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Old 09-08-2013, 10:12 AM   #15
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I mounted 3 of those 12v pancake fans near the top of the "chimmney", just under the top vent, to help exhaust the heat. I also constructed a baffle back there to close up the space. There is some good reading on here about frig problems and some cures.

Due to the nature of the Airstream design there is way more space behind the the frig that it needs to exhaust properly. Baffles and fans help to get the heat out.

John
John

I could not agree more. The shape of the Airstream with the curved walls behind the fridge requires the installation of baffles to get the best performance from the fridge. The reason that it is important is not to get the heat out, but to increase the heat transfer from the hot air behind the fridge to the coils and the condenser. The baffles direct the air flow through the coils and fins, not allowing the air flow to bypass around them. The baffles and fans also increase the velocity of the air flow which increases the heat transfer to the coils and condenser fins.

The use of baffles and fans improves the performance of the fridge in two different ways. First, it lowers the temperature of the fridge for a given setting. For example, I have my fridge set on two and the fridge temperature varies from 34-38 throughout the day. Without the installation of these baffles, the fridge temperatures would be much higher like maybe 44-48, I don't really know because I did not ever operate the fridge on setting two before I installed it with the baffles. The second advantage is that it takes less energy to operate to maintain a certain temperature. For example, I used to run my old fridge on the max setting to keep it under 40. This meant that it was running all the time. With my new fridge and the installation of baffles, I set it on two, 34-38 is maintained in the fridge, and it operates the heater element only 60% of the time. This saves 40% of the fridge energy bill. Details of this test are in a separate thread.

I am curious how much baffling Airstream installs behind the fridge in recent models. My 66 Tradewind did not have any.

Could you please provide a photo of your two fans in the plenum? I may install some to see how this affects my fridge performance and efficiency.

Thanks, Dan
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Old 09-08-2013, 10:30 AM   #16
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I pulled the frig out to mount my fans. Not hard but but a 2 person job to get it out, move it out of the way.

Mounted the fans on a board that went across the width of the chimmney, under the top vent. Wired them together, hooked in to the 12v on the terminal block on the back of the frig. I used a switch, located inside the rear vent compartment, instead of a thermostat. Works well. Sorry I didn't take any pix.

Another option is to simply put a regular 10-12 inch household fan inside the compartment, lying on it's back, pointing up. The 110 is already there in the compartment where the frig plugs in. Mine has a double receptacle there. Won't work for boondocking of course but sure is a easy, quick fix, and that fan puts off a bunch of air.

John
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Old 09-08-2013, 04:10 PM   #17
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Another option is to simply put a regular 10-12 inch household fan inside the compartment, lying on it's back, pointing up. The 110 is already there in the compartment where the frig plugs in. Mine has a double receptacle there. Won't work for boondocking of course but sure is a easy, quick fix, and that fan puts off a bunch of air.

John
If there is adequate room, 13.5" x 13.5", you could use an endless breeze fan by Fantastic that operates on 12v. That way you could use it while boondocking without the need for an inverter.
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Old 09-08-2013, 08:16 PM   #18
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Quote:
Originally Posted by sandlapper View Post

Mounted the fans on a board that went across the width of the chimmney, under the top vent. Wired them together, hooked in to the 12v on the terminal block on the back of the frig. I used a switch, located inside the rear vent compartment, instead of a thermostat. Works well. Sorry I didn't take any pix.


John
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Installing 3 computer fans to help the airflow sounds like a good idea. I think that I am going to try installing 3 fans in the inlet to the fridge vent area that is accessible from the bottom of the belly pan. This should help my fridge operate even more efficiently. We will see. I just ordered 8 of them off Amazon for $25 including shipping. Here is the link in case anybody is interested:

Amazon.com: Cooler Master 120mm Silent Case Fan 4-in-1 Value Pack - (R4-S2S-124K-GP): Electronics

I just may take the extra computer fans and make a "window fan" to install in one of the side windows to provide some economical cooling at night.

Dan
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Old 09-08-2013, 08:27 PM   #19
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Two other places popular with the fan crowd:
  1. Under the top horizontal row of cooling plates on the back, fans blowing up and through them.
  2. Inside the refer in the lower section, clipped to the fins. The purpose is to move the air around inside the refer to give max cooling.

Here is a link to one of the cooling unit refurb companies that has a neat solution for the inside ones.

I want to try all of them, but it's tough to get my DW to loosen her grip on the existing refer so that I can experiment with mounting the four fans I want behind the refer, and the two inside.
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Old 09-08-2013, 08:47 PM   #20
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Here was brief thread

Quote:
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Did you discuss this here or post photos? I'm about to add fans and I'd love to see your installation..?
Look here:
http://www.airforums.com/forums/f425...ns-109193.html

Of course fused. I picked up 12v from 12v power at fridge access door.

