ATF: Bighorn - Whisper Quiet ducting design issue

It seems logical that the flange would partially block the airflow, although I think the most likely effect would be to roil the airflow. But it also seems logical, at least to me, that the air pressure from the blower motor would force air out somewhere.

You might try wadding up some paper and stuffing it just past the last vent to make sure there's no unintended alternative exit for the cold air.

Thanks for the replies. I got a name and number of a Ron Scarberry at Heartland to call and get some details on the design. Talked to him today. His basic answer was that it should maintain a 20 degree differential from the outside temp, and it doesn't, I'm SOL. He wasn't any help, couldn't recommend any workarounds, and wouldn't really address the issue that multiple people are reporting: the air isn't getting down into the coach, and therefore the coach isn't cooling to spec. The only thing he offered was to check to make sure the cavity isn't crushed, which mine is not. He said there's nothing they can do under warranty, even though it's not cooling to manufacturer specs. Very disappointed to say the least. Shouldn't be having these issues on a high-end camper, 2 x 15k units are plenty to cool that coach (I'm only getting an 11 degree drop on a 90 degree day). The guy next to me has a low end Infinity RV with a 13k and 15k btu units, 40 ft, and his cools just fine.

danemayer said:

You might try wadding up some paper and stuffing it just past the last vent to make sure there's no unintended alternative exit for the cold air.

Click to expand...

Dan, we did that first. There is plenty of force behind the air, and it is cold. But it's just not going downward out the current vents.

In our plan, there are 4 slides in the living/kitchen, so quite a bit of square footage (at least 210 sqft) There are only 4 vents on the doorside ceiling to provide the cooling for this space. Three to the rear of the AC unit as it sits on the roof, 1 in front.

I'll do some more measuring, but an infrared thermometer measures inside the vents at 66* (farthest) and 52* (nearest).

The room in the center reads 80.

I had a thought, (I know scary), if you got on the roof with your infared gun and located the duct and followed it from front to back it should all be the same temperature. If there is a leak it would show up as a cooler spot to one side or the other.

Be careful grinding... the louvered vent cover clips atop the edge of the screw on vent opening.
I have spent alot of time dealing with ac vent issues, and the OP has a potentially perfect solution. The first thing that I noticed when poking around the ductwork was the big lip on the screw on flanges. Now... I seem to be getting enough airflow, but more is better. I think replacing the cold side would be a great idea... Look forward 3 to the outcome of this little test!

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danemayer said:

It seems logical that the flange would partially block the airflow, although I think the most likely effect would be to roil the airflow. But it also seems logical, at least to me, that the air pressure from the blower motor would force air out somewhere.

You might try wadding up some paper and stuffing it just past the last vent to make sure there's no unintended alternative exit for the cold air.

Click to expand...

In our case the cold air is being forced out somewhere, but the problem is the air is going to the bedroom instead of the living room.

The openings have no vent-parts in them today. Today it's 96 degrees, interior is 85. This isn't going to work.


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TravelTiger said:

The openings have no vent-parts in them today. Today it's 96 degrees, interior is 85. This isn't going to work.


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Click to expand...

Oh no! I had big hopes that changing the vents out would help. Did you try my fan option experiment from my previous post? I do think that it helped a little.
see below:

We may have found a possible solution to the l/r cool air going into the bedroom and leaving us burning up in the main area of the coach.

We ran the bedroom thermostat set at fan speed on high (either with a/c on or off). (Not set on auto, as usual).
And ran the living room a/c with the fan on low speed. This allowed the bedroom fan to basically block the cool air from traveling up to the bedroom and forced it out the vents in the living room. We could actually feel a dramatic increase in the air from the vents and we stayed much cooler.

I will try this again in hotter temperatures as the weather in gulf shores for the rally was cooler than up in north Alabama.
As per usual, when I go south I bring cold weather with me.

I will report back when I am in hotter temps and try this method again.
I hope this helps anyone with this same issue.

I don't have new vents yet. Just today was hotter than it's been. Now after 7pm, its cooled off to a nice 76 inside.


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In my experience with our Landmark, the only place that cools 20 degrees below ambient is the bathroom. This depends on the outside humidity. Last summer in Nashville, it took several hours to cool the inside from 90 when we set up to below 80. 70 was a pipe dream. The heat loss/gain in these rolling boxes is very high. To maximize the cooling in the desired area, I've thought that vents with closable louvers would help. Vents in the bedroom could be closed for maximum cooling in the LR/Kitchen and vice versa. D & W Spaceports make such vents, but I'm not sure how well they work. Since I only have 2 bedroom vents, it might be worth getting a couple to try.

https://www.google.com/shopping/pro...d=0ahUKEwiEyJ32_NDMAhUF7IMKHXWxBQIQ8wIIiAEwBQ

http://www.rvplus.com/d-and-w-space...0&cadevice=m&gclid=CMbzzIX-0MwCFZY1aQod2bgMaQ

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No AC expert but here is a thought. If the back end of the flange is level with the duct and the front edge is slightly higher, say 1/4 inch, would that not act as a dam and force some air down at the vent? Considering the vent height, that small dam should not impact the flow to the other vents. Again, just a thought.

