Need help identifying and repairing old woodburning furnace

Discussion in 'Homesteading Questions' started by Pony, Jan 19, 2005.

  1. Pony

    Pony Well-Known Member Supporter

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    Hey all, I'm Pony's DH, and wanted to post a poser that would take me too long to dictate to my sweet Pony.
    My parents have a woodburning furnace of some unknown vintage in the cellar of their farmhouse. It has never worked since they bought the place, partly owing to the following: a) the previous owners didn't know how to run it either, b) there are no instructions anywhere in the house, c) there are unlabeled wires hanging off it, and d) there are no markings of identification or instruction anywhere on the machine! I'm trying to identify it, in hopes of getting it working, and maybe even finding spare parts or owners instructions.
    The only potentially branding mark it has is the stamping of a crown on the firebox door- five or six prongs on the crown with round balls at the tips. No other markings anywhere else on the sides or back of the furnace. Stickers on the blowers and electrical bits regard only those pieces to which they're stuck.
    The body, blower box and duct box (the chamber to which all heating ducts connect) are all 18 to 22ga sheet metal. The firebox itself looks to be 1/4" sheet iron or heavy steel. The body is about 48Hx24Wx36D". There are two doors on the front- one for the firebox, about 12x10", and the other for the ash pan, about 12x6", with a blower fan between them, probably for stoking the fire. There are also two other handles- one slides in and out and controls an odd sort of damper or flue at the top of the firebox. The other is below what I'll call the stoker fan, but above the ash pan door. Its only function at this point seems to be to shake something underneath all the packed-down ashes, probably to shake ashes into the ash pan.
    The firebox is about 28Hx18Wx24D", and is lined on the bottom and the bottom third of the walls with firebrick. There is no wood rack to speak of, and just a heavy layer of ash at the bottom. The "flue" is a long, rectangular box at the top of the firebox into which the top handle goes, which connects to a plate that covers a round hole in the bottom of the "flue" box. It does not, however, cover the exhaust pipe at the back, as evidenced by many dessicated carcasses of birds, squirrels, and mice in the firebox and ash pan. One small squirrel carcass was less than a month old.
    The blower box is mounted to the back of the furnace at the bottom, and injects air directly under the firebox. The air flows around the firebox inside the body and up into the duct box, and then out the ducts to the vents. In fiddling with random switches, Dad and I discovered a hum. We traced it back to the blower fan, and after getting the squirrel cage freed and moving, we were able to activate the blower. Cool! Now we have air conditioning... :haha:
    The wiring is very confusing, but I think the gist of it is this- power comes in to the main shutoff switch, and out through a mercury switch. The mercury switch is currently hanging outside the furnace, but could be mounted in one of two holes: one in the duct box, the other in the body directly adjacent to the firebox. Power from the mercury switch goes down to a 24VAC transformer that connects to a relay and the thermostat upstairs. Power also goes to a fan safety switch (case of which is stamped "WHITE RODGERS"), which seems to somehow influence the main blower and stoker fans. I'll try to complete some sort of wiring diagram from my scribbles and post it to my Yahoo Photos site, and link to it here later.
    From what I could tell after looking it over, I'm hoping that once we make sense of the wiring, a cleanout of old ashes and change of firebrick, and we'll have more than just electric baseboard heat in the winter! :D
    Thanks for any tips anyone can give,
    Nick (Pony's DH)
     
  2. Ross

    Ross Moderator Staff Member Supporter

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    The thermostat should control the "stoker" fans, or a power draft. The mercury switch, (curled bimetal?) proabably should go closer to the fire box than the plenum, but it might not matter much. It will kick on the blower fan once the fire is hot enough to heat the switch. I wonder if it is a two speed fan?? My wood furnace can run full time on low but the switch will kick it on high speed if it gets hot enough or if the low speed is off and there is a fire heating things up. It sounds as if it has some old tech draft control to limit the down draft for starting which is kind of neat but with a power draft, redundant. It shouldn't need a grate to sit the fire wood on.
     

