Refrigerator upgrade question

DiverBob

2018 Unity TB
After our 10 week trip to Alaska and with the temperatures up in the 90’s for a lot of that time, my wife and myself are not satisfied with the operation of the refrigerator. The internal temperature varies widely and many times we saw it at or above 40ºF. The freezer at least keeps things below 32ºF but not by much.
I have read several of the refrigerator upgrades that have been done and was looking to replacing ours with a 12v compressor only unit. Since we have 400 amp-hr of lithium batteries I believe this is very doable on our UTB. Just to make things interesting I found out about another option, rather than just replacing the whole refrigerator, how about replacing just the cooling mechanism. It turns out that a company in Indiana, JC Refrigeration (https://jc-refrigeration.com/), makes a unit that replaces just the refrigeration unit so you keep the same refrigerator box.
This option sounds very appealing as there are no modifications needed to the refrigerator opening to accommodate a new frig, the replacement just bolts on to the same points that the old unit did, they provide detailed instructions on how to DIY along with all the materials needed for the conversion.
So, my question is whether or not anyone has taken this approach and what did they think of the results? I haven’t contacted them to check out the prices yet to see if its more affordable than replacing everything with a new unit.
 

SSTraveler

2014 LTV Unity Murphy Bed
People on other RV forums highly recommend the JC Refrigeration conversion. It's about the same cost as a completely new compressor Refrigerator and lets you keep the original refrigerator that fits the space. I just didn't want to fool around with a conversion of the old Refrigerator. I had the old single door Dometic so I really wanted a new Refrigerator with a separate freezer and refrigerator. I don't know what the operating specs are for the JC conversion but I like that other compressor Refrigerator manufacturers off compressor Refrigerators that operate on half the power of Dometic and offer Smart energy controller options so the energy consumption can be even further reduced for people who use batteries for much of the time like on Boats. I picked my Isotherm compressor Refrigerator because I liked the design and I liked that they offer a Smart power consumption option so if my camping style changes and I use more battery consumption I can always upgrade to the Smart Energy controller. I strongly believe that the key to any Refrigerator operating well in temperatures above 90 degrees is to have them sealed off from the outside. You can't expect anything that produces heat to cool itself by using outside air temperatures in excess of 90 degrees. My advice to anyone contemplating replacing their Dometic Refrigerator is to first pull it, disconnect the propane (and cap off line) and seal the Refrigerator compartment off from the outside and reinstall the Dometic and operate it on 12vdc/110vac and see if it doesn't run more suitably using the cooler and consistent house air temperature as it's operating environment. If it still doesn't work as reliably then make a change. I struggled with my Dometic 3 way for 5 years so I was more than ready for something new but if I had a newer model Dometic I would have tried sealing off the exterior and see how it operated before investing in another Refrigerator so soon after buying my Unity. You really have nothing to loose since you have to seal off the exterior anyway for a compressor Refrigerator install.
 

JHMooney

2018 Unity MB
I like the idea of not having to modify the opening by keeping the same box. This option also has the added benefit of retaining that wonderful, easy to use drawer in the bottom of the dometic. :lol:
 

harrysalit

2019 Wonder FTB
SSTraveler,
What is involved in sealing off the exterior? Does that include the vents? Obviously no propane use!
What material to use?
Our Dometic is 4 months old, in NWP weather ran fine, defrosted it it 4 days ago, has been very slow cooling freezer down, today finally at 10. Box oK at 35.
Maybe time for compressor?
 

TampaSteve

2018/2019 Unity CB
Your advice on the Isotherm has me just about settled on the same solution. I've already done the Lithium battery upgrade to double my capacity in anticipation of a compressor fridge. Now I just need to decide for sure Isotherm vs Novakool.

On the JC site last I checked I thought my fridge wasn't on the list. I thought it was mostly larger RV fridges unless I just missed a page.

