Fridge Cooling Fan

Discussion in 'Tech/Mech General' started by John Laidler, Aug 8, 2015.

  1. John Laidler

    John Laidler Funster

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    There have been a few thread on here about fitting a PC cooling fan to the back of the MH fridge to improve performance in hot weather. Although we haven't suffered from poor cooling in hot weather we also haven't suffered any extreme temperatures either so far but I guess it is only a matter of time before we do so I went ahead this week and fitted a fan to our fridge.

    The following describes what I did.

    The two main parts are a temperature controller, which although not essential I felt it was a bit more "elegant" a solution to have a controller rather than just switch the fan on and off when I felt we needed it. The other was the fan itself and I went for quite an expensive one as I wanted the fan to be quiet and the one I bought is almost inaudible but you can get much cheaper ones.

    The temperature controller was this one, part number SKU107685 bought from here for the massive price of £3.29 with free postage. http://www.ebay.co.uk/itm/50-110-C-Digital-Heat-Cool-Temp-Thermostat-Temperature-Control-Switch-DC12V-New/351399680014?_trksid=p3693.c100102.m2452&_trkparms=ao=1&asc=20140212121249&meid=175a4e0473394837baacdf26e6e9c221&pid=100102&

    This came within a couple of days but it was free of any instructions but a bit of Googling found this website which explains what the terminals are and how to use it. http://www.banggood.com/-50-110-DC12V-Cool-Heat-temp-Temperature-Control-Switch-p-912023.html

    The fan I bought was this one: http://www.ebay.co.uk/itm/121552181987

    The installation after I had finished looks like this:

    P8080013.jpg

    Of course in our PVC access to the fridge is very easy as it is behind one of the rear doors.

    The temperature controller was fitted inside a modified Raspberry Pi case but you could use more or less anything which holds it in place. As mentioned you can get cheaper ones but this one is very quiet. This fan has three wires, the red is positive 12v, black negative and the yellow is the control wire which is not needed. It comes with a second bit which has a resister in it to make the fan run slower and even more quietly which I modified by cutting off the resister and using what was left as the connection to the temperature controller after pulling out the yellow wire from the plug.

    P8080007.jpg


    The fan and the Raspberry Pi box were all held in place using cable ties fitted through the plywood shelf the cooker fits on.

    P8080012.jpg

    In the picture above the leftmost cable tie is holding the temperature sensor. The tie which runs transversely is securing the temperature controller and the bottom of the Raspberry Pi box.

    Rather than try and draw a wiring diagram I will explain the wiring using the four terminals on the temperature controller which are marked K1, K0, +12v and GND, which you can see on one of the pictures here; http://www.banggood.com/-50-110-DC12V-Cool-Heat-temp-Temperature-Control-Switch-p-912023.html

    The +12v terminal was connected through an in-line 1 amp fuse I bought from Halfords to a 12 volt supply I took off the back of the cooker where there was a convenient terminal block I could tap into. The GND was connected to the negative wire from the cooker.

    The K0 and K1 I initially thought were for the load but they are simply connected to the contacts in the relay and close when the set temperature has been reached. So to get the power to the fan I connected a loop of wire from the GND terminal to K0 and the connected the fan across the +12v and K1 terminals with the red wire going to the +12v terminal of course. This does mean the fan is permanently "live" as the switch is in the return but this was just the way it happened. It would be better to have the switch in the positive feed I think but this can easily done. You might be able to see how it is wired this in the picture below:

    P8080009.jpg

    The red and black wires coming out at the bottom are the supply to the fan. The little white plug in the top right is the connection to the temperature sensor.

    There are three little buttons on the temperature controller. If you press the one marked "set" once the display will flash and you can then use the + and - buttons to set the temperature the fan controller will come on. I set it to 25C at first so I could test everything worked as you can then hold the sensor in your fingers to warm it up and after seeing the fan start up you can let go and when the temperature gets to 23C the fan will switch off.

    You could do this for under £10 although I spent a bit more. It isn't a perfect installation as the 12v feed from the cooker is permanently on and is not part of the "Aux" circuit which is controlled from a switch inside the MH but I couldn't find any 12v switched supply anywhere near the fridge other than its own 12 volt supply which only comes on when the engine is running. So at the moment the fan can only be permanently switched off by removing the fuse - which isn't hard but I need to put a switch in there somewhere.
     