  3. Cindy in KY

    Cindy in KY Well-Known Member

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    That sounds exactly like our woodfurnace. Ours is outside in a metal shed. Our thermostat controls the squirrel cage blower of hot air into the house. The thermostat is screwed on the right side of the body at the top of the jacket. We set ours to blow at 100* I think. When the air in the jacket goes below 100*, it kicks off. That screw inside the thermostat needs to be tight up against the jacket, it works itself loose often, and when it does, it won't kick on like it should. Our thermostat has a little white button you can pull out, and the squirrel cage will kick on and off with the temps, pushed in it stays on all the time.

    The little blower above the ash pan in the front, we have a toggle switch, on the left side in the back, to manually turn that on and off. I would not want that blower to come on by itself. There is wiring in a metal flex pipe going from the back left to that blower in the front. The little fire blower, has a circle opening it that can be opened or closed for draft, that is our draft, wether the little fan is on or off. With the little fan off, the circle is 3/4 of the way open for draft. With the little blower turned on, the circle is only open maybe 1/2 inch, just a tiny bit open. It really blows allot of air. We tape our draft to stay where we want it so it won't accidently fall open if the little blower is on. If we're burning cedar, or scrap wood, the draft is barely open, as those burn hot anyway. We have a wood grate in ours, that the ashes fall into the ash drawer from. Our big handle above the wood door, for the flue draft, is always set at 3/4 closed, with a rock there holding it. We open it before we open the wood door.

    You need to get some High Heat caulking and caulk all the edges of that jacket, or the hot air will pour outta there with the pressure. Check to see that the screws are tightened down on the jacket too, before you caulk it. I don't know much about wiring, but when it gets light outside, I could go out there and look and see where our wires go.

    We made a sheet metal box to go over the squirrel cage & motor & wires on the bottom back, so nothing would drip down on them from the flue. Our flue goes out straight, and then up out the roof. I have to clean that flue at least twice a week, as it really builds up soot. We also just put a new gasket on our big front wood loader door.
     
  4. Cindy in KY

    Cindy in KY Well-Known Member

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    Forgot to say that the squirrel cage, where it sucks in air, is supposed to be your return air from your house going in. That is so smoke from opening the wood door won't get sucked into the heat vents. When I clean out my stove & flue pipe, I turn it off so it can't kick on. I can clean mine out easy even with some coals & smoke as it's outside.
     
  5. TheBlueOne

    TheBlueOne Well-Known Member

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    It sounds like an excellent furnace once you get it running.

    The "hum" from the motor means the bearings are dry, even if the cage turns. Pick up a can of 3 in 1 Motor Oil (about $2.00 or so) and oil the motor bearings well. There should be two oil points, one on each end of the motor. I just replaced my blower motor for the same problem as the previous owner of the house must have never oiled it. The heat from the furnace as it was running made the problem worse. The new blower motor was $140 so it's worth taking care of ASAP.
    I was also wondering what the exhaust (chimney) setup was. Cindy's statement, "I have to clean that flue at least twice a week, as it really builds up soot" points to inadequate draft and possibly inadequate combustion. Consider a chimney cap to keep the creatures out.
     
  6. Cindy in KY

    Cindy in KY Well-Known Member

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    I don't know why ours builds soot up so fast. Even if the fire is burning hot, hot, the soot is dry & flaky. Our flue pipe has the stupid elbow in it, so the dry soot falls down and clogs the elbow if I don't keep it really clean. They should have made it with the flue going right out the top, then it would fall back into the fire box and not be a problem. We do burn allot of dog food bags, paper feed sacks, cereal boxes, scrapwood, chipboard, etc, anything burnable like that, along with the firewood. Maybe that's why.

    I go up the ladder, and pop the flue with a stick, then go back inside and pull the flue off the back of the furnace, and then stick my arm way up in there and pull all the soot out of the elbow into a bucket. Only takes a few minutes. Our stove won't draft good if the flue is not clean. The flue on top of the metal building is only about 5 feet high. The furnace is not one of those air-tight ones, just a really big woodstove with a jacket and big blower. I used to have a Hot Blast wood furnace, a new one, years ago, and I didn't like it because it was so air-tight, I was afraid to open the thing, it would get so wicked hot.
     
  7. rambler

    rambler Well-Known Member Supporter

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    Sounds like you have a pretty good handle on it already.

    For access to a bunch of people very knowlegeble in wood stoves, you might want to copy & paste your message into this Yahoo group:

    http://groups.yahoo.com/group/woodheat/

    I think you need to sign up, but it's free to join. Bet someone there can identify the stove from the crown.

