Add-on wood furnace

[friends59]

I installed a wood furnace and ran hot air ducts to my living room and hallway next to the bedrooms. Last year I spent $5,000
on oil. If I had continued to burn only oil this winter I could spend $6,000 to $7,000 for the heating season. I stopped using my
18 year old oil furnace from making my domestic hot water and now I only use my oil furnace for backup heat if nobody is home
to use the wood furnace. I now use an electric hot water heater for domestic hot water. I purchased 2 tons of Envi-blocks and
have approx. one cord of oak seasoned for 18 months stored in the basement. If I burned approx. 1200 gallons of oil before
installing the wood furnace and electric hot water heater, how much wood will I need to heat my house which is a ranch style
1352 square feet not including the basement. The wood furnace can heat up to 3,000 square feet. My house has new thermopane
windows and R-49 attic insulation in 464 of the total 1352 square feet, and less insulation in the rest of the attic as the house was
built for electric heat in 1970 and five years ago built the addition. The wood furnace does not heat the basement with the exception of the flue pipe. I really don't want to use the oil furnace except if I'm at work and the house temperature dips blow 50 degrees.
I pick up unwanted wooden pallets at work and cut them up to burn. 7 to 10 pallets per week are available (hardwood).

 

[oilbegone]

I had a similar set up for about 25 years. Oil hot air furnace and separate oil fired hot water heater with a wood furnace tied into the duct system that used the blower from the oil furnace. At the time the house was about 2100 sq ft not including the basement. The years oil was inexpensive I burned about 1100 gallons of oil and very little wood. Years that I burned mostly wood and used the oil for hot water only averaged 7 to 8 cords of wood. The old furnace died last spring so I am now installing a Tarm Solo 30, looks like we have another couple weeks of fairly warm weather coming so I should be done in time if the plumbers schedule works out. Hope this info helps.

 

[SteveT]

If I'm reading this correctly the insulation has been there right along so that won't enter into the calculation.

Ballpark, consider 25% of your oil was for hot water and 75% was for heat (that could be way off if you have a large family, lots of showers etc.) So you burned 900 gallons of oil for heat.

Two pallets of Envi-blocks will replace about 230 gallons of oil.

One cord of oak will replace maybe another 160 gallons.

As a REAL WAG let's say each hardwood pallet is 1% of a cord. Seven pallets each week for a 30 week heating season would therefore be about two cords or another 320 gallons replaced.

So - 900 gallons needed, and 700 replaced with Envi-blocks, cordwood and pallets -- 200 gallons of oil over the heating season.

 

[friends59]

Thank you. I had a gut feeling about not having enough wood unless I continue to cut up pallets. One more change that might
save energy dollars - using a tank to bring the city water up to room temp before it enters the hot water heater. What if I clamped
a couple three foot baseboard heater pipes right to the wood furnace flue pipe. If I re-route the cold water supply for the electric
hot water heater so that it passes through the pipes clamped along the hot flue pipe, would the water be warm but never hot enough
to boil in the heater pipes clamped to the hot flue pipe?

 

[WoodNotOil]

I've seen stove pipes wrapped with soft copper before but not baseboards. Not sure how well it would transfer. You would want a way to bypass that when the boiler is off. Imagine that cold line sweating onto the stove pipe during the summer. What kind of add-on do you have? They make DHW coils for many models. I have one in my Tarm.

 

[friends59]

England Stove Works did not offer a DHW coil on this add-on furnace. It would be fairly easy to
add one myself using stainless steel pipe, but I want to keep things real simple and not have to
rely on circulators and circuitry, really all I want to do is slightly warm up the cold water before
it enters the electric hot water heater, so I'm not going to have to burn wood in the summertime
to make domestic hot water.

 

[deck2]

I am know expert but wouldn't cooling down the stove pipe/ flue gasses add to creasote build up in your chimney??

 

[friends59]

I'm using an EPA certified wood furnace which has a metal baffle inside that ignites
unburned wood gases when the secondary air enters above the hot metal baffle.
There is much less smoke that enters the chimney than with older stoves. There
shouldn't be much creosote as long as the fires are small and hot using no green
wood, and no softwoods like pine and fir.

 

[laynes69]

Your furnace isn't EPA rated. There are only a few on the market that are. What model of furnace do you have? I also wouldn't install a hot water loop if it wasn't rated for one. One wrong move and you have a hell of a bomb. I would say you should use around 4 cords of wood, maybe 5.