Refrigerator Baffle and Fan Mod (finally!)

Discussion in 'Refrigerators and Coolers' started by SirLancelot, Aug 16, 2012.

  1. SirLancelot

    SirLancelot Member

    249
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    Sep 28, 2010
    I know I'm one of many, but considering I'm no electrical genius I'm proud of this mod:

    Baffle and 120mm fan:
    [​IMG]

    On/off switch to the right of the galley:
    [​IMG]

    The 120mm fan was more expensive than I was expecting for some reason ($15 @ Radio Shack), but with the switch and fan I was still into it for less than $20. I had the materials for the baffle laying around the garage already.

    We leave again tomorrow for Eastern Washington (100-degree temps forcasted) and it was 90 in my driveway today. I fired the fridge up without the fan at first and it came down from 70 to the high 40's in a couple of hours (baffle only at this point). I turned on the fan at about 5:00 and by 8:00 it was down to 35 inside! The outside ambient temperature was still 88 at this point, there was still a lot of sun exposure to the trailer, and the interior wasn't vented at all (completely sealed up and was HOT inside)!

    My multimeter showed the battery had 12.41 volts before I turned the fan on and after about 3 hours it was only down to 12.35 or so. I was expecting it to have more of a drain on the battery but at this rate I could leave the fan on for an entire 4-5 day trip and use lights normally at night and probably not get below 8 or 9 volts.

    This thing ought to rock!
     
  2. LjohnSaw

    LjohnSaw So many fish, so little time...

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    Jun 24, 2011
    Northern California
    Actually, that is pretty bad. Your battery is beyond dead at that point. You will greatly shorten the life of the battery. Someone will chime in here as my chart is locked up in my Pup, but I recall that you should not go below about 10v, maybe higher!
     
  3. SirLancelot

    SirLancelot Member

    249
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    Sep 28, 2010
    I seem to read from most people that 50-60% of the battery level is generally considered the cutoff limit - hence the reason for the deep cell battery.
     
  4. LjohnSaw

    LjohnSaw So many fish, so little time...

    804
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    Jun 24, 2011
    Northern California
    Go to this web site http://www.windsun.com/Batteries/Battery_FAQ.htm and near the bottom of the page (a LONG page) you will find this table in really pretty colors:

    State 12 Volt Volts per
    of Charge battery Cell
    100% 12.7 2.12
    90% 12.5 2.08
    80% 12.42 2.07
    70% 12.32 2.05
    60% 12.20 2.03
    50% 12.06 2.01
    40% 11.9 1.98
    30% 11.75 1.96
    20% 11.58 1.93
    10% 11.31 1.89
    0 10.5 1.75

    You really don't wan to go below 12 volts!
     
  5. SirLancelot

    SirLancelot Member

    249
    3
    Sep 28, 2010
    Ahhhhhhhhh, I figured 50% of 12V was, well, a simple math problem. Apparently I was wrong. Still though, I used very little power during the 3 hrs the fan ran. I'll keep tabs on it when we're out this weekend.
     
  6. SirLancelot

    SirLancelot Member

    249
    3
    Sep 28, 2010
    Well after crossing another camping trip off as a success we returned from Eastern Washington with it's spectacular dry heat. Friday and Saturday were in the high 90's and low 100's (LOW humidity though). The fan functioned well, but any benefit it truly made was relatively insignificant as it scrubbed perhaps 5-degrees off the temp.

    We returned from another Eastern Washington trip a few weeks back with similar temps, but found the baffle alone kept the fridge in the mid/high 40's in the heat of the day. With similar temps this trip the addition of the fan kept it in the low/mid 40's. The extra few degrees help, but the $18 spent to get there really weren't worth it. As the fan and switch are already installed I'm just going to leave then there however.
     
  7. BigBaron

    BigBaron Dreaming of Tommy's chili cheeseburgers...

    4,583
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    Jun 21, 2012
    The air needs to be ducted around the cooling coils. The majority of the cools are still cooled by the air around them. The baffle needs to look like the shroud around a car radiator to be effective. You also really need two fans.
     
  8. poncho62

    poncho62 New Member

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    Jul 1, 2011
    So, you are saying that the baffle should go back to the coil, but not block off the air coming up and through them?
     
  9. BigBaron

    BigBaron Dreaming of Tommy's chili cheeseburgers...

    4,583
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    Jun 21, 2012
    Yes. The idea is to force the air through the coils, but if air can just go around them, it will. Everything always takes the path of least resistance.
     
  10. BigBaron

    BigBaron Dreaming of Tommy's chili cheeseburgers...

    4,583
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    Jun 21, 2012
    I stole this from ? (he has all the Mustangs but I can't look up his name right now) it is a really good drawing of a fan mod.

