Community Forums

JohnBoyToo · 08-29-2012, 05:15 PM

Been following the excellent threads throughout here regarding increasing the efficiency of our refrigerators.

Ordered both the interior and exterior fans... hope to install next chance I get... but in the meantime went by the storage area and opened the top vent on my kitchen slide to see how I would mount it...

WOW, is mine different from any I've seen so far

my fins are way at the top !

This is a video showing the bent fins before I straightened them, and the small fans already down there:
Top Refrigerator Vent - YouTube

Wondering which way would be the best way to mount the
12VDC FOUR-FAN ASSEMBLY | AllElectronics.com

thought sure I would just mount it down inside blowing up... but MAYBE it would be best to mount it right by those fins blowing OUT ?!?

What do you experts think ?

Thanks in advance,
JBT

OH, when I was sticking my head in there looking down I noted a LOT of heat in there and NOTHING was on or plugged in and it's in a covered parking spot (but it does face west and gets afternoon sun)

Muddypaws · 08-29-2012, 05:25 PM

I think you'll find that putting the fans at the top and sucking air UP through the fins and out the vent works better than trying to blow it through from below.

Trying to force hot air down & out the lower vent would be going against nature.

Dr4Film · 08-29-2012, 05:59 PM

Absorption refrigerators were never designed to be installed in slides. To run efficiently, they need to have ALL of the heat removed quickly from the top cooling fins and the coils below.

Since heat naturally rises, the vent should be at the roof-top but in a slide that's impossible so they put one in the slide at the top. Unfortunately, where the vent ends up is NOT the very top so therefore heat will accumulate in the dead space at the very top. Not a good design.

I would mount those fans as close to the top near the fins as possible making sure that the fans also line up with one of the vents in the cover.

I would recommend using a Fantastic Fan for that space versus the four in-line fan package that you purchased. Two friends of mine, Tom Cherry and Gene Simmons, had Dometic fridges in their slides and they had installed Fantastic Fans with great success. I have attached the writeup they did explaining their installations.

The Fantastic Fan will remove more heat through that large vent area which is available at the top vent.

Dr4Fil ----- Richard

Dr4Film ----- Richard

JohnBoyToo · 08-29-2012, 09:10 PM

Appreciate the responses...
Agree removing heat from the top is the best method,
but if you look at the video,
that top most finned unit is right at the top of the opening with a cavity above it...
is that the only set of fins those dometic rm1350's have ?
I looked here
http://www.dometic.com/d2b969f8-5525...dabd885e.fodoc
but couldn't identify others will have to go back by rv and pull bottom vent off to see.

The top vent opening is 12"H x 20"W and think about 3 or 4 " deep only...
is this the FF your friends used?
Fan-Tastic Vent 01100WH Endless Breeze 12V Fan : Amazon.com : Automotive

So I'm thinking the best mounting will be with the fan mounted against the fins,
blowing directly OUT the top vent 'sucking' the heat past the fins as best as it can...

can test with some smoke to see if the air flow thru the fans will not allow it to pass through those fins... but at any rate getting the heat out should help...

still trying to figure out how to get the flow across the fins if I can't mount the fan ABOVE the finls blowing diagnollly toward the opening... if mounted below or in front of the fins (space will be an issue) the flow will NOT be across the fins...
have to study it more

appreciate any insight and glad to post more pics...

Dr4Film · 08-30-2012, 10:32 AM

Yup, that's the one they used.

If you look closer at the Dometic diagram showing how to properly install a fridge into a slide, the cooling condenser fins are situated well below the vent opening. Because most slides are too short in height, that is impossible.

Therefore, if using the small array of fans, place them as high as you can to remove the heat accumulating at the top.

They went with the bigger Fantastic Fan because it moves more air through the entire outside vent versus only a small strip of air.

Good luck with your project.

Once you finally get discouraged with the lousy performance of the absorption fridge, a residential is the ONLY way to go. I did in April with a Samsung RF197 and it was the BEST decision ever. 50% more capacity and no headaches.

Dr4Film ----- Richard

JohnBoyToo · 08-30-2012, 12:39 PM

How'd you know I'm easily frustrated ?!?

thanks for the insight -
trip this weekend got canceled thanks to Isaac,
but that's a little bother compared to the people fighting the rain and water in Miss and Louisiana OTHER than New Orleans ...
Left that area about 30 years ago and just an fyi - Nawlins is NOT the center of the universe as the media makes out

hooverbill · 08-30-2012, 01:28 PM

I mounted a small AC powered fan in the upper corner of the back of the refer.

Muddypaws · 08-30-2012, 03:41 PM

I believe that the real problem is the control circuitry. I tried an experiment and my result seems to indicate that no matter what control panel setting you select (1-9) the thermistor will turn the heater down or off when it gets to around 40F.

Try it yourself! Remove the thermistor from the cooling fin and just let it dangle. Mine got down to 20F in a few hours. Then, within an hour of putting it back on the fin it was back up to 42F. This indicates that the evaporator is capable of cooling pretty well even without additional fans. But my ambient temp was only in the mid 70's so that may change as the temp go up to 100+. BTW, My Norcold is mounted in a slide.

