Pros Cons Swapping Absorption for 12VDC Refrigerator

[Josephine517]

After struggling to make the absorption refrigerator in our 2017 23D work, we contemplating swapping it out for a 12VDC. For the record the 23D has two exterior street side heat exhaust vents, we have installed heat exhaust fans and an interior fan. These changes helped a lot. We learned to not put room temperature items in the refrigerator, run on propane when temperatures are above 80 degrees and add ice to the refrigerator section when temperatures go above 90. But that’s what it takes to make the absorption refrigerator work.

I’ve read here in the forums airstream is now putting in the Nova Kool RFU6800 12V DC single 5.2 amp compressor in the newer model 23CB. This model will fit in my 2017 if I remove the microwave. The newer models vent the heat through the roof so my side vents my require a fan blowing out the top vent for hot days. Also my two side vents make a large opening for venting.

I’ve read one thread where the 12VDC was having the same issue as the absorption refrigerator keeping cool. I don’t know if the venting in the new airstreams is adequate, single roof top vent. But the poor performance lead me to look at another refrigerator model. The Nova Cool RFU6400 with dual compressor, 4.2 amp per compressor. This configuration allows for separate freezer and refrigerator control. This model will use more power to initially cool. I have no idea about power consumption after the initial cool down.

But the venting for this model is below the refrigerator. Appears to me taking air from the coach but I’m not sure how it vents out (i.e., vent into coach or out the back.)

So all that said, pro cons to switching to DC refrigerator. A working refrigerator is worth the extra power consumption for us. But switching from one problematic refrigerator to another problematic refrigerator is a no go.

https://www.novakool.com/rfu6800-1

https://www.novakool.com/rfu6400-d-1

[richard5933]

If you are doing this on your own keep in mind that you have options other than the Nova Kool.

In our coach we have a Vitrifrigo. They produce models in similar sizes to the Nova Kool. Not sure of all the variations from one to the other, but I do know that in our coach the Vitrifrigo will keep ice cream rock hard and the fridge at 35F-40F with ambient temps in the 90s and no a/c running in the coach.

That said, you will need adequate battery capacity regardless of which 12vdc fridge you install, as they all use more battery juice than an LP fridge running on LP.

[Josephine517]

Originally Posted by richard5933

If you are doing this on your own keep in mind that you have options other than the Nova Kool.



In our coach we have a Vitrifrigo. They produce models in similar sizes to the Nova Kool. Not sure of all the variations from one to the other, but I do know that in our coach the Vitrifrigo will keep ice cream rock hard and the fridge at 35F-40F with ambient temps in the 90s and no a/c running in the coach.



That said, you will need adequate battery capacity regardless of which 12vdc fridge you install, as they all use more battery juice than an LP fridge running on LP.

Thanks, I’ll look at Vitrifrigo also. Working in 90 degree temperatures without AC is exactly what I want to hear.

[uncle_bob]

Hi

Both the 6400 and 6800 come in dual compressor versions from Novakool. No matter how you look at it, the dual compressor version will do a better job on the freezer section.

All fridges (even the one in your kitchen at home) require some amount of air flow past them. They all have to dump heat somehow. This either involves a lot of fans or a "cold air in the bottom / hot air out the top" setup. There is no escaping from this.

I believe that both the 6400 and 6800 are "cold in bottom / hot out top" as they come from the factory. Any fans to do this or that to them are either options or aftermarket installs.

Keep in mind that the compressor fridges use quite a bit of 12V power when off grid. Folks with them often bump up to fairly fancy lithium battery systems ....

Bob

[Josephine517]

Bob, hmm maybe the justification I need for Lithium. [emoji57]

[jondrew55]

What do you mean by "after struggling to make the absorption refrigerator work..". Is it non functional as in broken, or just does not meet your expectations in hot weather. I can tell you from personal experience the Nova Kool FRU 6800 does not appear to be any more effective than any absorption fridge I've ever had. It does cool down quickly, but in extra hot, humid weather you're lucky to get the fridge much below mid 40s F.

[Josephine517]

Originally Posted by jondrew55

What do you mean by "after struggling to make the absorption refrigerator work..". Is it non functional as in broken, or just does not meet your expectations in hot weather. I can tell you from personal experience the Nova Kool FRU 6800 does not appear to be any more effective than any absorption fridge I've ever had. It does cool down quickly, but in extra hot, humid weather you're lucky to get the fridge much below mid 40s F.

Yes I read through your posts on the problem. And appreciate you documenting your issue. It great to hear from someone with first hand experience. That’s what got me to wondering if 12V is or is not the answer for us.

Is my refrigerator broken, no. I was told by airstream in 2017 when we first encountered this issue, my absorption refrigerator is working as design. I take them for their word. It’s a bad design. I’ve owned other travel trailers that didn’t have this issue.

I believe the problem is an undersized coolant unit with inadequate ventilation. The ventilation part of the equation falls squarely on Airstream. The “fixes” I did for this refrigerator that got it to work in temperatures above 90 degrees rather than 75-80 degrees as designed. So my expectation is a RV refrigerator that works to keep food in the safe zone when outside temperatures are in the 90s without adding ice and I’ll add an expectation I want faster recovery time when you open and close the door.

