[BROILER] homemade woodburning boiler

Discussion in 'How-To Threads of the past' started by gobug, Dec 21, 2003.

  1. gobug

    gobug Well-Known Member Supporter

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    I just closed on a heavily wooded 14 acre South Central Colorado Mountain property. It has electric, well, septic, phone, 864 sq ft garage, and the house burned down. The property is 130 miles from my primary (current) residence. The garage floor is dirt. The property has lots of dead wood on the ground plus wood building debris from former construction efforts.

    Long term(3-5years), I want an off the grid homestead. It has excellent southern exposure for gardening and the well is zoned for livestock and residential use. I want to start by putting a hydronic heating system in the garage floor so I can work and be comfortable year round.

    I plan to build a water tank (1200 gallons or so) and an outside woodburning boiler to heat the water in the tank. The floor will contain antifreeze and a computer will control the floor connection to a heat exchanger. I will also hook in a couple of solar panels to keep the water tank temperature up while I'm not there.

    My boiler design calls for a firebox big enough to put in limbs and boards and pallets without cutting and stacking. I want to run a couple circuits of copper pipe. The first will be imbedded in sand between the firebox and the outside of the boiler. The second will be in or around the flue after the firebox. I was thinking of snaking the flue through sand above the firebox. I want a fast burn to release all the energy in the wood and a lot of copper to capture as much of the heat as possible and store it in the water.

    I'm looking for your input. Should the firebox be steel, or ? I know they make a special "fabric" product that becomes ceramic when the firebox heats and cures. I also know to use high temperature mortar. I know cement and copper are not good together. Any other ideas?
    Gary
     
  2. agmantoo

    agmantoo agmantoo Supporter

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    I like to recycle existing components that already have a lot of effort done by the previous user. That said here is my suggestions. Locate a propane tank large enough for your firebox, also get a fuel tank large enough for your hot water storage (1000 gallon plus). In one end of the fuel tank mount the propane tank at a low but convenient wood feeding height. Construct from the end of the propane tank that protrudes from the fuel tank (front of firebox/propanetank) what will be you firewood feed door. From the back of the propane tank have at least 6 each 3 inch schedule 40 pipes exiting the propane tank and running horizontally and exiting the back of the fuel tank. Construct a steel box for the 6 pipes to enter and on top of this box mount a 8 to 10 inch pipe to become the chimney. Opposite of where the 6 pipes enter the box construct a door,The purpose of the door on the small box is so that you can open the feed door on the front of the firebox and push a cleanout rod through the stove forciing the soot out the back of the boiler and exiting the small cleanout door. You will vent the fuel tank at the top and a small solar pump will circulate the hot water through whatever area you want to heat. Being a non pressurize system will make the heater safe.
     

  3. The Hahsa does exactly what you're planning. The design uses cement blocks for the structure and the firebox. The firebox itself is lined with fire brick and topped with a thick steel plate reinforced on the side away from the fire by angle iron. The firebox is large enough to take whole pallets if you use the large door.

    The thing has to be built in place. It's not portable. It has far more thermal mass than the outside furnaces. It is also not subject to the warpage and leakage problems of some of the cheap outside furnaces. Supposedly it doesn't smoke as much but I wouldn't count on that. You could make the stack as high as you want which would draw a lot more combustion air.
     
  4. Blu3duk

    Blu3duk Well-Known Member

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    If you want to be off grid totally and not dependant upon fossil fuels for your power needs, by all means start learning about steam power and alcohol production by starting here http://www.mikebrownsolutions.com/sitemap.htm

    Mike used to and may still have a radio program thrugh AFN [urlrican freedom Network] I just spent the morning today looking over his site and that of Tiny Power, Inc www.tinypower.com as well as the Live steam magazine site but the message board there is not very active. Back Woods Home Magazine has an article every now and again concerning Steam power [boilers produce steam].

    The other thing you are talking about is using a radiant floor, most radiants do not use anti freeze because eventually they will leak and it is not very safe to be around.....

    You sound like you are on the right track and i hope the links i provided are helpful in your project endeavors.
     
