Cooling fan for 3way caravan fridge

Submitted: Thursday, Jan 14, 2016 at 14:10
ThreadID: 131358 Views:8291 Replies:12 FollowUps:7
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Hi Troops, I am having trouble keeping the 3 way Dometic fridge section cold,in the caravan. I read an article with the procedure of how to install a cooling fan, cannot remember the site, open to any suggestion, ? does this method work, last year we travelled during March to July and had tis problem.Plan to do same again. Bob Kelly
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Reply By: TomH - Thursday, Jan 14, 2016 at 14:55

Thursday, Jan 14, 2016 at 14:55
Get a couple of 12V 120mm computer fans and install them at the bottom to blow up across the fridge. Some put switches or even temperature controlled switches on them.

Can be run off the 12v supply to the fridge
AnswerID: 594906

Reply By: Member - Boobook - Thursday, Jan 14, 2016 at 14:56

Thursday, Jan 14, 2016 at 14:56
is it hard to cool when on gas and 240V, or just 12v?

If the latter then you need to do 4 things and it will be fine.

1)Use MINIMUM 6 B&S wiring in your vehicle.
2)Replace the fridge wiring in your van with minimum of 6B&S wiring.
3)Take ou the fridge and surround the fridge with home insulation
4)Add the fan you suggest.

If it is not ok on gas and 240v then start with item 3

AnswerID: 594907

Follow Up By: Maisie K - Thursday, Jan 14, 2016 at 15:00

Thursday, Jan 14, 2016 at 15:00
Thank Boobook,I have the same prob with gas and 240v. Wish I could remember the site as it was a video of the installation. Bob
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FollowupID: 863466

Reply By: Lakers - Thursday, Jan 14, 2016 at 15:07

Thursday, Jan 14, 2016 at 15:07
Hi Bob, here you go... http://www.dreampod.net/boroma/fridgefan.html

I have 2 x 120mm Arctic fans inside the top vent sucking the hot air over the condenser fins and out. IMO this provides better control than having fans pushing air from the bottom.

Cheers
Greg
AnswerID: 594908

Follow Up By: DesF - Thursday, Jan 14, 2016 at 16:11

Thursday, Jan 14, 2016 at 16:11
Hi, I had the same problem when camped and the breeze is coming from the door side , I bought a 6" fan from DS about $10.00 from memory, it is 240v as only needed when set up, I mounted it on the inside of the top grill with Zip ties and just run it when needed, needs to be exhausting the hot air, if mounted on the bottom it pushes hot air out of all the cracks into the van,
Cheers Des.
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FollowupID: 863470

Follow Up By: Notso - Thursday, Jan 14, 2016 at 16:38

Thursday, Jan 14, 2016 at 16:38
Yes, I find the top mount blowing out reduces the temperature in the fridge compartment better than the bottom mount.. It still sucks the air in through the bottom vent so the best of both worlds.

The other thing to look at is the way the fridge is installed. Some of them are just put in the hole with none of the recommended additions such as the angled shield at the top to direct the hot air out through the top vent.
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FollowupID: 863472

Follow Up By: Bobjl - Thursday, Jan 14, 2016 at 22:14

Thursday, Jan 14, 2016 at 22:14
'My Dometic 3 way failed to operate as needed in ambient temps greater than 30 degrees. The cause of the problem was improper installation in that the upper vent was opposite the cooling fins. That prevented adequate air flow to pass the fins and cool effectively. I initially installed a computer type fan at bottom to [hopefully] push more air past the fins but little change/improvement.
Then had van manufacturer install a Dometic roof hatch, this was a success as it naturally allowed improved upward flow of air.
I also tried using the fan after the hatch was installed, but felt little change/improvement, I then blocked off the top vent and believe further improvement achieved using fan in hotter conditions.
It's another hole in nthe roof with potential for leaks, but it hatch properly installed should be fine.
Trial and error - good luck with your issue.
Bob
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FollowupID: 863501

Reply By: Notso - Thursday, Jan 14, 2016 at 17:46

Thursday, Jan 14, 2016 at 17:46
This is a link to what Dometic says is the optimal installation Guide.

Dometic Optimal Installation Guide.
AnswerID: 594914

Reply By: Member - Andrew W14 - Thursday, Jan 14, 2016 at 20:48

Thursday, Jan 14, 2016 at 20:48
Save your money and time on a fan to force air past the condenser. Hot air rises anyway - - if installed correctly why would you need a fan to make the hot air rise??. Besides that the condenser needs to run at a certain temperature to evaporate the coolant. Use of fans can reduce that temperature so the condenser can never work.
The critical factor is as stated. It must be installed correctly. the major fault in this area is having a gap bigger than 25 mm from condenser to caravan wall. The air just runs past and not through the fins. The other issue is that is must be totally sealed from the inside. i.e. as stated insulation round the sides and top to ensure the fridge cannot become trapped in a 'balloon' of hot air.
If all that does not work bear in mind these 3 way fridges are useless and any temp above 32'C anyway!
Andrew (who replaced a well known 3 way with a compressor because nothing could make it work!)
AnswerID: 594918

Follow Up By: Member -Pinko (NSW) - Friday, Jan 15, 2016 at 08:24

Friday, Jan 15, 2016 at 08:24
Andrew
It is not only the cost of replacing the 3W with a compressor fridge.
You also need DCtoDc battery managment, solar setup and couple of deep cycle batteries.
About $2000 on top of the fridge instal.
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Follow Up By: Member - Andrew W14 - Friday, Jan 15, 2016 at 08:59

