Ducted Air Conditioning; Sound Level Numbers

[mefly2]

Originally Posted by mefly2

Of course these sound level readings will be relative...but from a SmartTools sound meter app on my phone, I measure: 63 db at 6' while seated at the cushion juncture of the dinette; all a/c vents are open and fan on high. Directly under the main a/c vent and in front of stove: 84-85 db. Sitting on the bed: 65 db. So, as would be expected, the sound level drops inversely by the square of the distance (if you could hear that accurately).

Note that reducing the fan speed lowers the 6' reading to 59db; significant but not quiet nor sufficient flow to keep us cool (75) when the outside temps climb in bright sunshine.

For comparison ... Normal conversation at 3'= 60-65dB
City Traffic (inside car) = 85dB

As promised ... we finally took a break from enjoying / playing in our EB w/ ducted air to get the
following ducted air conditioning sound level background readings;
* fan on high, compressor running *

Seated at the cushion juncture: 54-55 db; down from 63 db / 59 with fan on low; reduction of 8-9 db.
In front of stove directly under inlet for ducted air: 60 db; down from 84-85 db; reduction of 24-25 db !!!
Sitting on the front bed: 54-55 db; down from 65 db; reduction of 10-11 db.

Even by this unscientific means, those difference numbers are significant and dramatic for sound reduction.
The ducted air is also very effective in cooling (and heating) both ends of the trailer (and even the Head).

It is really now quite amazing that we can be sitting in cool comfort and listen to Pandora or a movie at the same time as the AC is on with the fan on high. I can now talk to my wife when she is in the galley area under the ducted air intakes and not even need to raise my voice to communicate. It eliminates the stress of the loud A/C background noise when inside the AS trying to do much of anything other than sleep... we spent much of last weekend just sitting inside of the Eddie Bauer listening to the quiet while the outside temps were above 90 F. Do we like the ducted air and is it worth the depreciation on our trade in ??? YES !!! Emphatically; however, YMMV.

[RVDreamer]

Thanks for the Info, Mefly2.

We have our new 2015 Serenity coming in October with the new ducted air and two a/c units. Can't hardly wait!

[mefly2]

Originally Posted by RVDreamer

Thanks for the Info, Mefly2.

We have our new 2015 Serenity coming in October with the new ducted air and two a/c units. Can't hardly wait!

You are welcome RVD. Hopefully this may help others making the decision between buying a 2014 or a 2015 ...

[Silversun]

We are buying a 2015 23' FC. in just a few days.

I wonder if the 2016 23' model will have ducked air?
Or do they feel is it unnecessary because of the smaller size..

[PharmGeek]

Do we now have some conflicting data? I recall in another thread an RV tech measured ducted vs. non-ducted model and numbers were very similar as I recall. Now these new figures read as dramatically lower.

Seems that most people notice markedly lower levels and easier conversation and such with this new design.

Just wondering why the apparent discrepency.

I am intrigued by this new design for many reasons, and am quite envious of you folks...sounds like its going to be awesome. ENjoy.

[PharmGeek]

"
There is a 27FB with non-ducted air conditioning in the shop now. I took db readings at 4' off the floor at the front, rear, and directly under the a/c unit. The readings for it are:
Front (bedroom):52
Center (under the a/c unit) 60
Rear (at the dinette) 58

We have a 27FB with ducted a/c that is going to be available for testing later today or tomorrow. I will use the same measuring device, at the same elevation and locations in the trailer, and post those figures here when I get them. "

"Okay, I just performed the same test in the same location in the ducted 27, and the results may suprise some people.
Front (bedroom)- 50db
Center (under the a/c)- 61
Rear (dinette)- 57
"

[daveswenson]

Perhaps more important than the raw db numbers are the frequencies involved.

[moosetags]

Along this same line, I have an observation. For almost nine years we had a 2005 Safari 25FB with the then standard 13,500 btu ac/heat pump unit. We spent almost 1,400 nights in that 25FB, and are intimately familiar with the noise level that it produced. Almost a year ago, we replaced the 2005 25FB with a 2012 23FB with the much newer 13,500 btu ac/heat pump unit. We noticed immediately that the inside noise level was significantly higher than the 2005 unit. Both units cooled and heated with about the same efficiency. The new unit is so loud that it is almost offensive. I would hardly notice when the 2005 unit was running.