In my case sealing off the external openings and insulating to test the Dometic wouldn't really help as it just draws too much power on DC to be useful for me as I do dry-camp a lot.

In fact I'm still a bit hesitant because I'm concerned that even the Isotherm may not work perfectly when I'm driving down the road with the sun blaring on the refrigerator side, insulated or not. At those times, especially when we pulled over to the side of the road in 100 degree heat and got out to walk around, the Dometic zoomed up over 50 degrees.

If I go through all of this and still can't keep it under 40 I'd be disappointed to say these least.

People on other RV forums highly recommend the JC Refrigeration conversion. It's about the same cost as a completely new compressor Refrigerator and lets you keep the original refrigerator that fits the space. I just didn't want to fool around with a conversion of the old Refrigerator. I had the old single door Dometic so I really wanted a new Refrigerator with a separate freezer and refrigerator. I don't know what the operating specs are for the JC conversion but I like that other compressor Refrigerator manufacturers off compressor Refrigerators that operate on half the power of Dometic and offer Smart energy controller options so the energy consumption can be even further reduced for people who use batteries for much of the time like on Boats. I picked my Isotherm compressor Refrigerator because I liked the design and I liked that they offer a Smart power consumption option so if my camping style changes and I use more battery consumption I can always upgrade to the Smart Energy controller. I strongly believe that the key to any Refrigerator operating well in temperatures above 90 degrees is to have them sealed off from the outside. You can't expect anything that produces heat to cool itself by using outside air temperatures in excess of 90 degrees. My advice to anyone contemplating replacing their Dometic Refrigerator is to first pull it, disconnect the propane (and cap off line) and seal the Refrigerator compartment off from the outside and reinstall the Dometic and operate it on 12vdc/110vac and see if it doesn't run more suitably using the cooler and consistent house air temperature as it's operating environment. If it still doesn't work as reliably then make a change. I struggled with my Dometic 3 way for 5 years so I was more than ready for something new but if I had a newer model Dometic I would have tried sealing off the exterior and see how it operated before investing in another Refrigerator so soon after buying my Unity. You really have nothing to loose since you have to seal off the exterior anyway for a compressor Refrigerator install.
 

RandyJohnson

2018 Unity TB
TampsSteve

Can you run your AC on the batteries? If so, while you are driving you cAn cool the house as well as charge the batteries.

This means the compressor will pull better temp air into the coils for much better cooling than using really hot or really cool ambient air through the vents.


Sent from my iPhone using Tapatalk Pro
 

TampaSteve

2018/2019 Unity CB
No, I would need a much bigger inverter to do that, (and many more batteries if I was off grid). We did for brief periods drive with the generator on and the house AC running, which works fine but I don't want to run the generator all the time or even the house AC.

But that would almost certainly work, as if we pull into a campground with hookups and turn on the house AC the fridge slowly returns to safe temps.

TampsSteve

Can you run your AC on the batteries? If so, while you are driving you cAn cool the house as well as charge the batteries.

This means the compressor will pull better temp air into the coils for much better cooling than using really hot or really cool ambient air through the vents.