My hope is the newer 12V compressor types work to my expectation but I’m not convinced it will after reading your posts. I have noticed the 2022 23CB airstreams do not have any street side refrigerator vents in the side wall. I assume a roof vent is included. But after reading your posts, I’m now wondering if airstream designed into the new models inadequate ventilation once again. My thought is maybe a 12V will work better for me since I have large refrigerator heat exhaust vents with fans already installed. I expect compressor type recover time is significantly less.

Like I said I appreciate your first hand experience, that’s what gave me pause. It would be a huge disappointment to find out the refrigerator still has cooling issues after going through a swap out. We run our absorption refrigerator strictly on propane since the electric element isn’t up to the task when temperatures go up. I assume there are other advantages to 12VDV compressor but may not be worth the swap out to only change the power source.

[jondrew55]

On last weeks trip, it was hot, humid, but not constantly hot/rainy/humid like the previous trip. The fridge cooled down to about 40 overnight in covered storage (the AC was not on, so it was in the 80's inside the trailer). We had partial shade at the site we were at and kept the AC at 75-76 during the day, 71 at night. The fridge would still go above 40 during the day, especially when we were using it a lot. Overnight it would get down to about 38, which I think is acceptable. We also kept a cooler with water and sodas outside filled with ice to reduce opening up the fridge door. S this was a distinct improvement over the previous trip. And probably as good as my fridge will ever be.

[Josephine517]

Originally Posted by jondrew55

On last weeks trip, it was hot, humid, but not constantly hot/rainy/humid like the previous trip. The fridge cooled down to about 40 overnight in covered storage (the AC was not on, so it was in the 80's inside the trailer). We had partial shade at the site we were at and kept the AC at 75-76 during the day, 71 at night. The fridge would still go above 40 during the day, especially when we were using it a lot. Overnight it would get down to about 38, which I think is acceptable. We also kept a cooler with water and sodas outside filled with ice to reduce opening up the fridge door. S this was a distinct improvement over the previous trip. And probably as good as my fridge will ever be.

Wow, that’s a huge disappointment. My absorption refrigerator with the fixes I did works better than that. Yours is working about like ours did before the fixes. Any idea if it’s a ventilation problem?

[uncle_bob]

Hi

If you take a look at how AS does ventilation on the compressor fridges (both in vans and in trailers) it's all over the place. Some vent outside through panels. Others vent outside through roof vents. Some vent inside through various levels of "ducting".

There does not seem to be one "strategic plan" in terms of venting these fridges. Some have speculated that the "shell" of this or that trailer will be modified on future ( = who knows when) models to eliminate the absorption style outside venting. That could be correct or it could be bunk. Only time will tell.

What is true: If you pull air-conditioned air in past the fridge as opposed to hot outdoors air, it's going to have a *much* easier time staying cool. Not much help there while your trailer travels down the road ....

Bob

[Josephine517]

Sounds like I need to give the ventilation a lot more thought before moving forward with a swap. The refrigerators are on a 5-6 month backlog so a swap isn’t happening anytime soon anyway.

[skyguyscott]

I strongly suspect that the issue is not at all the type of refrigerator, as physics is physics, but rather most likely a ventilation issue.

I would wager that if adequate airflow made it past the coils, and carried the heat clear away, the thing would freeze ice.

Note that I have a '69, with the original Dometic absorption unit in it, still working like a champ. It has a roof vent directly above and behind it, with a large and adequate air intake directly behind it; no biscuit fans needed. I dread the day when the unit dies, it has been working for over 50 years now. It uses no electricity whatsoever in propane mode, as it lacks any problematic DC control boards. It can freeze water in the Fridge portion on a humid 90 degree day without even being set to the coldest setting.

[Daquenzer]

I really have never had an issue with the absorption refrigerator/freezer. I do think that if I had an awning on the side where the fridge is that it would be more efficient. Have you tried putting a fan in your fridge? I put a small one in mine and it seems to cool more evenly.

[uncle_bob]

Hi

Absorption fridges use more energy / get hotter / need more cooling than a compressor fridge. That's just physics. It's shown in the data sheets on the absorption fridges vs the data sheets on compressor fridges.

The important distinction is that absorption fridges run on easy to find / easy to transport propane for a *long* time. We'll get a summer out of a 40 gallon tank. Most of that goes to the fridge while in motion or off grid.

My absorption fridge works fine. Have there been hiccups now and then? Sure there have. However it's been chugging along at 33 degrees in this 90+ degree heat for the last month ( and for many summers before that).

Bob

[Josephine517]

Originally Posted by Daquenzer

I really have never had an issue with the absorption refrigerator/freezer. I do think that if I had an awning on the side where the fridge is that it would be more efficient. Have you tried putting a fan in your fridge? I put a small one in mine and it seems to cool more evenly.

