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Modifying roof a/c cover

georgelesley
Explorer
Explorer
I just watched a YouTube video about cutting out the rear of the a/c cover and replacing the air exit part with a hi flow metal mesh to improve air flow from the a/c. The idea is if the hot air exits faster more air can flow thru the condenser thus improving cooling.

Makes sense to me, just wondered if anyone else has done it and what the results were.

I really do not know how to post a YouTube link or I would have, but i found it searching by searching for โ€œupgrading rv roof air conditionerโ€ it is about 16 minutes but only about 10 pertain to the roof a/c.
George 20 yr USAF & Lesley
14 REPLIES 14

JIMNLIN
Explorer
Explorer
smthbros wrote:
I would have liked to see the youtube guy measure the average flow thru the condenser with the cover off and again with the cover on before he modified the cover and again after the modification. I suspect the airflow improvement would be less spectacular.
X2...owning three truck campers and three 5th wheel trailers over the years with roof mount A/C I add hardware cloth to all the intake slots and exhausts on the covers to stop a very bad mud dauber problem.
I saw no changes in cooling the camper in 100-110 degree heat.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers

'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
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smthbros
Explorer
Explorer
I would have liked to see the youtube guy measure the average flow thru the condenser with the cover off and again with the cover on before he modified the cover and again after the modification. I suspect the airflow improvement would be less spectacular.

fj12ryder
Explorer II
Explorer II
Gulfcoast wrote:
I think it's a good idea, but I have one question. Why didn't the engineers that designed it think of the same thing?
Believe it or not, many of the ideas put forward as "common sense" by non-engineers don't work as well as it seemed they should have. Sometimes what works is actually counter-intuitive.
Howard and Peggy

"Don't Panic"

philh
Explorer II
Explorer II
Gulfcoast wrote:
I think it's a good idea, but I have one question. Why didn't the engineers that designed it think of the same thing?

Engineers are always balancing cost, function, and ease of manufacturing. This "change" would be more expensive to produce, and difficult to mfg. The design they produced is "good enough". Can it be better, obviously it can, but at what cost? Looking at a simplier change, I pulled the brand new 12V battery out of my trailer and installed two GC2 6V batteries. For 99.999% of customers, 12V battery is "good enough"... but it wasn't for me.

Rick_Jay
Explorer II
Explorer II
Hmmmm....I have the "low profile" A/C units and shrouds on our rig and there are NO louvers cut in the covers at all and the A/C's seem to run fine. I'm assuming the designers had some idea of what they were doing and I like the lower profile.

That said, and expanding on prichardson's comment, for this mod, the problem that comes to my mind is that the back of the A/C shroud is most likely a "low pressure" area when the rig is travelling. Ever wonder why the back of your car, rig, van or SUV tends to get dirtier than the rest of it? When travelling forward, the back is a low pressure area that draws in road dirt, water, exhaust, etc. and deposits it on the surface. Even when you see vehicles travelling down the road in the rain, the low pressure area behind it tends to atomize the road spray, giving that "cloud of mist" right behind the vehicle reducing your visibility. One reason why it's nice sitting up high in the Class A...you see right over that. ๐Ÿ™‚ But I digress...

My concern for this mod would be that when travelling and the roof A/C units AREN'T being used, will that mesh screen he made, with the smaller holes, tend to become plugged up quickly with deposited material? I realize that with the original louvers, some of that stuff made it through to the condenser, which is why it needs to be cleaned periodically. But about half of it was left on the structure of the louvers. That structure is now removed. With this mod, I'm guessing the condenser will stay cleaner, but that grill might need to be cleaned more frequently as it's now the first line of defense against the debris sucked in by the low pressure area.

When the A/C is running, this probably won't be as much of an issue because the fan will be forcing debris out the grill.

On a lesser, more technical note, I also am not 100% his anemometer readings can be completely trusted. With the original louvers, a large part of the anemometer sensor was over a louver, not a slot. A truly accurate test, in my opinion, would have to include the airflow through the entire louver structure in a "wind tunnel" sort of set up. I'm not saying this doesn't improve air flow. It might. On the other hand, I also know that fans draw air through a screen much more efficiently than blowing air through a screen, and what he installed there is borderline to being considered a screen. Again, I'd like to see the airflow numbers on a full mock-up, not just a single reading on a selected part of the screen. I'm sure for BOTH systems, you do not get constant numbers as you move the anemometer around the path of the airflow. Such being the case, it's pretty easy to make the result LOOK much better than they actually ARE.

Actually, now that I think about it more, the aerodynamics and flow rates might change quite a bit while the rig is in motion due to the low pressure area created. In my mind, that casts even more of a doubt about the accuracy of the airflow numbers presented. Obviously this isn't an issue when parked, but at highway speeds, there might be some drastic differences in the airflow numbers.

Anyway, take all of this commentary for what you will. It's just my $0.02 worth. I'm not sold that it actually would be an improvement, and might be a detriment. As I said, my A/C covers have no louvers and I'll stick with that. ๐Ÿ™‚

~Rick
2005 Georgie Boy Cruise Master 3625 DS on a Workhorse W-22
Rick, Gail, 1 girl (27-Angel since 2008), 1 girl (22), 2 boys (23 & 20).
2001 Honda Odyssey, Demco Aluminator tow bar & tow plate, SMI Silent Partner brake controller.

Cummins12V98
Explorer III
Explorer III
"Wasn't this exact subject word for word, posted up a couple of months ago ??"

Does it matter? Same "can I tow" or "Tires?" topics abound.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
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georgelesley
Explorer
Explorer
MrWizard wrote:
Wasn't this exact subject word for word, posted up a couple of months ago ??


Not by me. I did not see this subject before.
George 20 yr USAF & Lesley

prichardson
Explorer
Explorer
Actually that metal mesh is likely more restrictive to air movement than the grid with large openings that was removed. It is all about open free air area.

Dave_H_M
Explorer
Explorer
I agree with the Wizard, and if mine ain't broke, I am not going to fix it. :C

MrWizard
Moderator
Moderator
Wasn't this exact subject word for word, posted up a couple of months ago ??
I can explain it to you.
But I Can Not understand it for you !

....

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Gulfcoast
Explorer
Explorer
I think it's a good idea, but I have one question. Why didn't the engineers that designed it think of the same thing?
RV'ing since 1960
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IAMICHABOD
Explorer II
Explorer II
Here ya go Youtube Video
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TurnThePage
Explorer
Explorer
I intend to do it. It's on next years list. My main purpose will be to keep the wasps out.
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philh
Explorer II
Explorer II
I previously watched it, and it made sense to me. Increasing air flow is a great idea, and due to molding constraints, they are balancing cost, mfg, and performance.

I haven't done it, because my AC is working really well.