Domestic RM2554 replacement

[GregGIII]

Our old Dometic RM2554 in our Roadtrek recently gave up the ghost; the ammonia tank failed (basically rusted out) and leaked all the coolant. The techs at Camping World say it's not repairable. Their suggested replacement is a Norcold N512.3 or N512RU, which are similar in size and functionality but are very pricey. Neither is manufactured anymore but a few are available. Dometic's suggested replacement is the RM2354 or the RM2351, both of which are much smaller (3 cu.ft. v 5.5 cu. ft.) than the now-deceased RM2554.
Q1: Does anyone have a lead to an RM 2554? I have searched widely with no luck. Q2. Has anyone out there had a similar problem but been able to replace the coolant system? Q3: I hear mixed reviews about Norcolds. Does anyone have experience - good or bad - with the Norcold 512?

 

[Gary RV_Wizard]

I don't have any insight for you on the N512 but just wanted to say "Welcome to RVForum!".

 

[Kirk]

RV Fridge Guys They say that they have one.

 

[CharlesinGA]

Why not replace the cooling unit? The link is for a brand new cooling unit for that model, $830. If you are anywhere near Shipshewana Indiana, or willing to travel to them, they will install it for $160.

You do need some mechanical aptitude to do this, a lot of care needs to be put into assuring good contact of the coils with the cold plate and this is done by a test fit using prussian blue or fabric marking chalk that will transfer when pressed into place. Its not difficult, just requires some care and workmanship to do a good job.

From this thread I'm reproducing the following by RVFixer.................

Title: Re: Fridge questions
Post by: RVfixer on November 03, 2020, 10:19:02 AM


I thought I would report back and update this thread.

Short Review: My fridge quit...lights out on eyebrow panel and ammonia smell. No fridges were available unless you wanted to buy one with an RV wrapped around it. I hesitated ordering a new cooling unit until I resolved the electrical problem. The reason for no lights and no attempt at cooling was the that thermal fuse had popped due to overheating caused by the cooling unit failure.

I ordered a new build Amish cooling unit from David Force at The RV cooling Unit Warehouse online. During the job I emailed David a couple of times and he replied within minutes each time. The shipping was fast, the CU arrived in perfect condition. I worked the job by myself so I had to work out some interesting workarounds on working alone to get the fridge out, the new cooling unit in place in the fridge box and the fridge reinstalled. I took my time and was happy with the results.

I have read a few posts and heard from a few RVers where they were not happy with the cooling after a cooling unit replacement. There are two main items that can cause this....Not properly sealing in the foam block containing the cooling tube and not getting the cooling tube up against the metal freezer plate. Some of the cooling unit sites say not to use the canned insulation foam to seal the unit in...Instead they recommend using weather stripping. Luckily I read my warranty paperwork before starting the job. On the Amish cooling unity warranty it says, "Failure to use the provided foam to seal in the CU foam block voids the warranty."

The instructions say to make sure you get the cooling tube in the foam block hard against the metal plate back freezer wall. It doesn't tell you how to do that. Then it says that due to the variances in the fridge boxes the foam block may not go down flush, it may stick up a little after installation and that is OK. Mine did stick up a little. When you put the CU on the back of the fridge the foam block goes into a recess on the back of the fridge....So, how do you know if the foam block is all the way down (especially when it sticks up a little) and how do you know that the cooling tube inside is against the freezer metal plate?? In my opinion this step and sealing in the foam block are the most important steps for success and good cooling.

I thought of a few ideas to be sure the foam block was all the way down and the zigzag cooling tube in that foam block was against the freezer plate. The one I used was chalk on the cooling tube. I did a dry (no thermal mastic and no foam sealant) fit check after trimming down some foam block high spots, When I removed the cooling unit I had a zigzag line of chalk down the freezer plate. Works for me!

For my final installation I put the bead of thermal mastic on the cooling tube and two rows of foam insulation beads on the recess walls in the fridge box and installed the CU into the fridge box. To get the fridge back in it's cabinet I reversed the process that I used to remove it. I used a little roller that I move my generator around on at home and stacked two rows of short boards on the roller up to the level of the bottom of the fridge. I slide the fridge out of it's cabinet onto the boards, rolled it to where I wanted to work it in the trailer and tilted the fridge back and forth, taking one board out at a time and walked the fridge down. I walked it back up on the roller and reinstalled the fridge in the same manner. Job complete. The following was my start up test: (After doing all this work you have to play with it...Right?)


Outside temp. = 10:30 AM 68 degrees F. Today's high to be 72

Starting temp: Inside fridge box = 60 ..........Inside freezer = 60

After one hour.... Fridge = 58 Freezer = 32

After two hours 45 15

After three hours 35 +5

After four hours 33 +2

After five hours 33 +2

I let it go for 2 more hours without opening the doors and got the following

After seven hours 33 0 degrees

** Notes:

* Fridge and freezer were empty
* I opened the doors every hour
* It is a cool, no sun day
*** Works for me!

I responded........

