Propane 3 way Adsorption Refrigerator's and what Ive learned so far..

Hello everyone. 

I'm in the design phase for a cargo trailer to toyhauler conversion I will be boondocking in 6-8 months a year.    I'm researching propane 3 way adsorption refrigerator's now..

The complaints Ive read about usually include propane refrigerators that are side vented, or units not rated for the ambient temperatures they are used in.

Side vented, meaning no roof penetration requiring the heat rejected to travel horizontal instead of naturally straight up which is usually addressed with a aftermarket fan to help move the hot air sideways.

And rated for the ambient temperatures that are used in refers to the temperature drop the refrigerator is capable of achieving.  I'm reading that if you have an S rating, then the fridge is a "Sub Tropical" and will only drop the inside temperature 36 degree's.  But if you buy the T "Tropical" rating, then they will drop the temperature up to 43 degree. 

Are there any other considerations Ive overlooked other than going 12v solar?  Will I be satisfied if I buy a Norcold roof vented T rated adsorption refrigerator in the lower 48?

Thanks!

Gas refers are ideal for doing a lot of boondocking. They will not require the amount of electrical power that a residential refer does. But they are not without their own issues.  When parked especially in hot weather try to keep direct sunlight off of the side of the rig that the refer is mounted on. Also minimize the amount of time that the door is opened as they do not recover the inside temps very quickly.

As long as you recognize the requirements of the gas refer and stay within them it should serve you well for your purposes.

A roof mount vent is usually better for cooling the coils better on the back of the refer as it requires constant air moving across them to remove heat. Two cooling fans in back of the refer are better than one as it removes the heat quicker.

A roof vent allows a natural chimney effect to set up and draw fresh air past the refrigerator's rear coils to carry away the waste heat.  When this stops in hot weather, adding a small fan or two to blow air over the coils will greatly improve the cooling performance.

Slide mounted refrigerators with two horizontal vents have less vertical room to set up the chimney flow, so they need fan assistance all of the time.

rebar said:

Are there any other considerations Ive overlooked other than going 12v solar?  Will I be satisfied if I buy a Norcold roof vented T rated adsorption refrigerator in the lower 48?

Thanks!

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We replaced our 3way Dometic refrigerator with a Unique 12v unit.  Costco sells this one.  https://www.costco.com/Unique-9.0-CuFt-Solar-Powered-DC-Refrigerator---UGP-260L-W.product.100362122.html 
Ours is the larger 13cu ft model and so far we're able to operate it with minimal other electrical draws, lights, computer etc.  Our 2 6v batteries with 230Ah, will run it for about a day and only use about 50% of the battery.  Currently we're in a warm area with high humidity and it runs for about 8 or 9 hours during the evening on about 25% battery.  That's with one or two fans running off a 1000 watt inverter and a 300 watt inverter.  Heat definitely affects usage and we left our roof and rear vents open.  However, the manual says it only needs 3 inches of side and roof ventilation.  Most are used in off-grid applications and consequently don't have RV type vents.  They're expensive, but compared to the 3ways pretty reasonable.  We have yet to test it using only our 100 watt suitcase solar.  So we keep use the motorhome 5500 generator and our Honda 2000i going to top off the batteries. 

Three ways are great. I wish I had one in my class A. At some point, the 12 volt option began to look unnecessary and isn't included in many designs.


The gas option offers the best recovery time with 110 volt electric a close 2nd


The 12 volt heating element works mostly as a maintenance of existing cabinet temperatures. This option is used primarily while travelling. It can still do the job while boondocking but it would not take many door openings and closings or increased outside temps to fall behind.


Long ago I had a three way fridge. During the day time hours I would run the fridge on propane. Before checking out for the night I would set it to 12 volts. It worked great and I wasn't worried about that flame burning while I was sleeping.


The other issue with these fridges is that they do not like warm products placed in the cabinet. It is good to put already chilled or frozen products in the cabinet. The one thing I have done that works very well is to pre-chill products in the freezer section then move them into the lower cabinet. This works for me very well mostly because I do not use the freezer for food products. I keep a couple of gallons of frozen water in there for emergencies and use it for pre-cooling.

Thanks everyone..

