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Old 06-03-2004, 01:19 PM   #1
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Refrig fan noise FIXED...really

Although a thread was started on this subject, it really belonged in this section. I am going to describe and attach pics showing how I totally FIXED the noisy fan issue and actually improved airflow at the same time.

Using SilenX fans (www.silenx.com), I created a new refrig cooling unit that utilizes 2 of the 120MM 11DBA fans. I purchased mine directly from SilenX for $55.75 including shipping. These fans are large volume, high efficiency fans with quiet blade technology. They also come with silicone mounts to further isolate any noise produced.

My goal was to eliminate BOTH inside AND outside noise as both were major issues with my '02 Bambi (shared with all recent models lacking roof ventilation for the refrig).

In designing my new cooling system, I made a significant change from the original design in that originally, the fan mounted vertically and PULLED air thru only the center 4" of the refrig condensor. The design of the outside door greatly restricted the airflow exhaust plus it forced the air downward where it could be immediately pulled back into the lower louvers of the vent and circulated back thru the condensor (ie a hot air short circuit). In my new design, the fans are mounted BELOW the condensor and PUSH air thru almost 9" of the condensor. I also eliminated the potential for the hot air short circuit by blocking the section of the upper access door residing below the fans (ie incoming air NOW is pulled from the lower door which is about a foot lower). All of this will be clearer in the pics.

As I was installing 2 fans, I also added the ability to run them either in series or parallel (electrically speaking). Running in series, they run quieter while still moving significant amounts of air. In parallel, I have max cooling and very acceptable low amounts of noise.

Results...FAR better than anticipated. Even when running full speed (ie in parallel), the fans are virtually silent. You have to put your ear DIRECTLY against the upper door louvers to even hear anything. In series mode (half speed), there is simply ZERO noise...PERIOD. Inside, running full speed in parallel mode, you can barely hear a slight noise, BUT it is MUCH quieter than even the Magnetek converter fan. In series mode, NOTHING inside or out.

Okay for the details. I purchase aluminum angle stock, aluminum bar stock and aluminum sheet stock at Home Depot.

Using the aluminum angle stock, I made two brackets that actually hold the fans. I cut away the section of the aluminum that would otherwise have blocked a section of airflow on both fans. Using the included silicone mounts, I mounted each bracket to the fans. As the two brackets are NOT attached to each other and the silicone mounts are very flexible, I also made small brackets that mount on the top of the fans as well as the side aluminum brackets. This provides rigidity at the expense of some of the noise isolation capability of the silicone mounts (minor).

Using the aluminum bar stock, I cut a length the width of the upper door opening and riveted it to the fan assembly backets already constructed. This acts to support the front edge of the fan assembly. I also cut another section of bar stock and bent it to form a support going vertically from the backside of the fan bracket thru 2 bends such that it arrives at the same plane as the solid bar attached previously, but several inches lower. This bracket acts as the rear support for the fans. The fans do NOT touch the refrig at ANY point as this could allow noise to transmit thru the refrig to the inside of the trailer.

The final additions were some baffles to direct the airflow more precisely. The new fans, being slight wider than the condensor above needed a small baffle to ensure that all the airflow was THRU the condensor and NOT creating a air barrier to escaping hot exhaust air from the condensor. You can see this baffle located in the center section of the horizontal mounting bar. I also added another baffle at the top of the refrig cabinet as the original baffle left a dead air space that trapped hot air above the upper louvers of the access door. I made a baffle that extended from the top edge of the upper door to an area just above the rearmost portion of the condensor and then angled it downward to where it was 1/2" or so above the top of the refrig. This pretty much mirrored what A/S installed, but mine eliminated the dead air issue. I left the original top baffle in place. You can see this baffle in a follow on email as I already have the max 5 attachments on this post.

