Replacing 3-way fridge with 12v
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Forum Name: Podmods, Maintenance, Tips and Tricks
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URL: http://www.rpod-owners.com/forum_posts.asp?TID=14548
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Topic: Replacing 3-way fridge with 12v
Posted By: Dromsie
Subject: Replacing 3-way fridge with 12v
Date Posted: 13 Apr 2021 at 4:22pm
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I tried searching for this topic but no luck. Please redirect if a thread already exists. Has anyone replaced the stock 3-way fridge with a high efficiency 12V fridge like you find in most camper vans (I've been looking at Isotherms)? I'm tired of dealing with the fluctuating temps that result from using gas. I've figured out a few tips for keeping the temp consistent, but they can be incovenient. I'm just wondering if anyone has done this mod and can share what model fridge they bought and how difficult it is (I'm handy and have done lots of mods already). Here are my tricks for keeping fridge cool 1). Try to park with side of R-Pod with fridge vents pointing north, so they don't get direct sun. 2). I removed the microwave and made that area a storage cabinet. I realized that this area collects a lot of heat from the fridge, so now I leave the door open and don't store anything up there, so the heat dissipates into the camper, but I lose valuable storage. I plan to install a vent on the side of the cabinet and put a little fan up there. 3). Can add more fans and baffles to vent compartment 4). Make an "awning" for the fridge vents to keep direct sun out. Thanks, Seth
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Replies:
Posted By: offgrid
Date Posted: 13 Apr 2021 at 6:22pm
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There have been several threads on This topic you could do an advanced search for.
The isotherms and equivalents pretty much all use the Danfoss/Secop dc inverter based compressors which have been around since the 1980s and are well proven all over the world. I personally installed them in medical fridges in Africa in the early 80s so can vouch for their quality and reliability. The issue is that you will use a lot more energy from your battery. So if you boondock you'll need more battery and solar and/or run a generator significantly more. If that's ok with you then go for it. If not then stick with the propane. It's much less efficient but propane contains about 200x as much energy per pound as a lead acid battery so way more than makes up for it. ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
Posted By: jato
Date Posted: 13 Apr 2021 at 6:23pm
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Hi Seth, Good ideas above. I have done #1 and #2 from the time we first got our 177 back in 2011. #3 - I found out after struggling with the vacillating temps for 4 years my brother re-positioned the bi-metal switch placing it just less than 2 inches from the cooling stack chimney. The resulting change was amazing, the 2 muffin fans kicked on at lower temps and stayed running a lot longer resulting in much lower temps in the fridge. Unfortunately the original fridge 'kicked the bucket' last fall (lasted 10 years) so I ended up spending the big $$$ to replace it with the identical RM 8501. Having had a couple minor issues with the new one (broken eyebrow that encases the display panel/mother board - which they replaced) and a button that didn't light when pushed (electric mode) even though the fridge would cool in this mode FR decided to send me a whole new fridge! So now I have an extra, built last October. If interested you can look under the flea market tab. Sorry I can't give any advice or wisdom for what you are looking for but wanted to say that your four points listed are valuable ideas that all of us could utilize for a more efficient and stable temp inside the RM 8501 unit. I do know of an individual who tried to use a household gas model but it was short lived - didn't appreciate the bouncing around that home fridges aren't built for. ------------- God's pod '11 model 177 '17 Ford F-150 4WD 3.5 Ecoboost Jim and Diane by beautiful Torch Lake "...and you will know the Truth and the Truth will set you free." |
Posted By: StephenH
Date Posted: 13 Apr 2021 at 6:25pm
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Well, I can't answer your first question. I have a 12V Free Piston Sterling Cooler chest that came with a 120V adapter. It does work quite well and will run in the vehicle overnight without running down the battery. I have appreciated having it to hold things that should not get above 40 degrees, such as meats. We move it between tow vehicle and RPod as needed. Your suggestions on keeping sunlight off the side of the RPod with the refrigerator are good. I did add a couple of muffin fans to the top vent and wired them into the existing vent fan circuit so they turn on and off with the existing one. I have not added any baffles. I do clean the gas burner and vent periodically to make sure it is clean and will be working at top capacity. I also added a double-fan that attaches to the fins in the refrigerator to circulate the air. Everything together seems to help and unless I put something warm into the refrigerator, it does seem to keep good refrigeration temperatures. I have resorted to removing the freezer compartment so the full cooling will be used to cool the refrigerator when the temperatures were very high. We will be doing some travel out west this summer and will likely have to do this to keep things cool. Even so, the FPSC unit will be the one which will make sure the really sensitive items stay cold enough. I can live with warm drinks. I don't want to risk food poisoning. As for searching, use the advanced search. It will allow you to expand the date range. The default is to only search posts no older than six months. The advanced search will allow you to search without a date limit. ------------- StephenH Happy is the man that findeth wisdom,... http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
