Yes I'am about 50 mi from Cuba.
I have the limit switch and my blowers run about half the time.
Right now outside temp is 25 deg and it is 70 deg inside. So not bad even with my issues.
I have dampers in place on the hot blast before it goes to the plenum.
The only issue here is with the return. I did try blocking it off with a piece of sheet metal. Should have tried it during the day. Wife had the main furnace turned up and I heard it kick on about 2am.
I shagged but down to uncover the cold air intake. Havn't tried it since. Also requested the wife not fiddle with the knobs till I straightn all this out.
Here is one interisting thing to read about add on furnaces and cold air returns. http://www.warmair.com/html/add_on_wood_furnace.shtml
Beam: you really lost me there in your explination. I will keep reading it and maybe It will sink in.You guys have alot to offer in the knowledge department.
Right now I have researched myself into a headache lol. Headin to bed.