Ducted Roof Air - questions

[rv_safetyman]

I am getting a bit closer to doing my ceiling.  I have Carrier AirV units and want to think about ducting them as opposed to my present non-ducted system.

Questions:

1)  Does ducting reduce the noise?  My units are pretty darn noisy.

2)  What material do use to fabricate the ducting?  Manual says that it should be insulated.

3)  What do you use for the outlets?

Thanks for any help.

Jim

[Nick Badame Refrig/ACC]

Hi Jim,

Are your Carriers set up electrically for ducted? I mean the controls.

Jim, you can use ridged poly styrene, 1" would do fine. Then use aluminum foil tape to seal the joints. [Duct tape will not last as long]

For your outlets, travel trailer/motor home, 3" ceiling vents will work good available at any rv supply.

Good Luck
Nick-

PS, it's hard to get a Carrier quiet... lol

[jjrbus]

I have been listening to my ducted roof airs roaring away for several years!  I am sitting here one day and had a moment of clarity, the light bulb went off over my head.  I DID NOT duct the incoming air!!!!!!! The motor, fan and compressor are just seperated from the living area by a thin filter!! Just no fixen stupid!!!  Way too late for me now, but not for you.
After reasearching, I used wood for my ducts, been about 7 years now with no problems.

[luvrbus]

Jim, my daughter has ducted Carriers in her 5th wheel and they are quite plus they have a remote control and you need 12 volts to make the units work cost me 85 bucks to find that out

[JackConrad]

Jim,
 I made my ducts from an insulated duct board that is only 3/16" thick. It comes in 4X8 sheets, (that they will cut  down to make "UPS Shipable"). The board consist of 1/8" high density closed cell foam with a layer of heavy aluminum foil on each side. It is cut, creased and folded to make the ducts, using the aluminum tape to seal the joints. I got it from Innovative Energy, Inc in Lowell, Indiana. 1-800-776-3645. No interest in this company, just passing on a good supplier for us busnuts.  Jack
PS: HAPPY BIRTHDAY, i missed that the other day.

[JohnEd]

I read a while ago that ducted was definitely quieter.  It will also cut down on the "effective" BTU of the unit.  That seems plausible to me just on the surface.  Another Knut said he integrated a squirrel cage blower to augment the AC units internal unit and he recovered the cooling he lost to ducting back pressure.   He must have been talking about an AC basement unit as i haven't a clue how you could do that for a roof top.   I also read that a roof top can be made more efficient if you take off the shroud and let it "dump" directly into the room.  That makes some sense, also.  Good info if you get jammed up at Furnace Creek or Lake Havasue and the mercury hits 120.

If, and I mean "IF", I use roof tops I will install three.  They are noisy and intrusive, I know from experience.  With three I expect I can run two at the "other" end of the coach and keep everything cool  8)and circulated and I can stay in the quiet(est) zone.  Just my thoughts.

John

[jjrbus]

John, that is what I do. If in front I run rear AC, if in bed, I run front AC.  HTH Jim

[rip]

Jim; I also used the material from Innovative Energy and it is really great stuff. I have 3 roof airs and used fourteen 4"round vents in the ceiling.After fulltiming for 5 years this system works for me.
   Don

[FloridaCliff]

Jim,

I have the Carriers with the ducted option.

I used used a 3/4 rigid insulation panels to build my ducts, each piece was taped and duct sealant applied.

There is a formula from Carrier for the overall duct size and area of the outlets required.

I ran a split duct system, one down each side of the the main distribution trunk connection.

The passenger side, because of the spin of the fan has a higher CFM of air.

The ducted are much quieter than the standard blow down setup, but not as quiet as most basement air.

I ran ducts all the way up to the driver and the only thing I have left to do on mine is add a in-line duct blower for when I want a little more volume when heading into the Sun.

Almost forgot one thing, I had to build an extension of the main distribution due to my ceiling being dropped from the roof line.

Best of luck

Cliff

[Greg Roberts]

I used 3 Carrier AirV roof air units with the digital remote controls. For the rear unit I ducted to 2 outlets and I also ducted both outlet sides of the unit forward to the 6 bunks. Each leg turns down into a set of 3 bunks and each bunk has one 2X6 outlet. The driver side also is ducted to the bathroom.

I ducted the center and front units together into two main ducts that run from the center of the coach all the way to the front. Each outlet has a closable vents so that I can force air from both air units to the front greenhouse area if I need to do so. I can also run only one of these units and serve all of the mid to forward area of the coach.

I did raise the roof on my coach and dropped the ceiling back to allow room for the ducts and plant of refer foam insulation. This required fabricating extensions for the extra thick area between the ceiling and the outer roof.

The ducts are made from a high tech foil covered foam (not really as high tech as the manufacturers think) that is only 1/4" or so thick and the joints area taped together with foil tape. All turns are long radius to reduce back pressure. I can't remember the brand of material I used at this point but I believe a search of my threads in this and the other bus forum will show the name brand.

I have had the coach in 110 F weather and did just fine on 2 units while still and I use all three units underway in the hottest of weather.

I can run on a 20 amo pole with one rear unit going in very hot weather and be just fine with the sliding door shut.

The units are fairly quiet as compared to the normal roof air configuration, however, the roof air units are much louder due to non ducted air intake. On the good side though, the units blow very strong and do a great job with a duct with few turns and restrictions that most basement units tend to have.

I personally love the ac units on the roof because I WANT my coach to look like a bus conversion as opposed people coach and I also love the flexibilty for for removal, repair and replacement. I also like the extra room in the bays. Lastly, to do the sort of ducting that I wanted to do made the roof units much better in terms of ducting restrictions and I like the idea of having the lower area completely gas sealed from the people area.

Good luck doing it your way!

[makemineatwostroke]

I have 4 ducted low profile penquins on my Eagle a 45 ft bus and do not like the looks of them would love the look of a peoples bus if it wasn't for the extreme cost to remove them I would do it and go with basement or a split system.Prevost converters spend large bucks for faring to hide the roof tops I notice

[JohnEd]

MMA2,

But how do they perform.  Gotta be enuf cooling.  Hot spots?  Noise?  How many needed to handle 100F ambient?

I think the splits are very cool

John

[makemineatwostroke]

Johnny  I use 2 and 3 most of the time but in Vegas when it was 117 I used all 4 at Circus Circus in the sun but they do not move enough air on low so the 3 speed is not a great option for me very seldom can you run them on low and you get the drip condensate when in Houston and New Orleans or the Gulf Coast.I think the splits like Cruise Air or basement models would be the best way to go.And I also had 2 with seals leaking and that is hard to detect and locate when they are ducted and sooner or later they will leak so I am told