Back when i used to be a certified heating and a/c specialist I will never forget the hardest Heating and A/C upgrade task I ever had to do. That was the upgrade of a rooftop Heating and A/C system. Rooftop heating and a/c units are way harder to install than your common residential heating and cooling system! There is so much more entailed in the upgrade process. On top of that, having to haul that large and severely heavy heating and a/c device up to the roof of a commercial building is also quite a task. I almost have an anxiety attack just thinking about what both of us had to do! It was just me and one assistant heat and a/c system specialist and both of us had to put this thing on a pallet and then hook that onto a dollie. Following that it was hauling it up many flights of stairs. Of which during that me and the other heating and a/c worker nearly got ourselves killed. The people I was with and I almost lost control of the rooftop heating and a/c system and had that 2 ton things knock us down the many fights of stairs, crush us, and then blow up the building! I am not kidding you on this. It was a real major hassle and headache. I am so glad that out of my entire 30 years in the heating and a/c business I never had to install another rooftop heat and a/c system device again after that one and only time!