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Can you offer some advice on refrigeration?

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  • Basketcase
    started a topic Can you offer some advice on refrigeration?

    Can you offer some advice on refrigeration?

    We have an off grid house on an island and our Dometic RGE400 fridge is giving us a hard time this year (pilot wont stay lit) and honestly, I've never liked the unit in the first place. I would really like to go solar. We already have a small solar setup, and I upgraded the charge controller in anticipation of a larger system to run a fridge. Hopefully I can present the challenges I have, and you can steer me right.

    The reason I don't like the propane fridge are because it is too small (8 cubic feet) and that temperature regulation is challenging. This is a 4 bedroom house where we stay for a week or 2 at a time, so we need to bring enough food for everyone for that long. Once you load that thing up, not only does it take a while to get down to temp, but on really hot days, it struggles to get there at all. I think we exceed it's capacity and expect too much from it. We PACK it full, and there is nothing but convection to circulate air.

    I see two options. My preference, mostly due to familiarity, is a typical residential fridge run off an inverter. I've done the math, and the size fridge I need wants about 900 watt hours/day. The benefit of this fridge is good temp regulation, large size, and price of the fridge itself if it needs replacement ($500-$600). Down side, I need an inverter (psw) and larger solar array/batteries than other methods.

    My other option is a 12/24v fridge. I know nothing about them except that there is one other one on the island. I have not asked them how they like it. The downside is the cost. One similar in size to the $600 conventional one is over 2k and does not seem to have a significant wattage reduction at about 650 watt hours/day. (although after reading that, I realize there is loss through the inverter as well) My wonder is, how well do they work at regulating temp and how do they like being packed full? Is it similar to a conventional fridge or my current propane fridge? The benefit is lower energy use but not by a dramatic amount IMO.

    My other loads are cell phone chargers and some LED lights. A worst case scenario of 300 watt hours if the house is packed. (we also use a lot of kerosene lamps). I have the benefit of only needing to do this during the summer months and really only loading the house up during july and august. The house is used from may to september, shuttered and closed after that.

    It appears to me that initial cost will be about the same. I need to upgrade my solar no matter which route I choose, but obviously more if I go 120v. One benefit is that I have a local supply of panels at .50/watt. I really don't want to sacrifice on size and better temperature regulation would be great to have. What advice can you give? I've read a lot on here about this. Obviously what I'm hoping for is confirmation that MY way is the best way. lol. That being said, I take advice when it is given so I appreciate what knowledgeable people have to say.

  • Paul Land
    replied
    Originally posted by Logan5 View Post
    search for solar chest type refrigeration. vertical front load units will run the compressor each time you open the door, chest type will cycle much less often and for a shorter run time. chest types can also maintain temp for many hours w/o power.
    Very close to what i use, chest freezer with temp control kicks on for seconds multi-times very cool but butt ugly. just set temp to 34-37F very low power consumption
    freez1.png
    Last edited by Paul Land; 01-16-2019, 09:07 PM.

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  • thastinger
    replied
    Originally posted by Moonie View Post
    I didn't see where you're calculating LP cost. I'm dealing with this exact ordeal at my off grid vacation cabin. I've burnt through 320 gallons of propane in 14 months, and at $1.79 a gallon that adds up. I'm going with a Dometic 65 dual zone. They make a larger 95 qt version that you might look into. Not spending $500/year on propane will pay for the Dometic in 2 years. I leave the fridge on year around, because they take 24 hours to cool down and I like keeping cold drinks, condiments, etc there so I don't have to haul those everytime I go.
    Do you have 120V power? I converted a chest freezer to a fridge and it only consumes .5Kwh a day.

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  • Moonie
    replied
    I didn't see where you're calculating LP cost. I'm dealing with this exact ordeal at my off grid vacation cabin. I've burnt through 320 gallons of propane in 14 months, and at $1.79 a gallon that adds up. I'm going with a Dometic 65 dual zone. They make a larger 95 qt version that you might look into. Not spending $500/year on propane will pay for the Dometic in 2 years. I leave the fridge on year around, because they take 24 hours to cool down and I like keeping cold drinks, condiments, etc there so I don't have to haul those everytime I go.

    Leave a comment:


  • LETitROLL
    replied
    Catch 22, you either get more cost and less selection with DC refrigerators or good price and great selection with Ac units but must run an inverter, the inverter will be the weak link and the new problem that you grow to hate with your plan, if you get a decent $500 to $800 dollar quality inverter then you wont have too many problems, but i have not seen too many sub $400 units that are going to be happy about cycling that fridge surge 10-20 times a day and hold up for very long, I like your plan on panels, batts, etc. just make sure you really check out inverters well and don't be overly optimistic about that side of things and then i think you will be okay. Everything else in the system may last many, many years but i would not expect the inverter to unless you spend the extra money for a premium heavy duty one, the startup surge on ac fridges is very significant and many times a day over weeks, months, years can take its toll.

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  • Basketcase
    replied
    Originally posted by J.P.M. View Post

    And don't be around when the ice melts and the container fails catastrophically.
    Exactly. I used to work at a restaurant and we'd get meat packed in dry ice. We used to put the dry ice in the big olive containers (plastic). It was fantastic. Of course this was when you could do stuff like that without getting put on a list.

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  • J.P.M.
    replied
    Originally posted by Basketcase View Post
    And dispose of "extra" dry ice in a 2 liter bottle
    And don't be around when the ice melts and the container fails catastrophically.

    Leave a comment:


  • Basketcase
    replied
    And dispose of "extra" dry ice in a 2 liter bottle

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  • J.P.M.
    replied
    Originally posted by SunEagle View Post

    Don't forget to use gloves. That stuff is cold.
    ~ -110 F. or so, FWIW. And on a serious note: Handle only in well ventilated areas.

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  • SunEagle
    replied
    Originally posted by J.P.M. View Post
    And for all treehuggers, mostly carbon neutral too.
    Don't forget to use gloves. That stuff is cold.

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  • J.P.M.
    replied
    Originally posted by Mike90250 View Post
    When you purchase your load of groceries for the 2 week visit, get a chunk of dry ice, it will help cool down the fridge the first day
    And for all treehuggers, mostly carbon neutral too.

    Leave a comment:


  • Basketcase
    replied
    Originally posted by Mike90250 View Post
    When you purchase your load of groceries for the 2 week visit, get a chunk of dry ice, it will help cool down the fridge the first day
    That's actually a pretty good idea. I may try that.

    Leave a comment:


  • Basketcase
    replied
    Originally posted by bcroe View Post

    On "bad days" your PV solar power may drop to 10%; even less if covered with snow. More "cheap panels" can
    be used to raise that, and the same panels can lengthen your solar day with multiple orientations. Bruce Roe
    The house is only used in summer so no snow to worry about. If the charge drops to 10% for too long that could be problematic though. Is that likely in July? I have a perfectly pitched, directly south facing roof for my panels that has no obstructions such as trees.

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  • Mike90250
    replied
    When you purchase your load of groceries for the 2 week visit, get a chunk of dry ice, it will help cool down the fridge the first day

    Leave a comment:


  • bcroe
    replied
    Originally posted by Basketcase View Post
    Since panels are so cheap, I feel like I can keep my battery bank smaller because it will be charging longer throughout the day, and even on bad days I should have plenty of charging. I'm trying to make it idiot proof so when I'm not there and there are people using the house, it will just work.
    On "bad days" your PV solar power may drop to 10%; even less if covered with snow. More "cheap panels" can
    be used to raise that, and the same panels can lengthen your solar day with multiple orientations. Bruce Roe

    Leave a comment:

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