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Author Topic: My homemade/modified forced air wood furnace  (Read 28292 times)

ribs1963

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My homemade/modified forced air wood furnace
« on: November 19, 2009, 08:22:10 AM »

Hello,I'm new to this forum and I thought I'd share what We did at our home.I had researched outdoor wood furnaces for about a year and I wanted to go with a forced air unit.I had some idea on making my own but never got around to it.This past summer a co-worker offered me an indoor add-on wood furnace that was in the basement of the house he had bought a couple years ago.This was my chance get things going.I thought I could modify it in order to put it outside so there wouldnt be any mess inside and my insurance company told me that as long as it was outside they didnt care if we had one.We hauled it home and tore into it only to find that the fire box was warped and rotted through in many places from the previous owner leaving the ash in it and rainwater entering from the chimney.This was obviously a major problem.My brother in law is pretty handy with a welder so I took it over to him and he had no doubts that he could beef it up and get it going for us.I also purchased a junk livestock trailer around the same time for $50 and I took it to ny brother in law so he could use as much metal as he needed to get the stove back in shape.Two weeks later I went over and we test fired it to check for leaks and found absolutely no leaks.I hauled it back home and started installing it.I placed it about 40 inches from the house,put it up on concrete blocks.bought some 8 inch duct work to pipe the hot air into the house and also 8 inch ducting to run a cold air return back to the furnace.The next step was a blower fan.I knew it need to be fairly small so it would'nt overcool so I went down to the scrap heap at the back of our farm and pulled out a clothes dryer that I had taken back there a couple years ago and took it to my barn to dismantle the blower motor/fan assembly.I used the sheet metal from the dryer to make a plenum in which to put the fan and attach it to the lower back of the furnace.tested the motor,wired it through a fan limit switch that came with the original add-on furnace.I also ordered some high heat insulation to place inside the outer casing of the furnace.With buying the chimney,raincap,duct work and the stock trailer i probably have less that $150 in the whole unit.I fired it up in late september of this year on a night when the temp dipped to 26 degrees.and man was i surprised.This little baby kept our whole 2400 square ft house warm as toast.we have been using it off and on for about six weeks and I have never been more pleased with one of my projects.I ran the heat duct in through my living room window and made a plywood frame with foamboard insulation so that no cold air can get in and no hot air escapes.I also wrapped the duct with the high heat insulation so I dont have to worry about the framework in the window getting hot.I placed an oven thermometer in the duct work and we average from around 100 degrees to around 200 degree air coming into the house and the return duct is hooked into our central heating return air duct so the air circulates through the whole house. 
 
   
 
 
« Last Edit: November 24, 2009, 07:50:32 AM by ribs1963 »
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murph

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Re: MY homemade/modified forced air wood furnace
« Reply #1 on: November 21, 2009, 02:54:15 PM »

I don't even know where to begin with this set up! You definitely need to send in some pics because (maybe its just me) but I have no idea how this is legal in any state. Your wood boiler is only 40" from the house?Did you pipe it directly to your existing chimney? I find it hard to believe you mentioned this to your homeowners insurance. Did you ask your town for a permit for this? Its hard to imagine an inspector saw this setup and ok'd it. Up to 200 degree air blowing in the house? Really? What is the type of heat exchange process that your using? You say you have 8" ducts coming in through the window of all places, and a cold air return going back to the boiler. Why do you need a return? I could be way off on this but I am very confused by this setup. Please reply to this Ribs1963 to further explain. I'm not trying to come off as rude here, I'm generally concerned with the safety of this. I can't believe no one else has commented on this.

Murph
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Dirtslinger

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Re: MY homemade/modified forced air wood furnace
« Reply #2 on: November 21, 2009, 04:45:50 PM »

I don't even know where to begin with this set up! You definitely need to send in some pics because (maybe its just me) but I have no idea how this is legal in any state. Your wood boiler is only 40" from the house?Did you pipe it directly to your existing chimney? I find it hard to believe you mentioned this to your homeowners insurance. Did you ask your town for a permit for this? Its hard to imagine an inspector saw this setup and ok'd it. Up to 200 degree air blowing in the house? Really? What is the type of heat exchange process that your using? You say you have 8" ducts coming in through the window of all places, and a cold air return going back to the boiler. Why do you need a return? I could be way off on this but I am very confused by this setup. Please reply to this Ribs1963 to further explain. I'm not trying to come off as rude here, I'm generally concerned with the safety of this. I can't believe no one else has commented on this.

Murph
Murph
He does not have a boiler its a hot air furnace fan pulls heat off of the furnace and to the house and the return is supplying the air that it is blowing in his window.
Just like a forced air furnace in your  house
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ribs1963

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Re: MY homemade/modified forced air wood furnace
« Reply #3 on: November 23, 2009, 07:48:51 AM »

I'ts not a boiler,Just forced air.The furnace is insulated and cold to the touch even when the plenum temp is 200 degrees.The duct is also insulated so no part of this furnace is hot on the outside except for the chimney which is meets fire codes for our county.Google outdoor wood furnace and you'll find a few out there and this one is similar to most of those except this one didnt cost $1600 to $3000.I dont think you were rude at all just curious. This unit's fan is also wired to a circuit that can be switched over to run off my generator when the power goes out during winter storms so the unit wont super heat during a power outage
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ribs1963

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Re: MY homemade/modified forced air wood furnace
« Reply #4 on: November 23, 2009, 08:04:57 AM »

On another note,It's much safer,and cleaner than having the add-on furnace in the basement which was my goal and I think the goal of most people that install outdoor furnaces
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ribs1963

