Quieting the Roof A/C Units

[dbledan]

Originally Posted by jvalich

I'm unable to do any air flow measurements but by feel, it appears between the Quick Dump opening now being blocked and the much better designed filter element, when sitting on the couch I feel more air movement and indeed, the ceiling vents "feel" like they are blowing harder. I just can't quantify it.

I would suggest to everyone who hasn't, remove the air distribution box and check the installation of the a/c unit. Frequently the openings in the ceiling that makes up the "duct work" running throughout the ceiling is not sealed well. This will cause conditioned air to bypass the duct system and get picked up by the return of the unit. dbledan that could be why your seeing the unit freeze up when you use the duct mode and not when using the Quick dump mode.

Yea I have been meaning to check but just have not gotten there yet. I have a camera to attach to my phone to check it without too much disassembly. I did make sure the return was not open to the output to prevent cold air circulation and there is clear separation there. I could do that without a screw driver using the camera.

I do get cold air out of the vents with or without the dump enabled so it it is not blocked but possibly open to the roof is something i have not checked for yet.

[Thurman]

"jvalich's" post is good. A few months after purchasing my TT (Jan '14) I wasn't happy with the amount of cooled air coming from the A/C unit. I removed the AND and found that nothing was sealed. This allowed cool air to go into the attic area of the TT. Using aluminum tape I sealed the divider between the warm air and the cooled air, the area between the top of the ceiling material and the A/C ducting had at least 1/4" gap--sealed all of that. Then I removed all six ( 6) ceiling registers and found all of them had gaps between the ductwork and top of ceiling material. The duct that goes to the front bedroom had no solid end to it, air blowing into the attic, I used a short piece of foam pipe insulation and duct tape internally to cap that off. I had began to wonder if FR had a new idea of cooling the attic area to keep the TT cool. So now that I have all of my cooled air coming into the TT, the 15K Dometic unit quits on me. Yes, it was under warranty and so we're the other two (2) I had to have. Yes, I'm now on my third Dometic 15K A/C unit and so far all is well

[Larry-NC]

Originally Posted by jvalich

I'm unable to do any air flow measurements but by feel, it appears between the Quick Dump opening now being blocked and the much better designed filter element, when sitting on the couch I feel more air movement and indeed, the ceiling vents "feel" like they are blowing harder. I just can't quantify it.

You can use a dollar bill or a similar-size slip of paper as a poor man's anemometer (wind speed meter). Just hold one end, a few inches from the source and see how much it deflects. This works well if you are doing A-B comparison tests.

Larry

[2ondago]

Originally Posted by frank4711

Help please explain quick dump thanks

I don’t see a response so I’ll try to help. Not sure if all main return vents have this feature or not but it is a combination of a main supply vent and return air vent that can be opened for quickly cooling the local area or closed partially or even all the way to force supply air into the duct system. The question was does this new vent eliminate the quick dump supply option. In looking at the product further it appears it may not be designed for these type vents or they deliberately obstruct the supply.

[2005gts]

Originally Posted by 2ondago

I don’t see a response so I’ll try to help. Not sure if all main return vents have this feature or not but it is a combination of a main supply vent and return air vent that can be opened for quickly cooling the local area or closed partially or even all the way to force supply air into the duct system. The question was does this new vent eliminate the quick dump supply option. In looking at the product further it appears it may not be designed for these type vents or they deliberately obstruct the supply.

I agree, the 'dump' is a worthwhile feature
Bill

[mlmay12]

Originally Posted by 2ondago

I don’t see a response so I’ll try to help. Not sure if all main return vents have this feature or not but it is a combination of a main supply vent and return air vent that can be opened for quickly cooling the local area or closed partially or even all the way to force supply air into the duct system. The question was does this new vent eliminate the quick dump supply option. In looking at the product further it appears it may not be designed for these type vents or they deliberately obstruct the supply.

I looked at the installation instructions and it calls for the sealing off of the area that would allow a quick dump for Dometic AC's and forces all the air into the duct system.

[frank4711]

Originally Posted by mlmay12

I looked at the installation instructions and it calls for the sealing off of the area that would allow a quick dump for Dometic AC's and forces all the air into the duct system.

I have never used the dump feature ... so I might be ok with the quiet ?? How often do you us it??

[2005gts]

Originally Posted by frank4711

I have never used the dump feature ... so I might be ok with the quiet ?? How often do you us it??

here in FL with the temps in the mid to hi 90s the ducted a/c will run CONSTANTLY for 10/12 hours, never shutting off. with the 'dump' it at least cools down quicker and cycles on/off.

try it, report back how it works for you
Bill

[frank4711]

Originally Posted by 2005gts

here in FL with the temps in the mid to hi 90s the ducted a/c will run CONSTANTLY for 10/12 hours, never shutting off. with the 'dump' it at least cools down quicker and cycles on/off.

try it, report back how it works for you
Bill

Yes I am here in central Florida... we have been lucky our sites have had shade for 1/2 a day I will check it out next trip. Thanks Frank

[bedubya]

I have looked at that and decided I do not want to loose the ability to open the vents on the unit. It cools the main living area MUCH faster with the vent open than it does when closed and only blowing through the ducts.

