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Build a Woodstove Water-Heating Attachment

Discussion in 'Back to Basics' started by Pax Mentis, Oct 11, 2016.

  1. Pax Mentis

    Pax Mentis Philosopher King Site Supporter

    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.

    Continue at:
    Build A Woodstove Water-Heating Attachment - Do It Yourself - MOTHER EARTH NEWS
    GOG, Seepalaces, chelloveck and 2 others like this.
  2. Bandit99

    Bandit99 Monkey++

    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.
    chelloveck likes this.
  3. BTPost

    BTPost Old Fart Snow Monkey Moderator

    We have a 6", 4 turn, 1/2" Copper Pipe Coil inside the Stove Pipe Flue on the small Wood Stove that heats our Beach Cabin, that makes ALL the Domestic Hot Water we use. It is connected to a 50USG Galvinized Tank with Pressure Relief Valve, in a ThermalSyphan setup. The Tank also acts as a Heat Radiator for the cabin. This is similar to our Main Cabin Domestic Hot Water setup, only the Copper Coil is in the FireBox, just above the Open Pot, burning Diesel Oil, and a 120 USG Water Tank. There is no need to worry about the Temp of the Copper Coils, as long as there is water in the Coil, and Tank, it will never exceed 210F. We have been using both Systems for better than 30 years, and only have replacd the Coils, on each system, a couple of times, in all that time. Our Main Cabin System is documented here on the Monkey, in the Off-Grid Forum, and it includes Pictures...

    Domestic Hot Water from a Woodstove | Survival Monkey Forums Post #12
    Bandit99 and chelloveck like this.
  4. Cruisin Sloth

    Cruisin Sloth Special & Slow

    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 .

    Last edited: Oct 12, 2016
    Ganado and chelloveck like this.
  5. duane

    duane Monkey++

    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.
    Ganado likes this.
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