    Nice message, you described the details needed. :)

    --->Paul
     
  8. Pony

    Pony Well-Known Member Supporter

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    Nick here again...
    Thanks to all of you for your great responses! I've got a really good idea how to progress from here.
    Ross: Yes, the mercury switch does seem to have a curled bimetal, but not in the way you'd think, like the old mercury thermostats. This one spirals inside a stem about 10" long or so, which matches what Cindy In KY said- there is a round hole in the side of the jacket, and if the stem of the switch were in there, I imagine it would at least get close to the firebox if not actually touch it.
    Cindy, thanks for the tips on sealing. I know the plenum has to be mounted to the jacket properly, as it's just sitting on top right now. The jacket itself seems to be seamless, but I'll check it again when we're up there next. The blower fan has a box around it as well, and there's a slot in one end for a 16x24x1" filter. We took it out so I could reach the squirrel cage, and it was so decrepit it fell apart.
    Thank you for the info about the stoker fan- I don't know how this one is supposed to behave, but it too has a plate that covers its intake to limit the amount of air it sends. Perhaps it blows all the time, and the heat is adjustable with the plate and not the speed of the fan. Once the wiring is squared away, we'll certainly find out!
    Also, I'm guessing your soot problem isn't from the wood, it's from the paper products you're burning. If you toss them in a hot fire, it shouldn't be a problem, but if it smoulders, there's your soot production. Some papers (glossy, heavy glues, etc) may soot anyway, I'd save those for the burn barrel.
    TheBlueOne, the hum wasn't from the bearings, it was from the motor straining against itself. The armature was stuck, but once I freed it, I would flick the cage in the direction of rotation while Dad hit the main power switch (a trick with which he's well-acquainted, thanks to a bad starting capacitor on his radial arm saw!) Once it started, slowly, he left it on, and as it moved it built up speed until it was at full. When I tested it again the next day, it started fine on its own, but I will be sure to check the motor ends for lube caps and take care of that.
    Paul, thanks so much for the link to the Yahoo group! I'll have to check that out tomorrow, maybe re-post my original message (with what I've learned here) over there and see what they can come up with.

    Thanks again,
    Nick
     
  9. Ross

    Ross Moderator Staff Member Supporter

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    The strip wrapped around a rod as you describe is what's in my wood furnace (it's in our oil furnaces too) Some are on top in the plenum some are along the side. Good luck it does sound like a dandy heat source!
     
  10. Cindy in KY

    Cindy in KY Well-Known Member

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    If it is like ours, then you won't want that little fan on all the time, as it really burns up wood fast with it on. Really fast. I only use it when I'm cold, and only if I am home & up. Never while we are gone or asleep. The wood would never last all night with it on either. I burn all the other stuff during the day as to save on wood, as we have to buy our firewood. I save the biggest chunks for night time.

    Our plug wire, thermastat wire, and little fan wire all go into the toggle switch box. I can't see the squrrel cage wires under the box, but if you need help, Steve can see for you. Our jacket isn't seamless, the cast iron of the stove itself shows in the front and back, with the jacket on the top and sides. It's a yellowish jacket. We built a homemade sheet metal box for the top, with an elbow to hook the air vents into. There is no name on our stove anywhere. I looked and looked with my reading glasses on too. We got it used in the paper for $400 a few years ago, and none online look like ours that I can find.
     
  11. gearyb

    gearyb Member

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    Wood furnace. I've got one that isn't made anymore and I've had to change a few parts out. You need: Thermostat (round with mercury in the glass tube), a Fan center (provides low voltage control of lin voltge fan motors)(tell the HVAC store you need a transformer), a fan contol unit (Honeywell, mounts on the plenum). AC goes to the transformer as does the thermostat, backside of transformer connects control unit and both fans. Can be complicated wiring since instructions are for modern HVAC units. Idea is, when thermosat indicates need for heat, intake fan kicks on (blower between door and ash pan) (leave fan switch always on), air causes fire to burn hotter, heating plenum, when plenum reaches whatever temp you have the contol unit set at (mine is on at 150 off at 100) it starts the blower motor the backside, cooling the plenum to where it again kicks on the intake blower.
    Problem with a wood furnace is, if heat is not really needed, the intake fan does not turn on giving a air starved fire, hence the creosote build up.