What the heck happened??? I have always thought that as technology advances, machinery gets better. This is not the case with Dometic RV air conditioners.

Brian

[daveswenson]

I think it would be more useful to see a comparison using an Audio Spectrum Analyzer. This would be more useful than just db numbers.

Audio Spectrum Analyser - free software

[Hibby]

On Friday, we took delivery of our 2015 FC 30' Bunkhouse and although I don't have the proper tools for detailed analysis, I can say without hesitation that the noise levels are AMAZINGLY improved. We ran A/C for the entire weekend (single 15,000 BTU) and LOVED it!




Sent from my iPad using Airstream Forums

[Del Gurney]

Great thread.
I'm sitting in my '05 25 at the moment.
Out in the driveway is a '65 26' Overlander I just got
and gutted...but that's another story all together.
I just turned on my AC for a few minutes to give it a test.
Even on "low fan" I doubt I could sleep with the AC/Heat on
unless it was critically hot or cold.
At this time I'm mulling over what kind of climate control to
put in the Overlander.
I full time in the Safari (in a barn so that helps a lot) and
even in the dead of winter I get by with a little Honeycomb
Ceramic heater and only fire up the furnace if I've been away
but just long enough to get up to 70F then the ceramic heater
takes it from there.
I'm not going to put a furnace in the Overlander - it's too loud
and scary.
The basic thing is (to me) that one wants heat coming from floor
level as it rises so I'm considering building in 2 ceramic heaters.
One wants "cold" coming from above as it sinks and I think ducting
to locations near the bed (s), lounge and maybe the shower/head
would suffice.
These roof top installations, though industry standard, seem really
weird to me b'cuz it's like saying "Lets put the noisiest appliance
right in peoples faces".
So I'm just going to throw this out there:
"Why not put the AC unit under the trailer, insulated mounts, and
plenum the AC up to ceiling ducts".?? Seems to me the fan could
"push the air" up 7ft.
I realize that I would have to be very creative in protecting the unit
"in the bilges" but these new thin units would fit in the area above the
belly pan I expect.
I also realize accessing for service would be an issue but I've had
the belly pan down as part of an under-carriage refit and am just starting
to drop the one on the Overlander.
I looked under some SOB's and note that some use a heavy mesh type
material and I've concluded that this Alum. belly pan is a bunch of hard to
remove nonsense...it also conducts heat/cold right through.
The Overlander is getting mesh that can be removed WAY easier.

Moosetags: could it be that in your "05 Safari you had soft fabric interior and
attenuated the noise somewhat vs. your newer one with the Alum. walls?

Any comments would be very welcome.
Del

[Foiled Again]

Originally Posted by Del Gurney

Great thread.
I'm sitting in my '05 25 at the moment.
Out in the driveway is a '65 26' Overlander I just got
and gutted...but that's another story all together.
I just turned on my AC for a few minutes to give it a test.
Even on "low fan" I doubt I could sleep with the AC/Heat on
unless it was critically hot or cold.
At this time I'm mulling over what kind of climate control to
put in the Overlander.
I full time in the Safari (in a barn so that helps a lot) and
even in the dead of winter I get by with a little Honeycomb
Ceramic heater and only fire up the furnace if I've been away
but just long enough to get up to 70F then the ceramic heater
takes it from there.
I'm not going to put a furnace in the Overlander - it's too loud
and scary.
The basic thing is (to me) that one wants heat coming from floor
level as it rises so I'm considering building in 2 ceramic heaters.
One wants "cold" coming from above as it sinks and I think ducting
to locations near the bed (s), lounge and maybe the shower/head
would suffice.
These roof top installations, though industry standard, seem really
weird to me b'cuz it's like saying "Lets put the noisiest appliance
right in peoples faces".
So I'm just going to throw this out there:
"Why not put the AC unit under the trailer, insulated mounts, and
plenum the AC up to ceiling ducts".?? Seems to me the fan could
"push the air" up 7ft.
I realize that I would have to be very creative in protecting the unit
"in the bilges" but these new thin units would fit in the area above the
belly pan I expect.
I also realize accessing for service would be an issue but I've had
the belly pan down as part of an under-carriage refit and am just starting
to drop the one on the Overlander.
I looked under some SOB's and note that some use a heavy mesh type
material and I've concluded that this Alum. belly pan is a bunch of hard to
remove nonsense...it also conducts heat/cold right through.
The Overlander is getting mesh that can be removed WAY easier.

