AC plenum

[Life-in-Him]

Have a 2020 Cougar 24sabwe.
While cleaning the ceiling AC outlets (4) we found 2 (1 front, 1 rear) had the plenum open beyond the outlet.
Putting my hand in there was nothing between the opening & the end of the plenum.
Any ideas? I'm thinking of inserting some foam to block airflow going into that empty space.

It's hitting the 90's here in AZ & chilling unused space seems a waste.
Thanks
MOT

[wiredgeorge]

Originally Posted by Life-in-Him

Have a 2020 Cougar 24sabwe.
While cleaning the ceiling AC outlets (4) we found 2 (1 front, 1 rear) had the plenum open beyond the outlet.
Putting my hand in there was nothing between the opening & the end of the plenum.
Any ideas? I'm thinking of inserting some foam to block airflow going into that empty space.

It's hitting the 90's here in AZ & chilling unused space seems a waste.
Thanks
MOT

I used pool noodles to block the flow of air into the voids. I also redid all the tape using foil HVAC tape especially in the lower A/C unit as much cold air was escaping due poor tape job. I have an RV airflow unit installed now which makes a good bit of difference in airflow from the other outlets. I added very dark film to the windows and also use a 14.5K BTU portable to augment my 15K BTU Dometic A/C. It sometimes get a bit warm here in Texas as well.

[JRTJH]

If your ducting is an "S track" configuration, putting a piece of foam rubber cut to size or even a piece of a swim noodle cut to size will work. Insert it into the "END OF THE DUCTING" through the last vent so the foam blocks the cooler air from blowing out of the ducting and into the trailer roof/attic space....

Keep in mind that usually there is a "end of duct blockage" that is placed several feet beyond the last duct. It is put that distance from the last vent to prevent "air rush noise". So you might want to look into the ducting or take a photo with your phone to visualize if there is a plug beyond where you can see by looking into the duct at an angle...

Also remember that in many Keystone trailer brands, the air conditioner ducting is a "racetrack configuration" and it DOES NOT END after any duct, but continues to circle throughout the trailer.

Here's an old diagram of both types (the S-type" is in the upper right corner).
The diagram depicts what was in the Laredo line some years ago. Keystone has incorporated the "racetrack configuration" in quite a few of their brands in recent years.

The 2020 Cougar full size fifth wheels and SOME (not all) of the half ton fifth wheels had racetrack ducting. I'm not sure what was in the Cougar travel trailer lines (east or west coast build), so, make sure what you have before you "go improving something" only to find out that you actually screwed it up....

[Life-in-Him]

Thanks for the insight guys.
I'll use my boroscope to follow the path.
We only have 1 AC but
as i look @ where the outlets are, 1 is centered on the door side the one on the rear end is closer to mid roof (that's one that seems to empty into nowhere)
Then there is another one forward of the AC but closer to the slide side. Forward from there in the bedroom is the front one, also on the slide side & of concern about dumping into nowhere. The plenums are coated with what is likely sound deadening.

That all makes a "Racetrack" duct design likely.
Guess boroscope will define the reality & indicate if blocking will work.

We had retaped all the outlets years ago after reading one of your posts of air leaks. Thanks.

Will let you know what we find re-racetracking.

[JRTJH]

You may not have the racetrack ducting system, I simply don't know, but sure wouldn't want you to block off a duct and wind up with half the trailer not having any cool air flow... Then again, if yours isn't a racetrack system, you just could have most of your cool air flowing into that big "nothing space" between the interior ceiling and that walkable (or maybe not) TPO membrane....

Definitely worth fixing if it's broken but only a good inspection will tell you which type ducting system you have.

[sourdough]

As the previous illustration posted earlier shows you can tell the racetrack system by the rows of vents down each side vs random placing when looking at the ceiling. Of all the videos/pics I've looked at I do not see an indication from the few views of the vent placements that it has the racetrack design. In that case blocking the ends of the ducts would be OK....but, I haven't seen it closely nor seen a spec for it. Below is a link for the 2020 Cougar line, racetrack ducting is not mentioned as a highlight as they do with the units that have it;

https://library.rvusa.com/brochure/2...e-Cougar-1.pdf

[Life-in-Him]

The build date on our 2020 is May 2019.
So some things have been a nut or bolt different than the brochure.
In late 2020 model year they began promoting a 20% increase in AC air flow due to changes in "Blade" diverter "technology"
The vents they show are very different from ours. New ones have something sticking into the plenum.

Still haven't dug out the borescope because the refer decided to die.
Looks like we got that working but the black tank started its I'm full burp.

Well that's life in the big city where only 6 rigs among the 55 are still here.

[Life-in-Him]

Originally Posted by sourdough

As the previous illustration posted earlier shows you can tell the racetrack system by the rows of vents down each side vs random placing when looking at the ceiling. Of all the videos/pics I've looked at I do not see an indication from the few views of the vent placements that it has the racetrack design. In that case blocking the ends of the ducts would be OK....

