AC Not keeping up

[Ford truck guy]

Originally Posted by rob_fla

I made all the changes some time ago posted by Ford Truck Guy plus a few more and our A/C performance is now acceptable all summer long.

1. Vent collars were too long into the vents, shorten the collar for better air flow
2. Vents were NOT sealed between the HVAC duct and collar, sealed vents so cold air does not leak into the attic space
3. The foam separator in the condenser had had fallen out, sealed with foil duct tape
4. The front cap had virtually no insulation (it had fallen down) climbed in front cap area of our 38FL and added insulation and secured it so it would not fall down (made a big difference in Front Living Room area)
5. Added ceiling registers (according to A/C manufacturer Redwood should have installed a minimum of 5 Registers per A/C unit (we only had 7 registers total, now we have 12 total, much better Air Flow / AC performance)
6. Added 2 additional returns on each unit and unblocked return area restrictions for better air flow / AC performance.

Rob, do you still have the drawings that you made of your modifications? It was your write up that helped me fix my AC flow in my last Redwood....

[gossamar]

I will second following Rob's original fixes from many years ago. The Rushmore was built in 2014 as a 2015 model, I had enough supply vents 11 total in my 35-foot springfield, but was severely lacking in return capacity. The one bedroom ac would frost up on its own without the additional airflow from the living room ac. So, I made sure all of the coils on the ac's were clean, doubled checked the gasket on the roof..all good there.
I then cut 4-additional 9x9 return vents, two per ac and covered them with 10x10 return grills from Menards. Due to the wiring in the return duct this will be the largest hole that can be cut. What I did find was the crushed return plenums where it crosses each of the supply runs. So, I took some rigid foam insulation, cut to size and stuffed on each side in the return plenums to support additional airflow. I did the tissue test both before the mods and after, afterwords on the return side it would almost suck the tissue out of my hands.

Then onto the collars inside the supply ducts. I am currently experimenting here as I removed the collars and have not replaced them as of yet. I did foil tape every supply outlet as per the noted mods. Airflow has definitely been improved.
Last but not least, I removed the front shoe box and like others, almost no insulation or it had fallen. I picked up some mineral wool from menards and started on the front closet wall. I then added the foil reflextic on the outside stapled as a means to hold the insulation in place with the spray glue. I did add some insulation to the cap area and re-insulated the shoe box with reflextic as well. The front cap insulating has made a difference, the front closet still gets warm on those 90 degree days, but there is not the massive heat transfer into the bedroom like before.

With one ac running I am easily seeing 20-degree difference in return/supply temperatures now and when both are running 25+ degree difference. When i pulled out to the campground this week, it was 96-degrees in the camper. I placed circulating fans and fired both ac's up. Within the hour I had dropped over 15-degrees and within two hours I was in the low 70's inside with sun on the one side with outside temps still in the high 80's.

[Char & Steve]

We have also done all the mods listed above early on in 2015 -2016 if I remember correctly. It's been OK but far from perfect. We are going full time now and biggest complaint was in the bedroom at night it would get to warm. We like it around 70 max if not cooler when sleeping. I could not get this in hot weather so just a few weeks ago I cut a hole in the ceiling. Made some creative dampers that can close off the supply ducts to the rest of RV. Installed and nice looking vent and now it gets as cold as we want at night.

[Greg C.]

I have not insulated my front cap on my 38rl. To those of you that have I noticed there are screws in the corners of each shoe storage box. Is that what you have to remove to install insulation? Do you stuff that area to the sides of each box with batting or do you use an adhesive to attach it to the cap itself? One way or the other I will get this unit to cool down and cycle on and off?

[drj564]

Originally Posted by Greg C.

I have not insulated my front cap on my 38rl. To those of you that have I noticed there are screws in the corners of each shoe storage box. Is that what you have to remove to install insulation? Do you stuff that area to the sides of each box with batting or do you use an adhesive to attach it to the cap itself? One way or the other I will get this unit to cool down and cycle on and off?

Yes, those screws are what you remove. I pulled mine on our 2018 39MB and it was insulated. I think what these really need is some kind of thermal barrier plus insulation like said above in previous posts. Reflectix should work for this. I’m just not positive which side it should be on. The shelf side or cap side. Redwood put a decent amount of insulation in our front cap but it traps the heat in there. I would assume the barrier needs to be on the cap side.

[piper guy]

We have a 2013 36RL. I stuffed the area full of 6” R30. Used two rolls. Tremendous difference in heat in bedroom. We’re in Arizona high desert. 100 degrees plus is everyday. Lol

[deerefever]

Does anyone have a link or more pictures as to where to mark to install the additional air returns? I thought I had found something on it once but can't find it now.

[XCMARK]

Originally Posted by deerefever

Does anyone have a link or more pictures as to where to mark to install the additional air returns? I thought I had found something on it once but can't find it now.

My suggestion is go up on the roof and remove the plastic cover and the sheet metal cover that is on the front section of the AC. Drill a hole down once your inside the AC return air section. You most likely will find there is a foam strip about 1" thick x 15" long between the cold air supply and return air plenum that is no longer installed correctly. . This causes 20% lost cold air to the supply side ducts. The return air filter are worth cutting the holes in the ceiling , I did notice a improvement after doing both AC. I used 10x14" return air grills and filter.

[deerefever]

Thanks for the reply, I actually just found the post I was thinking about on Facebook. I do have one other question, any idea if a 12x12 vent will work as that's what I ordered when I was researching this last fall and I don't feel like I would have ordered that size without seeing where someone had previously used that size. Thanks

[XCMARK]

I think you will be ok with 12x12 if I recall the roof trusses are 16" on center so you will be right against one in the front and one to the rear. I think you will find that one truss bay to the rear of the existing returns puts you right under the AC unit. The hole through the truss are small so you would benefit from being directly under the return .

[drj564]

Originally Posted by deerefever

Does anyone have a link or more pictures as to where to mark to install the additional air returns? I thought I had found something on it once but can't find it now.

The correct place is between the current returns.

I’m going off memory but when I did mine the return jumps through a truss at the ac unit. then the next bay is all return. Directly under the ac unit is both suck and blow in between those trusses. The biggest restriction is the jump through the truss IMHO.

I honestly didn’t notice much difference when I did the mod. 2018 MB and all 3 units were the same.