Al , ive fitted two fans to the bask of the top vent pannel with small cable ties .
ran a wire circuit from the 12volt accs to a toggle switch mounted in a small cupboard under sink ,just turn on when needed , day or night .

 Fans from old computors , about 90/100ml dia.
New are not very expensive if you need to go that way .
Power usage is not worth worrring about .

as the air at the back of the fridge is exhaust (hot) then extract would be best, I have yet to do this to mine but is "on the list" I like the idea of two, hadnt thought about it before

the fan in the fridge itself would be great if it was at a very low speed as the idea is to circulate and not blow the cream off the milk!

Thanks Jim, pretty much the same as mine

Jim

No doubt OT123's suggestion would provide the most efficient arrangement regarding the airflow. I wonder whether going to this much trouble in practice is worthwhile if a simple exhaust fan arrangement gives an adequate improvement in performance.

Most times I find I don't need to run the fan as the normal convective airflow is sufficient and only need it when the ambient temperature rises above the mid thirties in order to keep the main cabinet temperature below +5 degrees. For this reason I've taken care to ensure the installation does not significantly interfere with the normal airflow

Using a system of ducts and fans as suggested would commit one to using the fans at all times the fridge is running, including during the night when fan and airflow noise could be an issue.

Significantly changing the airflow pattern could have unintended effects such as uneven cooling of the condenser. As I've not tried this set up I can't establish this would definitely occur but this thought comes from my background in radio broadcast transmitters where it is a known issue.

-- Edited by jimricho on Thursday 14th of January 2010 06:32:10 AM

What Peter is saying is correct.  If manufacturers fitted fridges correctly there would not be the problems we all seem to have.
The important thing is not to have dead areas around or especially above the fridge.  These areas hold the hot air preventing the fridge doing its job.

On ours, it was fitted pretty well at the sides but has about 2 inches clear space above it.  I have used a baffle to block this area so now the only way air can travel is ...in the bottom vent, up through the fins and out the top vent taking hot air with it.

This has made the fridge function well but for even better performance in 40+ deg northern climes I fitted a fan from Jaycar (I will get a part number off it if anyone interested) and connected this through a temperature switch which is fitted to the boiler tube which turns on the fan if a preset temp is exceeded.

I think any talk of 3 way fridge operation should include a few words on HOW to operate the fridge. 

How many people do it correctly?

Too many people fiddle with the thermostat continuously trying to keep the temp down during the day.  Wrong!  Find the right setting and then leave it alone!

I use a wireless thermometer with the sensor in the cabinet on a middle shelf.  This way I can check the temp without opening the door.

On a setting of 3.5 to 4 (on gas) I have found that in the morning the temp will be close to zero.  Then during the day with opening & closing the door the temp will rise to 4.5 to 5deg.  This is fine.  I am happy with that.  Even on 240v I may only increase the setting to 5.  On 12v of course it makes no difference as it runs flat out.

A couple tips.  To prevent, or anyway greatly reduce the frost build up on the fins, I have a tuppaware type box in which I put tomatos & lettuce etc in.  It keeps them fresher longer and stops the moisture they give off freezing on the fins.  For the same reason if I have a jug of cold water in the fridge I put a plastic bag over it and secure it with a rubber band.

These things work for me and hopefully help someone else.

Cheers Neil

ah!!!! the "only way to do it" Hmmm!!!........now I'm thinking where have I heard that before!!!

the ONLY thing that needs doing is disposal of the waste hot air!!! a fan or fans placed in a strategic position will do this, the circualtory positioning of the fridge SHOULD have bee done in the initial installation

if your fridge is not installed correctly then this is the first step to take!!!

at it again I see!

oldtrack123 wrote:

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Hi Dave & Jim

Dead  air space is a real problem
The problem with many installations is the large gap between fins & wall of van &dead air space above fins, detracting from the natural draft effect.
The heat from the boiler adds to the problem  with hot air mixing with the cooler air & being drawn thru the fins
The boiler does not need /should not be cooled,
The fins can not be over-cooled
Correct baffling will increase the natural draft effect
I have  had standard fridges operating very well into upper 30s  ambient [a lot hotter in the fridge compartment] 
To prevent fans running unless required I have fitted Jaycar part #St3831 thermostat on top of fins about 3/4 along from boiler. 
Actually if there is sufficient room I rather fit the fans directly under the cooling fins again with a shroud & baffles to direct air directly thru the fins
This minimizes blockage of the top & bottom vents.

The fans do not normally run in cool weather AS the air vents are NOT obstructed
& the air flow is directed to WHERE IT IS NEEDED
Fans normally cut in when ambient gets around 30
If YOU want Max possible performance  this is the only way to do it

Peter

-- Edited by oldtrack123 on Thursday 14th of January 2010 12:42:20 PM

-- Edited by oldtrack123 on Thursday 14th of January 2010 12:46:48 PM

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Do we really have to have all this type of crap again, no wonder so many left this forum.

 

reza wrote:

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WHAT has high frequency power and air cooled transmitter valves got to do with cooling the fridge down??????

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Hi Reza 
My reply was to Jim 
regarding his post
"changing the airflow pattern could have unintended effects such as uneven cooling of the condenser. As I've not tried this set up I can't establish this would definitely occur but this thought comes from my background in radio broadcast transmitters where it is a known issue.
"""""

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I think I have given the OP very detailed description on how to obtain the best results using fans

If anyone can offer better they are welcome to.
 
By The way I did my 1st such modification way back in the mid 50s
 So have had plenty of experience
 I got the idea when I saw kero fridges in an old far north Qld mining town with the condenser in a water bath on top of fridges.

-- Edited by oldtrack123 on Thursday 14th of January 2010 05:19:01 PM

-- Edited by oldtrack123 on Thursday 14th of January 2010 05:22:49 PM

Ma wrote:

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oldtrack123 wrote:

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reza wrote:

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WHAT has high frequency power and air cooled transmitter valves got to do with cooling the fridge down??????

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Hi Reza 
Are you the self appointed forum censor ?

Thought Reza had just asked a question.  Can't see any censorship.

 

 

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That's all Reza did Ma but we are dealing with oldtrack123 here, pedantic as ever.

 

oldtrack123 wrote:

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JRH wrote:

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Do we really have to have all this type of crap again, no wonder so many left this forum.

 

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Hi JRH
In your  opinion where are  my posts crap????

 

 

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It is the pedantic manner in which you present them, nobody else is right only oldtrack.  And what is more you continually put other peoples backs up.

This is my last word on the subject, I have better things to do with my time.

 

are they computer fans Ray what size are they and how do you power them! automatically or manually, did you find they are of any benefit!