Posted By: marwayne
Date Posted: 13 Apr 2021 at 7:10pm
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------------- If you want something done right, do it yourself. 2011 RP172, 2016 Tundra 5.7 Litre, Ltd. |
Posted By: StephenH
Date Posted: 13 Apr 2021 at 7:42pm
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Marwayne, How did you attach the support to the side of the RPod? Is it suction cups? I'm guessing it is PVC pipe. I recognize the Reflectix. Also, does it break down for compact storage when not in use or when on the road? ------------- StephenH Happy is the man that findeth wisdom,... http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
Posted By: Dromsie
Date Posted: 13 Apr 2021 at 8:47pm
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Offgrid, I currently have 2 6-volt batteries. I run a portable solar panel when camping. I'm in the Southwest, so plenty of sun. I believe those nice 12v fridges are very energy efficient...unlike the Dometics when in 12V mode. My buddy has a sprinter with one installed and he never has battery issues, and he doesn't have too much more solar than I do. I assumed someone has put one of these in their Pod, I'll try the advanced search. Seth
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Posted By: Dromsie
Date Posted: 13 Apr 2021 at 9:34pm
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Just to clarify, I'm thinking of a marine 12v fridge similar to this one (the dimensions are a little off). https://www.westmarine.com/buy/isotherm--cruise-130-drink-stainless-steel-4-6-cu-ft-ac-dc-left-swing-4-sided-stainless-steel-flange-no-freezer-compartment--17157389?recordNum=8 I think I'm looking at this correctly, but these type of fridges pull anywhere from 2-5 amps depending on the brand. The dometic that came stock pulls about 10 on 12v. With a 225 amp hour battery system and a solar panel, I don't think I'd ever have battery issues. Seth
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Posted By: marwayne
Date Posted: 13 Apr 2021 at 11:28pm
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PVC pipe, it rests on the fender, suction cups hold it to the wall. Reflectix is held in place via Velcro. ------------- If you want something done right, do it yourself. 2011 RP172, 2016 Tundra 5.7 Litre, Ltd. |
Posted By: marwayne
Date Posted: 13 Apr 2021 at 11:28pm
https://postimages.org/">
------------- If you want something done right, do it yourself. 2011 RP172, 2016 Tundra 5.7 Litre, Ltd. |
Posted By: offgrid
Date Posted: 14 Apr 2021 at 7:08am
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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.  ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
Posted By: podwerkz
Date Posted: 14 Apr 2021 at 9:50am
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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. ------------- r･pod 171 gone but not forgotten! |
Posted By: StephenH
Date Posted: 14 Apr 2021 at 11:36am
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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. ------------- StephenH Happy is the man that findeth wisdom,... http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
Posted By: Dromsie
Date Posted: 14 Apr 2021 at 2:26pm
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What do you mean by FSPC? |
Posted By: campman
Date Posted: 14 Apr 2021 at 2:39pm
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I do believe it is the abbreviation of "free piston stirling cooler". ------------- 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 |
Posted By: offgrid
Date Posted: 14 Apr 2021 at 2:46pm
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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 ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
Posted By: StephenH
Date Posted: 14 Apr 2021 at 7:32pm
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Ours has an Envirocooler label on it, but it is the same as this one: https://fpsc.twinbird.jp/products/detail.php?product_id=103 - https://fpsc.twinbird.jp/products/detail.php?product_id=103 This is the one I would like to get: https://fpsc.twinbird.jp/products/detail.php?product_id=104 - https://fpsc.twinbird.jp/products/detail.php?product_id=104
------------- StephenH Happy is the man that findeth wisdom,... http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
Posted By: offgrid
Date Posted: 15 Apr 2021 at 3:13am
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Here ya go
https://www.ebay.com/itm/FPSC-Free-Piston-Stirling-Cooler-Global-Cooling-DHS40-1-Portable-Freezer-25L-/283630513996 - Twinbird ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |