Outdoor wood burning furnace

Hey all,
I am building a shop and want to use an outdoor wood burning furnace to heat it for because I have an abundance of wood. For those of you who have these units, can you run an antifreeze in the lines to keep it from freezing up. I plan to use the furnace about 3 days out of the week but don't want to keep stoking her up on the days I wont be using the shop. I would go with a wood stove in the shop but I don't want the dirtiness of the wood inside plus the flame and painting cars/trucks and tractors wont mix well. I would rather keep the flame outside at a distance. Let me know how you run your outdoor wood burning furnace I would be interested in the pro's and con's. Thanks

I am on the 16th winter of a Central Boiler Classic. I am running water only, (with chemicals) but no antifreeze. Mine hold 185 gallons of water, so a 50/50 mix with antifreeze in northern Michigan would be quite costly. Because of that, I keep it running all winter long. It does sort of tie me to it. When our kids lived at home, and their neighbor friends, it was easier to have someone throw some wood in to keep it going. Now that all of them have married and moved away, and their friends have done the same, I am more limited in finding someone close by to do that. When it finally fails, or I do, I will not replace it. The cost of the stove itself has went up appreciably, and I have gotten older. It has served us very well, keeps the house warm and heats our hot water too. The technology has probably changed quite a bit with them since I purchased mine, probably are some with much less water capacity, and I think there are even ones that push heated air into a building instead of water. For an occasional use, one of those might be worth checking into.

Go for it! We love ours....

We have one, for a couple years now. It will burn anything tossed in, and don't have to cut the stuff down as far(less work) either. We are pulling a lot of heat off our unit(couple buildings, long snaps of cold waeather(teens/twenties...below) and nothing is really sealed tight), have to fire two/ three (or more) times a day to keep it happy.

For only one building, unless very large or heat turned way up, you might not have to stoke it over for a couple days at a time. They DON"T burn full out full time(like a fire place or stand alone inside furnace)... When water temp drops, then the draft opens to get air to the fire, once up to temp it shuts down. You open the door you'd almost think the fire was completely dead. Once running for the season better just keep it fed, or fight to get it going again everytime when not in use.

If you don't want to stoke it get one with a back up system to hold the water temp, they chew wood in a hurry with out getting heat in building just getting temp back up. In our unit The water lines, once in the building, go through a temp control valve, to low(under I think 150 deg.) it shuts down flow to the radiator/heat exchanger(causing cold building) and sends it all back to the furnace to be reheated.

the worst thing for them is heat cycle cold hot cold hot the metal expands and shrinks they will and do crack because of the heat cycles they are fine if they stay hot and then are shut down for the summer. don't get one any bigger then you need bigger is not better they have to get hot two keep them dry in side. have had one since 2004 and have one leak in the corner of the door welded it up and all has been fine knock on wood

Fred, we've used a Hardy outdoor boiler for 19 years. It has a fire in it year round - it heats our domestic water too.

If you are only wanting heat 3 days out of the week, I seriously doubt if your fire will ever go out. Just turn the thermostat down to minimum and the boiler will take care of itself.

A few years ago in late December, my wife and I drove a friend to St. Louis for major surgery. I loaded the boiler before we left on Sunday, and turned the thermostat down to minimum. When we got home late Wednesday night, we turned the thermostat back up and it went right to work. I thought my son had fueled it while we were gone, but he said he thought someone else was fueling it because it was fine every time he checked it.

The aqua stat cares nothing about your shop temperature - it just maintains 170 degrees boiler temperature.

Of course you want to run anti-freeze in it in the colder climates if you don"t run it steady. In central MN, a 30& antifreeze mix is fine. Old AF works well. No worries if shut down for a spell.

We're in central MI. We do not put any antifreeze in all winter. As Psimmer stated with a 180 or so gallon of water in them it would be expensive for the antifreeze and as you have to add water during the winter it would weaken your strength by spring. I just drain mine and flush it out each fall before I refill it for the winter. I keep water in mine all summer and burn the papers in it.
Why not just have an insulated cover to put over it while not in use. Then with the water circulating through during the down time it would help hold the heat. Also if you got a bigger one you could heat your house also. You would want one with the dual lines for that with separate pumps one for the house and one for the shop.

I've got one that I've had for 8 years. I just run water with the anti-corrosion chemicals. This winter has been so mild that I have only needed a fire a couple of days a week. Mine has an electronic thermostat so on the warm days I turn the water temp down to 90 degrees. I don't have to fill it up about every 3 days and when I need the heat it only takes an hour or less to heat back up.

I think you would burn more wood trying to heat the water back up than just turning the stat down. I have a central boiler and leave it burning all year to heat my water and even heat the pool with it.

had one, no more went to lp radiant tube heaters , oh how nice, and no more smoke always around the place. spent more time keeping wood then working in shop. wood is not free!!!! good luck

Agreed. It seems people I know that have those no longer have an abundance of wood or free time!

Ever heard of a hasha? popular in russia.
8'X8' cinder block building with a fire box and some ductwork, filled with sand.forced air!