Stefonius wrote:
Last weekend, I took the cover off of my A/C unit and noticed that it had probably been installed on a Friday afternoon. The gasket between rooftop unit and interior unit wasn't compressed, the separation between the intake and exhaust sides of the plenum was not taped, and there were open spaces where air could go right into the insulated space between roof and ceiling. I spent a couple of hours with a big roll of aluminum foil duct tape, sealing everything up. I torqued the four bolts holding the top and bottom sections of the unit together. I took down every vent in the coach and re-taped the openings, smoothing down anything that had lifted and adding tape in areas where it was too short. I taped the seams where the squirrel cage fan joins the exhaust plenum. I sliced my thumb open on a sheet metal edge and bled like a stuck pig (should probably have worn gloves).
The end result is that the unit's airflow is improved by about 40 percent, and it cools much better than ever. It's also quieter. My next task will be to make a sheet metal baffle to better direct air from the squirrel cage fan into the ductwork. On my unit, the ducting only comes off of one side, so it should be pretty easy.
I'm wondering if otrfun's coach has similar problems in the factory A/C installation.
Glad to hear you were able to get that much improvement and still retain use of your ductwork.
I checked all the items you did. As I mentioned earlier, I even used an inspection camera. However, I found nothing out of the ordinary. Although I have nothing to compare it to, the air flow out of the ducts seemed satisfactory. I can only chalk up the inefficiency to incorrectly sized ductwork---something impossible to correct at this point.
I really like your idea about using a sheet metal baffle to better redirect air flow into the ductwork. My unit has two duct ports in the plenum area. One is somewhat redundant and only supplies air to the area immediately around the a/c unit. However, the other supplies cool air to the bathroom. I may try custom fitting a small, curved baffle to redirect some airflow more efficiently to this one duct. As-is, all the air in the plenum has to move at extreme 90 degree angles to enter the ductwork---I'm no airflow engineer, but that sure seems like an awfully inefficient way to get air from point a to point b. A curved baffle would seem to be a much better solution.
Bottom line, it's unfortunate I probably won't be able to use the ductwork as it was originally designed. However, I can live with that as long as I can keep temps below 80 degrees when ambient temps approach 115+ degrees. For me, that's a fair trade.
