Outdoor wood furnace questions

I"m sure some of you guys are using them and I was wondering what your thoughts are on them? How much wood do you use? Pros and cons? Etc? I"m looking to heat about 8000 square feet(house & shop). Thanks for your reply"s.

My dad has the largest furnace that Hardy builds but I dont think it could ever heat 8000 square heat. It may take two.

As to how much wood?? That depends on the type of wood, type of climate, efficiency of the buildings being heated... My dad can go through an unbelievable amount of wood in a winter heating his old 3500 square ft drafty farm house... He loves the furnace!

PROS:

* You can burn anything even green or wet wood. Toss in wood with a foot of snow and ice sticking to it, it doesn't matter.

* You only have to light it once a year.

* No safety problem. Chimney fires are a good thing in an outdoor stove.

* During most of the winter, I would throw in wood 3 times a day: when I left for work, when I got home from work, and before I went to bed. When it's warmer a lot less times.

CONS

* Expensive. I put mine in back around 2000 and they were cheaper back then. The plumbing expecially.

* You can't go on vacation unless you find someone to keep it burning or (drain it). The do sell some models with built in gas or oil burners in them to keep the water hot though.

* THE SMOKE! Most of the time they're smoldering the wood, so they make a huge amount of thick smoke. Make sure to know the prevailing wind direction and put it downwind from your house. I've seen a lot of them in my area that were put on the wrong side of the house. Nasty. Also, if you have neighbors within 1500ft, you're probably going to make them dislike you.

* It's a "weak" heat. You don't get that hot blasting air out of your forced air unit like you do in a regular furnace. The water's only 180f and you're moving a lot of air through that radiator so it takes a lot of blower time.

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As far as efficiency goes, I know I burned MUCH LESS wood with my outdoor unit than I do with the indoor stove in my current house. That was a smaller house and better insulated though. I do think that they are more efficient as far as wood goes though. They do take more electricity though.

Lots of unknowns here...like how well insulated is your house and shop, how far north you are, temperature you want to keep house and shop. With 8000 sq. ft. to heat, I think it would take a pretty big furnace and that you might be feeding it 3 or 4 times a day. Are you going to use propane to supplement or back-up your heating needs or heating solely with wood? You might be using 10 or more cords per year depending on the answers to these questions.

Classic has a stove that should handle your needs just fine. Cousin has one that heats a 3000 sq ft house and 2400 sq ft shop with no trouble in MN winters.
I have a smaller outdoor boiler to heat my 1100 sq ft house. I use about 8 cords per winter. My parents heat 1n 1900 sq ft rambler style home. They use about 15 cords in their boiler. We burn any type of wood, but mostly poplar and ash.

With that kind of heating load you're getting into Garn boiler territory. Definately not cheap but highly regarded.

Between Dad and I have about 22 seasons burning wood in outdoor boiler in North Central Minnesota conditions. Average 10 cords/loose volume on truck 8 cords stacked tight (4'X4'x8')
per location a winter. I heat 36x36 shop/12foot ceilings, and newer 1600 square foot house.
He heats 24x26 shop 50deg. constantly and 2200 square foot older home. I also heat enough hot water to keep 4 kids, wife and myself in laundry and baths. You can burn just about any wood you chose but remember BTU content is key, If your going to saw and split 10 cords you might as well get most bang for the effort. I've seen many installations that were done poorly cost owner of these furnaces dearly in wood. Going cheap and shoddy on water line insulation my uncle and cousin with smaller houses, near myself burn 18-20 cords/year and grow beautiful January lawns above their water lines. My Dad's had excellent luck with mild steel construction and Central Boiler from Greenbush , MN his unit went 18 seasons without a leak. Mine is a Heatmor I bought rusted out and rebuilt the firebox. So far 4 years and no trouble + I only paid 100.00 for the unit. All in all not a bad way to heat if you have wood available and the
time to fill 2x day. Smoke at start up is considerable but short lived with seasoned wood and like was said above carefull placement accounting for wind conditions is also important.
Efficientcy is another matter, I think all manufacturers ratings are over stated and there is waste out the flue no matter what they claim.
I figure no mess, no insurance hassle, no fire hazzards, hot domestic water and unlimited wood supply works for me. It may not for others good luck!

I have been told they are great.
I have an indoor wood pellet burner, I love it.

A guy that works for me has a Charmaster indoor wood burner/furnace. He loves it, it is in his basement.

Do you have a steady supply of firewood?
Loading firewood day after day may be a PITA.

I looked into an exterior wood burner, called the outdoor wood furnace. This thing is forced air with a cold air return in the house. I thought about it and the installation for my home would be good but....I would want to have the hot air pumped into my crawl space, no basement. It would cost $3500 or so. Not a bad price but it would reduce my propane usage from 500 gallons per winter to 100 gallons. I dont run my pellet burner when I am at work. I have read (on this site) that a exterior wood boiler is $8000 or more with install.

I believe furnace quoted Dad last spring was 5600.00 + tax, Figure if new from scratch I think 8Gs would be pretty accurate figure considering needing in addition to furnace; water lines, pumps, exchangers, excavation electrical. Now doubt a good chunk of change to throw wood into.

I don’t do wood but every heating device should list a BTU output.

Are you now heating this space? If you are what are you heating with and what is the BTU rating of all of the heating sources? Is your present system adequate? How long does it run in the coldest temperature you normally experience?