I installed a heat exhaust fan and moved the thermostat on the fan that came with the refrigerator to above the heat stack so that it will come on sooner. I also deploy the street side awning when parked. That’s what took the working temperature from 75-80 to about 90. I add ice to the refrigerator compartment when temps go over 90.

Speaking of the heat exhaust fans, the fan that came with the unit was installed middle center of the refrigerator with a 130 degree thermostat switch attached to the fan. By the time the fan came on we were throwing away food. I added a second fan to blow heat out of the upper vent with a 90 degree fan thermostat I placed just above the heat fins. I also moved the original fan’s thermostat, the 130 degree switch, from the middle center of the refrigerator to above the heat stack. I found this arrangement works much better compared to how the refrigerator worked new. The upper fan usually turns on first. The fan in the middle turns on typically when the outside temperature goes above 80 when both fans will operate. I used a temperature gun over several weeks to determine the best spot to place the fan thermostats. But this is how I got to a working refrigerator.

I can say it’s embarrassing when I pull a beer out of my refrigerator and the beer is 50 degrees, a beer that was ice cold when I put it in the pre cooled refrigerator, and my son in his SOB trailer tells me to put my beer in his refrigerator and while I’m in there grab him an ice cold beer too. Then he adds, and why do I want an airstream?

I’m not new to travel trailers. I had four other trailer over 25 years before going all out to purchase our retirement trailer. None of them had the refrigerator design problem that our 2017 23D airstream has. Airstream told me the refrigerator is working as designed. I also want to say we love our airstream but airstream should be doing the engineering to install a working refrigerator, not me.

[skyguyscott]

Originally Posted by Josephine517

I also want to say we love our airstream but airstream should be doing the engineering to install a working refrigerator, not me.

After several years of reading these forums, witnessing the debut of new products like the BaseCamp and Nest, seeing some of the head-scratching changes and stabs-at-fixing those changes, I think I can honestly observe a lack of what I would call "engineering" at Airstream, if, by that term, you mean a systematic approach of measurement, calculation, purposeful design, comprehensive testing and implimenting actual improvement.

Perhaps with the new plant, which I understand includes some sort of lab, things will improve, but they need to do more than hire real engineers (you know, folks that understand physics, can do math and stuff rather than, you know, guess and try), they need to have the vision and support of management.

Or, to put it this way, if their bean counters were of the same caliber as their engineers, heads would roll.

[ITSNO60]

One of the things I found is that the RV manufacturers do not look at the installation instructions, I corrected several mistakes with mine. For one, the space between the back of the fridge and the back wall should be no greater than 1". Mine was 2" so I added 1" foam board to bring mine to within that 1", which forces air flow through the condensing fins instead of bypassing it. I also added a sheet aluminum curve to the top of the square fridge compartment where hot air was trapped which allows the hot air to gently flow out of the vent, 2 condenser fans on a snap disc and 2 very low speed 8" PC fans at the top vent. You don't want anything to radical as it will cavitate and interfere with the smooth, gentle convection. I also installed a Fridge Defend with fan control which controls my top vent fans. The only thing left for me to do is an evaporator fan and possibly an adjustable "snip the tip" thermistor.
I wouldn't feel comfortable with an all electric fridge but I don't have solar or upgraded batteries.

[drbrick]

Just to add to this discussion - our absorption fridge (Dometic) works as expected and is 20 years old... setting #3 usually about 39 at 4 - 35 in 90deg outside temp. Should mention this is the "old" style roof vent which works really well in heat dispersion (no added fans). My concern with with compressor type is "Boondocking". At a 5amp draw you need a whack of lithium batteries and solar. As it is we run 200amps of lithium and about 380wats of solar to feed our needs as Boondockers (talking 14 -21 days at a time).

[LilPeanut]

I have one of each. 2 campers. Pros of propane are the ability to go without hookups. The 12v use a lot of power. They are a hog second only to the AC which is in a league of its own. The benefits of 12v are no defrosting every month and rock hard ice cream. Personally I like ice cream a little soft anyway. I think I like our propane fridge better but they are both good.

Before such a drastic move, I would try to fix the propane fridge to be more acceptable. I have my thermostat that turns on 2 squirrel cage fans set to 80. I have a rooftop fridge vent, not sure if yours is on the roof or on the side. I could imagine the side vent is a greater challenge. Good luck.

[Trons4u]

Pro - you have more room in the compressor fridge than the propane. Compared mine to a buddy', ours is deeper and there are no fins that you have to defrost when they ice up.

I have the Vitrifrigo DP2600 in our '59 Tradewind that I installed, which is 12v or 120v. When we got the trailer it had an ICE box. Yep, you read that right. But after pulling everything out during the reno, I could tell at one time there was a propane fridge in there, it also had a 110v receptacle in the cabinet.

Sorry, back on track. The fridge has a built in fan that blows through the cooling unit. We have 300Ah of Battle Born batteries, we can go about 3.5 days before the batteries get down to 25%. I don't have solar yet, so use the generator to charge them up in about an hour.

It has worked well for us