We put 4 of the spaceport vents in the bedroom and 2 in the bathroom so we could turn off those vents during the day. It helped...a little. One thing though, the new spaceport vent screw holes do not line up with the vent part that is screwed to the ceiling. I used some heavy duty double sided tape from walmart and attached the vents to the frames, no screws so no additional holes if it didn't work. That was over a year ago and the vents have not fallen down yet. It is nice to be able to turn off the AC vents in the bathroom in the early AM.

Directing airflow is not as easy as we all think it might be. I have some vague recollection of a past project and learned a small bit about it.
Air movement does not like to go around corners without help. A good example is in our home forced air heating/cooling system there may be a 90° sweep. There are baffles in that sweep to prevent a cyclonic action that will pretty much stop airflow.
So just removing a vent will not help much, but as some here have found out that the lip inside of the vent will play a roll in direction of movement.
I have attached a small diagram of how airflow is affected by small changes in design. This does not relate to our RV situation but it does show a bit of how things work.
So, I suggest that if you want to get more downward airflow from the vents, you will have to install some sort of baffle in the ducting.


Peace
Dave

cookie said:

Directing airflow is not as easy as we all think it might be. I have some vague recollection of a past project and learned a small bit about it.
Air movement does not like to go around corners without help. A good example is in our home forced air heating/cooling system there may be a 90° sweep. There are baffles in that sweep to prevent a cyclonic action that will pretty much stop airflow.
So just removing a vent will not help much, but as some here have found out that the lip inside of the vent will play a roll in direction of movement.
I have attached a small diagram of how airflow is affected by small changes in design. This does not relate to our RV situation but it does show a bit of how things work.
So, I suggest that if you want to get more downward airflow from the vents, you will have to install some sort of baffle in the ducting.
View attachment 44985

Peace
Dave

Click to expand...

Thanks for the info, our next experiment. We did add some metal tape to curve the airflow where it comes from the AC unit to the long rig-length duct, and that helped. But getting it from the duct to out the vents is the next challenge.

Sounds like the Spaceport vents I have on order won't solve the issues, but won't hurt, either.

Just need a ladder and some time.

Erika, in our last coach I used some cardboard to fab some temporary baffles in the ducting near the outlet grill till I got it right.
I suggest a short baffle center across the opening installed at an angle to divert some of the airflow downward.
The leading edge and the trailing edge should/might move the air downward.

Peace
Dave

Shouldn't have to make these "fixes". Didn't anyone at HL test this system other than just turning it on? It's one thing to tweak something to suit a person's individual needs or quirks but this thread sounds like a downright design flaw.


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Erika,

If your 4010RD is 40'10" long, that's 2 feet longer than our Rushmore. Our A/C units struggled to keep up in Texas heat. Our living room and kitchen area may just have too much volume for that 15,000 BTU unit. You probably have even more volume and perhaps higher slide out ceilings. And we have dual pane windows. So I'd expect that you'd have more trouble cooling in Texas than we did.

I've done a lot of things to get improvement - each delivering a little improvement. I have the adjustable louver vents in the bedroom, bathroom, and kitchen. During the day, I keep them all closed and when it's hot, I set the bedroom thermostat to a very low temp to force it to run continuously on high output. And because the air from the bedroom fakes out the hallway thermostat for the living room A/C unit, I also set that unit to a low set point so it keeps going continously.

Even at that, I've learned that if I allow the afternoon temperatures to get ahead of the A/C unit, it won't recover until late evening. So I'll usually cool the trailer to below 72 in the morning so it has a head start.

We've also got sunshades that snap over the windows to cut the heat load. But Ann doesn't care for them being in her line of sight. So I only get to put them on the doorside windows when temps are really high.

I think window awnings would really make the most difference by keeping the sun off the windows, but I've been vetoed on that solution because it would limit the view.

I think your work on getting airflow through the vents will yield some improvement, but I'd expect there'll be more that needs to be done.

I have dual pane windows, unit is only 39 feet, and two AC units and I keep it as dark as tombs inside.
we should not be struggling to stay below 80 degrees,nor should we be freezing in the upper bedroom area. If we don't run the fan on high instead of auto we get an area of condensation in the ceiling over the kitchen island.
in any 5th wheel I've ever had, the bedroom area was always hotter, that's why you buy the second unit. At this point, we need the second unit downstairs.

I'm still going to take photos with my phone, this must a ducting issue. Just need to work out how to adjust things someway.

Thanks for all of your interest and comments and most of all your suggestions. We will try them all and perhaps solve it together!

This issue is not just with the whisper-quiet air conditioning system. I believe it's the ducting because It's been a problem for the last couple of years with Big Country, Landmark and Bighorn trailers. The whisper-quiet system seems to have compounded the issue.

On your guys systems does the air conditioner have a return duct in the ceiling? and does it look like the units on the gateways? I ask this because I was having a little bit of a cooling issue and it turned out that a baffle in my unit had come dislodged that separated the return from the supply. It was essentially recycling the cold air it was supplying right back into the unit. I had to remove the interior grill assembly and remove the baffle. After inspection I returned the baffle back to it's spot and sealed it with duct tape all over the seams separating the supply side from the return side. That alone helped considerably. I would hope that your whisper quiet units have some type of return air area otherwise they will never cool properly. Cooling is a compound effect and it needs the cooler air inside the camper to continue cooling the air until it reaches it's set point.