ATF: Bighorn - Whisper Quiet ducting design issue

stew0720

Member
I recently bought a 2016 BigHorn 3970 RD, it has the 2 15k ac units. I'm in Texas, the other day it was 85 outside and it wouldn't cool below 74. Granted, door side is facing west, there's alot of heat gain on the windows/door, but it should do better. I've already taken it back to dealership and they replaced the living room AC due to my complaints, I'm now realizing it's the ductwork design.

I have one supply in the living area that puts out literally no air flow, when you take the vent off, you can feel air rushing over, just none is coming down into the cabin. when both units are blowing into the same duct per the design, they fight each other and create static pressure issues. The ultimate result is that all the CFM isn't getting down into the cabin. 30k btu should be plenty to cool that cabin, but it's only getting an 11 degree temp drop at 85 degrees, with door shut all day and all shades down.. At 105 it's going to be unbearable. Has anybody had any luck with the Whisper Quiet system in hot temperatures?

There has to be a workaround to modify the ductwork to get all the air into the cabin.

Disclaimer: I own an AC company so I know a thing or two about duct design.

If someone could contact me to elaborate on the design I'd appreciate it.

Also, any tips to reduce heat gain on windows, over and above the pull down shades?
 
Last edited by a moderator:

sgtbigb

Well-known member
Could be a blokage in your out flow ducts, pull the vent covers out, run your hand as far you can to see if there are something blocking the air flow, I hade an similar problem and found loose foam that was blockung air flow.
 
Last edited by a moderator:

NHCelt

Well-known member
I have had issues and posted them on this forum. Assuming the ac's are operating properly, I would check the end of run foam blocks in the duct work. They should be at the end of each duct work channel...front and back. Mine were unsealed and in the wrong place. Moving them helped and sealing them helped a lot more. They were the cause of freezeups on my front ac unit.

I just spent 2 months in the FL Keys and was forced to get by on 1 ac unit. That unit cooled fine, interior always at or near 70. Now that I am back on the mainland and have the 2nd unit up and running, the system is even better. Two units running at once produces enormous cooling power for me.

I have also noticed that the airflow can go over the duct directional vents. It is easy enough to make an airfoil or some such thing to influence that issue. As a rule, these vents really should face front to back...side to side won't catch as much air.

Use the camera on your cellphone in conjunction with a small flashlight as a periscope to see up into the ductwork.

Good luck...Celt
 
Last edited by a moderator:

TravelTiger

Founding Texas-West Chapter Leaders-Retired
I recently bought a 2016 BigHorn 3970 RD, it has the 2 15k ac units. I'm in Texas, the other day it was 85 outside and it wouldn't cool below 74-75. Granted, door side is facing west, there's alot of heat gain on the windows/door, but it should do better. I've already taken it back to dealership and they replaced the living room AC due to my complaints, I'm now realizing it's the ductwork design.

I have one supply in the living area that puts out literally no air flow, when you take the vent off, you can feel air rushing over, just none is coming down into the cabin. when both units are blowing into the same duct per the design, they fight each other and create static pressure issues. The ultimate result is that all the CFM isn't getting down into the cabin. 30k btu should be plenty to cool that cabin, but it's only getting an 11 degree temp drop at 85 degrees, with door shut all day and all shades down.. At 105 it's going to be unbearable.

There has to be a workaround to modify the ductwork to get all the air into the cabin.

Disclaimer: I own an AC company so I know a thing or two about duct design.

If someone could contact me to elaborate on the design I'd appreciate it.

I hope you come up with a solution, we are having similar issues (4010RD is same basic layout). There's plenty of cold air blowing by in the ductwork but it's not getting into the room. We tried adding some heavy cardstock to the vent fins to help direct flow, but it really hasn't made a difference.
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
We did some experimenting this weekend. We removed the adjustable vents and the screwed-in vent frames. Once these were removed, the airflow coming out of the vent holes increased. We experimented with putting just the frames back in, and realized the 1" lip of the frame significantly reduced the airflow coming out of the openings.

The thickness of our Big Country ceiling duct and ceiling panel is only 1/4" thick. So air flowing down the duct seemingly cannot get past the 1" edge of the vent frame to proceed out the vent.

We are still trying to find a solution to this, but wanted to let folks know what we found. We have taken the vents and vent frames off the living room vents, and will have to wait for warmer temps to see if this creates a true improvement.


