Homemade outdoor wood furnace Temperature controller

Justink Posted By Justink, Nov 8, 2013 at 10:37 AM

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  1. Justink

    New Member 2.

    Nov 8, 2013
    I just finished the mechanics of an outdoor wood furnace. Now I need to get it to run automatically. My plan is to have the blower run constantly for safety and thermostatically control the draft fan. I will use an attic fan thermostat at the furnace to shut it down when temp get too low (run out of wood). Then from inside I will have a 120v thermostat for room temperature and another thermostat on the duct to keep output air at 120f and prevent overburn. At night I plan to turn this down to try and get all night burns. Is this a good economical approach. Already have electric baseboard thermostats i can use.
    I also have a variable motor controller to control the draft fan. This has been very useful to try to start and control the fire.
    The furnace is a double barrel wood stove in a 3'x5' metal shed with roxul insulation and hvac duct work looping around inside shed.

    I have been searching online for other thermostats that would combine the multiple thermostats into one unit but i havent had much luck. i seen some industrial looking one with big red digital temp display that have alarms which i think is a good safety feature but i dont think they will replace more than one thermostat.

    Anyone know of any thermostats that would at least replace at least 2 thermostats, have digital display, alarm and cost under $100.
    Thanks for any input.
  2. begreen

    Mooderator 2.
    Staff Member

    Nov 18, 2005
    South Puget Sound, WA
  3. brenndatomu

    Minister of Fire 2.

    Aug 21, 2013
    NE Ohio
    I agree, just use a typical run of the mill limit switch like the one BG linked to above, to control your duct temp (over and under fire, 1 side controls the duct blower, high limit side kicks off if over fire occurs - controls combustion damper/combustion blower, whatever you have) that's what they are made for. Forget the attic fan switch, at least for that anyways. You can find used forced air furnace limit switches pretty cheap all over fleabay.
    Just throwing out ideas here, what about just using common el-cheapo thermostat(s) and controlling multiple things by using regular old multi-pole relays? Or just go ahead, use multiple thermostats, so what? My Yukon Husky Multi-fuel furnace uses 1 stat for the wood side and 1 for the oil burner/A/C side.
    Heck, you could wire up an alarm by tying a N/C relay to the hi limit side of the limit switch, when the LS opens, relay de-energizes, sets an alarm, if that's what yer into.
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