I was so happy with a 7 cubic foot Norcold 3 way in my old featherlite that I want another.  I never shut it off and it ran on propane for weeks..  Never 12v.

But I'm not sure if my norcold was rated S or T..  Has anyone even heard of that rating, or did the manufactures build the S model for the RV market as a cheaper alternative?

I'm not sold on 12-24v electric compressor refrigerators because I would need solar, but feel they are the most efficient.  I wonder if I could ever reach a break-even or "paid for itself" status with solar given I will spend 6-8 months a year boondocking.

With both side and top venting you can "Supplement' The chimney effet with 12 volt fans.

What I understand
Gas works well. does not burn a lot (I use it when not plugged in)
electric works well too. but it eats about 350 watts which is kind of much compared to a compressor unit

12 volt (I do not have) well..  Not all that good  They tend to cut down teh wattage so it's not as good at cooling cause well at 12 volts 350 watts is what just shy of 30 amps (25 amp fuse per manual that came with mine)

There are also 12/120 volt compressor units.. These suck oh. around 40 to 50 watts.
(For compairson a 1141 lamp is 19-20 watts)

And rated for the ambient temperatures that are used in refers to the temperature drop the refrigerator is capable of achieving.  I'm reading that if you have an S rating, then the fridge is a "Sub Tropical" and will only drop the inside temperature 36 degree's.  But if you buy the T "Tropical" rating, then they will drop the temperature up to 43 degree.

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I've not ever heard of this rating for absorption fridges, at least not those used in the RV market. Perhaps in the marine versions?  In any case, the absorption fridges I've owned all readily managed a 43 degree drop in the fridge compartment and a 70-80 degree drop in the freezer. That's relative to the inside-RV temperature. If referring to the exterior temperature, ours worked fine up to about 98 F, dropping the fridge interior to around 38 (50 degrees) and the freezer between 0 & 10 F.
For thse curious to learn more of this obscure rating, see  https://appliancestop.info/climate-classes-of-fridges/

Why pay extra for the 3-way version is you plan to run on propane all the time. The 2-way would be a better choice if that's the case. The 12v mode is of very limited utility anyway, mostly just while driving. And you would need a hefty 12v supply to a trailer type RV to use 12v while underway.

Gary RV_Wizard said:

I've not ever heard of this rating for absorption fridges, at least not those used in the RV market. Perhaps in the marine versions?  In any case, the absorption fridges I've owned all readily managed a 43 degree drop in the fridge compartment and a 70-80 degree drop in the freezer. That's relative to the inside-RV temperature. If referring to the exterior temperature, ours worked fine up to about 98 F, dropping the fridge interior to around 38 (50 degrees) and the freezer between 0 & 10 F.
For those curious to learn more of this obscure rating, see  https://appliancestop.info/climate-classes-of-fridges/

Why pay extra for the 3-way version is you plan to run on propane all the time. The 2-way would be a better choice if that's the case. The 12v mode is of very limited utility anyway, mostly just while driving. And you would need a hefty 12v supply to a trailer type RV to use 12v while underway.

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Thanks Gary.. Great link.

The ST and T rating discussion I found this morning was on a australian van forum so I just realize the values were in celsius .  I hadn't, and imagine most people had never heard of climate classes, but maybe some of the warm or under performing fridges are caused by RV manufacturers installing under rated refrigerators?

Anyhow.. Good thing to keep in mind and maybe next time someone looks, check what rating you have.

Yes a 2-way would do for now.. But if the price isn't allot cheaper I'll buy a 3-way.  Its to bad adsorption refrigerator's are so inefficient running on electricity.  Because if a few years from now, after I buy propane appliances of course,  advances in solar panels, batteries and maybe even lower costs occur, I would probably want to buy all new electric appliances.  But only if I could leave the genny at home..

Does anyone subsidies solar RV's? 

I don't think you need worry much about the designed climate class for an RV absorption fridge.  Since you are doing a conversion yourself, I think any model you choose will perform well as long as you follow the installation guidelines religiously, specifically the part about ventilating the "chimney" and sealing around it.    If the model chosen does not include a fan in the back for improved ventilation, add an aftermarket fan. I also highly recommend an ARP Fridge Defend module to monitor and protect the cooling unit

thanks for the link Gary...I'll check that out later.

