RV Air Conditioner Performance Improvement Tests


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It seems like it’s about a thousand degrees in most parts of the country right now.  So if you’re like me, you’re thinking of any way possible to squeeze a little more performance out of your RV’s air conditioner.  One gadget that promises an average of 40% improvement is from RV Airflow Systems.  This product works only for ducted RV air conditioning systems – and we have one.  So I installed one in our Winnebago EKKO, and took before and after measurements of the airflow to check it out.

 

TL;DR:  Yes, the RV Airflow Systems product did increase the airflow from our air conditioner.  But in our EKKO, the changes were insignificant, and nowhere near the claimed 40%.  Save your money, and save your time.  Based on our testing, simply taping over the cold air dump in your RV’s air conditioner will get you the vast majority of the benefits of this product.  You don’t need to spend time making styrofoam insulation teepees like you see all over YouTube, either.  Just 10 minutes and half a roll of tape will get you most of the way there.

 

A Few Caveats, First

The first thing I want to point out about the RV Airflow System you see in the video, is that this was a factory customized unit.  You see, RV Airflow Systems are made to fit standard RV air conditioners within a standard set of dimensions.  The roof opening and vent locations in our Winnebago EKKO did not meet this set of parameters.  But if you call the factory and provide them dimensions, they will customize a unit to fit your opening.  I thought that was pretty cool – they’ll do it for anyone… no charge!  So it is possible that in a more standard RV roof opening, that the performance of the RV Airflow System might be better.

The next thing you should know is that we paid straight-up retail for our RV Airflow unit.

And the third – and probably biggest – thing you should know is that our “before” numbers were not from a stock air conditioner setup, but rather from an improved setup.  We had previously installed the RV AC Silencer (trying to make the air conditioner quieter).  Part of that install includes taping over the cold air dump that’s right below the fan in the air conditioner.  This alone seemed to get us most of the improved performance that the RV Airflow System claims.

The Tests

I don’t want to just repeat what’s in the video.  The tests are super easy, and you should be able to replicate them to see what kind of airflow you’re getting out of your current setup.  But people will probably want links to two things that I used to make the measurements.

The first is this anemometer.  I don’t think you have to use this one exactly – there are a number of seemingly identical ones for sale, and I don’t have any reason to believe that one is better than the other.  It’s only a $30 instrument, and I didn’t have a way to verify the absolute accuracy of the anemometer versus a laboratory standard.  But one thing I did before proceeding with the video though was to repeat the same measurements on the same vents on different days at different times to at least verify the *consistency* of the meter.  I was satisfied with that, so I went ahead with the test.

The second thing you might want is this funnel that I snapped onto the anemometer.  I just printed it out of PLA.  The opening on it is large enough to cover the whole of the vent openings in our RV.  The inner opening (where the airflow enters the meter) is 66mm in diameter.  When you do the math, that turns out to be a measurement area of 0.037 square feet.  The anemometer will give results in feet per minute, so the formula to get cubic feet per minute is just:

0.037 sq ft    X    Airspeed (ft/min)   =   air flow in cfm

When I used the anemometer to take readings, I set it on its “average” setting.  In this mode, the anemometer displays the trailing average for the last 15 seconds of readings.  This made it easy to capture the data, instead of trying to guess second-to-second peaks.  I just waited until the average stopped changing.

My Mod to the Mod

As it turned out, my mod with the parabolic ramps and whatnot didn’t improve the situation much.  I did succeed in reducing the airflow to the Nordic Blast over my bed, but improvements to the airflow in other parts of the coach were limited to single digit percentages.  I guess it’s better, and I’m leaving it in for now.  But if I knew then what I know now, I wouldn’t have bothered.  Based on that, I deleted the model for the parabolic ramps, so I won’t be tempted to waste any more time with it.  🙂

The Data

If you want to take a look at the data for yourself, I’ve uploaded it, and you can download it here:

RV Airflow Test Data

One other thing I should mention: The sound levels in the RV with and without the RV Airflow (with or without my mod) were exactly the same.  No change in noise levels on either low or high speed.

