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Thread: How to refrigerate a 20 sqft shed

  1. #1
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    Confused How to refrigerate a 20 sqft shed

    Hi

    despite of rumours about my death I'm still alive and working on some projects.

    Now I have a technical issue to solve: a shed with solar equipment / inverter / etc needs to be cooled down. It gets pretty hot inside and I'm looking for a viable solution to refrigerate such a tiny space.

    Several options came to my mind but I'm not yet satisfied. The problem is the tiny size of the space of about 20 sqft (height 9 ft).

    1) some TEC cooling, you can find TEC modules of different sizes on Amazon, however I'm not convinced that these are efficient. COP of TEC modules is somewhere around 0.5-0.7 (that means your cooling power is smaller than electrical power consumed, actually)

    2) I could run the gas line of nearby mini split through the shed and put a small heat exchanger there (made of copper pipe and a condensation pan, eventually + small fan), this is quite DIY however. Another problem with this is that the mini split may not run all the time but I need that space to be cooled under any circumstances.

    I estimate I need about 600-1000 BTU to keep that space at good temperature.

    Any other proposals? Something I do not know of?

  2. #2
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    Window unit. Or have somebody come put in a mini split and have it done nicely and no worries about if it’s gonna work good. Depends all on how much ya wanna spend.

  3. #3
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    Wine cooler unit.

  4. #4
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    Maybe gut a little mini fridge and build it in the shed. You could buy a used one cheap.

  5. #5
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    Quote Originally Posted by Hurst11 View Post
    Window unit. Or have somebody come put in a mini split and have it done nicely and no worries about if it’s gonna work good. Depends all on how much ya wanna spend.
    Walmart has them for $138. I've seen them as low as $89

  6. #6
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    Quote Originally Posted by oldguy1949 View Post
    Walmart has them for $138. I've seen them as low as $89
    far too oversized. And I do not want to cut a 2' x 2' hole into the wall. Refrigerant lines would be fine however.

  7. #7
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    Quote Originally Posted by Scoobie View Post
    Maybe gut a little mini fridge and build it in the shed. You could buy a used one cheap.
    yeah I was thinking about it. Get a mini fridge and dismantle it. The problem here is that I would need to put the lines through the wall, thus I would need to completely tear down the circuit and braze the system back together after putting the lines through the wall. The question here is, do these fridges have any valves inside to recover / recycle the refrigerant? I didn't service fridges yet, didnt look inside.

    Otherwise it is not a good job coz you have no easy way to pump out the refrigerant and I'm not going to release it to the atmosphere. If it is R600 then eventually you could drill a small hole into the line and burn it down, R600 is isopropane, burning it into CO2 wouldn't be a sin. Then I could braze a shradder valve onto the lines before putting everything together, for future maintenance.

    Another question then would be the regulation of the temperature, eventually getting too cold inside. I'm not supposed to cool the shed down to 40F! 70F would be fine, this is however not the temp range of a standard fridge.

    What I really lack sometimes are small portable mini split unit modules. In the range 500-1000 BTUs. Modular design that you can put together. Condenser, evaporator, controller, but as DIY modules. I know there are some small mini split modules for boats, they go down to 4000 BTUs, but this is still oversized and far too overpriced (2000 USD...)

  8. #8
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    Quote Originally Posted by gustavhorna View Post
    Hi

    despite of rumours about my death I'm still alive and working on some projects.

    Now I have a technical issue to solve: a shed with solar equipment / inverter / etc needs to be cooled down. It gets pretty hot inside and I'm looking for a viable solution to refrigerate such a tiny space.

    Several options came to my mind but I'm not yet satisfied. The problem is the tiny size of the space of about 20 sqft (height 9 ft).

    1) some TEC cooling, you can find TEC modules of different sizes on Amazon, however I'm not convinced that these are efficient. COP of TEC modules is somewhere around 0.5-0.7 (that means your cooling power is smaller than electrical power consumed, actually)

    2) I could run the gas line of nearby mini split through the shed and put a small heat exchanger there (made of copper pipe and a condensation pan, eventually + small fan), this is quite DIY however. Another problem with this is that the mini split may not run all the time but I need that space to be cooled under any circumstances.