If you are presently heating the total area and have the answers to the above questions you may be able to ball park a size from that information.

If you can’t size from the present heating equipment you may need a professional to calculate the heat loss, people in the HVAC trade use a program known as Manual J to calculate that value.

I have an old woodmaster and heat a old draft farmhouse on 10-15 cords of wood a winter, also heat my domestic hot water too. I burn green aspen, spruce, maple, tag alder, whatever else is handy.

I wouldn't go back to a stove in the basement in a million years. No mess in the house, no worry about a chimney fire, no insurance hassles. I load wood twice a day in the cold cold weather and once a day when its above 20*F or so.

I don't have one but I remember one state was passing legislation about them due to smoke complaints from neighbors, though I believe that the problems were mainly with earlier units. I have seen a number that have a roof over the end where the opening is, and two walls to protect fuel and make late night charging easier. I am glad that my coal stove is two times a day only.

Pro's - burn big wood, keeps mess outside
Con's - lots of smoke, especially in spring/fall, uses at least 50% more wood than high efficiency epa woodstove, about 35% more than an indoor wood furnace. Worse if you burn green wood.

I too recommend the garn. Its expensive but retains its value and burns efficient and clean.

We have a firewood boiler now for three years.
Firewood here in south eastern NY is over $200 per cord now.
When we left Arkansas, it was $90/cord split and delivered.
We use a combination of coal and firewood.
We bought a semi load of bagged coal for $4200. Hoping it will
last four years or more. Coal has more BTU's than wood.
The firewood boiler has to be reloaded twice a day to heat about
3500 total sq.ft. home & shop.
We shut it down in the spring through fall, and use a
propane demand hot water heater for hot water year around.
Part of the home has hot water baseboard heaters, and the rest
has the heat built into the floors.

If you burn dry wood instead of that wet, green & ice covered stuff you wouldn't have a problem with smoke. Burn a lot less wood too.

I have been useing a central bioler for 5 years. With the concret pad and everything to hook it up it cost right at $10,000.00. It has been the best money I've ever spent. I installed it myself. I heat a 3000 sq ft home with it. Have all the wood I need on the farm, so, all it cost to heat my home is my labor to cut the wood. As others have said. The mess and the fire are outside. I wish I had bought it 20 years ago.

You have recieved quite a few good, informative responses here.
we have a woodmaster 4400
heats the house and hot water during the fall, winter and spring (upstate NY)
installed it about 5 years ago, poured the pad ourselves and did the installation ourselves...i think the cost was in the $6000 range for the furnace and 125(?) feet of pipe - the pipe was the biggest expense but it worth it - it is 2 1" pex lines in plastic drain tile that is stuffed with insulation - it is very well insulated...we lose maybe a degree or two by the time the water gets to the heat exchanger in the basement.
burn about 18-20 cord a year...oak, maple, beech, elm and whatever else happens to be down in the woods or free. - if you have to buy wood...DO NOT buy an outdoor wood boiler...you will lose money in this case.
one thing mentioned in an earlier post was that the heat provided to the house is cooler...this is true - outdoor wood furnace circulates water into the house between 175 and 185 degrees (figured out how to tune it up 5 extra) whereas our oil furnace circuilates in the 205 range...so the radiators don't quite put as much heat
if you have wood...and don't mind a little work...a lot of work....it is a great investment.
as far as placement - know your wind and...if you have close neighbors...don't get one. but the smoke isn't nearly as bad in newer models as the older ones.
also think about where you will store a ton of wood and how you will move it to the furnace - we use a covered wagon that holds about a cord and store the wood a short distance from the furnace...so have to fill up the wagon once a week or so...

I am on my 5th winter on my Central Boiler Classic. I wish I had bought one sooner. In response to tjdub's pro's and cons. The pro stating putting wood in 3 times a day, my dealer sized mine to handle enough wood to fill once a day in the coldest of conditions. I refer to add wood twice a day (not completely filling, adding enough wood to last until I add again) when I am home. This gives the hot coals a chance to burn down. I believe that tjdub's method probably will use less wood than if he completely filled it. The con's, the huge amounts of smoke, I have had excessive smoke when I used poor quality and green wood. When I use good seasoned wood I get some smoke shortly after adding wood but clears up later to being barely perceptible. I do not notice the weak heat, when the blower is off there is a slight but constant heat radiating from the registers. When the blower kicks on there is instant heat rather than blowing cold air for a time before getting the hot air.

JD Tim, check out this site: http://www.hearth.com/ More there about burning wood in all types of units than you may ever want to know. Go to the "Boiler Room" in the forums. FYI, I have a Tarm Solo 30 Gasifier, a different animal than the "outside units", but with what I thought were many advantages. I am a fan of the gasifier technology; Tarm is only one of several manufacturers of this type, and they're not much, if any, more money than the outdoor types. The Garn mentioned above is in this category.

> If you burn dry wood instead of that wet, green & ice covered stuff you wouldn't have a problem with smoke.

Maybe some designs are different, but with mine (Taylor 450 I think), whenever the water was up to temp it shuts off the air supply completely and the firebox just smolders (making charcoal). It didn't matter what kind of wood I burned, it would always dribble out smoke when the blower wasn't running. Then when the blower kicked on it would shoot out a cloud of thick smoke for a while until the fire started burning good and hot, then the smoke would clean up. In cold temperatures this wouldn't matter much because the smoke rises, but in the spring and fall that smoke likes to stay down by the ground.