[Jeffjeeptj]

Before I saw this thread, I watched a Youtube video about improving efficiency and sound. As one of the above posts stated, there were a bunch of "holes" between the supply and return. I bought a roll of HVAC tape and sealed up as many as possible. The biggest challenge was closing the gap between the flat plastic air distribution cover (Dometic) and the curved ceiling.
I committed a sin in that I did not use a dB meter before starting the sealing work. DW and I agreed there was a significant improvement (seat of the pants) in ducted airflow, and sound. Scientific method was TV volume on 1 with AC off and 9 or 10 (pre tape work) to a 6 or 7 (post tape). THEN I saw this thread. Being cheap/skinflint/tight I removed the air dump cover and carefully folded a small microfiber towel to fit in as much of the air dump portion of the cover as practical. Re-installed the air dump and now amazingly quiet.
We can watch TV without changing the TV volume and the AC works as it should. Granted we are not in central Florida (used to live there for 15 years), but we were camping at Lake Gaston with temps in the upper 80s/low 90s.
We do not get an improved return filter, but, I did not spend much money. The "dump" function will not work, as the microfiber is blanking that off. Now with effective airflow into the ducting, it seems we will not use the dump. I can always slide off that panel for dump if absolutely needed.

[2005gts]

Originally Posted by bedubya

I have looked at that and decided I do not want to loose the ability to open the vents on the unit. It cools the main living area MUCH faster with the vent open than it does when closed and only blowing through the ducts.

Bill

[frank4711]

Opened the dump vents and seems to work good, still had some air flow out of ceiling ducts ... tested in bedroom with just that unit running ... I can see it would increase flow... at night when outside is cooling off we run just the bedroom while watching a movie or reading and it is colder than we need and when we go t bed we just reverse it and only run A/C in living area quiet as we need ....

[WFMB]

Will this work on all camper A/C's?

[sk734]

You get very poor cooling if you use the ducts only. I bought one of these so called quiet units a Crusader. When in the 90's inside temp was 80's. I open up that cold air pocket where the dump goes and we were camping in southern AL when outside temp hit 100. Inside the trailer RL area was a cool 72 degrees.

[GnS]

My quick dump louver does nothing. It’s a 15K Dometic. I’m wondering if they forgot to do something at the factory. Has this been the case for anyone else?

[sk734]

Originally Posted by GnS

My quick dump louver does nothing. It’s a 15K Dometic. I’m wondering if they forgot to do something at the factory. Has this been the case for anyone else?

Normally there is a hole cut out there. I had to cut mine out. If you don't want to do it have a experienced rv ac guy do it. Good luck.

[2005gts]

Originally Posted by GnS

My quick dump louver does nothing. It’s a 15K Dometic. I’m wondering if they forgot to do something at the factory. Has this been the case for anyone else?

interesting.... the 'quick dump' feature is actuated by sliding a tab in the middle of the louvered section that opens the path from the plenum that is directly above. closing the louver slide blocks off the dump flow and forces the air flow to go to the ducts.

maybe some blocked off the place above the slide so that the dump can't be used even if the slide tab is moved. it's simple enough to slide the tab and look up with a flashlight to see what's going on....
Bill

[GnS]

Originally Posted by sk734

Normally there is a hole cut out there. I had to cut mine out. If you don't want to do it have a experienced rv ac guy do it. Good luck.

I can certainly do the cut out. I’ll take a look. Thanks.

Originally Posted by 2005gts

interesting.... the 'quick dump' feature is actuated by sliding a tab in the middle of the louvered section that opens the path from the plenum that is directly above. closing the louver slide blocks off the dump flow and forces the air flow to go to the ducts.

maybe some blocked off the place above the slide so that the dump can't be used even if the slide tab is moved. it's simple enough to slide the tab and look up with a flashlight to see what's going on....
Bill

I’ve looked at it with cover off. There wasn’t a hole there. Based on the other reply, I’m guessing the factory missed that step.

Thanks to both of you for the quick replies. Much appreciated.

[jvalich]

When you purchase a new ac they don’t come with a ceiling distribution box, at least Dometics are separate. When I replaced the unit I had in my old 5th wheel I had to purchase a new ceiling distribution box because the original had become yellowed and brittle over the years. The distribution box was a separate item. I had a ducted ceiling which allowed me to get the ducted with quick cool. If you don’t have a ducted ceiling then the nonducted model is needed.

I would not be surprised to see manufactures put an incorrect distribution box inside as I’m sure the roof top unit is put in place before the interior is finished.