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Old 07-04-2021, 05:29 PM   #1
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Fridge condenser fan question

Been working on some mods and finally today decided to pull the fridge to take care of some issues with improper sealing and out of level mounting. On the back there is a single 92mm fan that is fairly noisy. It points upwards at the condensers but is off to one side and when they mounted it you can see the first hole they stripped out so they re-positioned it at an angle which catches about 1/2 of the condensers area and blows toward the snap disc which is clipped onto the condenser tubing. Thinking of replacing this fan with a quieter one and re-positioning it to blow straight up into the fins, and I am also considering adding a second one. Has anyone added a second fan in this location and found it to benefit cooling?
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Old 07-04-2021, 07:35 PM   #2
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Hi

I would guess that the fan in the picture is not something AS did as part of the stock install. It's AS, so who knows ....

There are a lot of fans you could use. They move a wide range of CFM and pull a wide range of current. Usually quiet does not go with high CFM / low current.

The "zen" of an absorption fridge is that it should not need a fan. It should be running up to snuff simply with a proper chimney. Since hot air flow is only one of many things that limit performance, there is a point of diminishing returns. Where that is depends a *lot* on how well the "chimney" works in your specific trailer.

Combustion wise, this is sort of a can't hurt / might help sort of thing. 12V power wise (if that matters) the fans do indeed pull current.

Fun

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Old 07-05-2021, 06:35 PM   #3
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Thanks for the thoughts, and yes the installation is in a Sprinter MH and no roof venting so the muffin fan was installed at the factory to help with the side venting. I have a squirrel cage blower on order from Paul at Fridge Defend along with the Fridge Defend protection system.
I have another question for the experts, I have been reading for days and learning a lot about these fridges, I learned that the rear wall clearance should be 1" or less and if not baffles should be installed so air flow does not go around the condensers but thru it. Since my fridge is out I went ahead and added 1" of foam board to make up the excess, I am now within the 1" minimum. I also learned how important sealing the space behind the unit from the coach is and mine was done horribly, I wondered why after every trip there was a lot of dust around the fridge area. When they applied the foam weatherstripping they applied it to the edge of the wood that the fridge butts against instead of the inside surface where the fridge would press into it.(see pic, red arrow indicates where fridge slides in) The fridge wasn't touching it at all in fact there was a gap that got wider at the bottom because when they cut the cabinet floor they made it too short and the back 2 feet of the fridge were hanging off so the fridge was tilted in the cabinet and only touching the back of it at the top. So I'm, fixing all of that but what's got me confused is why did they seal all the luan around the fridge with RTV? They even sealed at the top inside corners of the microwave shelf above. (see pics) I am opening all this up to add thermal insulation but can't figure any reason those cavities need to be sealed, they are just 2" hollow partition walls and not open to the outside or to the back of the fridge. I think the builders were probably barely trained (especially in light of the incorrectly installed weatherstripping) and were probably told "seal everything around the fridge" so that's what they did. Unless I am missing something? Any thoughts?
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Old 07-05-2021, 07:28 PM   #4
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I have changed and added quality computer fans to two Airstream trailers (23’ and 16’) with only limited improvement. The noisy fan problems were solved, but cooling performance improved only a bit. My estimate is that the fans averaged about 2 amp hours each over a typical 24 hour period.

The heart of the performance problem (in addition to the fact that absorption fridges do not perform well at higher ambient temperatures) is that Airstream has poorly designed their installation — the lack of a chimney being the major error. As you discovered, the compartment spacing has problems including a heat trapping dead air space above the fridge. Try to arrange the fans to create a flow over the fins and out the side vents.
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Old 07-06-2021, 09:08 AM   #5
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Quote:
Originally Posted by field & stream View Post
I have changed and added quality computer fans to two Airstream trailers (23’ and 16’) with only limited improvement. The noisy fan problems were solved, but cooling performance improved only a bit. My estimate is that the fans averaged about 2 amp hours each over a typical 24 hour period.

The heart of the performance problem (in addition to the fact that absorption fridges do not perform well at higher ambient temperatures) is that Airstream has poorly designed their installation — the lack of a chimney being the major error. As you discovered, the compartment spacing has problems including a heat trapping dead air space above the fridge. Try to arrange the fans to create a flow over the fins and out the side vents.
Thanks, I am planning to fix that dead air space above with a curved tin baffle to direct air out the vent along with fans. Do you have any idea why they sealed the interior partition wall panels around the fridge?
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Old 08-24-2021, 06:40 PM   #6
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Our fridge had vents at the top and bottom (not through the roof), and on warm days it would not cool when using propane, there was just too much heat back there. I put in a computer fan which we can manually turn on and that fixed the problem.
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Old 08-24-2021, 07:09 PM   #7
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Hi

We're getting examples from Sprinter vans, new trailers, and older trailers. Even within those sub categories (from other threads) there are is a *lot* of variation. It appears that AS is very much "in transition" even on these fridges.

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Old 08-24-2021, 08:57 PM   #8
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This link leads to a thread where my approach to achieve extra cooling is documented:

https://www.airforums.com/forums/f42...ml#post1320159
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Old 08-25-2021, 07:50 AM   #9
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SeeMore when I was doing my research your thread was one of the ones I bookmarked. My mods are complete and I suspect the unit is running as good
as it can now. That being said my original question of why the hollow walls around the fridge had been sealed with silicone was never answered. Due to a lot of other incorrect issues from the factory I came to the conclusion that it was done out of ignorance, the installers being told to "seal off the fridge" without understanding the idea is to seal between the inside and outside of the coach. Those hollow wall partitions are not open to the outside. I ended up filling them with thermal insulation and closing them back up. The important issue of sealing the back of the fridge to isolate the outside compartment from inside was improperly done and there was major air and dust infiltration from that, which is now fixed.

Conclusion is that side vent only absorption fridges can benefit from fan assist where roof vent installations can operate as designed with no added fans. I also added a Fridge Defend which gives me peace of mind.
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Old 09-13-2021, 07:58 PM   #10
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Just to update this thread I recently took a 5 day trip with daytime temps over 90F for most of it. Parked on shore power and parked on propane fridge did great and even got too cold during the nights, but driving with fridge on 12 volts did poorly, reaching over 50F on the last day's 9 hour drive. I had read about voltage drop being responsible for poor 12 volt performance due to undersized supply wires and long, meandering wire runs. Sure enough I had 13.3 volts available at the terminal block with engine running but no load applied but once fridge powered on it dropped to 11.2 volts! I am almost finished with my wiring upgrade which is #8 AWG to replace the #12 and coming direct from the battery bank making the run 8 feet instead of the original 15 feet of #8 to the fuse box and another 15-20 feet of #12 from the fuse box to the fridge. At 11.2 volts the element only produces 125 watts. If I can boost that by one volt I will get nearly 150 watts, if I can get close to the 13.3 running volts I will get 170-177 watts. That's huge. I am installing a Smart Shunt at the same time and will finish tomorrow and post my results.

Here is where I read about the low voltage problem, scroll down to the last section. (pay no mind to the 240 volt reference, the author is in Australia) Good venting tips here too
https://www.fridge-and-solar.net/fridge_vent.htm
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Old 09-14-2021, 03:13 PM   #11
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Finished re-wiring the fridge with #8 and tested, I now have 13 volts at the fridge instead of the 11.2 volts I had with the factory wiring (engine running at idle). That is a gain of 44 watts or approx 35% increase. Looking forward to see how it does on the road now.
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