Moosetags: could it be that in your "05 Safari you had soft fabric interior and
attenuated the noise somewhat vs. your newer one with the Alum. walls?

Any comments would be very welcome.
Del

Del and others....

Read about the split system install Smokeless Joe did in his Argosy. He's decided to retire from RVing so it's currently for sale in the classifieds. Here's the link to the thread on his unique view of restoring.

One thing I really admire is the "totally diesel" Argosy - no "kaboom" factor as can be associated with propane.

http://www.airforums.com/forums/f227...ase-18448.html

Paula

[CDONA]

I have lived full time (10 years) in an Alfa with the basement air/hp. Aside from the compressor starting whump, quite easy to live with. Now with the 15K unit on the roof, summer in Az, I hate the noise, I have to crank up the volume on everything, headphones help, but the noise of it all wears on me.

[mefly2]

Originally Posted by PharmGeek

Do we now have some conflicting data? I recall in another thread an RV tech measured ducted vs. non-ducted model and numbers were very similar as I recall. Now these new figures read as dramatically lower.

Seems that most people notice markedly lower levels and easier conversation and such with this new design.

Just wondering why the apparent discrepency.

Listen to Hibby...

... and, I stand by my previous numbers; I took the time to measure and share the information... they were triple checked. I compared apples to apples in a 2013 Eddie Bauer 25 versus our current 2015 Eddie Bauer 25. They were both owned by me and the measurements were taken by the same software using the same device in the same location with the trailer parked in the same spot - not a shop environment. ... we would expect the same background noise to be present. Pick the numbers apart if you wish!

My frequency analyzer between my ears expressed a significant reduction in noise level between the ducted and non-ducted. If it would be more useful and you are inclined to get more specific with a spectrum analyzer, then I applaud you. Apparently my efforts to be helpful do not meet with the approval of all; however, they were good enough for us to make the significant new purchase of an Eddie Bauer with ducted A/C.

Seated at the cushion juncture: 54-55 db; down from 63 db / 59 with fan on low; reduction of 8-9 db.
In front of stove directly under inlet for ducted air: 60 db; down from 84-85 db; reduction of 24-25 db !!!
Sitting on the front bed: 54-55 db; down from 65 db; reduction of 10-11 db.

Even by this unscientific means, those difference numbers are significant and dramatic for sound reduction.
The ducted air is also very effective in cooling (and heating) both ends of the trailer (and even the Head).

[PharmGeek]

I apologize if I seemed to be dismissive of anyone's contributions....not my intention. Instead by me regarding the contributions of both airforums members as they both appeard rigorous in their methods, I was left to speculate how this came to pass.

I greatly appreciate all that people have contributed regarding these new units...and indeed, I would go on to say that if I had not bought my 2014 bunkhouse in late summer 2013, and was doing it today, I indeed would have bought the 2015 unit...not only for what appears to be more quiet operation, but also improved airflow distribution....

I just wish that I did not have a macerator electric toilet...have not had a problem yet, but I just cringe to think about the annoyance of it if/when that occurs.

[RVDreamer]

Really it is hard to say what might be causing a discrepancy in the sound level numbers.

It could be background noise not related to the A/C. It could be different fan speeds in the A/C. I suppose that even different A/C units may have different sound levels.

Airstream says that the new ducted A/C is significantly quieter, insulation is much greater, and the distribution of air is improved.

I really see no reason to doubt their claims.

