Woodstove w/ waterjacket for hydronic ?
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Does anyone out there know where I can get info about using a wood burning stove to preheat (darn near replace ) boiler water for hydronic heating ? This is an idea only at this stage, but while I have my basement floor jackhammered out I thought I’d ask. Has anyone done something like this before? how did you configure the zone valves,relays etc?
thanks, Bill
Edited 4/26/2002 1:35:01 AM ET by Bill S
Replies
1) There are wood-fired water heater/boilers available off the shelf.
2) I've converted about 20 cast iron (and one soapstone) wood stoves to heat water. We'd drill two holes in the side and install a stainless steel U-tube inside. The piping was 1-inch pipe size and either a U-bend or a J or a double U depending on how much length and volume was available. A couple of nuts threaded on (inside and out) and some stove putty and you're done with the stove. We'd install thermocouple heat sensors to a controller to turn the pump on and a special high-temp blow-off (for safety during power failures) located very close to the stove and routed outside to a dry well.
The hot water from the stove would go the solar tank which served as a pre-heat to the regular domestic hot water tank. During periods of lots of sun or lots of stove use, the regular water heater never came on.
This scheme did NOT generate the kind of BTU/hour you'd need for hydronic heat. For that, I'd suggest you look at the purpose-built wood-fired boilers.
Bill, We use just such a stove to preheat water in our house. The stove is a box made of 1/4" sheet metal. The upper sections of the right, left and back sides and the top are hollow and filled with water. The floor and lower sides are protected by firebrick. It appears to have been manufactured by a small outfit in S PA ("Mascot"). There are a number of other commercial manufacturers around but a decent fabrication shop could make one.
A circulator on a thermostat sends water in an endless loop from the wood stove to the water jacket in our oil furnace. A second thermostat controls the damper and a third will start the house distribution circulators should the water get too hot. The radiator circulators on the oil furnace still are in charge of sending water to the house when needed.
It's a simple system that paid for itself rather quickly although I think it could be improved by adding an insulated storage tank in the loop. Be warned, these systems burn a lot of wood.