So What Do I Recommend?

Well, first, remember that this approach only works for ducted RV air conditioning systems.  If you’ve got an air conditioner with a single-location air distribution box, then none of this applies to you.

Next – before you buy any product for your air conditioner, and before you start cutting sheets of styrofoam to fit inside your plenum, try the super cheap and easy approach.  Simply get some foil tape, and tape over the cold air dump at the floor of your air conditioner’s plenum.  Seal up any other gaps or sources of air leakage you find while you’re in there.  See if that ten minutes and half a roll of tape improves your performance enough to make you happy.  I’m guessing it will.

In our Winnebago EKKO, simply taping this over with foil improved the airflow so much, that there wasn’t much left for the RV Airflow System to improve.  Now granted, your RV and your duct system may be different from ours.  The tape might not work as well in other RVs, but it’s so easy and so cheap, that it’s at least worth a shot.

 

That should just about do it for this one.  I’m sure there will be comments and questions, so leave them down below.

Stay cool, everyone!



James is a former rocket scientist, a USA Cycling coach, and lifelong fitness buff. When he's not driving the RV, or modifying the RV (or - that one time - doing both at once), you can find him racing bicycles, or building furniture, or making music. In his spare time, he works for a large IT company.


    27 thoughts on “RV Air Conditioner Performance Improvement Tests

    1. Don

      Hi James – On our ’21 View we took your advice from awhile back and did the foil tape trick on the flood exhaust duct. It worked very well to modify the flow in the coach enough that we did notice an improvement in distribution and performance.

      We were hoping for an improvement in noise levels too, and yes, the foil tape trick did help a bit. But – what really helped to quiet the noise in the coach to levels where we could talk normally was cleaning up the intake plenum. Our intake was a rats nest of electrical wire that evidently was slicing up the intake flow, and creating vortices that resulted in objectionable noise. I zip tied the loose wires together and displaced the bundle to the side of the intake in an attempt to smooth the flow. It worked very well for us, really making it a game changer during times of using the AC.

      Thanks for all your great info.

      Cheers,

      Reply
      1. James - Post author

        Now THAT is interesting!
        If I get motivated to pull down the inside air cover yet again, I’ll certainly look for and clean up any messy wiring inside the intake.
        Others planning to tape things up should take the opportunity to do the same.
        Thanks for sharing!

        Reply
    2. Sev

      Great video James. Since I know you like to fiddle with things, haha… What about printing another 3D ramp/splitter (or modifying the one you already made) to direct ALL the air flow to the passenger side trunk? Not even giving the air a chance to go into the driver side duct work at all, so it doesn’t create any back pressure or turbulence.

      You might have to switch beds with Stef to be on the “cold side”, and possibly block the two first vents in line partially, but I would think that would really get the dinette vent cranking.

      Cheers, Sev

      Reply
      1. James - Post author

        I thought about that, but
        a) I’m tired of messing with it for now. And
        b) There’s a minimum air flow that’s required to keep the unit from icing up, and I think closing off half of it might get me closer to that than I’d like.

        Reply
    3. Joe McGuire

      Fellow engineer here that’s also tackling some AC issues. I recently switched to a Houghton 3400 on my Boldt, and it’s amazingly quiet compared to the Mach 10 NDQ. I can think clearly after a full workday. The houghton has a large axial fan rather than a blower fan, and I 3d printed a large stator on the ingress side to reduce the fan noise and increase fan efficiency. It seems to work pretty good, but has introduced a bit of choppiness to the sound that does remain. I really wish some company would create in a proper rooftop DC variable/inverter based system. I knew you wouldn’t be able to end with the solution as is – I know I wouldn’t. I’m surprised you didn’t bust out a endoscope camera to inspect the duct path. There’s a lot of concern on youtube videos about increasing the aggregate airflow, but that’s probably not the best goal to go after. The biggest goals to me are getting the airflow to reach the right areas, prevent the system from freezing up, and reducing the cold outlet air from being recirculated back to the unit. Having a slightly lower flow at 55 oF output vs a higher flow of 58 oF output probably won’t make much difference in COP.

