A warning.
Last year, I designed a system that used a DOWNFLOW 80% Airstrong furnace. Feature that mattered to me was that I could vent B vent out the side of the cabinet.

Installer installed furnace, but could not figure the instructions on rerouting combustion blower out the side.

I and supplier called Airstrong Air. Armstrong Air admitted the manual was wrong and furnace would not work as I had designed. Further, their only suggestion was to install a 95% furnace and then I could vent out the side. They also agreed to change manual to reflect this important fact.

My supplier, Locke, gave me a 95% furnace at no extra charge. Thanks. I was left paying the installer to remove and save old furnace and reinstalling 95% furnace, changing the venting through the roof and honoring warranty on a much more complicated and repair prone furnace. Also, the embarrasment of telling the customer that the equipment is wrong and we have to do it all over again.

Customer got a much more efficient furnace for free and the installer got extra work.

My profit was nil on this job.

Armstrong is associated with Concord, Ducane, Air Ease and Lennox. Arstrong has not yet changed their installers manual and has not paid me for my losses. THIS IS A SIGNIFICANT ERROR.