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Old 10-12-2017, 08:42 AM   #1
rsl
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Strange Fridge Problem

Ok so this will be a long post but bear with me......

Three Day trip.
Norcold 1210 (I think) Double Door Fridge mounted in slide so top and bottom side vent.

Hi temps during the day 75 and lows in 60's at night

While camping last weekend at the beach we had an issue where the 2nd day of camping the interior fridge temp started getting higher and higher. I went from 6 to 9 on the setting and it still did not help. The Laser temp gun showed around 40 initially then made it up past 50 on the fridge cooling fins. The freezer however stayed at or below zero the whole time. I have no idea why it happened but I think the wind that weekend may have caused it Day 1 until early morning of Day 3 the winds were 25-30 mph with gusts higher and the wind was blowing directly onto the vent side of the RV. May be just a coincidence but as the wind diminished Night 2 into Day 3 the temp slowly started going back down. The freezer temp stayed plenty cold the whole time.

By the time we packed up and made the 1 1/2 hour drive home the fridge had gotten back down in the mid 40's. I left the fridge running and checked the next day. Temps in freezer were still at or below zero and the fridge temp was around 32 degrees, I set the temp adjust back down to 6 and checked temp again. Freezer still zero and fridge around 38-40 degree.

I might add I did check the lower vent while we were camped and without taking the cover off I could feel heat coming from it (was much warmer then outside air temp of 60-something). I also put the fridge into diagnostic mode and my laser gun temps were within 1 degree of diagnostic mode (sensor) temp display.


Help, Thoughts, Suggestions??????????
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Old 10-12-2017, 08:46 AM   #2
Javi
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Was the cooling fan blowing?
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Old 10-12-2017, 09:05 AM   #3
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From your description, "I did check the lower vent while we were camped and without taking the cover off I could feel heat coming from it..." tells me that the "convection draft" that is supposed to carry cool air from the bottom of the "chimney" to the top vent was not working properly. Why? Probably, as you suspect, something to do with the winds against the trailer side. In "normal operation" the airflow should be into the bottom vent, up and through the fins (to exchange heat) and out the top vent (to remove the excess heat). If you felt heat coming out of the bottom vent, airflow was reversed and not proper. Typically, there are thermally controlled fans mounted under the fins to help push that convention current in the proper direction and to increase the amount of airflow. If wind was pushing air into the top vent, and if the temperature inside the chimney was low enough not to trigger the fan operation, that wind could disrupt that airflow and "stagnate" the cooling effect causing the refrigerator to not be able to release the absorbed heat. Sort of a "perfect storm" kind of situation, but likely that's sort of what happened.

Just my guess, but hopefully it was a "fluke" that won't recur.
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Old 10-12-2017, 11:59 AM   #4
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I could not say for sure if the fans were on or not, as the wind was making too much noise to tell. I was thinking since I have had no issues before or after this that it was related to the wind. The thing that confused me was why did the freezer stay nice and cold but not the fridge???
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Old 10-12-2017, 12:54 PM   #5
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Seems from memory (you know how that goes anymore) that there was a member on this forum that experienced the same thing when driving. If I recall it was the wind keeping the vents from working and they installed some sort of deflector in front of the vents to redirect the wind when driving. Sounds like the same problem you have but with the wind coming from a different direction. In the future, if you encounter winds like that again, you might want to find a way to block the wind in front of the vents to see if it stops the problem.
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Old 10-12-2017, 02:44 PM   #6
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Quote:
Originally Posted by rsl View Post
... The thing that confused me was why did the freezer stay nice and cold but not the fridge???
That's an easy one: The "cooling plate" for the entire refrigerator sits on the floor (in some models also on the rear wall) of the freezer. The fins in the refrigerator section are a part of that "freezer plate" and they offer "left over cold air" that drops by gravity in the refrigerator compartment.

So, by design, the bulk of the cooling goes to the freezer plate and "left over cold" flows to the refrigerator fins. The means the freezer is the first to get cooling temps and the last to lose it.

Just as it's cool "under the air conditioner vent" and warm in the bedroom, the same "general condition" exists in your refrigerator.
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Old 10-15-2017, 11:24 AM   #7
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So what you are saying is there was enough cooling there to keep the freezer at 0 degrees F but not enough to keep the fridge from reaching 50 degrees? Was this because it was cooling but the trapped heat at the bottom was not letting the fridge cool?
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Old 10-15-2017, 11:59 AM   #8
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No, it's related more to the limited amount of cooling capacity. The freezer is the first to get the "cold" and it uses what it needs and the rest flows down to the refrigerator. If there's excess, the refrigerator gets cold, if the freezer uses it all, there's nothing to flow down.

Let's say the absorption cooling system can produce 3000 BTU of cooling (heat absorption). Those BTU's flow to the freezer plate where heat is absorbed. The remaining BTU's flow on down to the refrigerator fins.

So, lets say, because of the lack of convection cooling behind the refrigerator (hot air being pushed down by the wind) your refrigerator absorption system could only produce 1000 BTU's of cooling capacity (2000 less than normal). That flowed to the freezer plates and immediately absorbed 800 BTU's of "warmth" in the freezer compartment. That only left 200 BTU's to flow to the refrigerator fins (normally there would be 2200 (3000 total capacity). That 200 BTU's of cooling capacity can't keep up with the heat generated in the refrigerator, so the temp rises in that compartment while the freezer (that got first dibs on cooling) stayed cold.

So, under "normal operation" your absorption system could produce 3000 BTU's and "loaf along" cycling on and off as needed to absorb the heat, but with the reduced convection chimney efficiency, the absorption system could only produce 1/3 of the total capacity (1000 BTU) and it kept working itself "full time" to produce that, trying to keep up, but couldn't because the "back side of the refrigerator" couldn't get rid of the absorbed heat fast enough to maintain "normal operation".....

Think of it like a leak in the bottom of a bucket. If you have a 5 gallon bucket and it is full (cold refrigerator/freezer), if you drill a hole in the bottom that leaks 1 gallon a minute (refrigerator absorption system with normal airflow in the back), as long as you can refill the bucket at 1 gallon per minute, the entire bucket stays full. Now, drill a bigger hole in the bucket and drain 2 gallons per minute (impaired airflow behind the refrigerator) and keep the same "refill rate of 1 gallon per minute) and the bucket will start emptying. The input can't match the output. Now, imagine the bottom of your bucket as the freezer and the top of the bucket as your refrigerator, which will "empty first"? The bottom of the bucket (freezer) will be the last to empty. The top of the bucket (refrigerator section) is the first to empty. This is a very crude explanation, but maybe it'll make sense when you think about it..... I hope it helps ...
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Old 10-15-2017, 02:45 PM   #9
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John: I like the way you explained it. I was trying to figure out a way of saying what you did..thank you.
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Old 10-16-2017, 10:37 AM   #10
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Thank you for the explanation, it was very simple and easy to understand.
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