Friday, Jan 15, 2016 at 08:59
The original post was about how to get a 3 way fridge working more efficiently. That was what I replied to in an attempt to help him get it to work better. All the fans you have listed are very noisy and expensive. If you have to use a fan ( which as I stated will not overcome inherent installation problems) the one to use is a MagLev fan from Jayco Totally silent and cheaper than others.

http://www.jaycar.com.au/Electromechanical-Components/Fans-%26-Accessories/Axial-AC-DC/80mm-Super-Long-Life-Low-Noise-MagLev-Bearing-Case-Fan/p/YX2580


Nothing to do with replacing with a compressor (having done that myself I fully understand the costs involved - and well worth it!)
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Follow Up By: Member -Pinko (NSW) - Friday, Jan 15, 2016 at 09:07

Friday, Jan 15, 2016 at 09:07
Holy Moly Andrew give us a break.
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Reply By: aussiedingo (River Rina) - Friday, Jan 15, 2016 at 08:07

Reply By: aussiedingo (River Rina) - Friday, Jan 15, 2016 at 08:22

Friday, Jan 15, 2016 at 08:22
and wait there's more!!

http://www.jtsonline.com.au/solar-fridge-fan.html
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AnswerID: 594934

Reply By: Member -Pinko (NSW) - Friday, Jan 15, 2016 at 09:00

Friday, Jan 15, 2016 at 09:00
I have two fans.
With an ambient temp of 28 degrees the temp in the cavity behind the fridge exceeds 50 degrees.
Yes hot air rises but needs a flue(chimney) and that is not possible.
With fans on the cavity temp reduces to almost ambient.
Temp inside the fridge also starts to drop.
Not mentioned before is a small 40mm fan inside the suspended by zips and stickybacks to circulate and stop cold air pooling.
Many times in early morning 1am etc I have to switch fans of because the fridge is reaching minus temps.
Also when mobile I run a 600 amp pure sine wave 12/240 inverter to run the fridge on 240v.
This keeps the fridge boiler percolating and it is hot when switched over to gas so no recovery period.
The inverter setup switches of when the ignition switches of.
This fridge is twelve years old and when it dies I will replace it with the same dometic fridge which are now made in china and I believe are even more efficient than the Denmark manufactured models
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AnswerID: 594937

Reply By: swampy - Friday, Jan 15, 2016 at 11:12

Friday, Jan 15, 2016 at 11:12
hi,
The idea from dometic is the heat thermally/convection rises . Best results are with only 25mm clearance wall to rear of fridge .The thermal air then is suppose to all pass thru the condenser and then out a radius bend duct at the top .perfect if not installed in a jayco.

In standard form
1st the gap between fridge is way large 50-75mm can be rectified with sheet foam
2nd if u fit a fan at the top it sucks air from the main cavity which by passes the condenser. The result can be vastly improved

Basically the thermal air travels diagonally from the fridge base towards the fan and then out the exterior top vent.
Some air will also come in from the interior top vent and flow ontop of the condenser and then out the side vent
Jayco Usa installs a duct from the vent to the condenser . Assuming there also must be a fan .

The duct also restricts the air being able to be sucked directly from the boiler . This needs to run reasonably warm and not cooled by fans .
There is a baffle installed in mine to restrict hot air escape from or cold air influence .
The condenser needs to be cooled well but I would be cautious with 2 large fans .

swampy
AnswerID: 594952

Reply By: dublediff - Friday, Jan 15, 2016 at 14:27

Friday, Jan 15, 2016 at 14:27
A couple of issues here,
1. 3 way fridges are not reaaly efficient on 12 v. This will only maintain the temperature you attain by leaving the fridge running on 240 volt 24 hoirs before leaving home.
2. A lot of fridges aren't fitted properly, ensure that, apart from adequate insulation as posted above, make sure that the hot air is able to create a venturi effect and exit via the top vent. I have corrected a couple of installations (in jaycos but I am sure this may be universal) where there is a cavity directly above the top vent that is not blocked off. The result is that the hot air rises inside here and does not create the flow to the exterior of the van, this is more of an issue in caravans as opposed to campervans that hace canvass above the fridge. Even in campervans the top of fridge should be fully sealed, with insulation or otherwise to avoid this hit air pocket as well.
3. Above 30 degrees most of these 3 way fridges will struggle even on gas which is the most effective. Imhave improved cooling on most caravans by installing a good quality 5" computer fan, not the 3" noisy ones. Buy a 12V sealed bearing fan from somewhere like Jaycar for about $30 and install to the inside of the top vent (i have used cable ties for this) positioned to draw air from inside and exhaust to the exterior. Inline with the power I placed a thermo switch (60 degree on) onto,the top of the condensor tube, also obtained from Jaycar. This system is the. Automatic, it switches the fan on when the temperature of the fluid starts to rise in answer ro the rising ambient temperature.
4. After doing all of this you will probably have to put an internal fridge fan inside the cabinet because you WILL freeze the lettuce!

AnswerID: 594968

Reply By: Bonz (Vic) - Friday, Jan 15, 2016 at 22:44

Friday, Jan 15, 2016 at 22:44
Great info, I have had this issue with my old Jayco, the new Theftford in the van is great
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AnswerID: 594984

Reply By: Maisie K - Sunday, Jan 17, 2016 at 10:27

Sunday, Jan 17, 2016 at 10:27
Thanks everyone for the great info, I have paid Jaycar a visit and with their helpful advise, purchased a suitable fan for inside and out, also rectifying the width of the gap so,combined with Greg and all you fellas input hopefully the problem will be solved, making the Lady of the van happy!! A happy lady makes me a lucky man. Cheers Bob.K
AnswerID: 595058

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