Wood furnace duct into end of main furnace duct run

[Anejo]

I'm planning to install a wood burning furnace and my primary challenge is connecting the wood burner to the existing ductwork. The furnace will actually be located under the last few feet of the central duct, so i could shoot a duct straight up to connect there. Routing it to the main plenum will be a challenge, and would probably result in at least 35' of new ductwork. How much efficiency am i going to lose tapping into the end of the main furnace duct, as opposed to the plenum? If I do tap into the end of the duct, the new wood burner duct would only be about 6' long - is that too close for safety?

 

[stihly dan]

CFM should be a problem, as ductwork done right is reduced for static pressure. If it's the same size, make sure there is a check damper.

 

[blades]

It you are going to go by code the first ten feet needs a 2" clearance to combustibles, 1" there after for solid fuel units. Other problem is where or how are you going to tap the cold air return system. With out doing a closed loop distribution is pretty poor.

 

[brenndatomu]

Some units spec 6" clearance for the first 6'...

I bet your gonna hafta have an oversize blower running high speed plus some to get much out of 'er at the other end...

 

[avarageerod]

I have a similar setup. I just ducted into three vents downstairs and capped them off from the furnace. it worked out great for me. I couldn't figure out how to duct into the furnace and still have enough cfm to move air through out the house. I also didn't want to take a chance of my evaporator coil getting dirty or overheating it.