Outdoor Wood Boilers

Back when I started the other thread (Hot Water Heat) I was looking for an alternate way to heat my new home that I was planning.

Part of my research was in outdoor wood powered boilers. In my research I found that they burn 10-15 cord per year, almost regardless to how much you are heating with them. For a somewhat energy efficient home, that is quite wasteful. If you were heating a barn, shop, garage and a house, all off one boiler, then maybe, it might be worth looking into.

I found that the outdoor boilers were all just too big for a moderate (2500 square) home. They spend a lot of their time just burning to keep going and not heating anything. Either going cold or "on the fan" going full blast to catch up again. All the while going through copious amounts of wood.

Overall I was not impressed with what was available at the time (2005-2006).



I settled on a "three way hybrid" system. I have an LP fired, forced air furnace, an LP fired boiler (for the in floor heat in my basement and garage) and a wood fireplace in the great-room which can heat the entire house.

This winter I have burned 500 gallons of LP and about 4 cord of wood (since September).

My neighbor has recently built a home with a similar system, but his combines the water heater and boiler into one unit. It is an on-demand type of water heater with a heat exchanger for his in-floor needs. I think it is a little more efficient than my direct vent water heater and separate small boiler.

The farmer down the road has an outdoor wood fired boiler. Never inquired about it, but it makes sense that they burn a lot of wood just to stay lit, even when the house doesn't need the heat.

Been using wood and oil heat for years. This winter started using coal.... It costs about $60.00 a ton, which is about two or three cords of wood burning and to buy wood, it is about $200.00 a cord if you don't cut it yourself. Coal lasts for eight to ten hours on a load where wood lasts about five or so. As long as it has air going to it, there isn't a smell either.

My wood stove has a grate, so the coal ash can fall down though it, but will be looking for a dedicated coal stove this summer. Pretty much shut down the oil heat from where it was at before.

Good idea on the coal, Foggy. (Unfortunately it wouldn't work in my fireplace, too messy. )

$200/cord is a little expensive, I'd say. I paid $450 for 5 cord of 8', oak logs last summer. I cut and split from there. I'm going to try and get a 10 cord load this spring as soon as the road limits come off.

Av8r3400 said:

Good idea on the coal, Foggy. (Unfortunately it wouldn't work in my fireplace, too messy. )

$200/cord is a little expensive, I'd say. I paid $450 for 5 cord of 8', oak logs last summer. I cut and split from there. I'm going to try and get a 10 cord load this spring as soon as the road limits come off.

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The do have the outdoor stoves that are set up for coal too, they work pretty well and you can throttle them back to slow the burn rate when it is warmer, some even do that automatically.

I would bet that coal is even cheaper there too. Oak is a good firewood, lasts a lot longer than spruce or birch does. $450.00 in coal here would last all winter and then some. That would be about seven to eight tons....

This winter started using coal.... It costs about $60.00 a ton, which is about two or three cords of wood burning and to buy wood, it is about $200.00 a cord if you don't cut it yourself.

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Foggy; How far do you have to truck the coal. I'm about 400 miles from the closes sourse, I've never checked on the cost of shipping it up here.
There are some good setups for coal burners (hopper bins,auto feed augers) a lot less work than wood.

My last house had a wood/coal burner in the attached garage that was attached to the ductworth in the house. Since I had all the coal I could pickup and put in a 5 gallon bucket at that time, I burned coal for a while. It sure burns a lot hotter than wood! The first night we woke up at about 2am and had to open the windows. Although it was near zero outside, it was over 80 inside.

Once I got it figured out, getting a good wood fire going first to get the coal started, it worked rather well. The only issues I had was that I sort of lived in a subdivision at the time. Some neighbors complained about a black layer of soot on their cars in the morning but never actually knew the source.

I have an outdoor boiler by Central Boiler and I heat my 3k sq ft home, all my domestic hot water and my 1500 sq ft garage on 18 face cords of wood per heating season. We do not use it during the summer months. I am however slowly reaching the age where I will not be able to cut wood. If anyone is interested in burning coal take a look at this site www.alternateheatingsystems.com. One of their coal units will be my next heating unit.

Very interesting topic. All this talk of using coal made me think of the stories of my Grand father loading two tons into his 1/4 ton 1940 dodge truck to deliver to folks in town.

Maybe we always had the efficient answer?....LOL


I too would question the true benifits of an outdoor wood burner. As we cna see it really depends on where you live, how many square foot you heat, and how much work you want to put into heating your home.

I recently installed a wood burner in the garage 32x48. So between it and a portable LP heater I saved a ton on my electric bill this year. I have an electric boiler for a heated slab and I love it very much except the bill. So at least this year I knew how much money I was spending up front instead of trying to guess on those colder days.

Hopefully I can add more insulation and cut back further on my bill.

I dont like the coal smell my nieghbors furnace makes. I took mine out since it would drfit the smoke right into the front of my elderly nieghbors house across the street. Plus the mess it would make transferring it to my basement. No thanks. The wood burning fireplace does much better and the smoke doesnt seem to settle down like coal does. It could just be the diffrent locations of the chimenies. Anyway I like to cut the wood. Well when I have time.

Snowcat Operations said:

I dont like the coal smell my nieghbors furnace makes. I took mine out since it would drfit the smoke right into the front of my elderly nieghbors house across the street. Plus the mess it would make transferring it to my basement. No thanks. The wood burning fireplace does much better and the smoke doesnt seem to settle down like coal does. It could just be the diffrent locations of the chimenies. Anyway I like to cut the wood. Well when I have time.

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Well if you don't keep air to the coal, it will get that smell and stink. As long as I keep air going to it, there is rarely any smell.