Can i hook up a thermostat to my hot blast wood/coal stove to control the heat in my home
Yes, you most certainly can. It depends on how handy you are and to what extent you are willing to go to make this happen. A lot will depend on how comfortable you are with electrical wiring and understanding HVAC controls and their function.
First though, this is the typical way a wood fired forced air furnace is designed to operate. There is a control transformer and relay to control either a combustion air fan (that you do not have) OR a motorized damper for combustion air that you also do not have. The relay closes on a call for heat from the thermostat and opens the damper from its minimum position to allow combustion air into the firebox. As long as there is solid fuels (wood) in the heat chamber, the fresh supply of combustion air will allow the fire to burn or begin to burn very quickly.
As the temperature in the wood furnace plenum increases, the automatic fan control will start the fan and it will run as long as the bonnet temperature is higher than the fan'on' setpoint on the fan control... Now the house warms up and the thermostat satisfies which allows the combustion air damper to spring back to the minimum position, causing the hot fire to die down due to lack of combustion air.
The now smoldering fire will not generate enough heat to keep the fan running too long, so the automatic fan control shuts the fan off until the house cools approximately 2 degrees below thermostat setpoint. The thermostat calls for heat and opens the damper and on goes the cycle....
An important item to remember is that on the automatic fan control, there is a 'limit switch' function. The motorized combustion air damper or the combustion air fan must be wired through the limit switch in case the bonnet temperature exceeds 200 degrees F. This function will then allow the damper to go to the minimum position or the combustion air fan to go off, causing the fire to cool down due to lack of adequate combustion air.
You don't want the thermostat controlling the circulating fan directly, because of two things: 1). If the fire is out, there is no heat to circulate but the thermostat wouldn't know that and it would start and run the fan continuously until a fire is built. and ....
2). You would still be running up and down the stairs monitoring the fires burn rate by opening and closing the lower door manually.
ALL the components you need are readily available from WW Grainger....basically : a fan/limit control
a 110v x 24v 40 va control transformer
a 24v spdt relay
20 ga. two conductor thermostat wire
24v actuator and linkages to mount to the existing combustion air damper. A bit of creativity is required here. I would not recommend retro-fitting a combustion air fan.
14-2 wg romex for wiring the fan control
Again, it depends to what extent you are willing to go to achieve the end result. Will it be exactly like a new system?? No, but it will operate a lot better than that which you describe. Read More At : Home...