# Looking for advice on wood stove heating coil project



## sain6815 (Aug 17, 2017)

Hey everyone,

Looking forward to being a part of the community. This is my first real post. I'm looking for advice on whole home heating with my wood stove insert. I have an older large triple walled buck stove insert that was already installed when i moved in. 

I'm looking to add a coil made from stainless or iron pipe in the firebox. I plan to use an open tank so there is no pressure and circulate water from the firebox to the tank via thermosyphoning. My plan is to use one circulator pump to move water from the tank through a heat exchanger located in my air handler plenum.

I have a masonry fireplace that runs from the basement up through the middle of the house. Woodstove is in the basement and the mechanical room is on the other side of the fireplace on the same level. So my tank will be elevated slightly so thermosyphoning can take place. 
Just looking for others who have gone ahead. 

I'm well aware of the dangers involved. I have a background in construction, plumbing and electrical. I'm also well aware of the dangers steam can create which is why i'm going with a pressureless system. I've done extensive research, just looking for anyone with personal experience that could advise me on design and performance expectation. 

Thanks!


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## Murby (May 24, 2016)

If you calculate the amount of surface area of the coil (Outside Diameter x 3.1415 x length of coil in inches) you can figure out how many square inches of surface area you will have in your stove.
Once you have that, you can calculate the heat transfer into the water by using the surface area of the coil, the internal temperature of the stove, the temperature of the water in the coil, and the thermoconductivity rating of the material you are using.
In all cases, its not worth doing... The amount of energy harvest is so low that it wouldn't even pay for the materials to make it. Not only that, but cold coils in a wood stove are going to be a magnet for soot build up which then further lowers your heat transfer. 

Also, with a system like that, you'll have to run distilled water... Mineral buildup from well water can coat the inside of your coils and plug them.. thus leading to the steam explosion you want to avoid.


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## ET1 SS (Oct 22, 2005)

We have 50 foot of 5/8 inch copper tubing coils inside the secondary combustion chamber of our woodstove, to heat water for our thermal-bank. It works well for us.


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## sain6815 (Aug 17, 2017)

Well after months of planning, I'm shelving the idea for now. I've heard a similar story from most I've asked that heat output will not be worth the investment and time.

Going to spend my money on replacing upstairs gas logs with a new set to replace the old inefficient ones and fix the broken blower and thermostat on wood stove. We don't mind cooler bedrooms. Hopefully with the downstairs door open and woodstove cranking, we won't be very reliant on electric or much gas from log set. 

We shall see. Thanks for the replies.


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## wy_white_wolf (Oct 14, 2004)

http://www.builditsolar.com/Projects/BioFuel/biofuels.htm#FireboxCoils has a few projects on the subject.

WWW


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## Meinecke (Jun 30, 2017)

Systems like that are a big thing in Germany...
But it is not really valuable with gravity pumps...
Typical setup example:
1000 quarts (closest expression to liter) or bigger water storage tank(extreme insulated and mostly holding additional heat sources) and equipped with heat exchange in top part to harvest heat from the storage tank(you dont want to circle the storage content in your house)
Fireplace with heat exchange in exhaust stream (pipes through water filled compartment)
Pump for the water, temp controlled to prevent boiling

The water will now start circulating between BOTTOM of water storage tank as soon there is a difference in temp between bottom of Storage tank and Stove heat exchange (hotter in stove of course) and will be cut off when is not (also secured against gravity driven exchange). 
This way, you start supporting your main heat source and even replace it over time of fire burning...
But as Murby already stated...mineralisation CAN by an issue, but if you do your Homework this should not cause issues
There are good pictures of professional solutions...that might be easy to copy if you are able to weld/hard solder


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