      Reply
      1. James - Post author

        I’ve actually been able to visualize the ducts in the past when it was humid, and I had the air cranked – condensation forms on the ceiling along the vent path!
        (Easier than a scope, anyways.)
        But I don’t know what to do with that knowledge, ya know. It’s not like there’s much I can do about it except try to close vents and adjust my expectations.
        One thing I never got around to mentioning in the video is that the RV Airflow – as well as just plain tape – is effective at preventing the cold air from being sucked back into the intake.

        Reply
    4. Bill G

      Cool experiments! (ha ha) Your results tell me the ducts are the controlling resistances. What is needed is a fan to raise the inlet pressure to the passenger-side duct. The geometry argues for a small centrifugal fan. Hmm, how to power it… there are lots of wires there!

      Reply
      1. James - Post author

        Interesting idea. The ducting is only 50mm high, so it would have to be a small fan indeed.
        As another idea, I had thought of small fans to “pull” the air at the two vents I want most flow from. I could run the wiring through the ducts. Those fans could be larger. I’d want them to switch on and off with the main AC fan though.

        Reply
        1. James - Post author

          Perhaps, but I think it would be more likely to pull air from the intake – working with, rather than trying to overcome, a much more powerful fan.

        2. Bill G

          Now that I have my own Ekko to play with I see there is no room for a helper blower in the A/C plenum. I can’t find a small one with enough flow, anyway. Same for adding fans to the vents. (BTW I think you need to review how fans in series work.)

          It is intriguing the hallway vent is fed by a duct that splits off and then reconnects to the kitchen vent duct, making part of the run to the kitchen vent is two ducts which increases flow rate. Where a parallel duct is really needed is from the A/C to past the second bedroom vent. An enterprising mad scientist might take down the ceiling paneling and carve a new vent in the styrofoam….

    5. Will

      I appreciate your curiosity and testing. It’s always a good watch and sometimes I even learn something!

      As far as ducted heating and air conditioning, you want to give your system the most efficient air flow possible (in flow and out flow) and closing grates or vents is not a good thing. Let your HVAC do it’s thing to cool or heat your entire living space. Use a fan to direct heat or cold toward you if you’re in a dead zone.

      And most of all insulate! The cab of your vehicle is a giant greenhouse with all of those windows. The cab is a giant heat or cold generator depending on the season. One of the greatest improvements to improve the heating or cooling your RV’s living space is to separate your cab from the rest of the vehicle with a thermal blanket. If that’s impractical, insulate the devil out of the glass areas up front. A single sheet of Reflectix is not enough!

      Last but not least, have you checked out SensorPush devices, James? They’re little battery powered temp sensors that bluetooth to your phone. I have one outside my truck, in my storage area, in the living area and in the refrigerator. And you can export data from the little buggers. It’s an engineer’s dream!

      Reply
      1. James - Post author

        Good points. The EKKO actually comes with a thermal curtain to put between the cab and the back of the vehicle. This video was focused just on the airflow, rather than overall Air Conditioner performance.

        Reply
    6. Rob

      Great video… love stats on the air flow. I was wondering if you could completely block (with tape or whatever the two vents over the beds so there was only one ducted air flow? Three vents in the bedroom seem a little excessive and reducing it to one would mean no air blowing directly on either of you.
      The second thing that struck me was your RV was over 106 degrees when the air was off. How quickly did it get hot in there after you turned off the a/c? Did you have windows or doors open that would account for such a high loss of cool air? Wondering how long it takes for a cool interior to get to hot. And yes..l lots of variables there, but it would be nice to know what it’s like in very hot weather. Thanks for always posting informative and really entertaining videos! Be seeing you!

      Reply
      1. James - Post author

        I’d be very reluctant to tape off any vents completely. It’s not a zero sum game… the air you block in one vent doesn’t necessarily come out of another one. By closing off vents completely, I would worry that I was not allowing the minimum required air to flow through the unit.

