Fuzion 420 Air Conditioner ... duct layout/fixes/improvements

[twvette]

Originally Posted by Frank G

It appears you have Coleman Mach 15 Air conditioners. For air movement they have a 1/3HP motor driving a squirrel cage blower rated at 325CFM for air movement. Air conditioners relies on proper air movement to prevent freeze-up's. Restricting air movement will give lowered discharge temperatures but not more BTU output. you only have 15,000 BTU's of output from each unit. Yes the distribution system has a lot to be desired but it is the best you can do with the restricted room in the ceiling. A more traditional way to do it would be to decrease the size of the main duct after each outlet. This keeps the duct pressure constant along with the air velocity. Constant velocity and pressure equate to equal distribution throughout the coach. By the book the existing ducts are undersized already, so they install two. To go back to the Squirrel cage blower, if it is connected to a undersize duct system the pressure rises and the output (volume) decreases. You may feel more volume out of a few vents but the overall system is underperforming.

Enough opining, if you want to get the most out of your AC system just open the vents on each unit. and quit trying to cool the hot under insulated attic.

Good points on possible freeze ups, etc. My rear AC stopped blowing cold air at end of last trip so need to look into if this is what indeed is happening on next trip. Only one of my outlets directly on the AC is open so might need to open both or perhaps remove one of my plugged ducted vents. I will find the right balance of vents and/or lock the fan on high to help with freezing if that is indeed happening.

Wish I could stop using the ducted vents but the Fuzion 420 with 2 AC's only has ducts in the living/kitchen area so have to rely on them to some degree.

For further follow up, have to say so far the changes I have done are working well as got a few more trips in. It was upper 80's, very humid, and a lot of direct sun hitting the rig and was able to keep the living room in the mid 70's but the ACs did run constantly (the garage AC would cycle off every now and then). The garage is nice is cool and the bedroom/bathroom will freeze you out. So, its not a great balance but much more comfortable than being hot everywhere. I am using just a 12in fan in hallway outside bedroom to get a lot of cold air towards the living room to help. Its actually cold enough in the rig that the only place my dogs will now sleep while AC is on is in the living room which they never did before LOL.