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Old 06-30-2010, 08:28 PM   #1
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I need better refrigerator venting

Replaced the bad cooling unit in our recently acquired '88 Winnie - it's a Norcold unit. The new unit seems to work quite well, but it has become evident that in hotter weather, the rear of the unit gets pretty hot - the cooling tubes don't seem to get enough airflow, so heat transfer suffers - the top cap on the roof seems quite low to the opening, blocking air flow, and the air inlet openings on the inspection door are also pretty minimal in size.

I figure that some sort of supplemental air movement would be a big help, and have sent for some 4 inch computer type muffin fans - I sorta plan to either fabricate a mounting plate for 2 or 3 of the fans to mount close to the inspection door vents, and direct air flow upwards past/over the cooling tubes towards the roof jack. Either that, or else fabricate a similar mount up at the roof level just inside the "chimney", and suck the air from that end.

I selected the PC fans, because they draw very little current, are quiet, and pretty efficient air movers.

The point of this thread, is to see if my "problem" is common or not, and what others have successfully done to correct it - hopefully, without creating other problems...
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Old 06-30-2010, 08:32 PM   #2
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On several RVs I have mounted a 4" muffin fan, but I mount it up at the top of the stack. It seems to work better at the top, bit is a bit more difficult to install due to running the wire. I ran a switch with a pilot light inside so I can manually turn it On or Off.

Ken
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Old 06-30-2010, 09:03 PM   #3
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On several RVs I have mounted a 4" muffin fan, but I mount it up at the top of the stack. It seems to work better at the top, bit is a bit more difficult to install due to running the wire. I ran a switch with a pilot light inside so I can manually turn it On or Off.

Ken
On mine, 12 volts DC is readily available at the rear of the refrigerator, and is only active when the refrigerator is in use...

SO, I gather you too have seen this design weakness - do the added fan, or fans pretty much eliminate the issue?
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Old 06-30-2010, 09:38 PM   #4
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Sounds a nice cheap mod that works. Same sort of thing as the replacement fridge vent top with solar panel /electric fan mounted inside.
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Old 06-30-2010, 09:44 PM   #5
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Sounds a nice cheap mod that works. Same sort of thing as the replacement fridge vent top with solar panel /electric fan mounted inside.
WELL, there's little doubt that the better we can cool the heat exchanger, the better the refrigerator will work - the trick, is in finding and properly installing low powered, quiet and efficient fans for the job - and then, the trick is in determining the right amount of air movement to get the job done adequately without getting too carried away...

My usual problem is my philosophy that if a little is good, too much should be just about right!
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Old 06-30-2010, 10:03 PM   #6
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If you do what Txiceman says and add a thermal switch the fan will come on and turn off at a preset temperature.
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Old 06-30-2010, 10:11 PM   #7
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If you do what Txiceman says and add a thermal switch the fan will come on and turn off at a preset temperature.
I already have a 150 degree sensor switch left over from another project I could attach at an appropriate point in the refrigerator boiler area - but since I also have a 12 volt source right at the rear of the refrigerator that is only active when the refrigerator is in use, that will probably do the job - but all suggestions and pointers are welcome!
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Old 06-30-2010, 10:17 PM   #8
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If you do what Txiceman says and add a thermal switch the fan will come on and turn off at a preset temperature.
I like that idea but the thermal switches are preset. Would you care to take a guess what temp rating they should be. On a hot day with heat build up on the side of the MH the temp would increase whether or not the fridge was running. If the thermal switch was too low temp then the fans would come on. Maybe that's not a bad anyway.
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Old 06-30-2010, 10:20 PM   #9
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Gary, I guess we posted at the same time. I was thinking about 100 degrees
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Old 06-30-2010, 10:30 PM   #10
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Gary,
Mine is set to go off at about 90F and turns off when it gets below. I can hear mine go off in the middle of the night when it's 65-70 deg. It's a small space with alot of heat. My thought is if it start cooling sooner it will stay cool longer. The other thing you could do is put another fan down below and draw the cool air thru the lower vent and use the upper fan to vent it out the top. Actually you could start one fan at one temperature and the other fan at a higher temperature and you could use smaller fans.
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Old 06-30-2010, 10:36 PM   #11
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Our Newmar came with a 5" muffin fan and thermo switch attached to the cooling fins. I added two 3" brushless PC fans that draw<300mA each. These cut the duty time to less then 50% at 95F.
On our previous coach I added two 3" fans: one on top, one on the bottom. They were manually switched.
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Old 06-30-2010, 10:49 PM   #12
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When the outside air temp is around 90F the refer compartment must be between 125-130F. You just can't move enough air thru the compartment at those temps. Beside, I think some of that heat finds its way inside the RV.
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Old 06-30-2010, 10:57 PM   #13
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Norcold recommends the cooling fans start to operate at 95* and cool down to 80* the more air movement the better for colder box temperatures.
Fans should be at top of coils or at the top of vent access rear of fridge.
If installed within roof vent weather will rust out your 12v fans over time.
On a hot day may run continuously but will cycle off and on if vent area is shaded by awning or trees.
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Old 07-01-2010, 07:10 AM   #14
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We have never been able to keep ice cream close to solid & I am a BIG ice cream fan (pun intended).

So, just exactly how do you position these fan(s)?

Blowing on the coils themselves? Our coach has two external removable covers, one at the top of the reefer, and one at the bottom. So, drawing air in at the bottom/blowing out at the top? Mounted vertically to draw in/blow out or horizontally to blow over the coils?
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