Sent from my iPhone using Tapatalk Pro
 

SSTraveler

2014 LTV Unity Murphy Bed
SSTraveler,
What is involved in sealing off the exterior? Does that include the vents? Obviously no propane use!
What material to use?
Our Dometic is 4 months old, in NWP weather ran fine, defrosted it it 4 days ago, has been very slow cooling freezer down, today finally at 10. Box oK at 35.
Maybe time for compressor?
I wouldn't through the baby out with the bath water just yet. Try closing off the exterior first and see if your Dometic runs better. If it does you just saved yourself upwards of $2000 by not having to buy a new Refrigerator. If the Dometic doesn't improved, well you cut your time to install a compressor Refrigerator in half by closing off the exterior first. Here is a summary of what I did. You can use several materials to close the vent openings i.e. styrofoam,  sheetmetal, plexiglass, PVC board, or some other thin material that is inherently waterproof. Also you might want to design the the bottom vent closure so that you can you it as a future access port. I sealed mine permanently so I had no room for error or do overs when I installed the Refrigerator. I was pushed for time when I did my mod but in hindsight I can see the value of being able to open that bottom vent to access the back of the Refrigerator from the outside. If anything comes up with my install I will have to pull the Refrigerator to get to the fan, compressor wiring, leveling feet, etc. For troubleshooting.  I used styrofoam to close off the vent opening and one sheet of this, https://www.lowes.com/pd/SurePly-1-4-in-Whitewood-Plywood-Application-as-4-X-8/50124674, to finish the interior compartment back wall. You can use any thin board material like wood or PVC paneling other than what I used or nothing at all but Reflectix. I didn't finish the sides of the Refrigerator compartment because the space isn't large enough to see into. You don't really need anything but installation, like Reflectix on the back wall but I thought this board would keep my several layers of Reflectix in place better so I didn't have to worry that the Reflectix may move around or come loose. I liked this board because it matches nicely with my existing maple finish and you don't see enough of it to realize it isn't a perfect match but blends very nice, and is inexpensive and easy to work with. I cut the styrofoam to fit the opening perfectly and then I used a healthy amount of DAP Dynaflex 230 (https://www.lowes.com/pd/DAP-Dynaflex-230-10-1-oz-Clear-Paintable-Latex-Caulk/50149252) to seal it in place. I actually used a tube on each side of the wall ( exterior  and interior) to seal the styrofoam and the opening, as if you were spackling a wall board in place. On the inside wall, once my caulk spackling job dried I added a couple of layers of Reflectix then screwed my wall board in place. I drilled through it all to create a hole for the drain line to feed through. When I got the Refrigerator installed, I sealed the outside around the drain line with more caulk and let it dry before reinstalling the vent cover. I tied a string to the drain tube so I could have someone pull it through the opening as I slid the Refrigerator into place. Then I cut it to length so it came through the Dometic vent cover louvers and you don't see it in between the vent louvers but the water drip out. With regard to the propane line, I just capped it off with a 3/8" Male Flare plug (https://www.homedepot.com/p/PlumbPro-3-8-in-Brass-Flare-Plug-04227/202275504), leak tested it and bent it slightly to make it flatter against the wall. The wall board may slope out slightly at the bottom to accommodate the shape of the abandoned propane line as it does stick out a bit more. I stuffed the area around the propane line with Reflectix for added insulation and to make a more even surface for the wall board to go against. The wall board is held against the wall with screws that I drove in at an angle so they would go into the framing around the back of the Refrigerator compartment. I was recently contacted by another member for support and he pulled his NovaKool compressor Refrigerator (because it was not operating well due to it's exposure to outside temperatures) and closed off the exterior. He hasn't gotten back to me on how the Refrigerator performance changed as a result. So feel free to contact me by Personal Message if I can be of help.
 

SSTraveler

2014 LTV Unity Murphy Bed
In fact I'm still a bit hesitant because I'm concerned that even the Isotherm may not work perfectly when I'm driving down the road with the sun blaring on the refrigerator side, insulated or not. At those times, especially when we pulled over to the side of the road in 100 degree heat and got out to walk around, the Dometic zoomed up over 50 degrees.

If I go through all of this and still can't keep it under 40 I'd be disappointed to say these least.
My Isotherm works great on 12vdc, driving down the Hwy with the sun blasting the exterior Refrigerator wall. I put the Isotherm setting on a little past the 3 setting and forget it. It maintains temperature the same on 110vac as it does on the 12vdc, whether the sun is shining on the side full blast or not. You may recall this picture I posted where the outside Refrigerator wall temp was 119 degrees and the Isotherm didn't drop a degree. I have my outside temperature sensor sitting next to the Refrigerator drain tube between the louvers of the bottom vent cover.
The Refrigerator temperature doesn't change when take short breaks when driving, but I run the generator and AC if we leave out dogs inside for longer stops. It is so much more effective and efficient than the Dometic, I'm loving not worrying about the Refrigerator maintaining its temperature anymore. West Marine, there in Tampa, sells Isotherm Refrigerators go talk to them. Isotherms are a very popular brand for boat owners. Refrigerator applications on boats face very similar challenges as on RVs.
 