  5. handy

    handy Member

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    My whole floor heating system is filled with antifreeze but it's the bio degradable kind for rv's. If it ever leaks it's no big deal. Warm concrete is great although we are using a electic boiler on off peak right now and they (electric company) ripple the usage about 8-10 hours a day right now. With the wood stove assist , it's working great. Add in a propane parlor stove and my wifes grandmas kitchen woodstove and heat is now a wonderful thing. Out side wood boilers are the norm up here in northern minnesota but they do need to be fired every day and it's like milking cows , you have to be there or have some one there. Handy
     
  6. johnkl

    johnkl Well-Known Member

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    Just a coupla tips.

    For the water storage tank I'd first suggest getting an old bulk milk tank. They're already insulated, have piping for heating them and can be had fairly inexpensively. I bought one for similar use---1500 gallons for $200.

    My next option for the tank would be a concrete septic tank of the appropriate size. You'd need to insulate it but it would work fine I think.
     
  7. gobug

    gobug Well-Known Member Supporter

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    Thanks Blu, interesting sites. I saved them. Amazing you can get so much hp out of those little engines. Regarding the anti-freeze, I might just make a basin to capture any leakage that might occur. All of the fittings will be together above ground and a concrete catch basin would be easy to build. Gobug
     
  8. gobug

    gobug Well-Known Member Supporter

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    from Handy: "Out side wood boilers are the norm up here in northern minnesota but they do need to be fired every day."

    Thanks Handy,

    Does the common wood boiler burn fast?
    Are heat storage tanks used?
    Is the fire box surrounded by a water jacket, or is the water heated in tubes?
    Is your heat exchanger for the hydronics in a tank?
    GObug
     
  9. gobug

    gobug Well-Known Member Supporter

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  10. I run a Classic CL 5648 from central boiler (http://www.centralboiler.com/). I use it to heat an old un-insulated farmhouse (3000sf) and it also heats the domestic hot water. This thing really is not too complex. It is just a large water tank suspended over a firebox. The water completely surrounds the firebox with the exception of the door. The water tank acts as the heat reserve. It is vented at the top of the boiler so it is a non-pressure system. In the event of a run away boiler, the hot water simply boils out the top like a teakettle. The water tank is insulated and holds about 500 gallons. Works as follows: Temperature in tank drops to 165oF, a solenoid fires and the draft (damper) is opened. Air is added to firebox, which ignites the fire and begins to heat the water. Once water is at 185oF the solenoid switches off, the air is turned off and the fire goes to sleep. Run time varies but it is usually about 10 minutes. Water from the tank is circulated constantly to the house using a water pump and insulated underground lines.
    How often the furnace turns on is determined by how much heat is lost from the water. Cold nights the furnace will spring to life about once every 20 minutes. During the summer it could all day(s) without turning on. Mine eats a lot of wood. On a cold week, it will eat about 1 to 1.25 cords, (house at 68F with 6 hot showers). I pushed an easy 35 cords through it last winter. I burn mostly softwoods (pine) that are salvage from the tree business but it will burn anything. Cost of wood is nothing, except time in smashing the wood up into chunks that you can lift to get them into the door. During the dead of winter, the furnace is filled every 12 hours, usually at 6am when I am heading to work and 6pm when I am coming home. I usually use the same schedule during warmer weather, just add less wood during the fill ups.
     
  11. agmantoo

    agmantoo agmantoo Supporter

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    Unregistered, If you had more water storage capacity the feeding of the heater would be extended and in the summer you could go for days. I do not understand why the water is circulated constantly? What are you using for a heat exchanger in the house?
     
  12. gobug

    gobug Well-Known Member Supporter

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    "Mine eats a lot of wood. On a cold week, it will eat about 1 to 1.25 cords, (house at 68F with 6 hot showers). I pushed an easy 35 cords through it last winter."

    Thats a lot of wood! Thanks for the detailed answer. Where do you live? gobug
     
  13. Runners

    Runners A real Quack!

