I have a 60L Evercool clone (Techniice) which I use as a freezer. I have it set to minus 5 degrees which for me (located near Yeppoon in Qld) is about the minimum to keep bread, ice trays and frozen food in a frozen state. Guess it depends on where you are regarding ambient temperature and what you want to keep frozen.
Cheers
Joe
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Hino Rainbow motorhome conversion towing a Daihatsu Terios
Run our 40 litre Everkool at -15 but have plenty of battery & solar capacity to keep it & my beer fridge (both mounted in boxes on the back of the truck) powered. If an extended period of bad weather did drain the batteries the Redarc 24/12V 40Amp DC/DC charger gets them back up after a reasonable drive.
Darrell & Sandra
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Love the bush & our native environment. Conservationist, not a bloody Greenie.
My experience from driving refrigerated transport -18 is the go, our home freezer is set on -18. If we were moving ice cream -22.
Chain of responsibility governed us in the industry for safe handling of food.
2 degs to and not above 4 degs was for chiller products, we had company policy with fresh fish, transported at zero and the management would down load information regularly from frig motor computer to keep us honest.
If you are storing meat for any length time try cry o vacuuming (placing the meat in sealable bags with the air sucked out) will at best keep your meat good for 16 days at refrigerated temperature. We did that on 2 major one month long trips camping with out any problems. Ask at your butcher, most will do it into meal size bags.
So to answer you question -18 deg cel. for the safe storage of frozen products. Ralph.