In order to do a real test you would need to be in a sound proof theater, use the same A/C unit in the same trailer, once built with ducted A/C, built again without ducted A/C. Sound levels would then need to be measured in many locations, mapped, contoured, and calculated to see what the RMS levels were on average in each case and compared.

[Hibby]

I would agree with Airstream's claims on all three points. We were running on LOW the entire weekend with no problems cooling. I tried turning down to 65 briefly to create a 20 degree difference from ambient temps and it got there in less than 20 minutes. We only have one AC Unit.

I'm confident that I'll be able to use it as a meat locker during deer season.

We'll use the air conditioning frequently now whereas before we would not use it because of the noise and poor distribution.


Sent from my iPad using Airstream Forums

[mefly2]

Originally Posted by RVDreamer

Really it is hard to say what might be causing a discrepancy in the sound level numbers.
...
In order to do a real test you would need to be in a sound proof theater, use the same A/C unit in the same trailer, once built with ducted A/C, built again without ducted A/C. Sound levels would then need to be measured in many locations, mapped, contoured, and calculated to see what the RMS levels were on average in each case and compared.

Real test ???
I posted REAL World comparison numbers
... take them for what it's worth to you! For all practical purposes (and to a reasonable person as opposed to a theoretical analysis), the unscientific numbers I posted give a very unbiased and fairly accurate "view" of the new ducted A/C.
All this pontificating ... over what is considered by most 2015 owners - to be a real improvement- at least it is in my mind ... YMMV.

Again, listen to Hibby ...

Originally Posted by Hibby

I would agree with Airstream's claims on all three points. ...We'll use the air conditioning frequently now whereas before we would not use it because of the noise and poor distribution.

[rodsterinfl]

Hey Pharmgeek, and everyone else. I am the one who did the dB numbers and compared it to my 2006 unit. They too are "real world" findings. I had to wait for a ducted Airstream to arrive at my local dealer. They were nice enough to plug in the power for me to run the comparison. I used the same meters to measure sound on both my unit and the new ducted AS. I also measured the distance from center area and both ends. Naturally the meters may/may not be matched perfectly to actual dB calibration (heck they both measured different starting point dB levels but, for comparison, they worked well. The conclusion was that the difference was as not as significant as I thought it would be. I posted the figures somewhere last year on the forum.

To me in FL, the AC is a critical part of my AS use. So, AC improvements/ducting is a major factor. I admit that there are two biases involved in my thought 1) that SOB reports I've read of ducting claim long cool times requiring temporary bypassing to cool down the trailer/motorhome, that there is benefit only after the trailer is cooled, hotter days require bypassing to maintain cooling. AND 2) I would compare it against my own unit in cooling and noise to gauge actual benefit.

First, the ducted units are quieter. That said, as someone else pointed out, there is a huge difference in noise level of the pre-2009 or so Dometic AC units and the post-2010 units. They changed compressors and cooling agent. There was an article on RV forum where one guy spent hours dealing with Dometic on his roof unit replacement as the new unit he bought was so much louder that he assumed something was wrong with it. After a second unit replacement Dometic came up with a grommet kit of some sort that finally lowered the volume to, as he stated, similar to the original and his other unit's noise (he had two of the same but had only replaced one, the other was original). My unit is pre 2009 so it would be, by description, quieter. I have now had the opportunity to experience a 2013 AS dometic AC at the dealer and, IT IS LOUD. So, what Moosetags is saying I have experienced as well regarding the old to newer non-ducted units. I believe it is more roof vibration. One improvement made to the non-ducted units post 2007 or so was the ADB multi-directional air-flow ducts. I fitted one to my unit removing the heater element. It made a big difference for my camping. The original box had limited front/rear air up/down control- no straight down or sides. When in summer, the front cools down faster. Once cool, I turn off the front, open the sides and direct it rearward where the back cools better. Could not do that before where it would blow cold air on your face all night as the only option.

I was in Costco the other night and noticed how quiet the Delonghi portable AC unit operated. I still believe there is much more that could be done with ac in RVs. Ducting, though new to Airstream is not new to RVs.

[mefly2]

I stand by my previous numbers and procedure.
Ducted air is SIGNIFICANTLY quieter!