AC Losing Battle

[Ttman]

We have an older Montana, but I pulled all of the vent surrounds and wrapped them with radiant barrier. I pulled the Skylight in the shower and completely blocked it with the same stuff. Roof vents cause a lot of heat into the trailer as the attic is not sealed off when you pull the covers off you can feel the crazy heat coming out. Then I put the vent pillows with radiant barrier on one side in each of the three roof vents. This made a world of difference! I’ve also found that if we are loosing the battle during the hot part of the day, I stop pushing AC through the vents and direct dump into the main living area. The 15k unit in the bedroom is always direct dump and can take care of the front half just fine and doesn't need the main ac units help through the three ducts which allows for more cold air in the main living area.

[Mikelff]

You should also pop the covers from all your roof ducts and make sure they are connected with no air gaps. If there are gaps, you are sending some of your air conditioning into your attic. Seal them up with the foil tape. This will also help with your cooling.

[Travelin’ Gran]

Originally Posted by pitman44

First, as someone mentioned measure the supply air and the return air temperature. There should be about a 20F difference. If there isn't a difference at all the compressor is not making cold.

Next, pull the grill off the bottom of the AC. The supply is on one side of the unit and the return on the other. They are most often separated by a piece of insulation put in by the RV factory. The static pressure difference between the supply and return air is HUGE. It's very easy for supply air to short circuit to the return side and that will kill the effectiveness of the AC. In fact there's a company that makes a custom fit foam block that eliminates that problem. Google "RV Air Flow". It should come right up.

In any case, make sure there is a very good seal between the supply and return. Also check the foil tape between the box and the ducts. Make sure they're sealed well and not blocking air flow. And make sure the box is sealed so air can't blow into your attic.

Then I would pop off a couple of the supply grilles. There's a tube that sticks up into the duct. In our Montana HV, they were sticking up too far into the duct. IMO sticking up into the duct at all is too far, but ours were 3/4" or so up into it. I took them all down, cut the excess off, put them back in and resealed them to the duct.

Finally I cut every other fin out of the grilles. All of these changes made a HIGE difference in how well our AC cooled our rig. I hope these help you.

All these ideas are great! The best idea is the RV airflow unit and cleaning your ac units and filters. Once the individual ducts are confirmed to be clear and the units clean, with the RV airflow unit installed correctly, our ac is easily 20c cooler than outside. We also carry a paper shredder sized dehumidifier and keep
an eye on humidity levels inside the rv. The rv airflow unit is well worth the $$ my husband said. The installation without power tools took about an hour being very careful to follow steps and foil tape as recommended. Good luck!

[432bartman]

I just came back from Paso Robles, CA and it was 109-114 and both A/C units kept the rig nice and cool. I did modify the vents of our unit by cutting out every other slat, which I feel helped out a lot.