BTW, the curvature seen in the pics is a artifact of my wide angle lens

After removing all the original fan hardware, I installed the new assembly as shown in the attached pic.

david
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Old 06-03-2004, 01:27 PM   #2
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Cooling fans PART 2

As you can see, I mounted the new assembly to the upper access door frame. I mentioned the upper baffle that I added and you can see it in the first pic below. Again the reason was to ensure that as hot air exited the condensor area, it travelled immediately to the outside via the door louvers.

The last baffle is to ensure that the hot air short circuit is not possible and you can see it in the last pic below. I simply cut a panel of sheet aluminum to fit the area below the fan bracket. Now I can be assured that all the incoming air is from the lower access door louvers. I also sealed the lower section of this baffle with silicone sealant as I have noted rain can blow in and collect in the lower section of the door frames.

I did not mention that I removed the original on/off switch and replaced it with a DPDT toggle switch mounted in the horizontal support bracket. This is a center position off switch, so I can switch from parallel to off to series modes. I have actually thought about adding a led indicator so that I can tell if the fans are running as they are so silent.

Sorry if this turned into a dissertation, but I wanted to provide sufficient detail so that others that wanted to duplicated my efforts would understand how, what, and why.

Lastly, I had the opportunity to field test the new design over the Memorial Day weekend. The daytime highs were in the lower 90s and I found the fans cycling on and off during the day, something the old design NEVER did. I also noted that the fans shut down shortly after sunset, again something that used to take an hour or two with the old design. These observations were made with fans running at full speed. I never switched them to series/half speed as I wanted to understand how well they worked and how much noise they created. I also measured the current drawn...in series mode, about 90ma, in parallel, about 260ma, meaning about 1/4AH MAX.

david
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Old 06-03-2004, 02:09 PM   #3
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David,

Looks good! Only one question. Does your refer compartment have two louvered doors?. I cannot tell from the pictures so I was curious regarding the intake of cooler ambient temperature air.
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Old 06-03-2004, 02:32 PM   #4
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Hey David.

Quite a job.

Question: Do your new fans completely replace the existing fan? I am assuming tthat there are just two wires going to the set-up. Is there a plug that just plugs into the new fans, or are they hard wired?

Nice job.

Jonathan
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Old 06-03-2004, 02:58 PM   #5
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David,

Can you share the dimentions of the fans. I have another application I am thinking of and need the measurments to see if those will work.

Thanks,

Eric
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Old 06-03-2004, 04:37 PM   #6
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Answers to questions

Yes, our unit has a 2nd louvered door just below the one you see in the pics. (see pic below). A/S uses this two door design all units without a roof mounted vent. With my redesign, NO air can be pulled in from the upper door, so all my incoming air is draw in from the lower louvered door and therefore is cooler and ensures a good flow of air when running on propane. Also as I mentioned, the factory design did nothing to prevent exiting hot air from being pulled immediately back thru the lower louvers on the upper door. This problem was really compounded when the entrance door was latched against the trailer. All in all, the original design showed a lack of any engineering or understanding of the how air flows.

Yes, the new fans TOTALLY replace the factory original. I can gladly send the wiring diagram showing the original and new configuration which includes the switch to allow half/full speed or OFF to be selected.

SilenX makes a whole series of fans. The ones I used are 120MM or about 4.75" square. The fans are 25MM or 1" thick. Check out www.silenx.com and you will see the series. Of course, the smaller fans move less air, but all are high volume units for their size. If noise reduction is what you are after, then order the lower DBA rated units. For every 3DB reduction in noise, you cut the noise level in half. So in the 120MM fans, 1 is half as noisy as the other, but the noisier unit moves almost 50% more air. After my success with this project, I am also thinking about changing out the horribly noisy fan in the stove exhaust. There is plenty or room for a pair of these fans in the housing and the amount of air these babies move is impressive. I am also thinking about using one of the smaller ones as a replacement in the bathroom vent. And there is also the fan on the Magnetek inverter. I can live with the Fantastic fan as is, especially since it moves a LOT more air.

david
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Old 06-03-2004, 09:17 PM   #7
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David,

