Keystone 395BR AC Low CFM in Vents

[mmcgahey]

Good morning forum, I am new to the site but I bought a brand new 2021 Avalanche 395BR in 2021. We have not really used the RV but about 3-4 times total but the AC vents blow little to no air with exception to the vents in the back and front restrooms. It has been like this since the day I rolled out of the dealer with it but just have not taken it in. I know it is out of warranty now and we are starting to use it more but the lack of CFM's coming out of the vents leads me to believe there is a duct issue. Has anyone ever had this issue and what was done to repair it? I have heard when the factory installs the AC's sometimes they miss the duct connections while installing. It seems the ceilings get cold. I am very mechanically minded and have the tools but is this something easily fixed or should I just take it in and pay a dealer to repair? Thanks for the help all!

[jsb5717]

Welcome aboard! There are a few things to check to make sure you're getting the maximum air you can out of your system.

First, do you have 1 or 2 AC's in your rig? For the size of your trailer I would expect 2. If so, do you run them at the same time? Also, what brand and model are they? Are they Whisper Quiet or is there in interior access to the plenum?

Sadly, these things often don't get installed as well as they should.

First thing to check is the attachment of the ceiling vents. Pull off the cover to each on and inspect that they are well sealed from the duct to the ceiling so that there is no air escaping into the attic space. With aluminum duct tape you can seal these yourself as necessary. Also, make sure that the vents are NOT sticking up into the duct. The top of the vent should be flush with the bottom of the duct. If not, correct this as well.

Second for me would be to use a boroscope to inspect the duct work itself to make sure that it is all open...meaning no collapses so that air is flowing freely throughout.

Third would be the air returns...depending on which version you have. More on this once you report which one you have.

Fourth...and maybe most difficult...is to make sure that that AC unit itself is properly installed on the roof. Again, depending on which one you have will determine the easiest way to check this. But a misaligned install can impede air flow into the ducts.

This is a starting checklist for someone handy and inclined to dig in him or herself. Give us more of the details I've asked for for more insight.

Good luck!

[wiredgeorge]

Originally Posted by mmcgahey

Good morning forum, I am new to the site but I bought a brand new 2021 Avalanche 395BR in 2021. We have not really used the RV but about 3-4 times total but the AC vents blow little to no air with exception to the vents in the back and front restrooms. It has been like this since the day I rolled out of the dealer with it but just have not taken it in. I know it is out of warranty now and we are starting to use it more but the lack of CFM's coming out of the vents leads me to believe there is a duct issue. Has anyone ever had this issue and what was done to repair it? I have heard when the factory installs the AC's sometimes they miss the duct connections while installing. It seems the ceilings get cold. I am very mechanically minded and have the tools but is this something easily fixed or should I just take it in and pay a dealer to repair? Thanks for the help all!

Not sure what type A/C or system you have but the ductwork is often shoddy from the factory and many folks remove the ceiling air vents and re-tape with HVAC tape. That helps. Next, the A/C itself often needs re-taped. If the bottom part is removed, there is often air escaping the out part into the in part and leaks around the holes that lead to the ducting. Taping helps some. Some have found ducting collapsed by sticking a cell phone and taking a picture of the inside of the ducting or using a bore scope or mirror, etc. There are a couple devices on the market now that greatly improve air getting into the ducts; I use an RVAirflow unit in my lower A/C part as it forces air into the ducting and increased airflow fairly dramatically. I also posted in another topic area on this forum about a new system that will greatly increase airflow. It is less expensive than the RVAirflow system I purchased a year or two back but looks like it works in a similar manner:

https://www.keystoneforums.com/forum...ad.php?t=55238

[mmcgahey]

It does have 2 AC's and I run them both but they never seem to keep the RV cool because there is very little air coming out of the bunk room the kitchen / living or the front bedroom. They pretty much run 24/7. Only the restrooms seem to get good air flow out of the vents. The units are Coleman Machs. Mechanically speaking I feel like the ducts are collapsed but being it is so widespread across the RV and that there is no duct schematic anywhere I'm not sure where to start but my friend who RV's full time said he's had these issues many times and that most of the time it's at the AC connection. There are two small returns in the front bedroom with some kind of little fabric filter and I'll have to look for the returns for the rear AC as I haven't really looked. The furnace ducts are on the floor so I believe they have a separate ducted system and I have no problem with heating this RV. I have pulled a couple of the supply grilles off but it's extremely hard to tell what is duct or ceiling. How big are these ducts anyway and are they just cut-in to the bottom of a trunk line? I assume they're not like a home with flex duct to each vent?

[tallen]

I think your ducts will look something like this, but not sure. I have the Coleman Mach V quiet, with the 12"x12" air filter on mine.

[jsb5717]

Originally Posted by mmcgahey

...There are two small returns in the front bedroom with some kind of little fabric filter and I'll have to look for the returns for the rear AC as I haven't really looked. I have pulled a couple of the supply grilles off but it's extremely hard to tell what is duct or ceiling. How big are these ducts anyway and are they just cut-in to the bottom of a trunk line? I assume they're not like a home with flex duct to each vent?

The ducts are typically made of a cardboard-like composite material that is pretty light weight. The look like the pic posted above by Tallen and are maybe 10-12" wide and 2-3" tall. The ceiling vents are round and cut into the bottom of the duct. They just need to be well sealed.

Sounds like you may have the Whisper Quiet AC's. They have 2 return vents but no interior access to the plenum. If that's the case then the only way to get a look into the plenum is from the roof after removing the AC cover, the foam insert, and the fan assembly...been there/done that. However, one important thing to check is the return vent duct work. Those are notorious for collapsing...ours were diminished quite a bit. There is a way with some 1 1/4" PVC pipe to force those to open back up. It helped on ours. There are YouTube videos on the subject.

[sourdough]

Here's a link to the racetrack duct system used in many Keystone RVs including mine - note post 3;

https://www.keystoneforums.com/forum...ad.php?t=23114

If you have just a line of ducts on one side of the trailer you don't have this system. The whisper quiet model was mentioned earlier, it only has 2 return air ducts and the a/c unit itself is completely on top of the RV.

From everything I've been able to see from pics it looks like the A/Cs sit almost on top of the bathrooms explaining the good air flow in those areas. It also would seem to point to some sort of ducting problems which have been talked about. Another point to consider is the sheer size of your RV and the floorplan which is sliced up into several small sections which then impede free airflow. Also, if you are trying to camp around League City TX in those very hot and humid conditions I think 2 15k units are going to have a hard time keeping a 41' 6" trailer cool - particularly in the middle.

[mmcgahey]

Ahh thanks, that little diagram helps a ton with understanding the duct layout of these things. I can see I probably just need to remove my units and see what's there and if the factory just slapped this stuff together during the Pandemic race to build RV's with no quality control.

[mmcgahey]

Sourdough I was thinking the same thing regarding proximity to the bathrooms. I'll just pull each AC unit and tryout these RFflow things too and see if any of these returns or ducts have collapsed.