Edit... Got proper and stable temp after 24 hours.. Took 36-48 hours before fans.
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Old 09-08-2013, 09:47 PM   #21
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Originally Posted by Aage View Post
Two other places popular with the fan crowd:
  1. Under the top horizontal row of cooling plates on the back, fans blowing up and through them.
  2. Inside the refer in the lower section, clipped to the fins. The purpose is to move the air around inside the refer to give max cooling.

Here is a link to one of the cooling unit refurb companies that has a neat solution for the inside ones.

I want to try all of them, but it's tough to get my DW to loosen her grip on the existing refer so that I can experiment with mounting the four fans I want behind the refer, and the two inside.
Aage

It does not matter where you put the cooling fans- at the top, at the bottom or in the middle by the fins. The increased air flow will improve the fridge performance by improving theheat transfer to the fins.

The only space I have to put fans is at the bottom.

Thanks for letting me know what other folks are doing to improve fridge performance.

Dan
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Old 09-09-2013, 10:38 PM   #22
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Quote:
Originally Posted by Aage View Post


Here is a link to one of the cooling unit refurb companies that has a neat solution for the inside ones.

.
Aage

Thanks for the great link. They sell three great ways to improve fridge performance. And they are all low cost: a baffle to direct flow through the condenser, fans to increase airflow past the condenser and interior fans to increase air flow past the evaporator fins. Anybody who has a fridge that is warmer than desired should try these low cost solutions.

Dan
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Old 09-10-2013, 01:23 AM   #23
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Fan location is important, further from the fins requires more air flow which consumes amps. If you want low electrical draw and maximum benefit you can consider a solution like mine. I get 34-36 on setting 3 on 95+° days. Check this thread for pics:

http://www.airforums.com/forums/f44/...ms-106595.html
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Old 09-10-2013, 06:25 AM   #24
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Our B190 had a fan above the exterior coils, that was on a thermal sensor and controlled by a switch inside - so the switch had to be on AND it had to be hot enough for the fan to run. After I figured out what it was, I bypassed the thermal sensor - I felt it was set too hot; that it should have allowed the fan to run at a somewhat cooler temperature. (It took me a while to figure out what the switch was for, because it didn't do anything the first few times I tried it - it wasn't until I happened to leave it on during a really hot trip, then heard a sound outside and investigated.) The B190 had the same disadvantage mentioned by someone else in this thread for their trailer - no roof vent, just two side vents, so air flow probably isn't as good as it should be.

We also bought a fan for inside the fridge that required two "D" batteries to operate. It seemed to help. They're perhaps $15 at RV supply places.

The night before a trip, I would move the B190 to the street and park it on the curb so that I could get it fairly level, then start the fridge. It was nice and cold by morning, and we'd load it then before heading out (which was kind of hard on keeping it cool, but what can you do?).

The (relatively new Norcold) fridge in our trailer, though, doesn't have either of those, and it works far better than the fridge in our B190 ever did. We also have the advantage now that we can start the fridge at the beginning of the season (March-ish for us) and leave it run through the end (our last trip each is usually over Christmas, but we had one in January this year); I suspect the B190's fridge would have done somewhat better if it had had this advantage too. Knowing how much they helped the B190's fridge, I want to put fans in the fridge compartment because it'd be a fun little project, but so far, even in 95+ degree weather with zero shade, we haven't needed it.
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Old 09-10-2013, 07:54 AM   #25
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I live in Texas and store my 2008 Classic 25fb under covered storage with electricity but when the temperatures are above 100F the metal roof and back side of the storage area transmits heat so inside its 100F in the shade. The Dometic 3762 fridge thermometer will show 43F to 44F with the fridge empty. Typically, for a weekend trip we start the fridge a few days before on AC. We store the weekend food in an ice chest and the pick up the trailer after we get off work on the Friday. When we get to the campsite that evening we turn on the air-conditioning and load the fridge up from the ice chest. By the next morning the fridge thermometer shows 32-33F. The temperature in the fridge may rise to 50F because of the loading process. I also have an external thermometer in the fridge velcroed to the inside fridge wall that transmits the temperature and sometimes it conflicts with the Dometic internal thermometer. Most of the time the two thermometers are close to each other.

The back fridge compartment has structure built up on the outside wall so the air has to go over the condenser fins. I'm not able to reach up to the fins. There is a rubber gasket around the outside edges of the fridge to keep hot air out. There is no cooling fan in the compartment to pull or push air up the chimney.