Since nobody makes an adjustable thermistor for Norcold my theory is that an old credit card or something like it between the thermistor and the fin might 'fool' it into getting the refer into the 35-38 range I prefer. But I won't be able to test this for a couple of weeks.

Anybody game to try it?

Dr4Film · 08-31-2012, 09:58 AM

Quote:

Originally Posted by Muddypaws

I believe that the real problem is the control circuitry. I tried an experiment and my result seems to indicate that no matter what control panel setting you select (1-9) the thermistor will turn the heater down or off when it gets to around 40F.

You are partially correct.

It states in the Norcold Service manual that if a Thermistor were to fail or is removed, then the cooling unit goes into a Backup Operating System, BOS state of cooling which is now based on time versus temperature. The BOS cooling state is basically calling for the heaters, AC or LPG to run flat out for a specific amount of preset time. They do NOT state what that amount of time is in the service manual.

When the thermistor is working correctly and placed correctly on the cooling fins, the temperature control panel selector, 1-9, is supposed to govern when the heaters come on and go off.

My Norcold aka NotSoCold is no longer living. After 9 years I gave up trying to deal with all of the headaches, frustrations and spoiled food.

While sitting in Florida last winter, on two occasions, the freezer temp was at -5F in the morning. By late afternoon, the temp was 25F and climbing. Totally unacceptable. I actually got into a habit of turning the unit off and back on once a day to "fool" the control board so it would NOT go into its deicing cycle. That did not work ether. The only thing I could do is when I saw the temp rising, turn it off and back on.

Before leaving Florida for Alaska, it was then I decided to have the Samsung RF197 installed. It was by far the BEST decision ever. Trust me you will never regret do it. No more spoiled food, no more soupy ice cream, no more lukewarm beer, no more ice cubes frozen into one big block of ice, no more fridge doors falling off or control boards failing, AND no more deicing the freezer every 3-4 weeks.

Dr4Film ----- Richard

Muddypaws · 08-31-2012, 06:52 PM

And yet I still think I'm on to something here.

I've been experimenting with it for a couple of weeks. I've been able to adapt a Dometic adjustable thermistor to my Norcold and have gotten it to stabilize at 35F, running on setting #2, in full sun, during a 75F week. It was definitely working properly and not in BOS mode as I was able to adjust it's temperature up or down by changing the resistance added to the Dometic thermistor.

Unfortunatly the Dometic thermistor is not designed to be mounted on the heat exchanger fin (moisture) so I have more experimenting to do.

If I can avoid the cost of an Amish coil, or adding batteries, inverter, and maybe solar to support a residential unit with a little 'skull sweat' and a handful of resistors I will do it.

Muddypaws · 09-05-2012, 11:45 AM

I haven't been able to continue my testing of the modified Dometic thermistor because I'm having a slide motor replaced. I should have it back by this weekend.

I've been in communication with the makers of the 'snip-the-tip' adjustable thermistor for Dometic refrigerators and the good news is that they are developing a similar product for Norcold and expect to have it on the market in a couple of months.

I volunteered to be a beta-tester. I will definately post my results here.

Off topic but related: In the mean time my residential refer has gone on the fritz and will barely hold 40F at it's coldest setting. I think it's only about 2 years old. It's an LG 3 door bottom freezer. The coils are clear, the fan runs (constantly), and the door seals are perfect. Finding the owners manual is this afternoon's project.

JohnBoyToo · 09-05-2012, 01:05 PM

OK,
spoke to all electronics since the fan was an orphan with no docs

the little phone person was very confused and I interpreted what she said as
the side with the wires is the 'back' and the fans turn clockwise when looking at that side...
for those that have this fan - is that correct ?

Muddypaws · 09-05-2012, 04:35 PM

What? You expected her to speak english?

There should be an arrow embossed into the outer cage of the fan showing the direction of flow when the voltage is applied correctly. There may be one showing the normal direction of rotation as well. The arrow markings may be fairly small and only on one side. If the blades have any 'foil' to them at all you should be able to figure out the direction of rotation and from there where the stream is going to go. Fans of this sort will definitely have a preferred direction of rotation for efficiency reasons.

I think what she told you is backwards. The 2 fans I just pulled out of my computer junk closet push the air out of the side with the wires.

JohnBoyToo · 09-08-2012, 05:36 AM

Well - no biggee if she's wrong, was just gathering info...hoping it was correct info - silly me

I plan to test it before permanent mounting...
hopefully today since it's supposed to be a ge-or-geous 85 here and not 108 like yesterday

for now,
I've remounted the fans on the 'inside' of the frame so it's only 2" or so deep
and temp wired the fans so that the 1st and 3rd are together and 2nd and 4th are together...
plan to run two 'circuits' so I can use two or four fans when needed.

the first pic is the fan so far,
the second is the tight fit by the upper coils
thinking I may just mount the 16" wide fans across the 12" high x20" wide opening blowing out since I can't get the air flow to pull THROUGH the fins.... (oh, and have already straightened the fins that I found bent!)