Hot Dawg 45 Install

[busted knuckle]

I have just ordered a Hot Dawg HD45 NG for my garage. The little lady complained for years about the smell of the propane chimney heater I used so I dove in. I will be doing a downward horizontal vent out the side of the garage and 90 up. Per the installation manual for a horizontal Catagory I, I am to have a 4-5" transition pipe to the outside. For a horizontal Catagory III venting downward there isn't a requirment to have a transition from the 3" pipe to a 4-5" pipe. Can some one shine some light on this for me?

 

[russlaferrera]

I needed one. I looked everywhere. Had to make one out of a 4" cap and a 3" ell. Cut the center out of the cap and rivet the ell into the hole.