Wednesday, February 03, 2016

Outdoor Wood Boiler/Furnace

We moved into our house in February but by the the time winter was done, we had spent nearly $3000 on propane heat in the house. The house is old and not well insulated and drafty so we were literally just pumping hot air right out the window.

I did what I could to prevent drafts - caulking windows and doors, but one big source of heat loss (a warped front door) still remains.  Also the insulation remains the same.

Lauren's dad told us about outdoor wood burner's and using them to heat our house.  The concept is a wood furnace surrounded by a water jacket, the heated water is pumped from the furnace to the heat exchanger through your existing ductwork to heat the house.

Buy furnace, Dig trench, buy pipes, buy corrugated pipe, buy PVC, bye crimps and crimp tool, buy heat exchanger,

Monsoon after trench dug, filled back in partially.  Ray and jake helped fig it back out and bury the pex.

Ray came by while hvac guy installed water to air heat exchanger into the ductwork outside the gas pack and wired up a second thermostat for the wood furnace.  We were out of town.

When we got back, I built a fire inside the furnace, with the fan off and the furnace door open.  Soon the fire took hold.  I opened up the supply and return valves and turned on the fan and the pump, shut the furnace door, and the fire started raging.  I turned on the thermostat in the house, the gas pack fan started blowing (no gas burning, of course), and warm air started blowing in.  1.5 hours later the gas pack fan ran nonstop, the temp in the house had increased by 5 degrees, the temp in the 175 gallon water tank was up to 180, but the wood was almost burnt through.

I added more wood.  2 hours later the gas pack fan was still running, and the furnace fire was on and off raging and smoldering with its fan switching on and off, and the wood was holding relatively steady so I think it will be fine overnight.

7 hours later, at 3:15:  the boiler temp was down to 112 and the fire was down to mostly coals.

4 hours later, at 7, the boiler temp was 151, the house was being heated by gas, and the boiler fire was down to about 25%.  I added a lot of wood, it smoked a lot, blowing to the south

I checked once more before I left for work at 8:15.  The temp in the boiler was 164, fan off, no flames, looked like nothing had burnt.  Was concerned it wouldn't catch back but it obviously did because the house for up to 70 while I was at work.

Got home around 5, boiler temp was at 111, and 95% burnt up, but there were coals.  I added a few pieces of oak in a north/south direction with a fee twigs and they went up in a couple min.  Then I refilled it.  Heavy smoke blowing to the north. Inside the house the temp is 68.

Day 2:  house warm all night despite outside temps in 20s.  At 7:45 am, boiler temp 91, 95% burnt, raking revealed red coals.  Laid down 8 pieces of wood n/s, caught fire right away.  Low smoke blowing west.

I ordered a delivery of green logs from Chris L, and a dump truck load of dry split wood from Matthew U, which lasted just over a month.  I ordered a load of cut but not split wood from MU on jam 2nd.  That wood burned very quickly and the fire went out a lot.

I think the best is a bottom layer of split wood with large log on top.


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