Attachments

Last edited:

TampaSteve

2018/2019 Unity CB
I somehow missed the post about the outside temp. :) I think I'm in final "pre purchase" mode. I've done all the prerequisites to be able to still dry camp (battery monitor, Lithium) and just looking at every last alternative before pulling the trigger, which at this point looks like 95% Isotherm. Thanks!

My Isotherm works great on 12vdc, driving down the Hwy with the sun blasting the exterior Refrigerator wall. I put the Isotherm setting on a little past the 3 setting and forget it. It maintains temperature the same on 110vac as it does on the 12vdc, whether the sun is shining on the side full blast or not. You may recall this picture I posted where the outside Refrigerator wall temp was 119 degrees and the Isotherm didn't drop a degree. I have my outside temperature sensor sitting next to the Refrigerator drain tube between the louvers of the bottom vent cover.
The Refrigerator temperature doesn't change when take short breaks when driving, but I run the generator and AC if we leave out dogs inside for longer stops. It is so much more effective and efficient than the Dometic, I'm loving not worrying about the Refrigerator maintaining its temperature anymore. West Marine, there in Tampa, sells Isotherm Refrigerators go talk to them. Isotherms are a very popular brand for boat owners. Refrigerator applications on boats face very similar challenges as on RVs.
 

DiverBob

2018 Unity TB
I found a forum that had a lengthy discussion with several people that went the JC Refrigeration route. They all sound pleased with the results. This discussion was started last year into the beginning of 2019 so it was good feedback on the system.
The cost isn’t bad either, a AC motor is $899, the DC motor is $1,099. Shipping is $175 but they will install in about 4 hours for $300. At this point I’m leaning towards the AC motor (since my inverter is always powered on) and having them install it. Normally I like to the DIY type of things but for $300 to take the RV down there vs $175 to ship, it makes sense to me to have the experts do it! Also I only live a couple of hours away from their location so it would be a nice drive down.
 

woundedpig

2018 Unity MB
I’m having trouble making sense of the recommendation to disconnect propane and seal off the rear compartment of a Dometic 3 way refrigerator. These things work by generating heat to make the absorption circulation process work, whether by propane, 12 V, or 110V. You would be giving up the most efficient means of cooling if the propane was abandoned as a heat source. This course also seems to assume that one will always be hooked up to power so the AC can be run to cool the interior. How about those who boondock or dry camp in warm/hot environments frequently? One would either need to use the generator or have a solar/battery capacity that in fact no one in a Class B+ RV has. Has anyone done this to determine whether the waste heat of the Dometic can be successfully dealt with by simply venting to the interior of the coach?

This rush to considering the expense of a compressor fridge seems to ignore the dozens of available strategies and tips to make an absorption fridge work well and without unreasonable effort once the imperatives of using these fridges are understood. I guarantee if you go to Quartzite or any other warm camping environment that you will find thousands of folks happy with their 3 way fridges.
 

TJLee089

2013 Itasca Reyo 25R
You point is well taken, however strictly speaking LP is not the most "efficient" heat source since the remaining heat in the exhausted combustion gases is wasted. With good insulation, AC or DC heating is close to 100% efficient, but not necessarily the cheapest; "free" is you're connected to shore power and not paying a premium for it, "very expensive" if you're running you generator for power.

The problem I have with sealing the rear and using only AC/DC is that an absorption fridge still needs to cool the hot gases from the boiler. If the rear is sealed, this cooling must come from the air in the coach, which will make the coach hotter, perhaps requiring more air conditioning. If the outside air is cooler than the coach air, sealing the rear would be counter-productive. I think SSTraveler missed this. I would never consider sealing the rear.

