Here I used some common wood boiler techniques and plumbing knowhow to utilize our existing wood stove and heat system more efficiently.
Like many outdoor boilers the idea is to heat water, pump it to a heat exchange, and push air past it to heat your home.
This project was meant to be a supplement to our functioning HVAC system but it has essentially taken over and now the electric heat is not in use except as a back up.
NOTE: Our electric bill last season neared $700 US dollars. This year $125 is the highest.
Step 1: Capture Heat
Bell and Gosset Circulation pump.
3/4 black iron pipe
Floor Flanges (to prevent pipe from shifting)
Upcycled Propane Tank
PEX pipe and fittings
Watts automatic float vent
First I constructed the Pipe 18 inches long with 90's and 12 inches going out the back through the flanges.
I added steel and fire brick to aid in capturing heat. More area ...more heat transfer.
Then I welded a street fitting in the propane tank to create an outlet. (the tank was cleaned excessively) The tank wasn't necessary but it adds volume to the system (nearly doubled it) and since it is such a small system this was a good addition. (< 20 gallons)
Then the pump and float were plumbed in and leak tested with a temporary loop.
All was good time to move on.
Step 2: Exchange Heat
Here things get a bit more complicated.
With the heat exchanger plumbed in hot air will definitely cycle but timing and temperature control are the key to success in this step.
16x20 Heat exchanger
PID temperature controller
More PEX fittings
Washer supply line
Washer supply valve
Watts float valve
Wiring the Fan only cycle to the second thermostat allows a second means to call for heat.
Wiring the PID controller in this circuit insures that even if heat is called for the circuit will not close until the preset temperature is met.
Now with the fire dead and the water cold the original thermostat still functions. With that being said the thermostats are set as follows
Wood heat 72F degrees
Electric heat 67F degrees
Step 3: Filling
I added Tee and a valve to add water from the washing machine supply (since it was close)
Warning any connection to a homes water supply should be done by a licensed plumber. Or at least use common sense and a backflow preventer.
WARNING Valves on the lines into the firebox could cause a steam explosion IN YOUR LIVING ROOM so, be careful ...do not make steam !
I have 2 Float valves, 1 Water heater pressure valve, and an analog and digital thermometer. These are not shut off valves. Trapping water and heating it will result in containment failure ie. BOOM