ...

there is no one among you who has a steel radiator
in the corner, morbihan finistere (south) .. lol

good luck, I will have to take measurements too ..

if this system is not efficient, I would make a loop
on the heating return when I understood how it works.


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[toto65]

Could we push the smoke rather than pull it?
I resume my diagram:

Do you think the duct will cool down too much? And will it clog, clog the duct?

what spacing do you recommend between two turns

I hesitate between two solutions
1- as close as possible. to reduce losses.
2- on the usable length of the flue.
As you use copper foil between the pipe and the coil,
It shouldn't cost you too much either.
Are you going to isolate everything?

[jonule]

Hello,
this is how it is with me:
regulation by 4-way valve, the boiler and the circulator all the time it requires less input (the burner is started not long), the boiler has a summer / winter position for DHW (domestic hot water), I also have a small 2000W 30L electric storage tank for the summer, to save the burner, which is ... 1972!



thus the thermostat controls the 4-way mixing valve, which is a stepping motor, also disengageable by manual, and which does:
- either the boiler turns on itself, so it consumes almost nothing and is maintained according to the aquastat that I set at 60 ° C (possible up to 90 ° C).
- either the flow and the return are mixed with the radiator loop, depending on the thermostat setting.

we can therefore imagine that if the return is + hot (heated by a wood fire) the boiler will force less on the fuel, while the cricator works!

on the other hand when the wood fire is not in service, the fuel oil heating heats the wood heating for nothing ...
I would like to clarify that in my idea the radiator is not placed in the smoke duct, but in a dry brick wall against the wood stove, as shown in the middle of the message.

the second idea is to consider a single cast iron radiator heated by a wood fire, like a solar panel, and to connect it to a modified hot water tank DHW (exchanger).

[patkersule]

Thank you very much for your details and sketches,
it's much clearer, I'm going to look
tonight behind my boiler (which is only 2 years old)

see how i can install all this ...

instead of making a coil around the duct
maybe I would put a similar system,
see costs / performance ...

about my essay,

I saw the copper sheets in gsb, I would be limited
for the installation of the coil by the size of this
leaf, I start on 1 m high ...

except that, depending on the spacing between the turns I put some
30 or 40 turns ....
for the price, it's hard to get a copper sheet
on the side of the road nowadays ...
so if someone has a steel radiator
it will already be that ...

[fc89]

Hello,

Toto65, a little warning for your fan-based system pushing the fumes, not rather a big warning, if never the blown air can come out or that you compress in the conduit by accident, it is the dead waiting for you all, then think well for such a system.

For the other system, recovery of calories through the flue pipe, I have already experienced it, with 3 m of copper surrounded around the pipe, I fired it after 2 months, because it had retained so much soot and the bistre that one day the smoke from the liver came out of the front window, after researching the why and the how, and I suspected it a little the exit of the body was almost blocked by a deposit of soot.
So make sure that the soot can fall back without accumulation.
A+

[toto65]

good evening everyone
fc89 you are right to remember the danger of hacking which can be very dangerous.
In the diagram I just indicated the principle.
No need to spend 3 hours on the computer with a real diagram for a bad idea at the base.

For 3 m of copper surrounded around the pipe you already foul!
What was your home? What was your hot water temperature?
Well, it chilled me. I clean up for fitness at home.
I barely have 50cl of soot a year.
Hase stove LUNO model. 6m of stainless steel sheath diameter 125 smooth interior wall.

[fc89]

Hello,

Toto65, it is very difficult for me to give you figures because the system no longer exists.
I still remember that I closed a valve in half to feel a difference in heat between the inlet and the outlet.
The pipe had a diameter of 14mm.

I can give you fresh figures, currently my Supra 18KWh chimney, it seems to me, heats a medium fire, some flames, some embers, 2 small logs of 12 to 15 cm in diameter and the outlet is at a temperature 350 ° (a probe is permanently there),
all the shutters are closed, 1m higher the stainless steel duct is only and barely 80 °.
I specify that my home is transformed into aqua-radiant.
A+

[loop]

Hello

Toto65, I think the problem with the air pushed into the chimney flue is that you increase the pressure in the flue and in the fireplace too
So, if there is a poor seal on the stove door for example, the risk is to bring out the fumes in the house
In addition, the electric motor will not necessarily withstand the heat near the duct, which is not the case with an extractor which is placed at the chimney outlet, propeller in the duct, motor above, outside
fc89 you are right to emphasize safety, it is essential, on the other hand your misadventures with the obstruction of a part of the conduit gave me an idea
Why not voluntarily cause fouling at a selected location in the duct
For example, on a part of the duct just after the hearth, why by horizontal, and especially of an exaggerated diameter to be sure never to plug it
One could even imagine that the heat capture (cooling of the duct) is located on the lower part of the horizontal duct, in order to facilitate their evacuation (and / or sweeping) at the same time as the possible condensation.
Also think that soot, if it does not settle in the duct, ends up in the atmosphere, which is not necessarily great

Good reflection

A+