    I estimate I need about 600-1000 BTU to keep that space at good temperature.

    Any other proposals? Something I do not know of?
    How did you come up with that load?

    Sent from my "smart" phone using Tapatalk

  9. #9
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    Quote Originally Posted by R600a View Post
    How did you come up with that load?

    Sent from my "smart" phone using Tapatalk
    scaling down 9000 btu for 500 sqft. as this is not a living space, it doesn't matter much whether you get 75F or 65F inside. I just need to get it colder.

  10. #10
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    Quote Originally Posted by gustavhorna View Post
    scaling down 9000 btu for 500 sqft. as this is not a living space, it doesn't matter much whether you get 75F or 65F inside. I just need to get it colder.
    You can take the wattage of all the equipment and calculate from the efficiency how many watts are being turned into heat in the room and you may find that the load is higher than you thought.
    I believe a fridge compressor is a bit small to cool a single computer let alone a power inverter.

    Growing up off grid all of our inverter and charging equipment was in an open air space so it stayed outdoor temp all year.

    Sent from my "smart" phone using Tapatalk

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  12. #11
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    Quote Originally Posted by R600a View Post
    You can take the wattage of all the equipment and calculate from the efficiency how many watts are being turned into heat in the room and you may find that the load is higher than you thought.
    I believe a fridge compressor is a bit small to cool a single computer let alone a power inverter.

    Growing up off grid all of our inverter and charging equipment was in an open air space so it stayed outdoor temp all year.

    Sent from my "smart" phone using Tapatalk
    well this approach may work however it is not possible to say how much wattage is dissipated e.g. from an inverter.

    For me it is just simpler: around 25 sqft, temp inside is about 100F, that needs to go down to lets say 75F, doesnt look too difficult!

  13. #12
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    Amana has a 7000 btu straight cool no heat ptac. It may be over sized but it would be better built than a window unit and cheaper than a mini split.

    Sent from my "smart" phone using Tapatalk

  14. #13
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    ps the load is mainly from sunshine, not from the equipment inside.

  15. #14
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    Quote Originally Posted by gustavhorna View Post
    well this approach may work however it is not possible to say how much wattage is dissipated e.g. from an inverter.

    For me it is just simpler: around 25 sqft, temp inside is about 100F, that needs to go down to lets say 75F, doesnt look too difficult!
    You can assume 80% efficiency and you should get a much closer estimate than using square footage.

    Sent from my "smart" phone using Tapatalk

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  17. #15
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    Quote Originally Posted by gustavhorna View Post
    ps the load is mainly from sunshine, not from the equipment inside.
    Is it insulated?

    Sent from my "smart" phone using Tapatalk

  18. #16
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    You might try
    https://loadcalc.net/

    Sent from my "smart" phone using Tapatalk

  19. #17
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    Really all you need to do is ventilate this space. Put a solar powered fan on there with some provision for outside air and it'll be fine.
    Since you stated pretty much all solar gain, maybe just painting the shed would take care of it paint it white or a reflective roof something like that.

    Sent from my SM-G950U using Tapatalk

  20. #18
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    Gus, Glad to see your still around. What Icy78 said. Most electronic equipment has an operating range of something like -20F to 158F. Yes keeping it cooler does improve reliability and service life. Insulation and ventilation (passive and mechanical) using solar powered equipment is a green solution. Use a fan with a temperature control and passive damper and it will stay warm in the winter too. Unless you have moved to the desert and using simple ventilation it not likely you will reach the extreme of 150F or more.

  21. #19
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    McLean midwest is a brand name as I recall that makes those small cooling units for milling machines in machine shops. They bolt onto the electrical panels to cool them, strait in and out airflow, small capicity.

  22. #20
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    How about a water coil, fan, drip pan, valve and a sprinkler. When it gets warm the valve opens to let water run through the coil, the fan blows through the coil cooling the shed, the water then runs through a hose to a sprinkler to water the lawn. If you want to get real fancy put in a sprinkler system and the water can alternate through different zones to do the whole yard.

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