replacing an absorption refrigerator with 12-volt

Now that we have our lithium battery system, we would like to consider changing out our absorption refrigerator to a 12-volt variable speed compressor refrigerator.   Has anyone replaced their absorption refrigerator with a 12 volt?  And if you did what make and model did you choose?  And what were the challenges you faced removing the old refrigerator and installing the new refrigerator?  thanks

Dave

Hi Dave,

I thought the industry common 3-way fridge, one of the three was 100% 12V.  Is what you seek a lot more energy efficient running on 12V?

Ron

There are a several reasons we have considered switching to a 12-volt variable speed compressor rather than an absorption refrigerator.  You are correct in that the 3-way absorption refrigerator does use some 12 -volt while using the propane function.  The newer 12-volt variable speed compressors use about 5 amps until they reach the desired temperature than drops down to about 1/2 -1 amp to maintain the temperature.  The biggest advantages for switching:  1) you can drive with the refrigerator on rather than the absorption where you should turn off the propane when driving 2) the compressor refrigerators cool down much faster only taking a few hours, 3) you don't have to be level for the refrigerator to continue to work efficiently, 4) you don't have to worry about the sun hitting the side where the absorption refrigerator is located.  Here is the best YouTube video I have found that compares absorption, compressor, and residential refrigerator: https://www.youtube.com/watch?v=RwHU_NY0Auo&t=124s

In prior posts, a few PC owners had the company install compressor refrigerators but that was a few years ago.  The variable speed compressors appear very efficient, provide more refrigerator space, and should easily fit into the same location as the factory installed Norcold absorption refrigerator.

Dave

Dave,

I watched that video.  It is surely interesting.

Since we boondock most of the time, the typical PC-installed 2-way propane/120V fridge is right for us.  But if traveling from one RV park to another, especially during hot summer 90+ conditions, I see the attraction of a 12V compressor type.

One thing I scratch my head about are the restrictions on propane usage.  Our 3 to 4 week trips out west, we run the fridge on propane nearly 100% of the time, including while driving.  The only time we make any kind of change, is turning off the fridge while filling the main 55 gallon gas tank.  On rare occasion, we find ourselves in an RV park for a number of days.  Then we switch to 120V.  Otherwise it's always running on propane.

Our first major trip in our PC back in 2007, we were green horns regarding a fully self contained motorhome.  We were oblivious to the amount of propane that was being used.  One night we ran the furnace, but otherwise just cooked, made hot water for taking showers, and fridge usage.  The 3 week long trip, we ran out of propane during our last day communting back home, roughly 8 hours away.  Ever since, I make it a point to fill once during a 3 to 4 week trip, and again at the end to have a full tank once back home.

I think the slide must be removed in order to switch fridges. I don't think the fridge will fit through the door.

Folks seem to really like compressor refrigs in motorhomes these days.   Personally, I prefer propane because properly maintained it is inexpensive and a refrig uses very little of it as Ron mentioned in his post.   Something to think about is that all those travel trailers and fifth wheels going down the road are using propane to run their refrigerators.   In our PC, my wife simply walks back there and turns the switch to off a mile or so from where I am going to pull in to fill up on gasoline.   

I guess I am just one of those lucky guys that never seems to have a problem with my absorption fridges over the years staying cool.   A lot of folks that have Class Bs add a small fan on theirs on the back of the unit to blow upward and assist in dispersal of hot air.   That seems to make them cool better on the Bs which by definition have small refrigs in a tight spaces.   

 

A lot of folks that have Class Bs add a small fan on theirs on the back of the unit to blow upward and assist in dispersal of hot air.   That seems to make them cool better on the Bs which by definition have small refrigs in a tight spaces.

Our fridge is not inside a slide-out so the chimney goes straight up out the roof and is also higher, both improving air flow.  But you with your fridge inside a slide-out can add a fan for better performance.  I think Phoenix was adding a fan in there, wondering if that has been a standard for some time now.

But you with your fridge inside a slide-out can add a fan for better performance.  I think Phoenix was adding a fan in there, wondering if that has been a standard for some time now.

It was standard in 2018/2019's with slide-out.  My 2019 2552 was built from about October 2018 through February 2019 and has the single fan mounted in the central "chimney" area of the slide out to enhance airflow through the condenser coil located at the top of the chimney.  There is also a wooden diverter constructed at the top to direct air flow as much as possible to the coil.