Sent from my iPhone using Tapatalk
 

danemayer

Well-known member
I wonder if you could insert a ramp just upstream of the vent so the air flows up over the lip/flange.
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
I wonder if you could insert a ramp just upstream of the vent so the air flows up over the lip/flange.

Actually, I've found some vents with a much lower flange (1/4"). We'll see if they make a difference.
 

GETnBYE

Well-known member
THIS IS FROM MY POST ON AN AC ISSUE. MAYBE WORTH A TRY FOR YOU ALSO:
We may have found a possible solution to our ac problem, 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.
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
THIS IS FROM MY POST ON AN AC ISSUE. MAYBE WORTH A TRY FOR YOU ALSO:
We may have found a possible solution to our ac problem, 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 did try this today, before we started taking down vents. It did not help us. With the living room on low, bedroom on high, barely any air would come out the living room vents at all.

Thanks for the idea, though!
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
Let us know which vents you find that improve the air flow. Thanks

They are ordered, I will report back when we get them and installed.

For now, we have just removed the vents and frames (on the output side) for all the LR and Kitchen vents.
 

GETnBYE

Well-known member
We did some experimenting this weekend. We removed the adjustable vents and the screwed-in vent frames. Once these were removed, the airflow coming out of the vent holes increased. We experimented with putting just the frames back in, and realized the 1" lip of the frame significantly reduced the airflow coming out of the openings.

The thickness of our Big Country ceiling duct and ceiling panel is only 1/4" thick. So air flowing down the duct seemingly cannot get past the 1" edge of the vent frame to proceed out the vent.

We are still trying to find a solution to this, but wanted to let folks know what we found. We have taken the vents and vent frames off the living room vents, and will have to wait for warmer temps to see if this creates a true improvement.


Sent from my iPhone using Tapatalk
Erika, I am going to look at your solution as well as my experiments, please share the type of vents you ordered. And where you found them. Thanks, Anita
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
Erika, I am going to look at your solution as well as my experiments, please share the type of vents you ordered. And where you found them. Thanks, Anita

I think that you would need to look at your current vents to see if my problem is your problem with the 1" flange sticking up into the duct.

Here are the vents I ordered with a 1/4" flange.... but like I said, I'm not sure they will resolve it just yet.

http://www.dwincorp.com/products/11/Bigport-9850-Louvered-RV-AC-Ceiling-Vent
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
A suggestion, take a vent off and remove the frame and see what thickness your duct+ceiling height is. Ours is 1/4". I would be curious to know if Bighorn and Landmark are different.


Sent from my iPhone using Tapatalk
 

Toy1Ton

Toy 1 Ton
I have a 2016 3760 EL had mine down yesterday and they are one inch. Thinking about grinding one have of the diameter down to a quarter inch high thinking it might catch some of the air flow and send it down in to the coach
 

danemayer

Well-known member
The thickness of our Big Country ceiling duct and ceiling panel is only 1/4" thick. So air flowing down the duct seemingly cannot get past the 1" edge of the vent frame to proceed out the vent.

Erika,

If I follow, you're saying the distance from the ceiling to the bottom of the vent is 1/4". The flange is 1". So there's 3/4" of flange sticking up into the duct.

And I suppose the duct itself is only about 2-1/2 - 3" high.
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
Erika,

If I follow, you're saying the distance from the ceiling to the bottom of the vent is 1/4". The flange is 1". So there's 3/4" of flange sticking up into the duct.

And I suppose the duct itself is only about 2-1/2 - 3" high.

Correct, the duct is 2-3/8" tall.

d7ea0de7fd6f5e0c7614a794c02b1772.jpg


Louvered vent and frame removed.


4681b8e1f298d678817d81066128b536.jpg


Duct with no vent frame

h
ba69bf3930e66f7d0c091be4dcab16b6.jpg


Vent frame sticking 3/4" into the opening.

Believe it or not, just this frame inhibits a large amount of airflow out of the opening.
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
I have a 2016 3760 EL had mine down yesterday and they are one inch. Thinking about grinding one have of the diameter down to a quarter inch high thinking it might catch some of the air flow and send it down in to the coach

That's a thought. We don't have the tools to try it, but that concept had crossed my mind.
 
Top