converting a chest freezer (top load) in a refrigerator... with a freezer!....

unicornio
unicornio Solar Expert Posts: 217 ✭✭
in Off Grid Solar & Battery Systems #1
hi guys! ...

these days of winter is best to work indoors ... I'm taking advantage to convert my chest freezer in a refrigerator ... I followed the threads that had around here for this, and some others forums, and blogs... and I decided not to add any external thermostat but adjust the thermostat itself that brought the freezer ... for that I followed the instructions and learned a lot in this thread in this homebrewers forum:

http://www.homebrewtalk.com/f51/guide-set-internal-chest-freezer-thermostat-32f-eliminate-external-control-249612/


I managed to fit perfectly, so the scale of the thermostat knob and can be adjusted to temperatures above 0 ° C (32F), in fact right in the center the refrigerator works with temperatures of +5 ° C (41F), that perfect!... and I have not needed to buy anything, and everything is a simpler solution without any power consumption, being a passive and cheap thermostat ...

has been a success! ... am delighted, works great, as already described, the power consumption is ridiculous and the space is so larger, is a miracle! ...;-)
( I will not insist again that all the benefits of this system of horizontal fridge, only confirm that it is true what has been said, and it's worth ... my old refrigerator ate almost 4 kwh day! ...)

but now, we have no freezer! ...
(Here begins the interesting! ...)

I found something that can fix it, but I have to try it ... and test it...so I'm need to say it on here, if someone very aware of these colding things can say me what can be my future! ...;-)

I thought put into the chest refrigerator other small peltier refrigerator ( a DC portable fridge with 60w peltier system that works very well) so i need to changing again this other thermostat to work below 0 º, trying to reach -15 or maybe to -18 (59F to 64F), for use it space in frezzer temperature margin ...

I mean I've already turned the freezer in fridge, and now I'll turn a refrigerator in freezer! ... this is great! .... hehehehe

my project is based on being inside the refrigerator at about 5 ° C, it will only have to cool a bit more to reach freezing temperatures, and what worries me most is the power consumption that I accumulate, as I think that the peltier system will be less efficient in terms of waste of energy than the typical compressor system ... what you think? ...
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: converting a chest freezer (top load) in a refrigerator... with a freezer!....

    Yes, Peltier systems are much less efficient than a good quality refrigeration pump. In your chest refrigerator, you would be dumping the "waste" heat of the Peltier device too--increasing the energy usage of the "refrigerator" to remove that heat (i.e., 60 watt pelteir, 60 watts of heat).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • unicornio
    unicornio Solar Expert Posts: 217 ✭✭
    #3
    Re: converting a chest freezer (top load) in a refrigerator... with a freezer!....
    BB. wrote: »
    Yes, Peltier systems are much less efficient than a good quality refrigeration pump. In your chest refrigerator, you would be dumping the "waste" heat of the Peltier device too--increasing the energy usage of the "refrigerator" to remove that heat (i.e., 60 watt pelteir, 60 watts of heat).

    yeah, that's what I meant, but I think it should cost little work for the compressor of the chest fridge, since it is very oversized now, and just work a few minutes every few hours ...

    but how the peltier can work in that temperature range ... all the electronics of the fridge will be around 5°C, only the internal heatsink and the fan, would have to bear polar temperatures! .... what would be the peltier performance in this temperature margin? ...

    sure, we double waste of energy, heat and peltier power supply... the peltier consuming around 60watts @ 24v ...
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: converting a chest freezer (top load) in a refrigerator... with a freezer!....

    Stick a 40-60 watt lamp in the fridge and see how well it works.

    http://en.wikipedia.org/wiki/Thermoelectric_cooling
    Thermoelectric junctions are generally only around 10-15% as efficient as the ideal refrigerator (Carnot cycle), compared with 40–60% achieved by conventional compression cycle systems (reverse Rankine systems using compression/expansion)..[6] Due to this lower efficiency, thermoelectric cooling is generally only used in environments where the solid state nature (no moving parts, low maintenance, compact size, and orientation insensitivity) outweighs pure efficiency.

    What I am not sure of is the current needed to keep the freezer cold when there is not much heat flow required (stable state) and if you use a thermostat to turn the Peltier device off, then you may have a pretty efficient thermal "leak" from the warm space to the cool space.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • unicornio
    unicornio Solar Expert Posts: 217 ✭✭
    #5
    Re: converting a chest freezer (top load) in a refrigerator... with a freezer!....
    BB. wrote: »
    Stick a 40-60 watt lamp in the fridge and see how well it works.

    i hope that a bulb of 60w (i mean incandescent old bulbs) produces much more heat than the "hot" side heatsink of the Peltier, and Peltier power supply will be on the outside of the chest fridge ...
    BB. wrote: »
    What I am not sure of is the current needed to keep the freezer cold when there is not much heat flow required (stable state) and if you use a thermostat to turn the Peltier device off, then you may have a pretty efficient thermal "leak" from the warm space to the cool space.

    yes, I will have to adjust the peltier thermostat to work only when needed ...
    is that we have, Peltier system is to put already frozen foods, or when we have to freeze some, it will be about 24 hours before in the fridge, so the temperature difference must be minimal...
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #6
    Re: converting a chest freezer (top load) in a refrigerator... with a freezer!....
    unicornio wrote: »
    ...or when we have to freeze some, it will be about 24 hours before in the fridge, so the temperature difference must be minimal...

    If there is a significant water content in the food, then the energy to cross the freezing point is a lot more than the energy to cool them down to refrigerator temperature or to take them well below freezing afterward.
    SMA SB 3000, old BP panels.
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  • unicornio
    unicornio Solar Expert Posts: 217 ✭✭
    #7
    Re: converting a chest freezer (top load) in a refrigerator... with a freezer!....
    inetdog wrote: »
    If there is a significant water content in the food, then the energy to cross the freezing point is a lot more than the energy to cool them down to refrigerator temperature or to take them well below freezing afterward.

    yes!, i know, but I want to try!... of course I would need to make some ice cubes, and also to keep (well) frozen foods, but I do not need to make an extensive use of the freezer ...

    to try to achieve greater efficiency and less power consumption, I got out of the chest all electronic circuits, and power supplies, to be located in the chest compressor compartment, only fans and Peltier will be on the inside...
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