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Splitting the power supply for temp controlled fermentation fridge.

Discussion in 'Electronics, Hardware & Software' started by thewobblythong, 14/5/16.

 

  1. thewobblythong

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    Posted 14/5/16
    Apologies if this has already been asked. I did do a search but came up with nothing...

    So i've got a large fridge set up with an STC 1000 and heating belt which is used as a fermentation fridge. This works great, and has vastly improved the quality of my finished beers, but i keep wondering about the freezer unit up above. Since the temp control unit is controlling power to the whole fridge, the freezer sits at room temperature most of the time while fermenting. Has anyone heard of anyone splitting the power supply for the fridge into two separate inputs? One for the fridge and one for the freezer?

    If i can get the STC 1000 just to control the bottom fridge section, then i can use the top freezer section for hops and yeast and such.

    At the moment it's a what if? And potentially a how to? If it is possible, then i'll hunt down a qualified electrician so I don't fry anything, but just wondering if anyone has done this before.

    Cheers,

    Wobbles.
     
  2. trevgale

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    Posted 14/5/16
    Typically with almost all fridge/freezers there is only one compressor and it cools the freezer, the cold air is then transferred to the fridge with a fan or just with baffles. There is no way to power the fridge and freezer separately.

    With some modification you might be able to let the freezer run normally, seal off the fridge section and use the STC to control a fan to transfer cold air to the fridge compartment when required. It would depend on the setup of your fridge as to how easy this would be. With how easy it is to find a cheap or free fridge/freezer on gumtree it is probably not worth the mucking around.
     
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  3. megabyte

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    Posted 15/5/16
    I think I'll be giving this a shot with one of my fermenting fridge/freezers. It seems to operate the way trevgale describes with all the cooling happening in the freezer and air being ducted into the fridge space as necessary. Just need to override that ducting fan then I should have a working freezer with STC-Controlled fridge compartment.

    Currently I store my hops in SWMBO's freezer so she'll be glad to see them out of the house.
     
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  4. thewobblythong

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    Posted 16/5/16
    yeah, same here. SWMBO has been very, very, very gracious about my brewing activities impeding on her personal space. if I can make this freezer functional, not only will i get hops out of her freezer, but I can possibly put some stuff that she needs in there, which is a double win.
     
  5. MHB

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    Posted 16/5/16
    Some fridges do have two separate units, one for the fridge, the other for the freezer, just have a look under the back of the fridge and see if there are 1 or 2 compressors.
    If one, probably not much you can do, if two you should be able to do something.
    What makes me wonder is that the freezer is at room temperature, if the fridge was the "normal' one unit type the freezer would still be cold.
    Mark
     
  6. klangers

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    Posted 16/5/16
    A domestic fridge has 1 compressor and two evaporators. One evaporator with a lower evaporating pressure (and therefore temperature) for the freezer, and the other set higher for the fridge compartment.

    Sometimes there is only 1 evaporator and that's for the freezer. In this case the air enters the freezer first.

    If you have two evaporators and 1 compressor, you can't do anything about it. As mentioned above if you have the second variety you can change the ducting of the air. In any case, the best you'll get is a freezer that doesn't work at all, and a fridge that does work (as you've ducted the air such that you've bypassed the freezer). The only way you'll ever have truly independent control is if you have 2 compressors, each on an independent refrigeration circuit.

    Note that the presence of two compressors doesn't guarantee you that they are on separate evaporators. Sometimes there are two so they act as a crude variable power output with cascading capacity control. One compressor on = 50% output. 2 on = 100%.


    Industrially, we put all sorts of valving trickery to enable us to vary the evaporating temperature, and we also have variable speed compressors and all sorts. You can't do that with a home fridge.

    I'd recommend to just let it run otherwise you're in danger of upsetting the very inflexible arrangment and getting slugs of unevaporated refrigerant through your compressor which will bugger it up.
     
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  7. Benn

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    Posted 16/5/16
    Having almost completed my Diploma in French electricity, I concur with the above.
     
  8. megabyte

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    Posted 17/5/16
    Thanks for this info klangers, I always wondered how they worked.

    For fridges with separate fridge/freezer temperature controls I can't imagine how they'd work using two evaporators (unless they vary the pressures somehow). Could it be that these types of fridges use the latter approach cooling the freezer then ducting air to the fridge as necessary?
     
  9. Moad

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    Posted 17/5/16
    Never thought to control something to push air down into the fridge. This could be very useful.

    Drive some kind of valve to hold open a cover and turn a fan on...
     
  10. Mikeyr

    " wait.. I had something for this.."

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    Posted 17/5/16
    PVC pipe with half an s trap and with a flap on the top, (held down by gravity), like a semi's exhaust pipe
     
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  11. klangers

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    Posted 17/5/16
    I daresay the temperature control works in preference to the freezer (ie freezer is "master" and fridge "slave" when it comes to calling for the compressor to be turned on). If the freezer requires cooling but the fridge doesn't, the fridge evaporator fan might not turn on. The designs do vary a bit, but the temperature control is pretty rough.


    I agree with this answer as something to try, but you'd need a pretty sizable fan to get the pressure necessary to raise the flap.

    Also, you'd need to do something about the fridge evaporator, if your fridge has one as well as a freezer one. Otherwise, it'll keep running too and the aim of pushing cold air from the freezer to the fridge won't really be of any value.

    If you only have one evaporator in the freezer, then off you go; best of both worlds. Keep your freezer freezing and your fridge fermenting.
     
  12. thewobblythong

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    Posted 18/5/16
    Cheers for the explanation klangers. Really appreciated. Great to get a better idea of the background of this. Suspect a chest freezer is next inline.
     
  13. Bribie G

    Adjunct Professor

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    Posted 18/5/16
    Aldi chest freezers must be on the horizon again by now, keep a lookout - they are usually dirt cheap but good reports, mine's about 3 years old now and purring away in the garage as new.
     
  14. Ducatiboy stu

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    Posted 18/5/16
    I was talking to a fridgy mate yesterday over a few beers and I asked him if it could be possible

    he basically said " Most modern fridges ( basically in the last 10 years ) draw cold air from the freezer to cool the fridge. You could modify the the air feed but it would be a bastard to set up and control.""

    His final answer was " dont fucking bother it probably wont work that well and its a lot of dicking about "


    Add that to what Klangers said
     
  15. Benn

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    Posted 18/5/16
    image.jpeg
     
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  16. Ducatiboy stu

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    Posted 18/5/16
    If you want to dick around with a solution that may not work then your answer is YES :)
     
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  17. SpillsMostOfIt

    Self-Propelled, Portable Meat-Based Filtration Sys

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