Sweet!!! I'm printing out your instructions right now and ordering up the fans too. Thank you for all the brain and lab work. I did an acceptable fix with the existing fan that can be seen on the thread titled "16CCD owners" but yours looks so much cleaner. Jamie
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Old 06-17-2004, 12:44 AM   #8
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It looks like there are some differences between the pictured 19 footer and my '04 16CCD. It would be much more difficult to mount the fans similar to this horizontal config. Instead, I mounted two Silenx 120mm 11 dB fans in the vertical position directly in front of the refer. cooling fins (in series), then added an aluminum sheet (baffle) screwed down into the lower edge of the upper access door which angles inward to the base of the fans; this to pull more air from the lower chamber. I am hoping this set up will still move sufficient air. The thing makes noise similar to cotton candy dropping on down pilllows. The previous fan started with a 5 second whine which sounded like a police siren a block away, then settled down to an annoying hum. If I were AS, I would be reading these posts and having my boys draw up a contract with Silenx folks.
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Old 06-17-2004, 01:16 AM   #9
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Halaleuah! I thought an air raid was going on every time my frig fan started up last night trying to get to sleep boondocking! I hope A/S is watching these forums so they can learn a thing or two! Now does it work on 22' CCD? I would want to call A/S to complain that this is not an acceptable design, and want a fix for my A/S (only 3 months old). Are you sure that this design will work on 22' CCD? If so, I think A/S should pay for this upgrade! (Or should I pay you for the grunt work to figure this out)
Great work!
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Old 06-17-2004, 07:48 AM   #10
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Sleep....

While MUCH is dead on with the Airstream designs and associated engineering, there are things that simply scream for improvement. A/S will not pay for changing out the fan as the factory design does the intended function (oh, you wanted to sleep...too bad).

If I recall, the 22CCD has the 3cu ft refrig, while the 19' models have the 4cu ft. I suspect that your unit has the smaller, molded outside doors like the 16' Bambi which uses the same refrig. I feel that my design could be adapted. While you could take Frozen Chosen's approach and mount them vertically along the lines of the original, I see no reason that with some simple engineering of a slightly different lower support arm, my design would not work as well.

Here to silenx....

david
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Old 06-26-2004, 07:02 PM   #11
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The photo below shows how I adapted the fans to fit my 16' CCD. I kept the silicone mounts on the bottom and added rubber washers for the top which I screwed directly through the top access door thinking this would isolate the vibration just a little bit more. Didn't bother with any baffles. Worked great. First night we were right on the beach so we wouldn't have even heard the factory fan but subsequent nights it was very quiet and the fans shut off early. But then again we were near the coast and it never got above 68 degrees. Still, I highly recommend this fix.

Many thanks to David for all of the information and help. To all that try this, be sure to remove the resistor that is attached to the fan wires or it will run too slow. Jamie
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Old 06-11-2005, 10:20 PM   #12
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I have a 2004 19 ft. Bambi with a very noisy refrig fan. I purchased two 12 v. 120 mm fans from silenex. I am not sure to how to wire them. Can you help me. I believe you gave a discussion of wiring in another thread, but I can's find it.

Will wiring in series burn up the fans? How did you wire so that can run in parallel of series?

Larry
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Old 06-11-2005, 10:33 PM   #13
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Wow! Talk about a helpful thread. I purchased and installed one Silenex fan for my 22' CCD a year ago (it fit perfectly in the exisiting bracket), and had a BIG reduction in noise (almost silent) and very good airflow. However, I have camped in temps over 100 and find I can use more airflow. So, I will be adapting the ideas here and will install a second fan soon. Keep up the suggestions!
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Old 06-11-2005, 10:35 PM   #14
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Rivet On off switch

I think AS has looked at this issue and have come up with some what of a solution. I noticed on an '05 Bambi model that near the front dooe there is an on off switch that turns off the fan. Not sure if this is a good fix or not but at least you will be able to sleep at night.
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