Electric Cooling Fans - Dometic RM 4200 60l 3 way fridge

Submitted: Sunday, Sep 28, 2014 at 20:21
ThreadID: 109652 Views:2383 Replies:6 FollowUps:8
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I am getting my Jayco Jayflite camper van ready for an upcoming trip. It has a Dometic RM 4200 60litre 3 way fridge which basically works OK. In the past the little freezer has worked well, able to ice creams frozen but the temp in the main fridge is a bit hit and miss.

Over the past few days I have had it running on 240v and it froze a glass of water in a couple of hours - on full, the main fridge gets down to -8 at night when outside temp is 8 but during the day with outside temp of around 22 the temp in the main fridge is up to 8 degrees.

This got me thinking about putting in a fan in the back of the fridge and maybe one inside to circulate the air.

I have taken the ventilation grills off the back of the frisge and I find that there just some plumbing at the bottom and the gas pilot light and electric heaters but at the top there is the heat exhaust from the heating element and what looks like a large cooling fin arrangement.

So my question is, if I went to put in a fan is it best to put it at the bottom so it sucks in cooler air and blows it up the back of the fridge and out the top or is it best to put the fan at the top so it sucks air up from the bottom and blows the warmer air out at the top.

Thanks

Garry
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Reply By: Notso - Sunday, Sep 28, 2014 at 22:34

Sunday, Sep 28, 2014 at 22:34
I always put mine at the top and blow the air out the top vent.
AnswerID: 539658

Reply By: Ross M - Sunday, Sep 28, 2014 at 22:50

Sunday, Sep 28, 2014 at 22:50
You need to seal the sides of the cabinet from the heated air which is at the back.
Foam or similar will do so the gap around the fridge is isolated from the heat.
That means less working heat is applied to the sides and top.

THEN.
Fit a fan to draw air into the rear of the enclosure near the bottom and one at the top to exit the hot air. That way YOU are creating a desired flow of convection and it will remove a lot of heat from the condenser, "the finned bit". Then the fridge will operate at it's full ability for the ambient temp it is in.

Just one fan doesn't provide a positive change of air and at the top it can be sucking hot air but also not positively drawing it through/past the fins on the condenser.
Computer fans run off a plug pack when 240v is available or house battery when away from 240v gives two options to select from and the same cooling ability.
AnswerID: 539659

Follow Up By: garrycol - Monday, Sep 29, 2014 at 10:00

Monday, Sep 29, 2014 at 10:00
Thanks for those tips - one at the top and one at the bottom looks to go.

Ross I had a closer look at the at the back with the grill removed - while two sides of the fridge are closed in there are large air gaps around the other sides that allows warm air from the back around the sides - this will have to be sealed in.

That will have to wait until after the trip.

I must admit I am thinking about getting rid of this 3 way and getting a 60l front opening compressor fridge to replace it - the temp in the 3 way is just too variable depending on outside temps.

Cheers

Garry
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Follow Up By: oldtrack123 - Monday, Sep 29, 2014 at 12:21

Monday, Sep 29, 2014 at 12:21
HI
Another thing check is the distance fron the van wall to the condensor fins that should not exceed 20mm

It you may need to fit a horizontal baffle at the fins, so as much cooling air as possible is directed through the condensor


PeterQ
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Follow Up By: DesF - Monday, Sep 29, 2014 at 17:12

Monday, Sep 29, 2014 at 17:12
Hi I have a Jayco Eagle and found the main part of the fridge was only just good enough if the breeze was not coming from the vent side, I have fitted a 6" fan from DSE. I found it better to have it exhausting the hot air out of the top vent as at the bottom it blows the hot air out all the cracks into the van.
Cheers Des.
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Reply By: Member - bbuzz (NSW) - Monday, Sep 29, 2014 at 14:48

Monday, Sep 29, 2014 at 14:48
Hi all,
Here is a blow by blow guide to installing the fans(s).

I run two at the top, with the sides and back of the fridge baffled and/or closed in.

They run off the van battery and I have an off/on switch behind the fridge to shut them off when the outside temp is not going to affect the fridges efficiency.



bill
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AnswerID: 539687

Follow Up By: garrycol - Monday, Sep 29, 2014 at 17:07

Monday, Sep 29, 2014 at 17:07
Thanks Bill - great information - is basically similar to what I was planning but I wasn't going to have the thermister - might rethink that now.

Cheers

Garry
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Reply By: garrycol - Monday, Sep 29, 2014 at 17:17

Monday, Sep 29, 2014 at 17:17
Why is it so.

The fridge is running on gas at the moment and I have a room fan blowing air up the back of the unit. Current outside temp is 27 and the temp inside the fridge is 15, which is far too hot for meat, milk etc if I was away somewhere.

