Insulate AC ducts in engine compartment

JimBath · 07-15-2021, 04:34 PM

Ok, I have insulated the dog house and the floors in front of both driver and passenger seats, manly for noise, but also for heat. Now I want to do something about the engine AC. The V-10 gets HOT, and the ducting coming from the AC through the engine compartment is simple plastic ducting. I have noticed on hot days (SWFL) after driving for a while the engine AC doesn't blow really cold air as I believe it should. It starts out very cold, but slowing loses that really cold air. So much so that I shut off the engine AC, turn on the generator, and run the front AC, which I always did on my DP's (better gas mileage and the diesel gen only used 1/2 gallon/hour on 50% load). I want to either change the ducting to something that is already insulated, or insulate it myself. The latter appears to be a bear of job. Anyone done something like this on their MH, doesn't have to be a FR3, but that's what I downsized to at my age (80). Thanx Guys and Semper Fi; Jim

robo44 · 07-15-2021, 04:43 PM

Following

Sunseeker16 · 07-15-2021, 05:13 PM

I have a 2016 Sunseeker 3010 DS and I can say that I don't have an issue with heat from the dog house or the floor. All I have ever used while traveling is the chassis ac with no complaints and here in Missouri it gets pretty hot and humid. No doubt insulation would help but I don't see the need on my unit.

frankie D · 07-15-2021, 07:04 PM

You are exactly right I insulted mine with fiberglass pipe insulation from Home Depot I cut to the length it would take to go around the circumference once and I kept adding till it was all covered then used foil tape on the seams it took a little while but totally worth it the dash board ac does the job and I lived in Florida at the time

JimBath · 07-16-2021, 09:15 AM

Quote:

Originally Posted by Sunseeker16

I have a 2016 Sunseeker 3010 DS and I can say that I don't have an issue with heat from the dog house or the floor. All I have ever used while traveling is the chassis ac with no complaints and here in Missouri it gets pretty hot and humid. No doubt insulation would help but I don't see the need on my unit.

The dog house and the floor mats were not for heat but noise, I think I may still run the front roof AC when the temps near triple digits. It sure helped MPG on the DPs. That engine AC certainly impacts MPG. If you've never tried it, you might consider it.

cariboo camper · 07-17-2021, 12:17 AM

I have a 2017 FR3 and do not notice a problem with AC not running cold. Maybe you should get AC checked out. Could be low on refrigerant.

JimBath · 07-17-2021, 11:17 AM

Quote:

Originally Posted by cariboo camper

I have a 2017 FR3 and do not notice a problem with AC not running cold. Maybe you should get AC checked out. Could be low on refrigerant.

Thanx for the reply. But no.it is not low on Freon, had it checked, all's well, works fine until I get in high temp area and that V-10 gets really hot. I am convinced it is that thin ducting in the engine compartment. I have stopped at rest stop and felt the ducting and it is almost too hot to grab hold of. Try it some time when you are in REALLY hot ambient temps. Insulating the ducting surely won't hurt, but may help for a low cost.

TitanMike · 07-17-2021, 01:48 PM

Walmart sells this in small quantities (online). 3/8" thick and for both sound and heat insulation.

Car Insulation 10mm Thickness Thermal Sound Deadener Blocking Heat Noise Proofing Mat 24"x39"

http://www.walmart.com/ip/Car-Insula...-x39/993018731

JimBath · 07-20-2021, 03:54 PM

Finished the AC ducts, but had to come in, too hot for an old man out there -- 96 degrees. Will take some pics tomorrow AM and post the results. It went well. I found the perfect stuff to do it.

bootsthecat · 07-21-2021, 03:08 PM

Quote:

Originally Posted by JimBath

Finished the AC ducts, but had to come in, too hot for an old man out there -- 96 degrees. Will take some pics tomorrow AM and post the results. It went well. I found the perfect stuff to do it.

Looking forward to your pics and material used.

JimBath · 07-21-2021, 04:25 PM

Okay, it is done. I bought all the stuff at Home Depot in the pipe insulation department. It was rubber wrapping with a yellow peel off taping. It is a large roll so trying to install it while on the roll is not feasible. I also bought some metallic foiled wrapping to cover the insulation.

The one long duct that goes over to the driver's side, I disconnected so I could wrap the entire duct. I also disconnected one of the two going over to the passenger side. The third one I did not disconnect as I figured I could wrap it while still attached with the other one out of the way.

Once the ducts were out of the way, I cut the zip ties holding the ducting up, there were three of them. They are held in place by a single screw. Once taken down you can pull one end of the zip tie off and cut of the other end. I had several different size zip ties. One slid into the attachment, but they were short so I had to use two of them to fit around the finished ducting.