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    I shudder everytime I hear of someone trying to make a steam boiler or operate one without any training. Boiler explosions level buildings! Stick with an open system - PLEASE! That means it cannot build pressure, anywhere.

    Say you've made one with an old 500 gallon tank, filled with water. You closed it off or sealed it, because you got tired of refilling what was steaming off. Imagine for a moment, it's cold outside, and you really fire that thing up, and the water temp reaches 213f, because you stoked it really good for the cold night. Just 1 degree above boiling, and you've got a little pressure, say 5lbs. One small leak - a valve cracks, plug pops, corner seam pops, a fitting cracks from expansion, etc., and the WHOLE 500 gallons of liquid instantly flashes to steam, expanding 1700 times, blowing the tank apart, sending metal shrapnal, brick in every direction... There goes the heater, the house, everything. You get no warning, it all happens in an instant.

    The question for everyone with a "boiler" is: What are you gonna do with the excess heat. What's the plan for an automatic / unattended emergency shut down? Who is going to inspect & certify your work? Will your insurance cover accidents caused by a unlicensed pressure vessel built by an unqualified, unliscensed individual?

    If you vent too fast - kaboom! Will your plans include a fuze plug, safety valve, pressure / temp relief valve, automatic fill valves and the rest of the safety equipment required by code? Believe it or not, they make Pressure Relief & Safety Valves - which are required by code on every boiler manufactured. A 1st class stationary engineer knows how to build and correctly size the right safety equipment, don't take chances, please! The boiler people are describing in these posts is known as the least safe in the industry (fire tube, bulk heaters).

    If a 40 gallon water heater can easily level a house, imagine what a 500 gallon tank could do. :eek: My advice, STAY AWAY FROM PRESSURE VESSELS unless you've got the training, certification and license. Better yet, enroll in a HP/LP Boiler class at your local tech school - and learn how to do it right & safe before experimenting - money well spent!
     
  14. The water capacity was determined by the factory. The furnace is about the same size as a “porta potty” and most people think it is a small smokehouse. If you increased the water capacity, the unit would be much bigger. The water is circulated constantly from the boiler to the basement of the house. The boiler with hot water tank is about 150 feet from the house and the water goes through lines underground. In the basement, there is a manifold with 3 smaller circulation pumps. One of the pumps is connected to the water-to-water exchanger on the hot water tank. One of the pumps is connected to the water to air exchanger (big radiator) in the plenum of the oil hot air furnace. The last pump is currently unused but could be connected to another zone (garage, pool, hot tub etc.) You need to circulate the water constantly as it would take too long to heat the house if it was traveling from 150 ft away. Kinda like waiting for the shower to warm up. In addition, the water returning to the tank is supposed to be about 10o cooler than the water coming out of the tank. If the return water is much colder it creates problems for the furnace and it would run constantly.
    We do burn a lot of wood but I am essentially heating a pole barn. Wood consumption on an insulated house would be a lot less. Before the boiler I ran two wood stoves and could easily burn 12 cords hardwood a year and you would freeze or cook depending on which side of you was facing the stove. I live in northern new England. Winters not too cold but we do have our share of negative nights. Wind is the biggest problem as it could blow the hat off your head inside the house. It just sucks the warm air out. On the plus side, I don’t have any trouble with snow building up on the roof!
     
  15. Runners

    Runners A real Quack!

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    "...The water capacity was determined by the factory..." In other words, someone has already engineered the unit, pressure tested, added all the correctly sized safety equipment, etc. They start around $3400 in these parts. A "steam boiler" is a little different animal, and requires a alot more engineering & equipment to safely operate.

    I'm familiar with the outside hydronic units, and might add one of them too - but it would be a commercially produced unit!

    I don't want to discourage experimenters from experimenting, but, a mistake with a steam producing boiler isn't very forgiving. I didn't even touch on water chemistry... anti-freeze does lower the thermal effeciency of the system, and it should be chemically tested every couple of years for potency & bacterial growth.
     