        And yes, it was 106 in the RV. But we’re at home. The air was off, except for the time I was inside the RV taking measurements. It started off at 100. Cooled a couple degrees while I made measurements, and then heated right back up. I don’t think there’s anything valuable to be inferred from that 106. It’s routine here.

        Reply
    7. Kitty G

      Did you try adjusting (close about 80%) your vent over your bed and measuring the flows with no other mods? how about the flows out the ducts before and after you taped the dump up? Also wonder if by taping up the dump would your overall flow from the A/C decrease due to possible back pressure making the A/C work harder, maybe even decreasing the life of the unit? (I am assuming no way to measure that as difficult to measure the dump air flow). Curious minds want to know…..LOL

      Reply
      1. James - Post author

        The louvers on the vents aren’t very good at closing off the flow. See my response to Jeffrey.
        If I were to close the vent over my bed, it would whistle! That’s worse in my book.

        I’d have to go back in time to measure the flows before the dump was taped up originally over a year ago. Haven’t mastered that one yet! But in any case, I have no worries about taping up the dump on a ducted system.

        Reply
    8. Jeffrey Ostermiller

      James: Love the video. I was wondering if the vents throughout your RV have controls to direct the air flow and air volume. Other than your solution to tape off the air dump it would seem that vent controls might work to better manage directing air to the desired areas.

      Reply
      1. James - Post author

        The vents throughout the RV do have louvers that sort-of-close to direct the air flow. They work for changing the direction, but only sort-of-work if you want to close off a vent completely.

        Testing shows that closing one of these louvers doesn’t necessarily direct that same amount of air anywhere else – though it does reduce the air coming through that particular vent. In other words, if there were 100 cfm of air coming through a vent, and you close the louvers, then you might have only 10 cfm coming through that vent. But the other 90 cfm don’t necessarily show up anywhere. They just dissipate as inefficiency, back pressure, and mystery flow to nowhere.

        Reply
    9. Andy & Kim

      Just a completely uneducated thought here.
      Take that foil tape and cover half (or so) of the output duct to the single bedroom vent. Wouldn’t that increase the pressure in the main output chamber and then feed the duct to the other 4 vents at a higher volume and velocity?

      Reply
      1. James - Post author

        That’s essentially what I was trying to accomplish with the 80/20 curved ramps, and it didn’t change much. This tells me there’s some inefficiencies and weirdness in the ducting.
        I could tape it up completely, but all the additional volume would not transfer to the other ducts. Instead, overall volume would just be reduced. (I verified this by closing all the vents using the louvers, and then opening one at a time. The volumes coming from an individual vent were nowhere near the total system volume. Not even close.)

        Reply
    10. Mathew

      The design of that duct system is wild. Who though it was a good idea to dump the majority of the cold air into the bedroom vs say the main living area with the kitchen and where you are likely to be during the day when it’s hottest?

      Reply
      1. James - Post author

        The Winnebago EKKO also has a pop-top model, and I think they made some concessions in the design of the ducting so that they could have a common roof framework between the two models.
        Just a guess, but that’s what makes the most sense to me.

        Reply
      2. Tsippi

        My early Cross Trek has a similar arrangement (two ducts over the full size loft bed), and I’m actually grateful they did it this way. Even when it’s insanely hot, the bed area cools down quickly enough for me to sleep. The newer Cross Treks don’t have ducted air, and I’m guessing the bed area gets pretty warm if you don’t plan ahead.

        Reply
        1. James - Post author

          I’ve always thought they made a mistake when they got rid of the ducted air conditioning in the Cross Trek.

    11. John Williamson

      James, love the engineering mind set, and stick-to-it-ness you demonstrate! I’m guessing the sound levels were the same as well?

      Reply
      1. James - Post author

        Ah, yes. I forgot to mention that in the video. The sound levels were unchanged.
        I’ll add that to the write-up now.

        Reply

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