I cut the wrapping in lengths of about 18" which made it easy to wrap and ensure I covered the entire duct. It is VERY sticky when you pull the yellow covering off so I peeled it off as I went rather than peeling the entire 18' at once. It adheres to the ducting perfectly.

Once I had all the ducting wrapped, I then wrapped it with the foiled tape. Likewise it was also very sticky, but no backing, so I cut it in 13" pieces which gave me one wrap of the duct with slight overlap.

Once everything was wrapped, I placed the ducting back where it belonged, reattached them to their respective connectors and and tightened the zip ties.

It took me two days because the engine compartment is in direct sun and this old man could only stand there sweating profusely for a few hours, plus I was doing some severe bending and stooping inside the engine compartment, and having had two back surgeries, when the back told me that's enough for one day I quit! LOL

I started the engine let it run for about 30 minutes (ambient temp was 96). Trust me it was the coldest air I have ever felt coming out of the vents inside.

I started the engine and let it run for about 20-30 minutes to get the engine compartment heated up. Ambient temp was 96, and it was the coldest air coming from the inside vents I have ever felt. For those who commented they have no issues with their AC in hot temps, I reckon I have an anomaly But it sure is cold now. Can't wait to get it out on the road at 60 MPG (fastest I drive) on a very hot day and see how it feels. Photos to follow.

Any question feel free to give me shout out Semper Fi, Jim

JimBath · 07-21-2021, 04:34 PM

Here are the pics, sorry they are rotated correctly, I don;t know how to do that. DUH!

robo44 · 07-28-2021, 02:56 PM

Nice work ... I will put it on my list of Mods for the future

LargoII · 02-06-2024, 09:12 AM

It looks like those ducts are 2" and 3" ID. Is that correct?
Thanks!

bubbles · 02-06-2024, 10:26 AM

Well, I'll be. I thought all F53 chassis motorhomes were the same using the HVAC system. All that ducting is located behind the firewall inside the cab under the dash of my Georgetown.

Twinboat · 02-06-2024, 07:42 PM

My Axis had all of the ducting under the dash except the fresh air intake.
For max cooling, I always ran it on recirculation, only drawing inside air.

I just got my 2023 Fr Rv FR30DS and haven't even looked at the AC system, but now I will.

LargoII · 02-07-2024, 09:13 AM

I haven't looked "under the hood" since the fall. When I did, there is a larger duct running across the firewall, perhaps five to six feet long. A quick measure of the OD was about 3.25". It is bare duct, no insulation. There is also a shorter bare duct on the passenger side which is smaller, so I guessed it was 2" ID. I asked the question about duct size to try and confirm my quick measurement and guess without having to open the storage cover to peak "under the hood" again. I'll go today and try to take a more accurate measurement. There are ducts inside under the dash, but also on the outside of the firewall.

ForestGump34DS · 02-07-2024, 10:56 AM

Quote:

Originally Posted by LargoII

I haven't looked "under the hood" since the fall. When I did, there is a larger duct running across the firewall, perhaps five to six feet long. A quick measure of the OD was about 3.25". It is bare duct, no insulation. There is also a shorter bare duct on the passenger side which is smaller, so I guessed it was 2" ID. I asked the question about duct size to try and confirm my quick measurement and guess without having to open the storage cover to peak "under the hood" again. I'll go today and try to take a more accurate measurement. There are ducts inside under the dash, but also on the outside of the firewall.

They are defroster hoses....nothing to do with A/C. All the A/C hoses and ducts are located inside the coach, under the dash.

LargoII · 02-07-2024, 11:55 AM

Quote:

Originally Posted by ForestGump34DS

They are defroster hoses....nothing to do with A/C. All the A/C hoses and ducts are located inside the coach, under the dash.

Interesting. I wonder how JimBath had significantly colder air coming out of his vents after insulating these ducts? Anyway, I'll still check it out the hose sizes as well as their sole use for the defroster. Thanks for the heads-up ForestGump. On one hand I hope you are right, it will same me a project. On the other hand I hope you're not, 'cause I was looking forward to some colder air this summer!

ForestGump34DS · 02-07-2024, 12:33 PM

Quote:

Originally Posted by LargoII

Interesting. I wonder how JimBath had significantly colder air coming out of his vents after insulating these ducts? Anyway, I'll still check it out the hose sizes as well as their sole use for the defroster. Thanks for the heads-up ForestGump. On one hand I hope you are right, it will same me a project. On the other hand I hope you're not, 'cause I was looking forward to some colder air this summer!

You may want to read this thread on the engine A/C. Many folks don't think the A/C can be used as a stand alone and supplement it with the domestic A/C. Couple folks have found the thermostat (engine compartment) to be a source of trouble.....

https://www.forestriverforums.com/fo...er-267893.html

Good luck with yours.....

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