Dear Dave,
First, I want to thank you all at RV travel for the great job you all are doing. There is a lot of great, useful information everyone can get from reading your articles.
My question for you is a little different. Our 2022 Sunseeker has two air conditioner units, front and rear. It has ducted vents in the ceiling. These duct vents from both units must be connected because when the rear unit runs you can feel the air coming out of the front ceiling vent and vise versa. Is this common? And when both units are running at the same time, would they not be pushing air against each other? Is this something that needs to be repaired? —Robert, 2022 Forest River Sunseeker
Dear Robert,
I do not know the percentage of units that have both roof air conditioners vented into a common duct; however, it is normal. Some manufacturers such as Winnebago have a single duct routed into the block foam the entire length of the unit on both sides so both roof air conditioners use the same duct.
Reasoning behind having one duct
The thought behind this is at night you can run the front air conditioner, close off the vents in the living room and kitchen, and get cool air into the bedroom but not have the noise of the overhead air conditioner in the bedroom. Same thing with the living room during the da: Use the rear air conditioner and close the bedroom vents and open the living room and kitchen vents.
I have never heard of an issue with the airflow “pushing” against each other using a common ducting system. If you have all the vents open and running both roof air conditioners, the airflow would follow the path of least resistance and flow through the closest vent. There may be a little push somewhere in the middle but not enough to do any damage or cause an issue with cooling efficiency.
Do all RV manufacturers use an open duct?
As I stated earlier, some manufacturers do a single vent and others do individual ones. I think it’s mostly a cost issue, or the fact that they offer a single roof air conditioner standard and a second one as an option. Typically, if the second unit is an option, it is a direct air flow from the unit and not ducted, similar to a window air in a residential setting.
You might also enjoy these posts from Dave
- Why does one RV air conditioner blow warm air while driving?
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- Can we test RV roof air conditioner with 110-volt outlet?
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RVDT2705
Anyone make a quiet AC?
The one issue that can come up with two ACs and one duct occurs due to location of the AC units. Newmar’s 36′ New Aire has one AC unit up front, approximately behind the driver/passenger seats, and the other over the kitchen area.
As Dave said, air will follow the path of least resistance, so many owners have complained that the front gets the bulk of the cold air and much less back to the bedroom. There are no ducts to close off.
My New Aire does not suffer this issue, but those that have it simply insert a piece of foam into the output air plenum immediately in front of the back AC unit. This effectively segregates the two units forcing the back unit’s air to the bedroom.
Thank you for the discussion, Dave! We have a single duct and some foam (?) material is in the duct to channel the front air conditioning unit’s output to the front, and the rear unit’s output to the bedroom. Have a great weekend and safe travels!