Add on wood furnace debate

[Stillson lives]

My buddy wants to connect his add on wood furnace to a trunk line instead of his main forced air (gas) stack. I said I would ask the pros here if this
Is possible. The furnace is too far away from his chimney and he thinks hooking it into a trunk line is good enough to get his heat upstairs. Is he right?

 

[begreen]

Usually this ends up with an inadequate and poor performing system. A proper trunk duct is sized in graduated steps, the largest being at the connection with the furnace plenum. When attaching to the end of the line the trunk will be smaller. That leads to poor airflow. Also, just pushing hot air into the trunk will not prevent it from taking the path of least resistance. Usually this ends up with the heat going through the furnace and its returns. Normally one would connect at the furnace and install back draft dampers to prevent this from happening.

 

[Stillson lives]

Usually this ends up with an inadequate and poor performing system. A proper trunk duct is sized in graduated steps, the largest being at the connection with the furnace plenum. When attaching to the end of the line the trunk will be smaller. That leads to poor airflow. Also, just pushing hot air into the trunk will not prevent it from taking the path of least resistance. Usually this ends up with the heat going through the furnace and its returns. Normally one would connect at the furnace and install back draft dampers to prevent this from happening.

Thanks Begreen! The problem is the wood furnace is about 30 feet away.

 

[webbie]

He'd be better with separate ducts (cut some new ones and then perhaps a return) or else running that 30 feet with heavily insulated duct - and/or a booster fan.