I'm installing a 75k Big Maxx and the instructions say to install the horizontal venting at 1/4 rise per foot. Shouldn't this be a 1/4 drop terminating outside vs. a rise?
This is the exact reason for running the exhaust back into the system. The heated air will cause any moisture to evaporate. I also believe that it is needed for proper venting, since heat rises.
I was confused when I first read the instructions because the reznor instructions has the horizontal venting sloping downward. I did install it sloping upward.
Now just waiting for the gas line to be installed and I'm in business.