Inside the trailer the cabinetry above the fridge can feel warm on hot days. There is no cabinet door above the fridge like in the Flying Cloud and International series. Seems to be a void. Since AS went to the effort to build the baffle on the exterior wall to form a chimney and put rubber gasket along the sides I'm sure the area above the freezer is blocked off from rising chimney heat. I'm not going to pull the fridge out to find out.

The inside of the trailer is hot this puts a strain on the cooling process. If you can run the air conditioning while the fridge is running when you are getting ready for a trip this will help. We used to do this with our 17' Casita. I could park it in my driveway, can't do that with the AS, turn on the fridge and AC. The small size of the Casita allows the air conditioner to cool down the interior fast and the fridge doesn't struggle as much.

Absorption fridges are just not efficient compared to compressor fridges. I've had several RVs most with 3 and 4 cu/ft fridges and thought getting a 7 cu/ft fridge with my AS with separate freezer it would perform better in the heat but it doesn't. I also find higher humidity makes them recover slower.

Kelvin
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Old 09-10-2013, 09:26 AM   #26
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Fan location is important, further from the fins requires more air flow which consumes amps. If you want low electrical draw and maximum benefit you can consider a solution like mine. I get 34-36 on setting 3 on 95+° days. Check this thread for pics:

http://www.airforums.com/forums/f44/...ms-106595.html
SeeMore

OK, I agree that having the fans next to the fins is the best location because all the air flow is going through the fins and improving the heat transfer and therefore fridge performance. However, in my application I have installed baffles that force 80-90% of the airflow through the fins. There is very little bypass. My point is since you have a closed plenum, whatever airflow the fans provide will be the same at any location in the plenum- bottom, middle or at the top. I will be installing my computer fans at the bottom because that is the best location available.

Dan
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Old 09-10-2013, 11:13 AM   #27
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Well, it seems that there is more than one way to improve the performance of an absorption-type refer. The main methods seem to focus around:
  • No changes to the refer, but hints on how to use it better: use of camp coolers, starting cooling earlier, use of AC systems to cool the TT
  • Baffles can apparently play a large role in moving air around the rear of the most advantageous parts of the rear of the refer
  • Use of fans: cooling the top row of rear fins, removing warm air from rear space behind refer with fans on the top vent, and small fans used inside the refer section to move cool air around in that area.
I am interested in adding fans to the back of the refer. But, I want to have them operate automatically as much as possible. Can anyone suggest a good thermocouple solution; that is, a thermocouple device that would shut down power to the fans when the temperature reached a desired level? I would also want to add an over-ride for use when I know the refer would undergo heavy use (starting off, party time, etc), i.e. a 'forced-on' switch.

I can buy low-draw muffin fans from a computer recycling store near me for about $2 a piece, and I am thinking that wood frames would be acceptable.

I would also be interested in doing one of the hi-tech-looking riveted aluminum solutions.

By the way, I am loving this thread! The ideas coming out here are excellent, and could serve as a benchmark for others to follow!
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Old 09-10-2013, 04:24 PM   #28
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Aage, my solution uses a thermocouple attached just before the first 90° elbow at the top of the vertical solution/gas pipe before the fins. I used a 110° thermocouple. The positive lead is wired to the 12v power for the frig (will only run when frig is on) and triggers the muffin fans once the temp is sufficiently warm to coinside with heat cycles, otherwise they turn off.

The aluminum pieces started as a single 48" length of extruded angle stock from my local home center and I used 5 pop rivets to form the frame after I cut the individual pieces. Two 3/4" #8 screws attach it the frig. The individual fans sit within the frame and have two screws each, diagonal from one another.

You can not hear the muffin fans running from inside. I tried the other approaches suggested but found them noisy and a higher electrical load. I prefer to boondock so amp use was key to my design. I left the larger, typical fan located at the top of the flue installed by the PO for those really hot days I encountered out west, but wired it to a manual switch inside the compartment (also off frig power bar).

On 100° plus days in no shade locations, placing a Tupperware type pan filled with water near the hatch door and activating this second fan offers an evaporative cooling boost which keeps our unit operating mid-30s even with sun on the shell siding.

So, I have both your desires covered.

Removing the trig is not necessarily a two person job. I cut an old discard 2x4 into four legs and made a 1/2" plywood top just smaller than the width and length of the corridor. Height needs to match the bottom of the frig's mounted position. Uncouple everything from outside and remove the two screws holding the metal runners to the floor, remove the edging inside of the frig facing and unscrew the four long mounting screws un the cabinet. Then go outside and push the frig onto the front edge of the table. Spin the trig 90°, mount your fans and reverse the steps.

Others may disagree, keeps the posts going strong when we all chime in, but I found blowing lightly in her ear up close works vastly better than trying the same from across the room ;-)
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