    Last edited: Aug 8, 2015
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  2. teensvan99

    teensvan99 Funster

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    That is a nice little unit. I shall fit one in my fridge fan circuit.

    steve & ann. ------ teensvan
     
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  3. Techno

    Techno Funster Life Member

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    Like it
    The kit option has a temperature cut in of 50c plus/minus 10%

    EDIT
    IMG_4523.jpg
     
    Last edited: Aug 8, 2015
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  4. bjandlin

    bjandlin Funster

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    Hello, I used this, found on ebay from China. Meant to control a fish tank heater.
    About £10 if I remember correctly. Has adjustment for high & low switching.
    Works well.
    Barrie.
    DSC01194.JPG DSC01215.JPG
     
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  5. John Laidler

    John Laidler Funster

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    That's useful to know, I wasn't sure what temperature to set it to. It seems high but of course there is a lot of heat generated at the back of the 'fridge.
     
  6. Techno

    Techno Funster Life Member

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    Yes I'm glad you didn't take it as criticism
    I figured if they manufactured that with those parameters that they must have done some research
     
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  7. John Laidler

    John Laidler Funster

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    I've got a 'fridge thermometer which has the sensor on the end of a cable and the next time we are using it I'll use this to see what sort of temperatures are reached behind the fridge. We are off the France next month so hopefully it will get some hot weather testing!
     
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  8. Tom A

    Tom A Funster

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    We have a Bessacarr with a factory fitted fridge fan. There's a switch to turn it on and off but I've never heard the fan running. Do I understand correctly that it won't come on until the temperature at the back gets to a certain level ?
     
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  9. Tom A

    Tom A Funster

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    Duplicate post. :(
     
    Last edited: Aug 8, 2015
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  10. Tom A

    Tom A Funster

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    Triplicate post. o_O
     
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  11. Judge Mental

    Judge Mental Funster Deceased RIP

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    Here's mine...works a treat:)

    IMG_20150808_180824.jpg
     

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  12. John Laidler

    John Laidler Funster

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    I'm not sure but I suspect there would be a sensor and if so it won't come on unless it gets really hot, which as I understand it is likely to happen when the ambient temperature outside the MH is above say about 30C - at which point the temperature behind the fridge could be something like 50C.
     
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  13. Robert Clark

    Robert Clark Funster Life Member

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  14. John Laidler

    John Laidler Funster

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  15. Robert Clark

    Robert Clark Funster Life Member

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    I was wondering if it would also be a switch?
    Plus it could be mounted in a visible location
     
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  16. John Laidler

    John Laidler Funster

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    Anyone who has a 'fridge which is more difficult to access than ours might like to consider trying to fit the fans from the outside. While looking at options where to fit the fan I found the external grilles are easy to remove. On the left hand side of the grille there is a catch which with a bit of coaxing could be slid upwards - as shown below. This is the catch which holds the left hand side of the the grille on but there is no equivalent on the right hand side, because there the grille is held on by a spring clip. If you now pull away the left side, pivoting on the right hand edge the whole grille will come free after a bit of gentle tugging. I think you will find there is room behind the grille to fit a fan, probably two I think as they will be less effective than a fan directly beside the condenser but of course you will still need to find a 12 volt feed from somewhere. The fans could be mounted with cable ties around the horizontal slats in the grille - cutting the insect mesh behind the grille carefully of course to ensure the bugs stay out - and/or just seal the holes with silicon.

    This advice comes with a big health warning of course - your grilles may differ so don't blame me if yours comes free in two bits!

    P8060004.jpg
     
    Last edited: Aug 8, 2015
  17. John Laidler

    John Laidler Funster

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    I can't see a switch on it so I suspect it will be like the one I bought - it springs into life as soon as it is connected. But if you had somewhere to mount it within the reach of the sensor cable you could also fit a little rocker switch next to it at the same time. Externally mounted like this, rather than hidden away like mine would of course give you something to play with!

    What mine does is it remembers the temperature setting when it is disconnected which is something you would want in any controller but the descriptions don't tell you this I found. If you had one that forgot the setting then you would want to fit the switch into the feed to the fan only and leave the sensor powered up - I think they only take a negligible current and if you have solar like we do then it isn't going to run the batteries flat.
     
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  18. bjandlin

    bjandlin Funster

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  19. Lenny HB

    Lenny HB Funster

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    Excellent post @DBK.
    This time I went for a couple of quiet fans but the airflow is not enough so probably upgrade to the ones you have used or something similar. Also find the electrical mechanical type thermal switches have a far too large hysteresis i.e. switch on at 50 deg but don't switch off until temp drops to 30 deg useless at the back of a fridge so looks like a change to one of the temperature controllers.
     
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  20. Techno

    Techno Funster Life Member

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    The ones I fitted don't simply turn on/off but vary the fan speed too so as the temperature drops the fan gets even quieter
     
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