When everything is correct the design works effectively, since (even in very adverse Oklahoma summer conditions), my refrigerator cools excellent on either propane or electric power.  I have to reduce my thermostat back from the highest setting after it cools down to keep the fridge compartment from dropping below freezing.  The balance is pretty sensitive though.  I reported previously about my propane cooling going to zero when a "dirt dauber" built a nest in my propane exhaust vent tube, partially blocking the vent.  Didn't affect the electric cooling, but although the propane burner was running normally, there was enough disruption of the exhaust venting to impede the heating cycle and the fridge wouldn't cool at all on propane.

I think the slide must be removed in order to switch fridges. I don't think the fridge will fit through the door.

The fridge has to fit through the door since not all units have slides. You might have to remove the screen.

Hi Dave,

I thought the industry common 3-way fridge, one of the three was 100% 12V.  Is what you seek a lot more energy efficient running on 12V?

Ron

Check out the current draw running on 12V with an absorption frige - chart here - https://lowvoltagecooling.com/how-many-amps-does-a-3-way-fridge-draw-on-battery-power/

9.6 - 19.9 amps. 

""The newer 12-volt variable speed compressors use about 5 amps until they reach the desired temperature than drops down to about 1/2 -1 amp to maintain the temperature. ""  is pretty darn impressive.

BUT.. I am loving my fridge on propane running down the road and doing gig work. I know there are pros and cons for running propane on the road, but nowhere could I find it illegal to use while underway. Refueling? It should be OFF. 

Anytime we are going to be using propane for an extended period, I attach the refillable tank. Treat the onboard tank as my reserve. Works well for us. And EASY to get refills on the road almost anywhere.

Should our current fridge fail, I would be looking long and hard at a compressor fridge. Running down the road, the charging system would easily supply the needed current. Might be some significant weight savings also.



 

Ron,
My understanding is the 3 way refrigerator does use more energy from your batteries when on DC as compared to the new 12 volt variable speed.  After reviewing several online posts, the energy draw, when first turning on the Dometic 4104 may draw up to 8 amps but once the temperature is reached will drop down to ~1amp.  The Dometic manual states that the system must be able to handle 15-20 amps when first turning the refrigerator on.  At this point I am not ready to switch out by Norcold absorption refrigerator until I get a better handle on power consumption and gather more data from those that have switched to a 12 volt variable speed compressor refrigerator.  https://www.youtube.com/watch?v=jBB-QUwKmW4

dave

Ron,
My understanding is the 3 way refrigerator does use more energy from your batteries when on DC as compared to the new 12 volt variable speed.  After reviewing several online posts, the energy draw, when first turning on the Dometic 4104 may draw up to 8 amps but once the temperature is reached will drop down to ~1amp.  The Dometic manual states that the system must be able to handle 15-20 amps when first turning the refrigerator on.  At this point I am not ready to switch out by Norcold absorption refrigerator until I get a better handle on power consumption and gather more data from those that have switched to a 12 volt variable speed compressor refrigerator.  https://www.youtube.com/watch?v=jBB-QUwKmW4

dave

I would have a hard time believing that a refrigerator that only draws 96 watts of power (12v x 8amps = 96 watts) is cooing more than briefly, perhaps enough to maintain it's refrigeration temp.   Even at its startup draw of up to 20 amps (240 watts) seems like it'd take a fair amount of time to cool down 6 to 8 cubic feet of a small RV refrigerator.

The old 3 way absorption refrigerator used a 12v heating element to heat the refrigerant and draw quite a bit of power.  Obviously, the 120v and propane settings only used 12v for the control board power.

As to your original concern that you couldn't use propane while driving is not a realistic concern.  Every propane powered adsorption refrigerator I have used over the last 25 years has never been turned off while driving and never had and issue.  They were all "shielded" to prevent roadway wind from blowing the flame out... And, should it somehow or other get the flame blown out, the control circuit will quickly relight the propane.  Should the propane not relight, the propane will be shut off and an error condition will show on the refrigerator panel.

But yes, when fueling, the refrigerator should be shut off.

Like MikeH said, summers here in Oklahoma can get pretty brutal at times.   Our 2013 PC230 with slide refrig performs just like Mike indicated:  very well and we have to watch that it is not set too cold or we will freeze goods in the refrigerator section..   Candidly I have never pulled the outside cover panel off the refrig to see how it is rigged, but it is 2013 stock and has never been a problem.  Unlike Mike, I have not suffered the dirt daubers stopping up anything.