I’ve always had a concern about the roof top AC unit. It seemed like it doesn't put out the quantity of air that it should.
Last week I was removing the AC unit in preparation for re-coating the roof. I looked carefully at how the air flow is routed, and wasn’t happy with what I seen.
With the ceiling cover off I ran the AC unit. The large squirrel cage blower delivers a lot of air, straight down, toward the floor. However, when the ceiling cover is installed, the air enters into the ceiling unit, and is restricted by abruptly 90 degree turn and a 2 inch restriction. the air then takes several more 90 degree turns before it exits out the vents on each end.
What the cover really needs is a vent opening just below the blower that allows the air to shoot straight down toward the floor, unrestricted.
See entire article with photos below.
Beat the heat – Improving air flow from the air conditioner ceiling unit | 2001 Coachmen Mirada 300QB