    Ahhh, but wood heat is so much better that baseboard electric.
     
  12. agmantoo

    agmantoo agmantoo Supporter

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    "This one spirals inside a stem about 10" long or so, which matches what Cindy In KY said- there is a round hole in the side of the jacket, and if the stem of the switch were in there, I imagine it would at least get close to the firebox if not actually touch it."
    The above item when used in an old furnace is a limit switch. It is used to prevent the device from overheating and when wired in a wood stove would IMO cut the draft fan off and possibly close inlet air to the fire.
     
  13. Cindy in KY

    Cindy in KY Well-Known Member

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    "when thermosat indicates need for heat, intake fan kicks on (blower between door and ash pan) (leave fan switch always on), air causes fire to burn hotter, heating plenum, when plenum reaches whatever temp you have the contol unit set at (mine is on at 150 off at 100) it starts the blower motor"

    So maybe we hooked ours up wrong. Big difference is we do not have a thermosat inside our house. (the Hot Blast Furnace we did) Our big old farmhouse is so drafty though, the little fan would never go off (always calling for heat) We just leave the draft way open, like a regular woodstove, and let the thing kick on and off. Steve said that the toggle switch used to be a little rubber switch when we first got it, and he replaced it with the toggle switch. Our thermosat for the jacket works with a spring, and it's a aluminum circle with temp notches on it.

    Our furnace really is picky with wood, our comfort inside the house really depends on what kind of wood we are burning. Like if I had a whole truckload of cedar slabs or scrapwood from framing, I could fill it up, and leave the draft just barely open, 1/4 inch, and our house would be toasty warm all day on a full load, no matter how cold outside. Seems the hardwoods, even if seasoned, just don't burn near as good, and don't make good coals, just ash, and the draft has to be way open, or the fan on, and I go thru allot of wood, allot more than cedar or scrapwood. My stove needs to be half way full of good, hot, red coals to really run good without eating the firewood.
     
  14. Cosmic

    Cosmic Well-Known Member

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    Maybe you want to try redesigning the entire affair.

    The better designs probably use automated draft doors / dampers and attempt to keep the furnace at some setpoint all the time. Draft varies with demand and the stored energy in the furnace can help even out swings in temperature. There is not much delay between the demand call for heat and delivery.

    Burning in a pyrolysis mode, being air starved can also give you a lot of soot and build up. A good model is the way the forced hot water automated draft units work. They have a regulator that can be adjusted to setpoint. The trick is to get the wood load into the charcoal phase before the draft turns down to a low value after the bulk house heat load is satisfied, from that point on they run very nice.

    Sounds like those units with blowers put a lot of energy up the stack in their idle mode. Could think about building a heat scavenger unit and tying that into the operation, even if it just dumps the heat local.

    Some good examples to look at.

    http://www.alternateheatingsystems.com/woodboilers.htm

    http://www.motherearthnews.com/arc/554/

    My HS Tarm uses the Samson draft regulator. Dandy little critter, probably can be adapted to use on a hot Air furnance. Lots of other similar ones around. Older ones called ARCO worked the same. The beauty of the Samson, is you can adjust the setpoint, means you can always use the same hook spot on the chain and dial in exactly the operating temperature of the unit similar to a oil or gas fired unit.

    http://www.woodboilers.com/hot-water-heating-systems.asp

    The thing at the top of the chain hooked to the damper is the regulator. The old American Standard forced hot water boilers worked the same way, only with even more complex ability to adjust draft. I may have one the guy who is going to buy my house is going to scrap. Be a damn shame, was converted to oil but probably could be converted back to wood / coal. Has a killer domestic hot water exchanger mounted on top too. Double pass internals, super easy to clean. I've told him a lot of people would love to have it. It will last forever.

    Probably can improve older units a lot by tinkering and redesigning how they work. Maybe trying to make the forced combustion blower more a variable speed unit to operate in conjunction with regulated draft. Might even want to think about two stage units where the existing unit is in essence a true pyrolysis unit that produces gases to be finished burning in a second stage. Induced draft units that operate as negative pressure units are safer than what appears to be these units mode. Using a blower to pressurize the fire chamber would scare the bejesus out of me, too many chances of CO leaks.