Temperature of Plenum?

I will be getting my Alaska 140 in about 1 week and plan on doing the install myself. But I have a question. What temperature would the plenum be? I am asking because I am going to use a backdraft damper.
Thanks
Tom

Most wood and coal furnaces are capable of generating hot air temperatures much higher than the normal 250* F. maximum. My magnet thermometer mounted on the outside of the plenum reads between 100-200 degrees depending on the demand for heat but the inside air temperature is 120-500 degrees only 18" away inside the duct. It reduces to 80-140 degrees out of the registers. I believe most back draft dampers that are motorized have a rubber seal, so I would recommend installing the solid fuel damper as close to the conventional plenum in a parallel set-up. That is were the solid fuel furnace is ducted into the conventional furnace plenum. This should reduce the rubber from getting too hot, warping it and eliminate any odor from the heated rubber seal. I once had used a parallel set-up and installed the damper too close on a down draft conventional furnace and when the fire went out the conventional furnace damper would not open because it was sealed shut from the hot air heat provided by the solid fuel unit. Since that incident I changed the duct system to a series set-up. Conventional unit flowing through the solid fuel unit but only using the conventional units blower.
As for your set-up you should be fine if you mount the damper some distance from the solid fuel unit.

DOUG, do you use a back draft damper in series configurations? I ask because I often read complaints about heat from an idling stove exiting out of cold air vents during moderated outdoor temperatures.

No I do not used a back draft damper in my series set-up. Series set-up is were the conventional furnace supply goes into the return of the solid fuel, but only using the conventional furnaces circulation blower. But I do use a few manual draft dampers in the solid fuel return (which is the same as the conventional supply) to direct the air flow into either one or both of the solid fuel furnaces I have connected in series. Most series set-ups do not have two solid fuel furnaces downstream from the conventional unit. I also have a manual damper in each solid fuel plenum (I guess you could call it a back draft damper) to direct the air flow through either one or both of the solid fuel furnaces, allowing the desired heat mix I want. I had also put the conventional circulation blower on a three speed switch to allow even greater flexibility of air movement for the needed demand. All functions of my system (hand fired unit, stoker fired unit, gas fired unit and the A/C) control the conventional circulation blower when it's called on to supply air movement through the system. I also built into the system a motorized door at the location at the hand fired return entranceas a safety measure in case of power failure to allow gravity flow through the system. It really works well. Something to think about for your system.