RMD 8555 replacement

[Vermilye]

I spent a lot of time whining about the 43°F+ temperatures even when set on the coldest setting (5) in my Dometic DM2663LBX 3 way refrigerator (stock in the 2017 21). Before throwing it out & switching to a compressor refrigerator, I decided to try changing out the Dometic electronic board and replacing it with one from Dinosaur. Now, while not perfect (I sometimes have to switch between settings 3 & 4) it has done well even in 95°F outside temperatures. The freezer is always frozen, and the refrigerator goes between 36°F - 40°F.

[BILLB]

Originally Posted by Vermilye

I spent a lot of time whining about the 43°F+ temperatures even when set on the coldest setting (5) in my Dometic DM2663LBX 3 way refrigerator (stock in the 2017 21). Before throwing it out & switching to a compressor refrigerator, I decided to try changing out the Dometic electronic board and replacing it with one from Dinosaur. Now, while not perfect (I sometimes have to switch between settings 3 & 4) it has done well even in 95°F outside temperatures. The freezer is always frozen, and the refrigerator goes between 36°F - 40°F.

Any idea why changing the control board would cause the refrigerator to run more efficiently?
Seems like the refrigerator’s ability to cool would be the same regardless of which board is controlling the unit.

[rbryan4]

Originally Posted by John in Santa Cruz

yeah, thats my experience, absorption fridges work OK in mild to moderately warm weather, but totally can't keep up with 100F+ outside temps for any lenght of time.



the RMD8555, with the rooftop chimney vent on my E21 certainly worked better than the small absorption fridges on either my old tent trailer, or my Casita 16, but in 100F weather none of them were able to keep up with 'cool'. The Dometic CMX3-75DZ compressor 'cooler' I;ve bought as a stop gap stays cold frozen well into the upper 100F range outside, so I'm totally convinced. Sure, long term, I'm gonna probably need to double my solar and upgrade to LFP, but thats all good.

It's been my experience too, but it really doesn't have anything to do with absorption technology. It has to do with how poorly it's executed by Dometic and others here in North America. Commercial absorption refrigeration for example has been around for a long time and works very well.

To this day I cannot understand why they sell absorption fridges in Australia for example that still work well even with outside ambient temps of 110F - and yet they won't sell them here. Instead we get the thinly insulated ones with lower cooling capacity and an SN climate class rating.

Having said all that though, if you have the constant supply of electricity needed, by all means go with the compressor fridge. It's the only true fix in our market for the fridge sizes we're talking about.

[Vermilye]

Originally Posted by BILLB

Any idea why changing the control board would cause the refrigerator to run more efficiently?
Seems like the refrigerator’s ability to cool would be the same regardless of which board is controlling the unit.

The control board "controls" the on/off cycles. I have a refrigerator thermometer (Sensor Push) that records daily/weekly/monthly, etc and it showed the cycling off & on of the boiler. With the original card it was not on enough to cool the refrigerator to below 40°F. The Dinosaur card has a temperature adjustment, and setting that close to maximum cold solved the problem by allowing longer heating cycles of the boiler.

[BILLB]

Originally Posted by Vermilye

The control board "controls" the on/off cycles. I have a refrigerator thermometer (Sensor Push) that records daily/weekly/monthly, etc and it showed the cycling off & on of the boiler. With the original card it was not on enough to cool the refrigerator to below 40°F. The Dinosaur card has a temperature adjustment, and setting that close to maximum cold solved the problem by allowing longer heating cycles of the boiler.

Very interesting. I wonder if the original board could have been made to work better by simply moving the refrigerator temperature sensor further away from the evaporator cooling fins. Seems like that would also cause more on time and less off time cycling of the unit.

[gbaglo]

Originally Posted by BILLB

Very interesting. I wonder if the original board could have been made to work better by simply moving the refrigerator temperature sensor further away from the evaporator cooling fins.

Or, by turning the temp control knob to "colder".

[Iowa Dave]

If you’ll look back on 8555 and 8551 discussions you’ll find extensive discussions. They include Thermistor location, drain tube techniques, door sealing, negative camper pressure, regulator pressure, internal and external fans etc.

Our 8555 works ok up to about 80 degrees ambient and then, if not in the shade, has a problem recovering. Camping in the shade last summer at 85 to 90 degrees we had a cooler for drinks etc so didn’t open the refrigerator door as much and did fine. The freezer has always been “superior” in performance to the refrigerated area.

Camping in Kansas at 108F it couldn’t keep up, but the AC sure felt good, never heard the AC run after my head hit the pillow. I doubt I would spend much money on modifications or repairs on the 8555. I’d go to a compressor unit and forget about the propane.
Iowa Dave

[rubicon327]

Originally Posted by gbaglo

Or, by turning the temp control knob to "colder".

Wasn't an option apparently. Jon said in post 41 - "43°F+ temperatures even when set on the coldest setting (5)"

[Vermilye]

Originally Posted by rubicon327

Wasn't an option apparently. Jon said in post 41 - "43°F+ temperatures even when set on the coldest setting (5)"

Most folks have not had problems with the Dometic DM2663LBX (Americana) refrigerators, at least up to 90°F or so. I suspect mine had an out of spec control board that the replacement fixed. It is quite possible that a Dometic brand replacement control board would have also fixed the problem.

