Amazing A/C airflow Improvement

[bill-e]

Is the ductwork the same stuff as used in the heat ducts or something else?

[JRTJH]

No it is a different material. Heat ducts are typically "very thin aluminum" in a square/rectangular shape attached to aluminized "coil spring" ducting (similar to dryer vent). The air conditioning ductwork is 3/8" or 1/2" rigid foam (insulated to keep in the cool air) and usually lined/covered with aluminum foil.

[15hideout27rbwe]

Just did this mod today with low expansion spray foam. Haven't tried it yet, but it's obvious that it will make a difference. Awesome mod!

[bitten]

2017 Montana 3720RL.

RV has the hidden a/c units. The return duct is 1 1/2 inch at the vent but closes to about 3/4 as it goes to the center of the roof and the a/c. How far up the ducting should I enlarge the hole?

THe supply vent covers really cut down on airflow. I run the air when the RV is plugged into the house, but just the front unit over the kitchen/living room. The two a/c units share common supply vents and if I remove a vent cover in the bedroom I get some serious airflow from the a/c at the other end of the RV. Anyone bought new vent covers for this model? Btw, all of my supply vents were properly taped at the factory. Current covers appear to extend 1/4 to 3/8 into the supply ducting.


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[thetanman1957]

Originally Posted by 15hideout27rbwe

Just did this mod today with low expansion spray foam. Haven't tried it yet, but it's obvious that it will make a difference. Awesome mod!

How did the spray foam work? What is the approximate dimensions of the ductwork?

[15hideout27rbwe]

Originally Posted by thetanman1957

How did the spray foam work? What is the approximate dimensions of the ductwork?

Haven't tried it yet. Of course I did the mod right at the end of the hot season. The foam seems to have filled the opening pretty good. If I remember I measured about 1.25" from the top of the ducting to the bottom, and is probaby about 2" past either side of the vent opening. I'd say about 8" wide overall by 1.25" tall give or take.

[lesleyinky]

I'm so glad more than a year later this tip is still coming in handy! When I originally posted I had no idea so many people would be interested.

A little update for us, while it did help significantly, we finally decided we needed a second a/c regardless. We decided we spent too much money buying our TT to not be 100% satisfied.

I will note that we saved some money by purchasing the new a/c off of amazon and then having CW to do the install. They charged $125 to install the one we bought, and we agreed $125 was worth my husband not having to fool with it!


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[IRV2]

Silly question before I rip off the little round vent cover, how do you tape it? are you able to get some of the ducting out through the vent hole after taking off the vent and tape around the outside of it? or are you placing tape on the inside of the ducting? I'm not close to my unit so thats why I ask. Also thanks for starting a thread like this maybe it should be a sticky

[John&Genny]

Originally Posted by IRV2

Silly question before I rip off the little round vent cover, how do you tape it? are you able to get some of the ducting out through the vent hole after taking off the vent and tape around the outside of it? or are you placing tape on the inside of the ducting? I'm not close to my unit so thats why I ask. Also thanks for starting a thread like this maybe it should be a sticky

The inside. When you remove the vent screws and pull off the vent itself, you will see that often they don't do a very good job of taping to prevent air from getting into the ceiling. That's what you are doing, plugging up some of the holes. If you have a vent cover that has a 1-1/2" collar, that will help as it will prevent some of the air from escaping. I just bought a bunch of new vents that had a higher airflow, did the taping with the aluminum tape, and we will see what happens next summer

And I agree, this is one of those threads that should be a sticky

[Sniper]

Thanks for the tip. I'll be checking this on my Raptor before it gets hot again. We fought it this summer and even took it back to the dealer to have the AC checked.

[jertour]

Checked the AC duct in our Xlite 28RKS and same as others ducts went past vents. Found some foam 1 ½
thick 18 inch wide,36 inch long in the sewing dept. at
WalMart. worked great

[Wildhorse]

I brought our 355TS Raptor home from the storage lot we keep it at to tinker this weekend. I stumbled across this thread and will probably look into taping, sealing, and blocking as others have done. But out of curiosity I didnt see in this thread anywhere where people had bypassed the racetrack ducting entirely with the slides on the AC units themselves to utilize the vents built into the cover of the unit. Because our AC's wont keep up in our Raptor as the heat builds outside throughout the day this was needed for us to even have a chance of being inside on hot days. I guess my question is really, if you have indeed used the built in vents on the AC units thenselves that blow a lot of air, but are loud, does the race track ducting once sealed and corrected for poor workmanship work more efficiently than the direct venting from the actual AC units?

We are finding that the dark tented windows on our Raptor get hot and radiate inside our trailer and are much more efficient at warming it than the ACs are to overcome to cool it down. The one at the top of the stairs at the little landing just outside of the bathroom and bedroom entrance is the worst. We simply cant have the pull down shade open, period...

[IRV2]

First I'd like to say since my post on this thread 10/25 that I have learned so much here. I almost laughed when I had the questions I was asking. Anyhow a couple of weeks ago I did finally pull the vent off only to find what others were finding, that the duct goes past the vent. I had some pipe wrap that comes on the roll. I cut serval pieces and stacked them, then using the aluminum tape I wrapped some tape on them it kinda of looked like brick. I wedged it in the duct and using the tape finished sealing inside the duct. I did both ends one in the living room and one in the bedroom.

[srvnt]

This did the trick, one on each end, the results are really amazing.

[JRTJH]

srvnt,

That looks like an open cell foam block. If it is, watch it closely. The cold air in the roof vents tends to collect condensation. Often it will push that condensation to the ends of the ductwork. If something (open cell foam) that collects and holds water is placed there, it can keep the area wet, create an ideal environment for mold and set up a problem that you won't notice until it starts smelling. So, you might want to keep an eye on it to make sure it doesn't stay wet. Closed cell foam that won't hold moisture is much less problematic.

[srvnt]

Thanks for the heads up, I will keep an eye on it maybe enclose them in a plastic bag and reinstall them

[MattHelm21]

Originally Posted by JRTJH

srvnt,

That looks like an open cell foam block. If it is, watch it closely. The cold air in the roof vents tends to collect condensation. Often it will push that condensation to the ends of the ductwork. If something (open cell foam) that collects and holds water is placed there, it can keep the area wet, create an ideal environment for mold and set up a problem that you won't notice until it starts smelling. So, you might want to keep an eye on it to make sure it doesn't stay wet. Closed cell foam that won't hold moisture is much less problematic.

Would the pool noodle foam be considered closed cell?

[JRTJH]

Originally Posted by MattHelm21

Would the pool noodle foam be considered closed cell?

If you mean the ones that float and don't absorb water, yes they're closed cell. Some of the older "blue rubber coated" pool floats weren't closed cell foam, but were open cell (think sponge). When the outside coating cracked or deteriorated, the inside filled with water.

I suppose, as a test, if you can put it under water, squeeze it and it doesn't soak up water, it's closed cell foam. If, on the other hand, it absorbs water like the old "O-cello sponge" then it's probably going to hold water if installed in the A/C ducting.

[captcolour]

So I got around to check my Alpine which has 2 A/C units. The A/C outlets on either end of the 5th wheel are slightly towards the middle of the 5th wheel, so no dead space after the vent. Problem I see is that both A/C units use the same plenum, so if only one unit like the bedroom is on, the air is being pushed the entire length of the 5th wheel. Seems I should isolate the two systems so each can run more efficiently when only one is running. Does this make sense that they are using the same plenum?

[Bob Landry]

Did the same thing to my Outback several years ago. That with snap on solar screens keeps my trailer at 75 degrees in the midday Texas sun.