    [​IMG]
     
  11. BigBaron

    BigBaron Dreaming of Tommy's chili cheeseburgers...

    4,583
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    Jun 21, 2012
    Raycfe - he's the trailer wizard, and pretty good with cars, too! ;)
     
  12. Aladin Sane

    Aladin Sane I'd rather be camping

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    Jul 3, 2008
    Iowa
    I can't agree that you need two fans to make this mod work. I also have a single 120 mm fan and it helped a great deal. I do agree that your current set up may not draw as much air across the coils as possible. You could be drawing air in through the sides of your upper vent panel and then just blowing it back out the center.
     
  13. Dubbya

    Dubbya Wherever you go, there you are...

    6,125
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    Aug 2, 2011
    Steinbach, MB
    To answer this, having TWO fans is definitely better. They actually allow you to turn down the fridge thermostat while using 120v power. Tried and true, that's my experience.

    Secondly, and just as important, while the OP may have spent $15 on a fan, I'd guess it only moves 54 cfm. You can pick up fluid bearing fans that move 74 CFM on eBay or at a local PC shop for $12-$20. The thing here is that, even with window screens behind the vents (to keep wasps and spiders out), they still move more than enough air to keep the fridge cool and they use about the same amount of power as the 54 CFM fans do.

    The idea here is to take cool air from the bottom vent (access door), send it up the back of the fridge, through the cooling fins, then out through the top vent. It appears as though the OP's baffle is more of a gate as it restricts airflow from the bottom vent completely. Not at all surprising that he'd see no appreciable difference in performance.

    While it's nice to have an on/off switch, I highly recommend tossing a thermal switch (thermal snap disk) into the mix. Norcold makes one expressly for this purpose. It turns the fans on at 130 F (closed at 130 F) and shuts them off at 85 F (open at 85 F).

    I picked mine up at a local dealer for $21.95. Their parts book lists it as:

    Norcold Thermostat
    Part# 618093

    Having a thermal switch in the mix turns the 74 cfm fans on only when required. If you think about it, they probably use less power since they move more air using roughly the same amount of power as two 54 CFM fans running constantly (until they're manually switched off).

    Again, a great mod. With a few changes, it'll work wonders. Using 120v power, two 74 CFM fans and the Norcold thermal switch, I went from the max setting ("7" on my Dometic fridge) down to 5. The interior (when full) was easily kept at a steady 2 degrees Celsius (35.6 F).

    That's dead perfect in terms of fridge temps.
     
  14. Aladin Sane

    Aladin Sane I'd rather be camping

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    Jul 3, 2008
    Iowa
    Dubbya, I am still not convinced that you need two fans to make this work optimally. I know a thing or two about heat transfer.
     
  15. pgordemer

    pgordemer Guest

    I have 2 fans in my original mod. It got the internal fridge down to temp in 1/3 of the time and had no trouble keeing 37 degrees even when in the high 90's outside.

    I did an experiment and turned one fan off and noticed no difference at all. I did 2 complete trips with just one fan, and again, not difference seen between running 1 or 2.

    If I don't use them at all, then it takes 10 hours to cool down and struggles to keep 44.

    So I agree with the statement that you really don't need 2 fans. A single fan starts the convection process moving well, a 2nd one doesn't really make it move much more.
     
  16. gwbeech

    gwbeech GO OUT AND CAMP!!!!!!!!!!!

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    Jul 11, 2012
    bought my on eBay 120mm 100cfm for 8.99 a piece
    free shipping they draw .25amps
     
  17. BigBaron

    BigBaron Dreaming of Tommy's chili cheeseburgers...

    4,583
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    Jun 21, 2012
    My favorite quote is, "If it doesn't work, use a bigger hammer."
    I'm going to install two fans in my trailer. Did everyone see Raycfe's temp switch install? I'm just curious where and how to install the switch.
     
  18. Aladin Sane

    Aladin Sane I'd rather be camping

    962
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    Jul 3, 2008
    Iowa
    While I find the temp switch interesting, I consider it overkill. The fan draws so little power, I don't really see the point of turning mine on and off.
     
  19. LjohnSaw

    LjohnSaw So many fish, so little time...

    804
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    Jun 24, 2011
    Northern California
    My results differed. When hot (85-100*) I need two fans to keep cool. It approaches 40-42* with both when outside is 100*. With one fan, I get a 5-8* rise in temp. My two fans differ - they look the same but one is noisier and moves a little more air (with a larger current draw).

    On the flip side, when the outside temp drops at night into the 60*, I can either go outside and lower the thermostat (propane) setting or flip off one fan. I have to be careful as I got down to 22* one time!
     
  20. Raycfe

    Raycfe Waterford Ct.

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    Oct 3, 2007
    Waterford, Ct
    One thing about my temperature sensor, I don't have to turn the fans on or off ....... its automatic.
     

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