Monday, December 4, 2023
Wood Boilers- indoor/outdoor, open/closed, gasification……what???
Will someone just level with me?
I have been in the Fire/Hearth/HVAC/Building industries for over 32 yrs.  The one thing I know for sure is that I don’t know everything……….the following is just my honest assessment based on my experience. 
One of the reasons I love what we do is because I’m always learning new things. Our goal as a company is very simple; help folks cut through the “hype” and figure out what they need to accomplish their goal. Our job in my opinion is to tell the truth and give honest advice based on our experience, what works and what may not meet the customer’s expectations.

Non EPA Compliant Wood Outdoor BoilersI have spoken with several folks who called me because they now have an outdoor boiler sitting in their back yards with CONDEMEDED DO NOT USE sticker on it. Worse yet, the unit is only a couple of years old.

What happened you ask?
They qualified for financing and the largest outdoor boiler company in the world was there with an aggressive sales force and before they knew it that had a note for anywhere between $10-20k depending on their installation. Did anybody ever take the time to tell them that there was a potential EPA problem looming on the horizon……….or that their community was fixing to outlaw outdoor boilers…….no, the sale was more important than the truth.
Smokey outdoor wood boilerThe folks above were not our customers; however, we like to think that we could have prevented their predicament with some simple friendly advice.  Let’s see if we can clear the smoke out of the air here, so to speak, and get down to honesty and some basic laws of physics, thermodynamics and simple reality. My hope is to lay a foundation for you to make an informed choice.
Outdoor boilers, why the bad rap? Well very simply…….most don’t burn very clean and are simple smug pots that smolder all day long. Top that off with a customer who has never burned wood before, or worse, a trash burner who thinks he now has an incinerator…….and you have a recipe for unhappy neighbors.  Combine someone with asthma, or other respiratory problems and things can get really bad fast.
Outdoor Wood Boiler Design CutawayThere are some very simple designs that will never work if you’re trying to achieve a clean burn.  In order to burn fire needs three things, fuel, air, and heat = COMBUSTION. To burn clean, wood needs to burn very hot, the hotter the better = the cleaner burn you get.
Valley of smoke from Outdoor Wood BoilerIt is next to impossible to achieve those kinds of temperatures with a firebox wrapped in steel filled with water. The water will always act as a heat sink and absorb most of the heat needed for total combustion. Most outdoor non-gasification boilers operate this way. In my opinion, unless you live in NW Montana or some wide open area and lots of smoke is still carbon neutral…..stay away from this kind of boiler. They cannot burn clean if the firebox is surrounded in water.

Outdoor Wood Boiler Cutaway
Outdoor Boilers………..think about that for a few moments…………let it sink in. Outdoor boilers are almost an oxymoron when you really think about it. You are taking the very expensive boiler and pumps that you’re using to heat your home, or shop……..and sticking it outside in the coldest possible place. Does that really make that much sense? Yeah ok, get the wood and bugs out of the house, I’m all for that, no problem, but I ask you what about the wood you are going to put in your nice new shiny wood outdoor boiler? Are you planning on dumping it on the ground out in the middle of the yard and dig your wood out of the rain snow and mud and use that to feed your boiler. If so, you’ll be sadly disappointed. Wet, green wood does not burn well. Furthermore it stinks and more than half the BTUs are consumed drying out the wood so it can burn. Even with the “most efficient boiler”, your efficiency will still would drop by half and the chimney will plug up with creosote and become a fire hazard.

Outdoor Wood Boiler Cutaway Underground Plumbing
If you stick your new shiny outdoor boiler outback so the bugs need to form an expedition to get to the house, there are some drawbacks. The further away you go, the longer the trench is that someone needs to dig to bury the lines that run hot water back to the house. Now think about that line that you’re going to bury in the ground. It is usually two PEX pipes wrapped in some kind of insulation in between, stuffed in a long black corrugated pipe. This stuff runs between $5-10 per ft. They make a better product with close cell foam injected which has a higher R-value for $10-20 per ft. 


Posted on Wednesday, January 2, 2013

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