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Re: My homemade/modified forced air wood furnace--update
« Reply #5 on: December 08, 2009, 10:22:36 AM »

It's been down in the teens at night and around 30 degrees in the day and the stove is working perfectly.We found the right combination of wood to keep the stove hot from about 11:00 p.m. till 5:00 a.m. when I get up.The firebox is fairly small but we fill it with aged oak chunks and some ash wood and the house stays above 75 degress all night and there's still some wood left in it when I get up in the morning.My son fills it once or twice in the day when I'm at work and everything is working perfectly
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rickado

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Re: My homemade/modified forced air wood furnace
« Reply #6 on: February 09, 2010, 06:41:43 PM »

Hello all,Im a newbie here with lots of questions.So if I ask a stupid question,well Im sorry in advance.A question I  have is for rib1963.I read your intro. and thought this is about the size I need.[maybe smaller] Just not sure about the size.Im in about 800sqft.house[cracker box] Id sure like to see some pictures of your set-up.And anyone have any idea on the size.Im just tired of paying for high natl. gas prices[T.Boone Pickens ownes it-atmos engery} Thanks & have a good day. rickado
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ribs1963

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Re: My homemade/modified forced air wood furnace
« Reply #7 on: February 10, 2010, 07:53:02 AM »

I dont have any pics yet but the firebox is approx 14 inches wide,27 inches deep,and I think it's around 22 inches tall with an ash compartment below.Then the outer insulated caseing leaves around four or so inches of space between the insulation and the firebox.The whole thing just looks like a common small forced air furnace.There are places online that you can get super high heat insulation that is used to refurbish old stoves.I think its spun ceramic and is rated at 2200 degrees.So far our Highest electric bill has been $175.The house temp hasnt fell below 72 degrees since we installed it and we've had it a lot warmer than that just to see what it would do.Theres a place in Missouri that sells manufactured ones similar in design to mine,I think it's called LIL' House wood heater.The one thing I forgot to mention was that I made a "heat dump" trap door on top of it just in case something should ever happen to the fan and I wanted to let all the hot air out before I could shut down the fire.
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rickado

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Re: My homemade/modified forced air wood furnace
« Reply #8 on: February 10, 2010, 09:19:29 AM »

For ribs1963,Ive ck. out Lil House site,Itried to find other sites to get a better idea.All I could find was big outdoor wood furnaces.Do you know of any other sites that sell the one on LilHouse?Cant afford to buy one just need more pictures[If I  can see it I can usually build it]Thanks for a quick responce.Rickado  Have a good day
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ribs1963

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Re: My homemade/modified forced air wood furnace
« Reply #9 on: February 10, 2010, 03:30:56 PM »

The only other manufacturer I know of is the firechief located in missouri also.Their outdoor furnace is really big but the basic idea is the same.Heatup the air surrounding the stove and blow it into the house.My brother-inlaw is building the one for his shop using a 100 gallon rectangular fuel tank standing on end for the firebox.It will sit inside a 250 gallon round fuel barrel as the heat exchanger.Thats still way to big for what you want to do but its the general idea,you just have to play around with the the size fan that you need versus the size of the air plenum surrounding the firebox.I just got lucky.Grainger sells a number of squirrel cage fans so you should be able to find one that suits your needs unless you have a few old clothes dryers around that you can toy with
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willieG

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Re: My homemade/modified forced air wood furnace
« Reply #10 on: February 10, 2010, 03:47:40 PM »

my father made one years ago and used it for 25 plus years for his shop (although it was inside the shop it is basically what you are talking about i think)

he heated his small 1600 sft house and his 30 x 60 shop

he used a 150 gallon tank insie a 200 gallon tank (round) hooked his plenum pipes to it and a regualr furnace blower. he didn't insulate it as it was indoors. the blower sent heat to the house and the shop just had a blower hanging over teh furnace and blew the air around the shop. it was always warm in both the house and the shop. he heated only with slab wood from a local sawmill that  he did machine  work for. he used natural draft and used one of those metal heat strips that expands when hot to open and clsoe the draft. he added a little weight to this to get the draft to open and close where he thought it worked best. and it did work fine. it still sits in teh building bot he no longer fires it as  he is now over 80 and wont mess with wood
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ribs1963

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Update
« Reply #11 on: December 03, 2010, 11:49:00 AM »

after over one year of service the clothes dryer blower motor finally gave out.The start up windings went bad and it would not start up on its own but would run if you could spin the motor while plugging in the power supply (not recommended).The company I work for has a house for it's drivers to take breaks and had an old maytag dryer in the basement that the heating portion had went out on.They gave me the dryer and i took the motor and blower out on lunch hour and took it home to wire it to my system.An hour and a half later,all installed and back in service.COST-- nothing,75 degree home,PRICELESS :thumbup:
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jackel440

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Re: My homemade/modified forced air wood furnace
« Reply #12 on: December 03, 2010, 02:11:41 PM »

That's awesome.But still no pics :photo:
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Yooper

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Re: My homemade/modified forced air wood furnace
« Reply #13 on: December 25, 2010, 11:53:23 AM »

Commercial units similar to this one include the Wadena home furnace, the Fire Chief made in Missouri, US Stove makes one and the previously mentioned Lil House heater.  All have the advantage of being cheaper and simpler than an outside wood boiler.
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Scott7m

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Re: My homemade/modified forced air wood furnace
« Reply #14 on: December 25, 2010, 01:00:08 PM »

I know a few people that have these.  They work but wood consiumption is higher because they have nothing to store heat in, "water"

Also, a couple of the people say that they are now having problems with the smell of creosote/smoke all through there homes.
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