The plan in a nut-shell:
Currently we have a new construction ranch style house (6" walls) with a oil fired, forced hot water boiler. My wife would like to have a woodstove in our livingroom for not only the appearence (she wants the glass in the door) but also to help with the ever rising cost of oil (pre-buy is already at $2.99/gal for next year). My concern is that the livingroom will be 100 degrees and the bedrooms will still be 50. I'm trying to think of a solution to transfer the heat in a single story, long house - so far I've come up with the following:
Obtain a large woodstove with built-in outer sheet metal shrouds that are now common on the newer style woodstoves. We've got a Napolean at our camp that might be a good candidate - here's a link to see the stove I'm referring to:
http://www.napoleonfireplaces.com/Webshare/wood/wood%20stoves/1900.html
Remove the shrouds on the stove and construct a heat exchanger out of the same heating element that is commonly used in hot water baseboard (3/4" pipe with aluminum fins mounted to it) then reinstall the shrouds. This hot water "circuit" would be on both sides of the stove as well as across the top (hopefully you will not even tell the modification was done without a close inspection). Pipe this heat exchange circuit back into the existing boiler resembling just another zone on the boiler - with the understanding that this zone really works backwards - it brings heat into the boiler instead of carrying heat away from it to the baseboards.
Use a thermal switch near the woodstove to activate the circulator on the woodstove zone so that when the thermal switch senses the heat from the stove it will automatically start circulating the water (heat) in the woodstove zone from the stove back into the bolier and, in turn, out to existing baseboards on whatever zone is calling for heat. When we don't use the woodstove - the boiler will sense that the temperature is getting too low inside the block and heats up the regular way using the oil burner.
Also, as a safety precaution, install a thermal switch (set to around 210) near the boiler on the outgoing line towards the woodstove. This thermal switch would sense the core temperature in the boiler and activate a "cold" zone in our garage (we use this zone to keep the garage just above freezing). This safety switch would prevent the wood stove from transferring too much heat into the boiler by dumping heat into a cold garage to cool the boiler to a more appropriate range.
Benefits:
Nice looking woodstove that can be appreciated visually. Any heat that is not absorbed by the heat exchanger will be directly dispersed into the livingroom. Uses the existing forced hot water system to distribute heat to the other end of the house. Saves oil. Relatively simple to install. Relatively safe since the boiler already has several expansion valves for safety as well as the addition of the over heat switch. The heat exchanger would be on the outside of the stove which would not significantly draw down the internal temp of the stove causing condensation and creosote issues. Automatic back-up with the oil burner.
Problems (all guesses on my part):
Disimmilar metals (copper, aluminum & steel) touching between the stove shrouds and possibly corroding? Not enough heat transfer to the coils to even make a dent at heating the boiler? BTU considerations? Too much heat entering the boiler? Other issues I'm not seeing?
There are a lot of guesses and assumptions in my plan - if you have any ideas or experiences that may help me - please offer them up.
Thanks, in advance, for any help you guys have to offer,
Scott