  16. two_barking_dogs

    two_barking_dogs Well-Known Member

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    Unregistered, How is the temp regulated within the house with the circulating pumps always on? I understand about the fire kicking on when the water temp gets low but not how the house temp is controlled. Thanks
     
  17. My outside boiler was grafted onto an existing oil fired forced hot air heating system and oil fired hot water heater. To heat the house you add a radiator into the plenum of the forced hot air furnace. To heat the hot water you add a water to water exchanger on the hot water tank. The outside boilers main circulating pump is always on. It simply circulates the water in a continuous loop between the boiler and the house. In the basement of the house is a manifold with 3 smaller pumps. Each of the smaller pumps is tied to a thermostat. When the house is cold, small pump 1 on the manifold pumps water out of the manifold (main circuit) to the radiator in the oil hot air furnace and back to the manifold. The fan in the oil hot air furnace is triggered using the same thermostat and hot air is circulated into the house. When the hot water tank is cold, pump two activates and circulates water to the exchanger on the outside of the domestic hot water tank and back to the manifold. Small pump 3 is currently not doing anything. Sounds more complex than it really is and the oil is always available as a back up if the outdoor furnace quits for some reason. The companies web site has a picture of the system (http://www.centralboiler.com/forcedAir.php) but they only use 1 pump (the main circulation pump) and no manifold. Trouble with this setup is that you would have no control over the temperature of the domestic hot water tank. It would be 185oF which is way too hot for children or uninitiated adults.
    As the last poster pointed out, this is non-pressure system. This is a hot water boiler not a steam boiler. It cannot explode and you don’t need a heat dump. If the boiler runs away, (left the door open, stick jams draft door) the water will simply boil out of the top of the furnace. There is a water gauge and a light on the furnace and you usually give it a glance when you add wood to the beast. The water in the tank is just water. Cost installed was right around $5500.00 but that was 5 years ago, we did all the dirt work, paid for the plummer and got the electrics done on a favor.
     
  18. agmantoo

    agmantoo agmantoo Supporter

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    I have a water heater stove on a similar house but mine is configured differently. My domestic water heat exchanger is in the reservoir of the stove and the water heater gets its replenishing water via the circulation through the tank and no pump is required. When the home thermostat calls for heat there is a delay relay controlling the circulation fan until the heated water reaches the heat exchanger in the duct system. Thus no burst of cold air! I store about 1000 gallons of hot water and I cycle the stove from about 130 degrees to something slightly less than boiling. I can get by without feeding the wood for a lengthy period. I burn as hot a fire as possible then essentially let the fire go out down to just coals. This reduces the buildup of creosote and the stove stays rather clean inside its firebox and exchange pipes. I do not understand why Runners got excited about a boiler as we have been discussing a vented system from the get go. My setup actually has 2 vents.
     
  19. Like the others have posted, the construction Gobug is considering using sand for thermal storage isn't a real boiler. The piping in sand approach solves a lot of the problems using a firewall because the pipe is never exposed to the fire. You don't have corrosion and warpage problems.

    On top of that, I doubt a large water storage tank is needed. The huge sand mass stores far more heat. Because of the construction you'll get more heat with less fuel.
     
  20. johnkl

    johnkl Well-Known Member

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    Darren, I beg to differ with your comments about sand holding more heat than water. On a volumetric basis water can store nearly twice as much heat as stone or sand, plus its a lot easier to move the heat when its stored in water.

    My circulating pump runs all the time too. I'd rather do that than freeze protect my entire system. The boiler runs 24/7 in the winter anyway but circulating the water insures the lines between the load and supply don't freeze up. When the thermostat calls for heat the blower kicks on. The heat exchanger is always hot so theres no waiting for hot air. What radient heat does escape the heat exchanger is "wasted" into the heated area so the blower comes on less often without it becoming unduly warm.

    I don't know what the dairy situation around there is but I'd first look into dairy supply places. If you find one they'll probably be able to steer you in the right direction to find a use tank with a dead compressor.. You wouldn't need a refrigeration compressor on the tank so that'll save you a bunch. Farmers will sometimes get rid of a fine tank with a shot compressor.