Answers to questions about RV Repair and Maintenance from RV expert Dave Solberg, author of the “RV Handbook” and the managing editor of the RV Repair Club. This column appears Monday through Saturday in the RV Travel and RV Daily Tips newsletters. (Sign up for an email reminder for each new issue if you do not already receive one.) Today Dave discusses rooftop AC units.
Why do my two rooftop air conditioners freeze up and one spits out ice and the other drips on my bed? We live in our 5th-wheel trailer full-time in Louisiana. Is there anything that we can do? I called Camping World, where we purchased it used in December, and the man said to turn the fan on high. It hasn’t helped. —Cynthia
There are several issues that can cause freezing and excess condensation in AC units. The first thing I would look at is the evaporator coil. As covered earlier in air conditioning Q&A’s, it’s important to understand how the air conditioner operates to track down the problem.
The fan motor turns the squirrel cage. That draws moist, warm inside air through the air return of your rig up into the unit. The air is drawn through the evaporator coil. It is similar to the radiator of your car and has coolant flashing through tubing inside. This pulls hot air into the tubing and removes moisture. This moisture falls to the drip pan and goes to weep or drain holes on both sides.
The air is cooled approximately 15 degrees and the squirrel cage pushes it back down into the rig.
Check the evaporator fins on the AC units
The next thing I would check is the evaporator fins on the AC units to ensure they were clear and allowing good air flow. Next, make sure the pan is clean and moisture is getting to the drains and they are not plugged as well.
Next, make sure all of your interior ceiling vents are open and have good air flow. I would take off the return air cover and take a look at the baffle and vents. Excess moisture blowing into the rig is caused by a buildup of moisture in the pan and not getting out.
What can cause freezing in the AC units
Freezing can be caused by poor air flow of the cool air building up in the ducting before getting to the vents. It can also be caused by exposed metal in the air conditioner and vents. Exposed metal gets cold and warm moist air coming through the return vent hits the cold metal and you get condensation.
Another issue is poor air circulation to the vents due to RV manufacturers not installing a baffle correctly. The air conditioner manufacturer makes their roof air models generic so the air comes down off the squirrel cage directly below. Models that do not have ducted roof air use this model with an interior shroud that has the controls and vents.
Sometimes baffles are installed incorrectly
Models that have ducted roof air purchase a baffle that is installed by the RV manufacturer that diverts air flow to the appropriate direction of the ducts and vents. This baffle needs to be cut to the appropriate length and installed with furnace ducting tape. Unfortunately, I have seen quite a few units that have this baffle cut too short and taped with a single piece of duct tape. That can allow too much air go to the wrong place. Or, worse, it falls out and blocks air flow and just recirculates into the return air and back. This could cause a buildup of cold air in places where it doesn’t get drawn back up and excess condensation results.
Check those items on your AC units. Also, try to get a little more air flow inside your rig and reduce moisture by cooking less of what causes steam, limit hot showers during hot/humid times, and don’t hang wet items like towels inside. Limiting inside moisture can help with this, as well.
Read more from Dave here.
Dave Solberg worked at Winnebago for 15 years developing the dealer training program, as marketing manager, and conducting shows. As the owner of Passport Media Creations, Dave has developed several RV dealer training programs, the RV Safety Training program for The Recreation Vehicle Safety and Education Foundation, and the accredited RV Driving Safety program being conducted at rallies and shows around the country. Dave is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.
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