Dometic rm2510 absorption fridge conversion to 12v compressor

[TouringDan]

The exhaust plenum to channel the propane exhaust from the absorption refrigerator will no longer be needed. Mine appears to be in reasonably good condition and I would be happy to donate it to anybody that needs it. Here is a photo.The RM2510 refrigerator has a volume of about 5 cubic feet. The absorption parts take up a fair amount of space behind, under and with in the refrigerator. I calculated it to be about 2 cubic feet. This means that after all the absorption stuff is removed that the refrigerator box can be enlarged by about 2 cubic feet to increase the total fridge volume from 5 cubic feet to 7 cubic feet.Basically this can accomplished by moving the rear wall back about 4”. Here are some photos.

[TouringDan]

Here are the photos.

[TouringDan]

[TouringDan]

[TouringDan]

By converting the RM2510 from absorption to a compressor fridge, I believe there will be the following numerous advantages:

1. An increase in the fridge volume from 5 cubic feet to 7 cubic feet.
2. More insulation around the refrigerator.
3. The refrigerator installation is now permanent. No need to ever remove it since it is just an insulated box. All the functional parts are in the wall cabinet.
4. It should be much more reliable since the equipment is easily accessible and can be easily cooled since it is right next to the exhaust vent. Here is a photo.Merry

[Wazbro]

Originally Posted by TouringDan

My original plan was to install an Isotherm 2012 with a 32” long evaporator plate. The plate would be installed on the rear vertical wall that is 32.5” high. About 6” of the evaporator plate would be installed on the rear wall of the freezer that is 6” high and the other 26” of the plate would be installed on the back wall of the refrigerator section. Logic tells me that if I did it this way, the freezer and fridge would be at the same temperature.. I am now thinking that I need to install an Isotherm 2017. This has an evaporator plate that is 39” long. 26” of the plate would be installed against the rear wall of the refrigerator section and 13” of the evaporator plate would be installed in the freezer. For this to work the evaporator plate would need to be bent into an L shape at the top. 6“ of the evaporator plate would be against the rear wall and 7” would go along the top in the freezer. I think this would insure that the freezer would be significantly colder than the refrigerator.

Here is a photo of the freezer section.

DanAttachment 427442

Are you sure the evaporator plate can be bent without damage?
It looks like the 2012 picture you posted has tubing going through it for the coolant to go through.

[TouringDan]

I thought of 2 more advantages.

1. The empty fridge box weighs 35 lbs. The absorption equipment weighs 35 lbs and the compressor equipment only weighs 20 lbs. So the compressor fridge that is 2 cubic feet larger than the absorption fridge will weigh 15 lbs less.

2. Since there will be no need for the outside access door this can be eliminated and just install a patch over the access hole. Another Tradewind owner may need the access door.

Dan

[TouringDan]

Originally Posted by Wazbro

Are you sure the evaporator plate can be bent without damage?
It looks like the 2012 picture you posted has tubing going through it for the coolant to go through.

Thanks for chiming in. No, I am not sure it can be bent. I thought I read somewhere that it could be bent and they do offer an L shaped evaporator plate for smaller refrigerators.

If it can’t be bent I may try to build a baffle around the upper part of the evaporator plate that is in the refrigerator section that would provide more cooling for the freezer section.

Dan

[TouringDan]

Time to go camping so time to finish the conversion of my RM2510 absorption fridge to a compressor fridge. I have decided to go with the 2012 unit with a flat evaporator plate 8” x 32”. It will be installed so that part of it is in the freezer and part of it is in the fridge.

I have decided to remove the back 4.5” of the fridge and replace it with a 9” section built from polystyrene and covered with fiberglass on the outside and lined with frp (fiberglass reinforced plastic) panels on the inside. It will also contain the evaporator plate.

Here is a photo of the fridge with everything removed and ready for surgery. It was mostly all foam and plastic with some aluminum for the freezer compartment.
I made an attempt at a first cut with my circular saw but it didn’t cut deep enough.
I then tried my table saw and it cut 3” deep which was adequate except for the small section between the freezer and the fridge. I had to cut this section with my oscillating saw. The end result was finally successful- the rear 4.5” of the fridge nicely cut off.
Interesting to note that there is 3” of foam around the freezer section but only 2” of foam around the fridge section.
Next will be construction of the new 9” rear section with the evaporator plate installed and then connect this assembly to the front section of the fridge.

Dan

[TouringDan]

I needed to build a new rear section that would make the fridge considerably deeper, about 6”. This added about 40% to the storage volume of the fridge. The original volume was 4.8 cubic feet. The new compressor fridge will have a volume of 6.8 cubic feet. I built it out of 1 and 2” polystyrene. Finding a good adhesive was a separate project. I ended up with heavy duty ultimate construction adhesive by Gorilla. It is expensive but very strong and remains flexible. You need to put weight on it or use clamps. After building the box I lined it with frp (fiberglass reinforced plastic) paneling. It is about 3/32” thick (.090”). I then caulked the joints using silicone caulking. Here are some photos.

