Replacing 3-way fridge with 12v |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Topic: Replacing 3-way fridge with 12v Posted: 14 Apr 2021 at 7:08am |
Don't compare the dometic absorption fridge on 12v to the Danfoss/Secop units. You'll never want to use the Dometic on 12v except while actively towing so you have your alternator charging.
5-6 A is about right for the Danfoss compressors during operation. That is a lot. If it ran at 100% duty cycle that would be about 140 amphours a day. You would need about 300 amphours of battery at 12v and around 400 watts of solar just for the fridge. That's roughly what I put on the med fridge boxes in Africa and Central America. In RV use it's not going to run at 100% duty cycle but even at 50% it will still need a big upgrade in your solar electric system (around 200 watts and 150 amphours) or a couple hours of generator recharge time daily. Presumably you are already using your existing power system for other loads, so it's not available to run the fridge. How much your fridge consumes is up to you. Think of your Rv fridge as a temperature maintainer rather than a cooler downer. Don't put warm stuff in itand keep the door sealed as much as possible. If you do that then the existing Dometic will probably work fine for you, as it does for most of us. The difference between it and the Danfoss based ones is that the Dometic will just get warm if you over use it, the Danfoss will consume all your electrical energy trying to keep up. Personally I prefer the former failure mode to the latter. What I and many others do is ice down a high quality cooler and fill it with already cold drinks when resupplying. That way the fridge only has food in it and gets much less load on it. Works well for us. StephenH, the free piston stirling cooler is a great technology and you are lucky to have one. They are capable of achieving much lower temps than vapor compression coolers I think the reason they didn't take off us because they are expensive and at normal fridge/freezer temps the Danfoss compressors have more or less the same coefficient of performance so there is no real efficiency advantage. Now if you wanted to transport some Pfizer Covid vaccine your fridge would be the way to go. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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podwerkz
Senior Member Joined: 11 Mar 2019 Location: Texas Online Status: Offline Posts: 966 |
Posted: 14 Apr 2021 at 9:50am |
One of the first things I added to my propane fridge was a thermostatically controlled 12v smart-fan on the top vent. It makes a big difference in cooling performance of the absorption fridge. My fan is set to come on slow speed at about 85 degrees and by 100 degrees it is spinning at full speed. |
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r・pod 171 gone but not forgotten!
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StephenH
podders Helping podders - pHp Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6326 |
Posted: 14 Apr 2021 at 11:36am |
The FPSC was originally for pharmaceutical transport (no biohazards). It is refrigerator only and is set to cool to 4 degrees C +/- a couple of tenths. It cools down quickly and once at temperature, does not take a lot of power to maintain. It can cool down warm items at the cost of more electrical use, but it also maintains the temps even when the outside temp is in the 90's F. It wouldn't be suitable for Pfizer vaccine, but I have seen freezer models. I was fortunate to find it at my local ReStore for what I consider a very reasonable $100. I should have picked up two when I had the chance.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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Dromsie
Newbie Joined: 03 Mar 2017 Location: Utah Online Status: Offline Posts: 29 |
Posted: 14 Apr 2021 at 2:26pm |
What do you mean by FSPC?
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campman
Senior Member Joined: 26 Mar 2021 Location: La Salle, MB Online Status: Offline Posts: 209 |
Posted: 14 Apr 2021 at 2:39pm |
I do believe it is the abbreviation of "free piston stirling cooler".
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Andy and Laurie
'16 F150 5.0 4X4 w/factory tow pkg '21 RP192 "If the women don't find you handsome...at least let them find you handy!" Red-Green |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 14 Apr 2021 at 2:46pm |
FPSC's are unobtanium now AFAIK. I think they didn't take off because the Danfoss units already owned the market. Since they have about the same COP there isn't a big efficiency advantage of one over the other, unless you need really low temps. L
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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StephenH
podders Helping podders - pHp Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6326 |
Posted: 14 Apr 2021 at 7:32pm |
Ours has an Envirocooler label on it, but it is the same as this one:
This is the one I would like to get: |
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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offgrid
Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
Posted: 15 Apr 2021 at 3:13am |
1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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