I’m having trouble making sense of the recommendation to disconnect propane and seal off the rear compartment of a Dometic 3 way refrigerator. These things work by generating heat to make the absorption circulation process work, whether by propane, 12 V, or 110V. You would be giving up the most efficient means of cooling if the propane was abandoned as a heat source. This course also seems to assume that one will always be hooked up to power so the AC can be run to cool the interior. How about those who boondock or dry camp in warm/hot environments frequently? One would either need to use the generator or have a solar/battery capacity that in fact no one in a Class B+ RV has. Has anyone done this to determine whether the waste heat of the Dometic can be successfully dealt with by simply venting to the interior of the coach?

This rush to considering the expense of a compressor fridge seems to ignore the dozens of available strategies and tips to make an absorption fridge work well and without unreasonable effort once the imperatives of using these fridges are understood. I guarantee if you go to Quartzite or any other warm camping environment that you will find thousands of folks happy with their 3 way fridges.
 
Last edited:

woundedpig

2018 Unity MB
You point is well taken, however strictly speaking LP is not the most "efficient" heat source since the remaining heat in the exhausted combustion gases is wasted
I was using the term efficient to indicate cooling effectiveness. Not good engineering-speak, I know. I understand and agree with your energy efficiency point. Most folks seem to find that cooling is best on LP, then electric/110, then 12V. That is my experience and the vast majority of other LTV owners I have spoken with.
 

TJLee089

2013 Itasca Reyo 25R
My main point is that an absorption refrigerator needs cooling in ANY mode. See attached. (The gas heater in the picture is just one possible heat source.) Sealing the rear is a bad idea unless some other provision is made for cooling. If the rear is sealed and cooling is via exchange with coach air, the coach air will warm. This would require a fan, since the natural convection provided by the original design is no more.

If the coach air is cooler than the outside air, this could work but would increase air conditioner load.

If the the outside air is cooler than the coach air (i.e. not using air conditioning), this would be counter productive.

If there is NO provision for air exchange with the condenser, the system will perform poorly, if at all
 

Attachments

Last edited:

RV2019

2017 Wonder MB
So does a compressor fridge operate cooler? Doesn't the compressor get hot too? If switched to compressor fridge and rear sealed, that heat goes into the coach.
How much heat does the absorption fridge generate?
 

avanti

2022 Ford Transit 3500
So does a compressor fridge operate cooler? Doesn't the compressor get hot too? If switched to compressor fridge and rear sealed, that heat goes into the coach.
How much heat does the absorption fridge generate?
Compressor refrigerators are vastly more energy-efficient than absorption units--something like a factor of 5, I believe. Since the energy consumed accounts for 100% of the net heat produced, compression refrigerators are indeed (much) cooler in operation.
 

TJLee089

2013 Itasca Reyo 25R
I certainly agree that compressor fridges are MUCH more effective at cooling than ammonia absorption, however compressor fridges have condensers which give off heat from the compressed refrigerant. In fact all of the heat removed from the fridge goes to the condenser. It is not insignificant. In your home this heat is rejected into the room. I assume that the heat from the condenser of a compressor RV fridge is rejected to the outside air, just like it is for the condenser of an absorption fridge.

Compressor refrigerators are vastly more energy-efficient than absorption units--something like a factor of 5, I believe. Since the energy consumed accounts for 100% of the net heat produced, compression refrigerators are indeed (much) cooler in operation.
 

RandyJohnson

2018 Unity TB
At home the ambient air around the compressor is conditioned.

The outside ambient air is not conditioned and can cause the fridge to be either a freezer if low or to hot if the outside air is to hot.

Empirically speaking I have seen the freezer part when I forgot to turn off the fans when the outside air went below 50 degrees.


Sent from my iPhone using Tapatalk Pro
 

Top Bottom