My Mirada came with an non-ducted rooftop Dometic 13.5 BTU AC unit. When I’m standing outside, I can barely hear the unit running, But when I’m inside, it makes so much wind noise that I swear a 747 is taking off. With all that wind noise, Why can’t I fell the air moving? When I put my hand up against the two air louvers, it just didn’t seem like I was getting the air flow that it should.
Last week I was prepping the roof for re-coating and had to remove the AC unit. When I took the inside ceiling unit off, I looked carefully at the inside to see if there was any airflow obstructions.
I ran the AC with the ceiling unit off to see how much air the blower actually put out – WOW, that blower delivers a LOT of air, straight down toward the floor.
Obviously the ceiling unit is severely restricting air flow when its installed. Air from the blower enters into the ceiling unit and gets restricted by several abrupt 90 degree turns, then gets forced through tiny 2 inch vents on the ends.
What the ceiling unit really needs is a large vent opening located directly below the blower outlet so that air can shoot straight down from the roof toward the floor, unrestricted.
I took measurements of the ceiling unit and began a search for louvered vents that would fit on the cover. The vents would need to be able to open or close to allow air flow to shoot straight down from the blower without any blockage or restrictions.
The vents I found required a 4 1/2 inch hole in the ceiling cover. CLICK HERE
These vents can swivel to point the air in different directions and they can be opened or closed.
I positioned one of the vents so it would be directly below the blower outlet, The holes were marked and cut out with a saber saw. I used 1/2 inch #6 stainless screws to mount the vents into the ceiling cover.
WHAT A DIFFERENCE – The vent located directly below the blower handles the majority of the air. When this vent is open, it doesn’t really seem to matter where the louvers are pointed, the air pretty much blows straight down. However, if I close this vent and open the other one, the air is directed to where the louvers are pointed.
If I want air to blow out the end vents, I simply close the two round louvers and the ceiling unit performs like it did originally.
UPDATE – We spent a week in Phoenix this summer when it was 115 outside. The AC unit had no problem keeping the inside cool. During the day, we’d turn the louver to blow air down and toward the front of the Mirada, at night we swing the louver to blow down and toward the bedroom in the back of the Mirada.
BRAVO!!!! This should be added by the factory to their production!
I WILL be doing this one!
I just drove home from our latest trip with our 2000 Mirada in near 100 degree temps. Just ordered 4 of these vents to modify both a/c units.
Finished the mod, it was well worth it. Works great.
Oh, WOW! I just finished this mod, and can HIGHLY endorse it’s accomplishment! This should be at the top of the list for anyone attempting to increase the efficiency of their NON-ducted rooftop RV air conditioner! It’s like night and day insofar as air flow is concerned. This mod allows it to MOVE some air!
Wow, I will take a look at this modification as part of my solution to getting more air into the coach. The option of open or closed is also important. The motorhome builders need to hire folks like you for the initial or final design of their work. Thanks.