By the way, I had already tried moving the thermocouple on & off the fins, an internal fan, etc. Since I dry camp for months at a time, I prefer an absorption refrigerator rather than putting most of my solar collection into a compressor refrigerator.

[LeonW]

Originally Posted by Oldtimer

Agree one need a left hand hinge in a 21

David

hmmm. And I thought it would be nice to have a right hand fridge just so the door doesn't hit the table in our 21. I know the aisle would be blocked while the door is open, but the fridge door is rarely open.

[LeonW]

Originally Posted by BILLB

Very interesting. I wonder if the original board could have been made to work better by simply moving the refrigerator temperature sensor further away from the evaporator cooling fins. Seems like that would also cause more on time and less off time cycling of the unit.

I did a few things to make the domestic work better: 1) installed a pair of fans that circulate the air in the fridge. I can't remember the make/model, but it is two computer fans that get attached to the fins, and also includes a blue light for the fridge. 2) Moved the thermistor away from the fins. Used a bit of electrical tape to tape it against an outside wall of the fridge as far away from the fins as I could get it. 3) checked the pressure at the burner, and ended up replacing the regulator. I also took the opportunity to clean the orifice by soaking it in alcohol. I think there was a tiny spec of dust in there, but couldn't be sure.

We have had issues a couple of times since we did this, but they have always been solved by cleaning the orifice.

[Rossue]

Hi Leon; X2! However, if/when the RMD8555 bites the dust there will be a decision then about a replacement. A compressor fridge is great( have an Isotherm 130 in a van build), yet would need to upgrade batteries at same time. Am leaning in that direction though.

[elongest]

I was involved with the group was experimenting with the 8555 modifications, each mod. seemed to help a little. As stated earlier the freezer seems to work fine in hotter weather. The frig box just gets the remainder of the cooling from the evaporation process. I also read that Dometic was trying to maximize space minimize weight and was using an all foam refer box on the 8555. I decided the thin foam box was the issue and worked the issue from that point.

Where is your major heat generated, on the back wall of your refrigerator with the burner, condensation coils and outside air. I lined the inside of the frig box walls with 1" rigid pink foam. The foam will fit in the air channel behind the shelves. It can be cut to fit above, below and between the main shelves. You can remove the door shelves and fit it into the front door cavity. I then sealed things up with HVAC tape. I did have to trim the foam around the door latches. You lose capacity but you get a colder frig. box. In hot humid weather I would get condensation on the front door around the door latches where it was not insulated well. Just saying what worked for a year for me until I sold my trailer but YMMV.
Eddie

[Mike Lewis]

Originally Posted by elongest

I lined the inside of the frig box walls with 1" rigid pink foam.
Eddie

How did you secure the foam to the sides of the fridge box? Did you use a two-sided tape of some kind? I'm assuming the HVAC tape you referred to was for other sealing. Thanks.

[John in Santa Cruz]

So, Norcold N2175 has been ordered, and should be delivered soon (1 unit in stock at my installer's distributor), but my installer is backlogged til February. Good enough, that will give me time to test its power consumption, AND upgrade my batteries, its nearly 5 years since I installed these Costco/Interstate GC2's so they will be due before long anyways.

[Centex]

Originally Posted by John in Santa Cruz

So, Norcold N2175 has been ordered, and should be delivered soon (1 unit in stock at my installer's distributor), but my installer is backlogged til February. Good enough, that will give me time to test its power consumption, AND upgrade my batteries, its nearly 5 years since I installed these Costco/Interstate GC2's so they will be due before long anyways.

A plan in motion, congrats!

Is it safe to assume no-hassle door-reversibility has been confirmed?

Looking forward to your power consumption findings and battery upgrade revelations

[John in Santa Cruz]

re: reversability,
A) I found no signs of any reversal kits on norcold's site
B) the N2175 parts catalog shows everything is symmetric.
C) the N2000 series owners manual has the procedure for reversing using the existing parts.

my installer looked over that same stuff and concurred with my conclusions, thats good enough for me.

[Centex]

Originally Posted by John in Santa Cruz

re: reversability, ....

[alanerickson]

Just read an article in the Wall Street Journal about steep lithium price increases. If you know what you want and need for batteries you may want to get them sooner rather than later.

[Rossue]

Frustrating to see that there is no direct replacement now for the RMD8555 as the RMD 105.XT is now discontinued. Dimensions are 49 H X 20 1/16 H X 24 7/16 D.

I know that some have installed a Norcold N2175 - and it appears there is a different part number for those wanting a left hand vs. right hand opening.
The Norcold N2175 appears to be a DC unit only.

The Nova Kool RFU 6800 can be purchased as DC only or AC/DC. Sure Marine in Seattle sells these units and has the AC/DC unit on order- about 3-6 weeks out. This unit lists for $2,540 and their price is $1,778. The doors are reversible. The cutout is 47 1/3 X 20 1/4 X 21 1/2. It does use a Danfoss single compressor. At idle it draws 2.25 amps and while running 4.5 amps.

I bought my Propex HS2800 from Sure Marine and was very happy with price & after sales support.
https://www.suremarineservice.com/Sh...Kool%20RFU6800

While I was able to get a Dometic RMD 10.XT and like it I would probably go with the Nova Kool if I needed a replacement at this time. Nice to have that AC shore power option with this unit as well.