Build a Woodstove Water-Heating Attachment

This is an excellent article I ran across and thought might be of value to some here...

One of the advantages of heating with wood is the variety of needs that just one stove can meet. Besides keeping us warm, a woodburner can cook dinner, dry clothes, and toast chilly toes. But wouldn't it be just dandy if that black box would draw a nice hot bath, too?

Actually, domestic woodstove water heating is nothing new . . . many cookstoves had water-tank attachments more than a century ago. The advent of the "airtight" woodburner and pressurized water systems has left most of those old batch-heating techniques by the wayside, though, and new methods based on closed circulation have been developed.

Modern Woodstove Water Heating
The majority of water-warming attachments employ heat exchangers that are fitted inside the firebox or the chimney of the appliance. The best commercial examples of this approach work very well indeed. If the stove is run most of the day, they can supply a whole family's hot water. For safety's sake, however, these devices are usually made from stainless steel (an expensive commodity) and must be pressure-tested to insure that they are able to withstand the very high temperatures they may encounter inside the heating system. As a consequence, quality internal heat exchangers carry pretty hefty price tags. Homemadeinternal devices, on the other hand, have developed a nasty reputation for scalding steam explosions.

Furthermore, extracting heat from either the firebox or the chimney of a woodstove can have unfortunate side effects: Pulling Btu directly from the fire (with a firebox exchanger) can reduce combustion efficiency . . . and if the products of incomplete combustion are cooled below the temperature at which they condense (by either a firebox or a chimney heat exchanger), heavy creosote accumulation may occur. There is doubtless no need to mention that the combination of a chimney fire and an internal, water-filled heat exchanger can spell disaster.

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Build A Woodstove Water-Heating Attachment - Do It Yourself - MOTHER EARTH NEWS

 

I believe this to be a very valuable article if indeed, God forbid, a disaster that stops normal utility services. I am going to read it more thoroughly and see if feasible and cost effective to build one now.

 

I 've heated water since the 70's this way !!Built 3 , & my last is also Bi-heat as in solar also .

tempering valve,safety pressure valve,use seamless extruded stainless ,and always convection built into the flow , So just power out it stills works , this is not just a pipe & water in a fire box .


Sloth

 

Works great, not real efficient but helps with the bills. Only change I made was to use a tempering valve, like they use with a boiler coming out of the heat storage tank and run it into my gas water heater. It runs 100 % heated water up to about 110 degrees and then mixes cold water with the heated water to keep it 110 so you can't burn yourself and if less than 110, the gas water heater comes on and heats it to 110. or holds it 110. You must always have a safety valve, for heat and pressure, as it can turn into a steam bomb.