Refrigeration

[gordon2]

Originally Posted by jim_ivy

...
Eventually I got a Dometic CF-50W and could not be happier. ...

The electronics have a programable shut off so that it will not drain your battery below the level you set...

Looks similar to the Indel B 31 I have. Both have Danfoss style compressors. My Indel B is smaller.

I too am happy with mine but I could be happier.

First, the low voltage shutoff is just a three way selection and my experience is that even on the least conservative setting, the voltage drop when the compressor kicks on is often enough to cause the fridge to shut off. This happens often if I have the fridge in the car and shut the engine off. Then the next time the compressor comes on the fridge shuts down. Note that this occurs when I use the heavy duty cigarette plug in the car.

In the camper I am using (basically) a short run of large gauge wire straight to a group 31 battery with only 30 amp Anderson PowerPole connectors for the disconnect. The lowest voltage setting works a little better than in the car (with the cig plug) but the other two more conservative battery saving settings cause too many fridge shut downs.

Second, these are "portable" fridges which has its advantages.. but they are also heavy. I see the Dometic CF-50W is 45 lbs before you even put food or drink in it. Since it holds (72) 12 oz. cans, it could be over 100 lbs. - rather much to be lifting. In fact I think my smaller one is as much as I want to lift and move around, but that means I am more limited in how much food it will hold. On the other hand, the larger models (up to a point) use the same compressor and assuming pre-chilled food, they use about the same amount of power regardless of storage volume.

Lastly, in some boon-docking situations propane still has advantages. Per the specs on Dometic's site you can expect to use 18.5 amp hours a day for 41F internal and 90F external temps. I think 37F is a better fridge temp so figure at least 20 AH /day of battery needed, and more if you open it a lot, add food, it's in the sun, etc. For a solar boon-docking setup I would figure 3-4 days of reserve for cloudy days and that pretty much requires a dual battery setup even with plenty of solar panels. Certainly doable if you want to go that route.

Other than those things I agree with all the plus points you mentioned and I am happy with my purchase. I do recommend the models with AC and DC operation if its a portable unit. That makes it very usable as a beer fridge, supplementary deep freezer, etc for the house.

[Mike Meyer]

I have owned an ARB 50 quart fridge freezer for about 7 years. I have not had the shut off issues only once when a loose battery connection prevented recharge. It worked fine on 200 watts of solar with 2 200AH 6 V Trojan golf cart batteries during the day but shut down at night. I could tell my batteries were low but they seemed to recover during the day.
We typically boondock on the Outer Banks and run it as a freezer. We rotate water bottles through an Rtic cooler. I have ice for cocktails and keep my shrimp and meat frozen.
I agree that they are heavy especially when full and if set up right are very useful , we use it often to keep food frozen when we travel to out of state family reunions or grocery shop at Jungle Jim’s in Cincinnati.
They seem to be getting more expensive over the years though.
If you want the Cadillac look up National Luna. Built like a tank to transfer medicine in Africa.

[gordon2]

Originally Posted by Mike Meyer

...
We typically boondock on the Outer Banks and run it as a freezer. We rotate water bottles through an Rtic cooler. I have ice for cocktails and keep my shrimp and meat frozen....

I ran some tests when I got my Indel B 31.... this was the result of one of them:

Test # 6: Used as Freezer (Setting 5 degrees, Eco mode,120 VAC inside house, food pre-frozen):
592 watts in 24 hours.

That would be be about 50 amp hours on your battery in a day (disregarding the losses involved in the fridge converting 120 VAC to 12 VDC.

As you would expect, setting it at 5F uses a lot more energy that setting it to 37F. Your solar is doing a good job.

I also ran some tests running it in the Scamp on 12 VDC with air temps in the comfortable 70s. Power usage usually ranged from 200 - 260 watts / 24 hours with typical use (occasional opening, pre-chilled food, etc) and with the internal temp set from 34F to 39F and eco or normal mode. So ballpark 16-22 amp hours a day on a battery when used in fridge mode.

I also "stress tested" it with 24 twelve ounce cans and the cans and fridge started at 68 degrees, fridge set to 34F, max cooling.

The compressor ran non-stop (at about 60 watts) for a little over six hours. The fridge consumed 360 watts. The upshot of this is for my group 31 battery is this. If only using the battery for power and I started with fridge off, loaded it with 24 drinks at room temp, and ran the fridge to cool the drinks and keep them at 34F (I like my beer cold)... then my battery would overly discharged in 24 hours. On shore power or solar it might be fine, but this gave me an idea of the power requirements and the importance of pre-chilling.

[John in Santa Cruz]

please stop confusing watts with watt*hours, it drives us engineering types nuts. watts is the amount of power a circuit is using at a given instant, while watt*hours is the total amount of power its used over a period of time.

592 watts for 24 hours would be 14208 watt*hours, or 14 KWH. I'm sure you meant 592 watt*hours in 24 hours, which is an average of about 25 watts.

