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Wood-fired boiler question

Paul Cooke
Paul Cooke Member Posts: 181
Check this PDF for an excellent overview of outdoor wood boilers:


(Make sure you look at the graph about one third of the way into the PDF -Figure 5.2)


  • Rob G.
    Rob G. Member Posts: 2

    I am looking at putting an outdoor wood-fired boiler in at my home but having just moved from the city to the country, I have no knowledge of anything other gas and oil-fired equipment. I would appreciate any info, comments, best value, do's and dont's.
  • troy_8
    troy_8 Member Posts: 109

    i heat with an outside wood boiler. First if you don't have a free wood supply- be aware you will not save fuel dollars. You will spend a lot of time and energy to heat your house. You must be able to attend to the fire every 4-8 hrs depending on your home size and boiler size. Just a couple warnings. I do enjoy the work. and it cleans up your woods if you burn the dead wood. Enjoy. just realize the facts.
  • Paul Cooke
    Paul Cooke Member Posts: 181
    Outdoor wood boiler

    You might as well just park 2 or 3 diesel trucks in front of your home and let them idle 24 hours a day. That is equivalent to the emissions that most standard wood boilers produce.

    Many states (like Washington) have strict air pollution standards that prohibit many of the poorly built standard US made models.

    Your neighbors will love you. Especially in the spring, fall and summer when you fire it up so that you can take a hot shower.

    If you do decide to install an outdoor wood boiler please make sure it is the most efficient model you can get. I would look to the European made gasification wood boilers.
  • Rob G.
    Rob G. Member Posts: 2

    Wood is no problem. That's one of the main reasons for my interest, I've got plenty of wood(s), but no place to burn wood. The system currently is a Heil heat pump and the previous owner had a heat exc. installed when the home was built. I just need some info on the stoves.
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,291
    OWB's not a good thing

    You want to get on top of the wood burning curve instead of the bottom. In a lab test done a couple years ago in which 7 different brands of OWB's were checked for emissions and efficiency it was found that they ran between 28-41% and emitted as much pollution as roughly 1000 (yea that is not a typo) oil furnaces.

    I know that right now the ease of installation and having it outside probably looks appealing but there are lot's of drawbacks to that scenario that the OWB guys don't mention. Like tending you fire at Odark30 in -10 weather..like having to cut, haul, split, stack and load 2X as much fuel as you would need in a unit of better design. In addition, due to EPA regs now in place there will be a "falling out" in that industry by companies that don't have the cash, engineering expertise and know how to design something that burns cleanly.

    I am personally involved in the wood burning industry and have installed just about every brand and type of product that there is. An OWB of any type, including the ones that meet the EPA regs would be the last resort for me and I wouldn't recommend one to my worst enemy. ("Do unto others.........")

    Look into some of the better units out there like Econoburn, Tarm, Garn and EKO. None of which are outdoor types but like I said, you don't want to go there anyhow IMHO. While you make your decision be aware that BTU storage should be an integral part of your system design. The minimum I recommend is 800 gallons for a heating load of 50-70,000 btu's. Oh, that brings up another topic. By all means approach this like a professional would and do a heat loss calculation on your house to determine what your actual heating load is. That step is paramount whether you are burning wood, gas, oil or even nuclear. :)

    Here's a couple websites to check out.



    PS to all, have you noticed the recent disconnect in crude prices and actual cost at the pump. They are going in opposite directions. Crude down, fuel price up. Something is going on here that may not bode well for the future.
  • I have been doing

    alot of research on these boilers lately. I have recently had by woods logged out for the solar system and they left mountains of wood on the ground. I believe one of the nicest units available is the Central boiler E classic http://www.centralboiler.com/index.htm

    Although Greenwood makes a very nice unit I like the gas light system on the classic also the lifetime warranty. These are both wood gasification units and are expensive ,10k or more. But if you like working out with wood and you have a lifetime of free wood, go for it. It is a better investment than any stock is and if you find you dont like it they sell high second hand.
  • hot_rod
    hot_rod Member Posts: 22,467
    go efficient and clean burning

    I heat my shop and office with an EKO 40 gasification unit. A 500 gallon pressurized buffer works nicely for my small, below 30K load. I heat with radiant floors so I can use the buffer down to about 100F.

    Most all gasification boilers, built in Europe, are intended to be installed inside. They are not real well insulated and would lose a lot of heat outdoors even if you did cover it. I suppose in a well insulated building it would be fine.

    Gasification units use 40- 50% less wood and burn much cleaner as they re-burn the exhaust gasses in a ceramic chamber at 2000F. One down side is most have small wood chambers and as a result need more frequent feeding.

    From what I have seen the new Central high efficiency looks pretty good. No first hand experience.

    I've installed one pellet boiler and it was a sweet running machine. much easier to control and a lot less fuel hassle.

    Remember with outdoor units you need well insulated, and waterproofed piping in the ground to minimize heat lose from the unit into the building.

    Wood boilers, properly installed, buffered and controlled can be an expensive under taking.

    Tighten up the building to get the heat loss to an absolute minimun, then size and design the heating plant.

    Avoid the temptation to oversize a wood boiler. Long hot fires are much better than smoldering conditions common with oversized equipment.

    Wood heating is a lot of work, ash removal and cleaning needs to be done every couple of weeks to keep the things burning efficiently.

    www.hearth.com is another good place to talk wood burning, at the "boiler room" some wild DIYer systems seen over there :)

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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