Thanks for the excellent write up. Replacing the cooling unit is probably the best way to go, the fridge fits in the opening, no remaking the opening for a different fridge, it certainly didn't cost as much as a new fridge, which you could not even get, and it works GOOD now that it is done. WAY TO GO!!! Glad to see people actually fixing stuff themselves and doing it correctly.

If I'd done the fit test I would never have thought of chalk, I would have use (very messy) Prussian Blue, because that is what I have. Excellent info, I may have to do this someday, I have an RM2662RB according to the trailer mfg spec sheet I have a pic of, will have to look again at the model numbers on the fridge itself.

DID YOU USE BLUE CHALK DUST LIKE YOU USE ON A STRING TO SNAP A CHALK LINE? Charles

GREAT EXPLAINATION ON HOW THE COOLING UNIT WAS INSTALLED………………..

RVFixer replied

CharlesinGA

You asked if I used string chalk. No, I had thought of several choices to get a transfer trace from the side of the zigzag coolant tube onto the freezer plate and most seemed messy. I decided to try chalk. Any chalk would do and I was going to run up to the store and get some blackboard chalk which I am sure would have worked fine. My wife does a lot of sewing as a hobby and she suggested and volunteered her blue tailors chalk. That chalk is a tad oily and doesn't drop powder...Worked great!

Because I was working with no helper I had to do some workarounds. The instructions call for putting the mastic paste on the side of the zigzag cooling tube on the back of the foam block. The mastic is in a tube that requires a sealant gun. It is a non hardening paste that is full of aluminum powder and aids in transferring the cooling from the tube to the freezer plate to the refrigerator section cooling fin assemble. You then install the cooling fin assembly onto the lower section of the cooling tube over the mastic in that area. The top portion of the cooling line, with a mastic bead on it goes against the freezer plate when the cooling unit is installed into the fridge box. Per the instructions you put two rows of the spray foam around the side walls of the recess in the freezer box where the foam block with the mastic coated cooling line and fridge fins fits into. The fins fit through a cutout in the thin plastic liner of the fridge section. Then the instructions call for holding the cooling unit parallel to the ground and lower it into the fridge box which is laying on it's face. Try doing that by yourself. I decided that was not going to work for me.

What I did I think I would do again even if I had a helper. The instructions call for you to lower the cooling unit into the fridge that is laying on it face. Most people crack the plastic lining in the fridge where the cooling fins passes through into the fridge section. That is not a problem but I'd rather not crack that plastic liner. Then the instructions call for building up the removals...power module, brackets, gas valve, burner box with probe, etc., route and hook up all the wiring, etc. I guess if you are doing this for a living and have done many...and have a helper that would work...However, the foam seal is curing as you do all that and you have not installed the freezer plate screws and pulled the cooling tube up against the plate yet. Below is what I did and would do again even if I had a helper.

I stood the freezer box upright. With the mastic and fin assemble installed on the cooling unit I could easily lift the cooling unit in the upright position and move it over to the fridge box. In this configuration I could look over the top of the foam block and line it and the fins up to enter the recess in fridge box. If the fins are a little high to pass through the tight cut out in the box just move the bottom of the cooling unit back a little, if the fins were low move the bottom of the cooling unit forward a little. When lined up well push it in...no cracking of the plastic liner or smearing of the foam seal due to having a good view over the foam block and full control due to a one person operation and not fighting each other. The other benefit of installing the cooling unit with the fridge box upright is that after you put the corner frame screws through the cooling unit frame and into the fridge box you can then install the screws through the freezer compartment and pull the cooling tube hard against the freezer plate before the foam cures and hardens.

Another tip: The cooling fins for the fridge section install over the mastic on the lower part of the cooling unit foam block with four screws. There is a lot of slop in those screw holes in the fin assemble. Because the fin assembly fits through a tight cutout in the thin plastic liner...I left the four fin mount screws just lightly snug. This allowed the fins to move a little and line themselves up while passing through the close fit cut out. After installing the freezer screws I put the final torque on the fin assemble screws inside and at the top of the fridge section. THEN, you can lay the fridge down on it's face and take all the time you want to reinstall all the removed items and route and hook up the wiring.

Another important part of this job, per the instructions: At the top of the cooling unit there is a set of cooling fins with a couple of tubes passing through. This is the condenser and is just a couple of inches below the top of the fridge box with the cooling unit installed. The instructions call for making sure that this condenser is level with the top of the fridge box. The frame and tubing of the cooling unit will move a little independent of the sealed-in foam block. The holes in the corners of the cooling unit frame are large clearance holes. It is easy to loosen those top frame screws and push the fame a little to level the condenser with the top of the fridge box. After doing that, and tightening the screws in the frame clearance holes. I drilled a couple of new non clearance holes through the frame and into the fridge box to install tight fit screws and make sure the frame didn't move in the clearance holes during rough travel. Because I read all the instructions before starting the job I was able to check the old condenser levelness once I got the refrigerator removed. It was pretty much off level. I guess you could say that, even though I an kind of fanatical about getting my trailer level for proper operation of the fridge...you could say the fridge has been running off level for over 9 years due too a sloppy factory install of the cooling unit!

I had fun with this project and fun writing these posts.