BUT the temp inside the little freezer section is -10. So why is it so??

If the freezer is -10 and the main fridge section is 15, I do not understand why it can be as I understand that the freezer and fridge run off the same cooling circuit like a normal fridge but because the main fridge is larger in volume it is warmer than the freezer but -10 in the freezer and 15 in the main fridge are at opposite extremes.

Any ideas

Thanks
AnswerID: 539693

Follow Up By: mike39 - Tuesday, Sep 30, 2014 at 07:29

Tuesday, Sep 30, 2014 at 07:29
I also suffered this problem and wondered why it was so.

If you remove the panel of fins from inside the main cabinet (4 self tappers) you will see that the fins must make good contact with a round surface (cold liquid tube coming from freezer).

Originally this contact would have thermal grease but over time gunk seems to get in there creating insulation.

In my old Dometic 90l. I installed fans, more insulation, baffles, more fans with thermo switches and so it went on without really improving anything.

An Engel 90l. upright now sits in the spot the Dometic previously lived in, no matter what the ambients the freezer is -12 and the cabinet 3-4 with a current draw of 2.5a. (`50% duty cycle)
Problem solved.
mike
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Follow Up By: garrycol - Tuesday, Sep 30, 2014 at 09:49

Tuesday, Sep 30, 2014 at 09:49
Yes - that is the way I am leaning to as well. The only problem us that any upright compressor fridges that can fit are even smaller than the domestic.

Cheers

Garry
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Reply By: garrycol - Wednesday, Oct 01, 2014 at 12:59

Wednesday, Oct 01, 2014 at 12:59
Thanks for all the input.

I put two 12cm fans on the back of the top grill and one in front of the cooling fins inside the fridge.

Difference was quite noticeable. You can feel the heat and the fan closest to the heat tube is hottest.

The fan inside the fridge also circulates the air quite well as well.

Also - the coils at the back were covered in red dust I guess limiting heat transfer - while it is not possible to clean them all up without pulling the fridge out I cleaned where I could from the top opening and that seems to have made a difference as well.

Cheers

Garry
AnswerID: 539757

Reply By: garrycol - Tuesday, Oct 07, 2014 at 14:14

Tuesday, Oct 07, 2014 at 14:14
I have just spent 4 days away with the new cooling arrangement for the fridge. Prior to leaving it was on 240v and was working perfectly. I wasn't prepared to risk using it for perishable food so loaded it up as my drinks fridge. I also put a dozen milk ice, ice creams in the freezer section as it has always worked well.

For the 10 hour drive it ran on 12v and also worked fine maintaining about 4 degrees until late afternoon when outside temp started to rise and the fridge temp went to 8 but cooled down as soon as the sun went down.

In site on gas - no issues with the ice creams remaining frozen and solid and the temp of the fridge rising and lowering with the outside temp (up to 27). The fans both internal and external seemed to work well.

Coming back home was more problematic and verified my choice not to put perishable food in the fridge. On the way back running on 12v the outside temp rose to 33 and very windy and the fridge did not cope as well with temps getting up to 13 (though the freezer was still working fine with the remaining 3 ice creams still frozen and solid.

So the two cooling fans in the back and the recirc fan inside work well but the temp cutoff for the fridge to work properly is about 30 degrees - above that it is no good so really could not be used in summer.

It was a great exercise but I think I need to look for a small upright compressor fridge but there do not seem to be any of a similar size to what I have.

That then brings in the other issue of batteries and power generation - we had full sun but in a shaded camp area and my 120w panels only managed to generate about 8Ah a day and the 55l compressor fridge used 5ah during the day and about 2.5ah at night so barely breaking even. An overcast day or so would make a major difference. (The old cheapie ebay fridge only pulls about 3amps when running).

But that is another topic for another day.

Thanks for all the input.

Cheers

Garry
AnswerID: 540025

Follow Up By: Bob Y. - Qld - Tuesday, Oct 07, 2014 at 15:51

Tuesday, Oct 07, 2014 at 15:51
Have you checked the seal on the fridge door, Garry?

With those sort of fridge temp variations, the seal or the fit of the door to the cabinet, or both, might be a bit suss.

Suppose you had the thermostat on "max"?

Bob

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Follow Up By: garrycol - Tuesday, Oct 07, 2014 at 17:00

Tuesday, Oct 07, 2014 at 17:00
Seal does seem OK - on 12v there is no thermostat but I did have it at max thermostat on gas. Interestingly when testing before I went away on both gas and 240v the fridge section was getting down to about -8 at night and there was only a degree or two difference between having the thermostat on hi and low.

The freezer works great, maintaining between -10 and -16 all the time - irrespective of what the main fridge temp is.

Cheers

garry
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