Tying Wood Furnace into main duct halfway

[edrobyn]

I am buying a wood furnace to heat the whole house. My main system is a heat pump that is an all-in-one unit where the unit is located outside and the main supply trunk line is in the center of the house from front to back. There is no main plenum to tie into, only the trunk running the length of the house. The location of the wood furnace will be at the midway point of the trunk line since I have the flue located there. I need to have the ability to run either the wood furnace or the heat pump with the heat pump being able to kick on when the fire in the stove goes out. I would like to tie into the line at the mid point. Has anyone done this? If I tie into the main trunk I am thinking I would need a "T". If I do this I am thinking that I might have a back pressure issue in that the air would be blowing into the wall of the opposite side of the main trunk line and might not disperse right and left from there very well. If I angle the duct from the wood furnace inlet where it flows in the same direction as the flow of the main unit I would not get heat in the opposite direction very well. If I install something like a "Y" diverter where I have flow going in both directions the branch that is going against the main flow would need a back flow preventer of some kind. Would this be the way to go or does someone have another suggestion? If this is the way to go where can I find a 8" or 10" duct with a flap that will allow air to travel one way but not the other?

 

[begreen]

Sounds like you will need backflow dampers and the airhandler plenum to prevent a closed circulation loop. This will close off the plenum when the furnace blower is on, but will open up when the air handler is blowing. Here is an example diagram for a Yukon wood furnace.

 

[edrobyn]

Sounds like you will need backflow dampers and the airhandler plenum to prevent a closed circulation loop. This will close off the plenum when the furnace blower is on, but will open up when the air handler is blowing. Here is an example diagram for a Yukon wood furnace.

View attachment 146668

Thanks for the reply but since I have an all-in one unit outside, there is no plenum to tie into. Only the main trunk supply line.

 

[JRHAWK9]

The above will work great as long as there's power. That setup won't gravity feed the heat from the wood furnace in case of a power outage though.

 

[edrobyn]

The above will work great as long as there's power. That setup won't gravity feed the heat from the wood furnace in case of a power outage though.

Thanks. Does anyone know where I can find 8 or 10" round duct backflow preventer?

 

[brenndatomu]

Just google "8" duct damper" there are tons that come up, more 8"s than 10"s, but some 10"s too, shouldn't be a problem to get.
I don't believe that tying straight into your duct is gonna be a problem at all. If it is, the easiest thing to do would be to just speed the blower up a bit to overcome the static pressure. This install should be pretty simple for you

 

[edrobyn]

Thanks I will try that.