I agree with Gary about the ARP device too!  I learned about it here from Gary and others when we first were upgrading from our popup and I installed it.  I personally haven't really verified the tech, but the thing does monitor the tempertaure and seems to do as advertised....and I sleep better having it

even if you aren't interested in it, his site has tons of info about these fridges.
Also, there's a version with a built in fan controller...that to me seems like it would be the ticket if I were ever to install fan(s).

As is, mine is a roof vented installation and has always worked very well for us.  We've even kept ice cream!

re. 3-way.  My popup had one.  I used to use 12V while towing to the campground to prechill the box.  It wasn't accessible top down so we'd bring our stuff in a cooler...prechill while driving..and stock the fridge once set up.
Anyway...one time I hitched up plugged the trailer into the truck, switched on the fridge ready to drive.  Something happened, I forgot what...a family member wasn't ready or something.  So we delayed departure, maybe an hour.... distracted, I forgot to switch off or unplug it....and I had to break out the battery charger to start the truck.  That thing drained the trailer's battery and my starting battery FAST!

Don't overlook the RV compressor fridge units from Norcold, Nova Kool, etc.  They can be had in DC only or AC/DC units. On DC (even AC/DC units, the primary source is DC and is the preferred way to use it) a 7 CF fridge freezer uses about 4 amp when actually running, which might be 1/2 the time on a hot day depending on how much it is opened. A 9 CF unit 4-5 amps.  A half way decent solar unit could keep batteries charged up just fine for that.  And the fridge could run overnight and would not be a major hit on a set of 6v 235 amp golf cart batteries in series. 

All I ever use now is DC compressor fridges.  They can operate fine at up to 30 degree off of level.  No absorption fridge can do that.  The same dimension compressor fridge will usually have 1 CF more actual food storage room inside compared to absorption models. And there is no internal fins that cool the inside that need to be kept clear and air circulated around them.  Very same cooling style as a residential fridge.

What I have learned so far regarding absorption fridges.... avoid them.  The do work, but not nearly as functional and value for the dollar.  Too many stupid issues the require all sorts of third party solutions such as the ARP thing, internal air circulators, roof top vent fans, etc, etc, etc. 

One comment on the Danfoss Compressor jobs being ablt to operatre 30 degrees (or more most likely) off level.

My Dometic says it will work up to 3 degrees off

now on an 8' axle that's about 5 inches

I missed my leveling boards and was thus less than 2" off level or about 1 Degree
I was not all that comfortable walking around the RV.  Sleeping no problem but walking was different

At 30 degrees it would not be the fridge I worried about (Rollver perhaps).

(I moved to atop the leveling planks)

Madcow said:

Don't overlook the RV compressor fridge units from Norcold, Nova Kool, etc.  They can be had in DC only or AC/DC units. On DC (even AC/DC units, the primary source is DC and is the preferred way to use it) a 7 CF fridge freezer uses about 4 amp when actually running, which might be 1/2 the time on a hot day depending on how much it is opened. A 9 CF unit 4-5 amps.  A half way decent solar unit could keep batteries charged up just fine for that.  And the fridge could run overnight and would not be a major hit on a set of 6v 235 amp golf cart batteries in series. 

All I ever use now is DC compressor fridges.  They can operate fine at up to 30 degree off of level.  No absorption fridge can do that.  The same dimension compressor fridge will usually have 1 CF more actual food storage room inside compared to absorption models. And there is no internal fins that cool the inside that need to be kept clear and air circulated around them.  Very same cooling style as a residential fridge.

What I have learned so far regarding absorption fridges.... avoid them.  The do work, but not nearly as functional and value for the dollar.  Too many stupid issues the require all sorts of third party solutions such as the ARP thing, internal air circulators, roof top vent fans, etc, etc, etc.

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Thanks Madcow, but have you owned a adsorption refrigerator?  I should consider a compressor fridge, but most of the people saying they like them have full hookups and stay in campgrounds.

  I haven't heard any full time boondockers say they liked a 12v DC compressor off grid more than a adsorption refrigerator and Ive never had a problem with mine, even underway.  What happens if it's overcast or rains for a couple days?  Time to get out the genny.

It's absorption, not adsorption.  Google each. RV refrigerators use absorption to cool.