harmon sf1500 flue

[ddad]

I have a Harmon SF1500 furnace. I want to install a round stainless smooth flex liner of 5.5 inches.
My existing flue = 6 1/8 x 11 1/4 inches (terracotta). The height is 21'.
Furnace has worked fine for 15 years or so with a barometric damper on it and (2) 90's, all 6". Does anyone have input on how it will burn for wood and coal going to a 5.5 inch liner? Hotter or colder? I am located near Harrisburg Pa.

Input I received was 5.5" round should work better than a 6" x 10 3/4 " rectangular liner.

Thanks

 

[laynes69]

I installed a 5.5" rigid liner for my chimney in late summer. My woodfurnace is rated at a higher output than the sf1500 furnace. I am getting longer burns with more heat output from the furnace. The old chimney was a 7x11 flue with 32' height. Its a night and day difference with the performance. On top of that with the proper sized flue, the unit is burning alot cleaner. I would recommend it.