Does anybody have any experience with heating circulating water in a half inch copper coil behind the heat shield on their woodstove?
Heating water with a copper coil inside the heat shield of the wood stove
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I have no experience in it, but it seems like the way you'd have to wrap the coils would open you up to possible steam pockets. That could give you very bad results.
brenndatomu
Minister of Fire
Ashful
Minister of Fire
There are stoves designed to do this, so if that's your end goal, you might do well to just trade up to one of those. Do note that there are also (nearly countless) stories of exploding boilers in wood-fired kitchen stoves, in the middle-1800's up thru early-1900's. Getting this right is not trivial, there's a reason boilers require certification, and I don't believe copper would be anyone's material of choice for this application.
There was a regular contributor to this forum who mostly focused on wood-fired cookstoves, was a reseller of such, and would be a good resource if you were looking to buy a stove set up with a boiler. Jebadiah stoves, was it? @begreen would remember.
It can be done but you have to come up with a way to absolutely guarantee flow through the coil whenever the stove is running and for a couple of hours after. Unless you have a backup power supply that means you can not burn the stove when the power is out. In addition, you will need a temperature and pressure relief valve on the high point of the coil and there cannot be a valve between the coil and the relief valve. I have a friend that has been doing it successfully for 25 plus years. He has backup power and has fittings that allow him to remove the entire coil if he is in an extended power outage. Note dependent on water quality the coil could scale up and in some cases rapidly so that would need to be considered and you may need to descale the coil at intervals.
My grandparents had one of the old cook stoves. It had a steel pipe from the back of the fire box come in make two 90's then back out. It was plumbed to a 20...? Gallon tank behind the stove and would thermosyph to heat the tank. That was their hot water for close to 50 years until they changed it in... 2005 maybe.
Oh and talk about hot water! The sink was 5ft away and had seperate hot and cold taps.
Oh and talk about hot water! The sink was 5ft away and had seperate hot and cold taps.
electrathon
Minister of Fire
Do you mean outside the firebox, between the outside of the stove and the heat shield? Or inside the firebox above the beat baffle near the chimney outlet?
I have a lot of experience with it. If you do it correctly, it will work. Do it wrong you will be boiling the water in your pipes, that is very bad. I need more information to give specific answers.
Wood1Dennis
Burning Hunk
My folks had a wood furnace was designed to do this. It was a 1980 vintage forced air furnace that came from factory with a heavy steel pipe, maybe 1" that made a pass through the firebox like that. It worked with thermosyphon, no pump, circulated water through a nearby 60 gallon water heater that had no heating elements of its own. It preheated the water that was fed to the power heater.
They used it for about 30 years and during heating season it took care of all the domestic hot water.
Like others have said I would not attempt that as a DIY project. So many potentials for disaster.
Sometimes I am a bit amazed they never had a problem. I do recall a couple of times when the safety release valve on the pre heat tank would vent, if not enough water was used.
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