Dan

[TouringDan]

Looking at the last photo, you see that there is nothing in the compressor fridge except for the evaporator plate and the temperature sensor- no moving parts to fail. These are all in the wall cabinet above the fridge. After I install the new fridge box I will install as much insulation around it as there is space available. I hope it will be many years before this fridge will need to be removed.

The wall cabinet above the fridge that will hold the compressor and thermostat was a bit damaged because I removed the exhaust duct that was required by the absorption fridge. Here is a photo of the damaged cabinet and the repaired cabinet.

Dan

[nvestysly]

Hi Dan, Thanks for the photos - hoping you'll have more pictures as you make progress with the conversion and installation. Keep us posted.

[TouringDan]

I have attached the new rear section of the fridge to the original front section. The original shelves were 11” deep. I will need to add 8” shelves and shelf supports to the new rear section. The total depth of the new modified fridge shelves will be 19”.
The third photo shows the freezer section.

Instead of 2” of air and some hardware required by the absorption fridge at the bottom of the metal fridge stand, I have added 2” of foam insulation. I am going to add as much foam insulation as possible when I install the fridge in our Tradewind.

Dan

[Bubba L]

It looks like a new fridge. I don’t think you can add too much foam. Looking forward when you plug it in and post the results.

[TouringDan]

I still need to make some new shelves. I noticed on another thread that some of the Dometic fridges come with plastic shelves that are cheaply made and outrageously expensive. My fridge has metal shelves that are well made. I am going to try to make some plastic shelves to accommodate the additional depth of the modified fridge.

The additional shelf depth is significant. The original shelf depth was 12”. The new shelf depth is 19”. This is a 60% increase! The freezer depth increase is even higher at 75%!

Here is a photo of the exterior of the modified fridge. I plan to wrap the exposed foam with aluminum tape to lower the radiation heat transfer.

Dan

[TouringDan]

I wrapped the entire fridge in aluminum tape and have installed it back in the Airstream.

Dan

[TouringDan]

After installing back in the Airstream, I added as much insulation around the fridge as possible. I added 1/2” on the left side and on top, and 1 1/2” on the right side.
I then installed the upper cabinets and installed the compressor and thermostat in the upper cabinet.
I then installed a new 15 amp dedicated circuit and lighted on/off switch to power the fridge. What I really like about this conversion is that all the equipment is in a small section of the upper wall cabinet directly over the fridge and the old fridge vent will be used to cool the compressor.
I was more than a little concerned and confused about making the refrigerant connections above the compressor. The instructions said to torque to 18-20 ft-lbs and tighten 1/6 to 1/4 turn past the point when you start feeling resistance. Seemed like two different tightening criteria to me. I torqued to 18 ft-lbs and this was slightly past 1/4 turn. It seems fine so far and it doesn’t seem to be leaking or anything.

Next it was time to start it up and just hope that it works and starts cooling.

YIPPEE, IT WORKS!!!!

I started it up about 4 hours ago and the thermostat is set on 3/4. That means that I can make it colder but let’s see how cold it gets at the 3/4 setting. The fridge temperature is 36F and the cold evaporator plate at the rear is 2F. I am thrilled! The outside temperature is 80F. I put water in an ice cube tray in the freezer and I am hoping that I have ice in the morning. We shall see. There is really no way to make the freezer colder except if I make it smaller. This is definitely an option. I can install a vertical wall or baffle in the freezer. It will be parallel with the front freezer door. If I move it back it will make the freezer smaller but colder. We shall see if this is necessary.

The fridge operation looks like it requires about 55 watts based on my Trimetric battery monitor. My SOC is 71%. Looking forward to seeing my SOC in the morning and to see if I have ice.

Here is a photo with everything completely installed.

Dan

[TouringDan]

I checked the ice cube tray in the freezer this morning and it was frozen solid. However the ice was only 31.8F, so just barely below 32F. The fridge temperature had decreased from the 34F temperature yesterday evening to 32F this morning. I will adjust the thermostat to try to get a fridge temperature of 37-38F. This will probably raise the freezer temperature above 32F so I will fabricate a movable wall to install in the freezer that will allow me to make the freezer smaller in volume but colder. I will use this movable wall in the freezer to control the freezer temperature.

The batteries were at 50% SOC this morning. This is lower than I expected and I don’t know why, but that is what the Trimetric battery monitor showed.

Dan

[nvestysly]

Hi Dan,

Thanks for taking time to document your refrigerator upgrade. I wonder if something like this is in our future. I like the concept of a propane refrigerator for boondocking purposes but ours simply doesn't cool properly when it's hot outside. A compressor style upgrade like yours may be just the ticket!

See Ya Down The Road

[Bubba L]

Just wondering. If I wanted to reduce the volume of the fridge interior for reduced space to cool, could I just cut a piece of 4” Foamular to the size I want and lay it in the fridge? I could paint it to match the interior color and it would be light weight.