[redbarron55]

Originally Posted by John in Santa Cruz

please stop confusing watts with watt*hours, it drives us engineering types nuts. watts is the amount of power a circuit is using at a given instant, while watt*hours is the total amount of power its used over a period of time.

592 watts for 24 hours would be 14208 watt*hours, or 14 KWH. I'm sure you meant 592 watt*hours in 24 hours, which is an average of about 25 watts.

Sorry, to be more correct it will be about 112500 Coulombs

[billnieman]

I too recommend the danfoss compressor style machines. I have four of them for various uses and they all work great. I don’t have a propane style absorption machine, and I have heard many positives and negatives about them. Personally, I would buy an RV based on many criteria, with the refer being one of them. But it’s no deal killer, for sure. You can always change out the refer if needed. I run these fridges on solar power mostly with very good results. And that solar power is used for a number of other needs, of course. But adding solar is adding cost, particularly if you also have a good house battery. So my recommendation here is to go slow. Just try the refer you end up with. Understand it. And if doesn’t work for you, move on to one that does. They are all very expensive, but when you’ve got one that works right for you, you’ll be camping very happy. But most importantly, get out there! :-)

[gordon2]

Originally Posted by John in Santa Cruz

please stop confusing watts with watt*hours, it drives us engineering types nuts. ... I'm sure you meant 592 watt*hours in 24 hours, which is an average of about 25 watts.

I'm not confusing watts and watt-hours.. But I was careless in composition (and none to happy with myself about it). You are of course correct but the edit time window has passed so to anyone who reads my post above.. that is watt-hours (Wh) over the 24 hour periods. You probably knew that and focused on the numbers, but watt hours should have been the term I used.

[Raz]

Power is the rate of energy use. The unit is watts. One watt equals one joule per second. Watt-hour or more common kilowatt-hour is also a unit of energy. It is preferred by your electric company because using joules on your electric bill would result in huge numbers. One kilowatt-hour equals 3.6 million joules. Of course were they to use joules it might give us the impression of getting more for our money. Kind of like getting your change in pennies.

[Joe Romas]

Baloney on absorption refrigerators only lowering the temperature 40 degrees, see my readings below and do your own math
Top is the refrigerator, middle is the freezer and bottom is ambient.
This is on my 1999 manual refrigerator running on propane with modifications any handy person can do. A simple fix will keep the pilot light from blowing out also. Casita switched to automatic refrigerators in 2005 but I think my manual is fantastic.

[gordon2]

Originally Posted by Joe Romas

... A simple fix will keep the pilot light from blowing out also. Casita switched to automatic refrigerators in 2005 but I think my manual is fantastic.

I agree that manual is better. Designing a fridge so that it requires electrical power (even if it is just a little) is defeating the primary advantage of using a propane fueled fridge. BTW, its not a pilot light.

[Raspy]

Originally Posted by gordon2

BTW, its not a pilot light.

Good point and it's a common mistake.

[dleverton]

Originally Posted by gordon2

I dont think you have necessarily been misinformed. I have seen an absorption fridge struggle in very hot weather. I have read A LOT from people who have also, and done many things to improve performance such as add fans, shade cloth, etc. Google "absorption fridge performance in hot weather" and you can also read A LOT about it.



But perhaps your concern is exaggerated. My Dometic 2410 does quite well the majority of the time. Properly used it only has some trouble in the hottest of weather. The main issue is recovery time becoming very long, so once the internal temp goes up due to it being off for a short trip, or opened a lot (for examples) then it takes longer to get back to a good temp. And the flame never blows out on the road but I have heard that others have that issue. Its been suggested that a port side fridge is more susceptible to blow outs.



But when reading about the issue, remember that performance is affected by many things like model and size, outside temps, frequency of door opening, side door vs top door, distribution of contents (to allow internal air circulation), etc. IMHO one of the big factors is roof exhaust vent vs side vent. I do think that a roof vent provides much improved performance.



It depends on your camping. If you dont need to cool very much food or drink, and can manage to supply up to 35 amp-hours every day* (plus whatever else you use outside the fridge), then a Danfoss type fridge might work best. But if you are boondocking and dont have that much power available (think solar) then an absorption fridge is likely the only good option.



Most new absorption fridges now use an electric control board. They do not use much power at all for the control board (when on propane) but they do require it and cease to function if your power dies. My 2015 Dometic RM2410 does not however and will run on propane with no electric for as long as you have gas (a month or more on a 20lb tank).



The one cubic foot Danfoss compressor fridge I have is AC/DC which is nice, and it can function as a chest freezer, easily getting to and maintaining zero Fahrenheit (at the cost of greater power use).



So the right tool for the right job.

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* In hot weather. Less in cool weather, if fridge is left closed, etc.

Very good summary. I too think one of the largest factors is venting and roof venting is far better. I have a 1300 Trillium with side venting and I’m seriously considering adding a stack thru the roof. Fans help considerably, but eat electrical power while good convection is free.