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mecamero

Fridge fans thermostat setting

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Hi, 

I have fitted a couple of 12v fridge fans to extract hot air and increase air flow at the back of my fridge, particularly for Summer visits to France. I have it controlled by an electronic thermostat, which allows me to set the on and off temperatures. I currently have it set for on at 23C and off at 21C. When it's hot weather it runs continually, when it's cooler it cycles, but I can hear it switching on every few minutes. I am interested to know if others have a similar set up, and what on/off temperatures you set? 

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Yes I have the same setup. I ran the fridge with the fans disabled and then measured the probe temp. (53c).  I then set the fans to run continuously and measured the temp after about an hour.   (38c).    I currently have the fans set to turn on at 48c. which is between the two temps measured above. The hysterisis is 2c so fans are off at 46c and on at 48c.

Has dramatically improved the fridge operation and cycles well when hot but fans are off when cooler.   23c is too low in hot weather, the fans just can't cool enough. Operation on gas produces slightly higher readings.  

 

By the way I am measuring the actual fin temperature not the air.   If measuring the actual air temp at the top vent  then readings will be different as they will be affected by ambient air. Fin temp is more constant.  

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Hi swaggy,

Thank you for your reply. I currently have the probe measuring the air temperature close to the fins. I like your scientific approach. I will adjust my probe to be against the fins and change the temperatures I have set. It worked for my holiday in France, as it definitely helped the fridge work more effectively in hot weather, but it ran nearly all the time in hot weather, and cycled on and off frequently on cooler weather days.  

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FWIW my setup uses two PC PWM fans and a little controller I made. It varies the speed depending on the temperature and is silent except in extreme temperatures. At the moment speed varies linearly from minimum to maximum between 20C and 40C. Temperature probe fitted by the fins.

 

Unnecessary bling but I wanted a project!

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Hi TinShack,

Is your 20 to 40C measuring the air temperature or the fin temperature?

 

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An alternative solution is to get two 4 inch 12V computer case fans and wire them in series. This will mean they run slower so make less noise but will still move air - which it is what it is all about. Put one fan in the bottom vent blowing in and one in the top vent blowing out - the direction of rotation and air flow are embossed in the outside edge of the fan frame. All you need in addition is a switch so you can turn them off when travelling.

Simples?

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9 hours ago, mecamero said:

Hi TinShack,

Is your 20 to 40C measuring the air temperature or the fin temperature?

 

 

It's not in good enough contact with the fins to properly measure their temperature. It's really measuring air temperature in the vicinity of the cooling fins. I may well adjust the temperature thresholds in time, but for now it's OK. The sensor is a DS18B20 One-Wire stainless probe, the 2 fans are quiet 140mm types mounted on a 22swg ali plate, and the controller is a little Arduino Teensy that measures temperature and generates the PWM signal. Power is taken from the 12v auxiliary connector on the back of the fridge. The ali fan plate just sits behind and is held in place by the top fridge vent and can be just lifted out after removing the vent. It's quite secure to travel with it in place if necessary.

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