Instructables

Wood Stove feeding radiators

Hi, I'm hear again with a completely different question. Again, any help is greatly appreciated :)

I installed a wood stove last year, and I'd like to install a coil to heat water and circulate it through my existing radiator loop.

I was wondering if I could do it as in the image, I would install a new pump to circulate the water.

I have a combination boiler, but I'm sure that doesn't really matter.

The green circles in the diagram are to illustrate taps, that way I can close off the boiler when I have the stove on and vice versa.

Picture of Wood Stove feeding radiators
Hack42Moem1 year ago
In case it's any help: at my local hackerspace, we are using a woodstove to heat up six adjoining rooms, using the radiators. BUT: we bought a woodstove that was already prepared to be used in this way. Still, the information we have on this project may be useful to you. So here it is.

Most of this page is in Dutch, some is in English; the diagram may be useful too. You can always run the page through Google Translate and see where that takes you.

Good luck!
dimmaz88 (author)  Hack42Moem1 year ago
Thanks for your help, I'll have a look now :)
gmoon1 year ago
I've got an old Mother Earth News book (pub 1983) with a section "Wood to Oil to Heat; The Triple Play". It's an external wood stove that heats oil for an indoor system. So it's not a new idea. Whether that can be retrofitted to an existing radiator loop, I don't know (antifreeze would be a must).

They do make commercial heating systems like this--we pass one every time we head to my in-laws. It's a large outdoor wood stove, about 25 feet from the house.

So look to the Mother Earth News website. They've got 30+ years of articles available online. Even if you're looking at recirc water rather than an oil system, I'm sure you'll find multiple references there.
dimmaz88 (author)  gmoon1 year ago
I've checked out those rocket mass heaters, they look great. Maybe I'll try something like that, I might do a test run on my garage :)

Thanks for the help guys
Just to sound a note of caution, you've shown a closed loop system; with a wood fired system it's important to have some form of pressure relief as the heat source isn't as controllable as oil or gas & can cause over pressure & burst pipework. The usual method is a header tank which is open to the atmosphere.
dimmaz88 (author)  GrumpyBadger1 year ago
Thanks for that tip, I didn't think about that.
:)
There are water jacket wood burning stoves built just for this.
To do this with with an existing stove risks the intergrity of the stove.
However coiling around the outside will transfer some heat.
coiling inside will transfer more heat however you have to cut holes in the stove to run the lines and weld them to the tubing to stop gass leakage. Also you could lose your house insurence for modifing the stove.
dimmaz88 (author)  Josehf Murchison1 year ago
I was either going to coil copper tube around the flue pipe, or have a smaller 'square coil' on the back, with a steel plate covering it. I think there will be enough heat to warm the radiators. I basically want to try and warm the house while having the fire going, I don't like using the fire in the living room and using the radiators everywhere else. It seems pointless.

Thanks for the input Josehf.
blkhawk1 year ago
How cost effective is your idea? Although some ideas are good they are not necessarily practical. Although in theory is possible to heat the water with your wood stove via a coil, wood stoves are designed to radiate energy. A boiler has thermal insulation that concentrates the energy around the coil so is designed to do a much efficient job of heating the water.
dimmaz88 (author)  blkhawk1 year ago
The wood I burn costs nothing, and I actually enjoy cutting and splitting it. So on that basis, this idea is very cost effective. It shouldn't cost much to set up, and once done will pay for its self very quickly. I just wanted to use some of the wasted heat in the chimney.
You are better off building a coil around a rocket mass heater, dedicated to warm the water of your home made radiator. With this type of heater you can insulate the coil with some type of reflective material, thus concentrating the heat around the coil. Sometimes vermiculite or perlite insulates the flue of the rocket mass heater. I do not have knowledge of any other form of insulation so you might have to experiment. 
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