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building a large wood water heater / boiler  RSS feed

 
matt hanneke
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im in the tree business, so i have a nearly unlimited supply of large logs up to ,6-8ft long 1-5ft in diameter most of which i end up giving away or pushing into a large pile and burning because i just create way more wood then i need, up till this year ive cut and split wood to heat my home but this is not the way i want to spend my time, ive looked into the large front and top loader furnaces and they r very expensive, 10k for a small one 20k for a decent size, what id like to do is build somthing very simple, efficiency is not much of a concern since i littereally need to burn wood because it accumulates so fast from my work, so my idea is to buy a 20ft metal shipping container 8ft tall 8ft wide, these have large double door for easy loading with a bobcat, place it on a gravle pad, these have a wood flood which would just burn off and then it would be gravle, place some metal water tanks or old hotwater heaters with the skins and insulation removed inside the shipping container, plumb the tanks together, also add a 8in or bigger flue and some way for adjustable air entry, and then biuld a fire inside and close the doors and load this once a day or what ever it take to keep the water temp up around 160-180f, and treat the rest just like any other installation with the water pumps and pex undergroud to the house. any suggestions to weather or not this would work or how to improve would be great thanks
 
Glenn Herbert
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Location: Upstate NY, zone 5
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Efficiency may not be important to you with an unlimited fuel supply, but burning an inefficient smoky fire will cause significant air pollution. Even if you don't have near neighbors and don't care about your own air quality, it sounds like an unfriendly thing to do to the environment. Surely there is a use you can find for wood; even big piles that rot down over the years will create fertile soil for the future. How much space do you have to work with?
 
Glenn Herbert
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Location: Upstate NY, zone 5
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To start to answer your water heating question, plumbing tanks together inside a big firebox is a recipe for an explosion. You need to handle the water in a completely non-pressurized way so if it boils there is no harm done. Any pressurized water heating by solid fuel should be designed by a boiler professional; this is a life safety issue and you should not cut corners.
 
matt hanneke
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The first reply about the smoke and effincy, i dont plan on it being smokey thats why im asking these questions im looking for people to help me build this as efficent as possible, the other reason why i need a big one is im planning to heat not only my house but other outbuildings and a greenhouse as well as water, im going to need a big unit to do this im guessing at least 500000 btu, and for the other reply about presure the system will not be pressurized, i plan to have a 1000 gal holding tank in my outbiulding that will act as expantion and extra btu capacity, water will circulate continuisly through the big tank and the furnace so it my take a few days to get the cold well water up to 180degrees but shouldnt be a problem keeping it there, im looking for advice how to make this work better so keep um coming maybe some ideas on flue size and if i need forced combustion air to control the fire size and smoke, i dont think i need to worry about boiling as it would take a hell of a fire to boil over 1500 gal of water
 
Glenn Herbert
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Location: Upstate NY, zone 5
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I believe that a big firebox such as you describe cannot help but be inefficient, or else would be so hot that it would burn up or melt the steel container. If you want an efficient combustion, you will need some strict controls on size and shape of combustion chambers and airflow. A container would serve as no more than a shell to hold the actual workings. You may be interested in the batch box style of rocket mass heater as developed by Peter van den Berg. A 6" diameter equivalent flue size is often sufficient for heating a house, while an 8" unit built in Montana has handled a large shop/auditorium space (somewhere around 1000+ square feet of high-ceilinged leaky space). A 10" system is probably larger than has ever been built, but I bet Peter would be interested in discussing the possibilities with you. You can find his threads about these systems on the forums at http://donkey32.proboards.com , and he also posts here regularly.
 
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