Basically with only 5 vents they kind of form 2 rows. The bedroom 1 & 1 closest to it in the living area are lined up on the "drivers side of the trailer & forward of the AC unit.
2 in the dining booth area are on the" passenger side" & basically lined up.
The 5 one is @ the corner of frig & stove.
That could wrap around & go back forward to join with the forward side.

Don't know but since this rig is probably an early showroom special or a build cycle test, we'll find out when we shove the borescope around.

@ 80+ we'd rather stay cool, dump the tanks after showers in the morning.
Then see what gives. DW just used the foam I'd planned to use, & made some pillows. Oh well, thanks again & we'll hopefully add some reality tomorrow.

[Life-in-Him]

Sorry my last post suffered from eyeitis errors. I said 5 outlets, but there's only 4.
2 on the foreward group going from the AC on the driver's side (never could keep port & starboard right)
& 2 on the passenger side going to the rear.
The end one on each side goes into never never land, or as far as my hand will reach.

[sourdough]

Sounds like you have the "S" duct configuration. From what I've seen and read their "blade" technology is just another way to interrupt airflow as you would like it to be into an "improved" (not at all) flow pattern as an advertised benefit.

[RacerX]

With our Cougar we have the Racetrack configuration…..however since we only have one AC, the racetrack in the bedroom is a broken bridge as the bedroom AC is intended to bridge the pathway around the track. For us this means that one bedroom vent is live….but the other is dead. I ended up using pool noodles and ac silver tape to eliminate unnecessary dead ends and exposure to heated space in the ducts. Basically without the second AC our Racetrack is more like a large “J”

Do you have two ACs?

[Life-in-Him]

We only have the 1 ac since we're 24'.
Where did you find your hot places. That'll give me some points to look at.
Still hasn't had an opportunity to boroscope or otherwise check out the ducts in detail since temps are now 90-95 & we're getting ready to relocate closer to Wickenburg AZ for DW"s knee surgery.
planning to pick up some pool noodles while in town to be prepared to block those hot places.

[NH_Bulldog]

Originally Posted by RacerX

With our Cougar we have the Racetrack configuration…..however since we only have one AC, the racetrack in the bedroom is a broken bridge as the bedroom AC is intended to bridge the pathway around the track. For us this means that one bedroom vent is live….but the other is dead. I ended up using pool noodles and ac silver tape to eliminate unnecessary dead ends and exposure to heated space in the ducts. Basically without the second AC our Racetrack is more like a large “J”

Do you have two ACs?

Even with only one AC and the bedroom roof vent blocking the "turn" from one side to the other, you should still have flow out of both sides of the system. Ignore the directional arrows in this image. Instead consider the location of the AC unit and air comes out of the ceiling both forward and behind the unit. If you get flow out of one side of the trailer at the front, you should get flow out the other side as well. There is no mechanism to only force air to flow in a single direction despite the visual of a "racetrack".

[RacerX]

Yes the racetrack is bidirectional depending on where the higher pressure (fan) is coming from.
Unfortunately every rig is somewhat different in design based in number of vents etc. In our 32RLI we have 9 vents on the “racetrack”. 6 in the main living space, 1 in the bath and two in the bedroom.

We do not have a second AC in the bedroom, which means that that end of the racetrack is blocked by the vent plenum…. So now our ducting is more like an elongated horseshoe in shape. However this is also compounded by the fact that there really isn’t a complete racetrack in our ducting. The ducting that is above the hallway has a solid block just about above the hall adjacent to the bathroom door. I suspect this is something to do with our specific model so others may be different.

Now that leaves us with 1) ducting that looks more like an extended “J” not a horseshoe and 2) an orphaned vent in the bedroom that has zero airflow and is exposed to the heated air in the orphaned ducting . (Orphaned because we don’t have the second AC).

So to answer your question, I used noodles to isolate that vent and also to cut off the 2 feet of the ducting from the working vent on the side that extends past it to the 2nd AC position. In effect that ducting being closer to the roof and with no AC flow just added unnecessary heating to the cool air.

I drew up a quick diagram of the above I will try to remember how to post it.

[Life-in-Him]

Thanks for the drawing.
That makes sense to my 80+ yr old-old mind.
That space into the cap was my concern, feeling warmer than around the vent.
Did you notice a change in the headboard area temp after blocking off the other vent?
We're shorter than you but if I find the racetrack loop going back to the AC blocking it off might increase the output in the 1 bedroom, & hallway vent by the bathroom door.

[RacerX]

We rarely camp in the temps you mentioned, but that said just a few circles around the answer to your last question.

Yes this “noodling” did improve cooling but with a few caveats. First our system has the “blade” vent system. If I really want to cool the bedroom, removing the blade cap leaves that vent as an open “dump” from the ducts and dramatically increases airflow to that vent due to less back pressure, but also will lower airflow to the remaining vents correspondingly.

Secondly, the blade system does have a partial “wall” where it inserts into the ducting which is meant to allow adjustments to the airflow. If that wall is inserted “backwards” eg between the airflow and the vent, it will impede airflow. In the attached picture you can see the wall insert at the bottom of the pic below the blade cover.