Possible replacements for Dometic RML 8555 fridge

TStiles

2018 Unity CB
There are many similarities in the challenges that both RV and boat owners face and refrigeration is an absolutely common issue. I replaced a number of refrigerators in boats in my many years and found only one manufacturer's product that I am confident in recommending. They offer standard sizes, but will also custom build most anything you need. Their standard unit is 12vDC and they offer the option of 120vAC / 12vDC auto switching for those who want the capability. What I especially appreciate is their remote compressor option. This allows for a larger refer internally while letting you place the compressor in a space where its noise cannot be heard. If you have an external locker that you aren't using that's in proximity to the refer, then you can place the compressor there. The company is Sea Freeze and they're located in Bellingham, WA. No, I'm NOT on their payroll. I'm just one of their many satisfied clients - purchased several units from them over 20 or so years and never had a problem, ever. When my Dometic craps out, I'll look to Sea Freeze for the replacement.
 

SSTraveler

2014 LTV Unity Murphy Bed
Well it took me 3 long days for this remodel and I am very pleased so far. I did not have time to take any pictures but it was a very challenging DIY remodel.  I worked furiously when I got the Refrigerator last week to get this done since we had to leave for Elkhart on Monday to get the new Levelers. I've only been using the Refrigerator for 2 days but already I love it. As you can see from my outside temp gauge, which has the sun on it and reads 119.4 degrees, that the old Dometic would be super challenged to cool to 40 degrees or less. This Isotherm Cruise 219 2 way AC/DC compressor Refrigerator is only on setting 4 of 7 and is -6 degrees F in the freezer and 35-38 (interior and door) in the refrigerator. It is so nice just to set it and forget it, no more adding ice and worrying. The temperature never changes whether on battery or shore power. It uses between 2-7amps versus the 10+ the old Dometic and all its cooling fans, temp gauges and temperature controller used. I took in the Refrigerator exterior compartment and sealed the outside wall and added Reflectix insulation. Even with the sun beating on it my Temp gun only registered 82-85 degrees on the inside wall now. The Refrigerator comes with a fan to exhaust its compressor area at the bottom left corner and then I added one 120mm fan from my old setup to help move air from behind the Refrigerator and to ventilate the microwave compartment. There is about a 4 inch space that is open from the floor to ceiling behind the Refrigerator/microwave so that should allow for good air exchange from the air conditioned room to the back of this new space. The extra fan is located just behind the left side of the microwave. To pull air from the 4 inch space and blow it over the back and left side of the microwave, where it's exhaust area is. The Toshiba microwave, at 900w, works much better than the old Hotpoint and is the perfect size for how we use microwaves. I shed 52lbs between the old and new. The Dometic weighed 99lbs versus 75lbs for the Isotherm and the Hotpoint weighed 55lbs versus the Toshiba at 28lbs. Nice added benefit! The Isotherm Cruise 219 is slightly larger at 7.75 cuft (6.3cuft Refrigerator and 1.45cuft freezer), than the Dometic, which is nice. It is so nice to have an ice bucket with ice in free moving cubes versus a melted frozen blob of ice cubes. And to be able to actually use the ice versus just carrying it to help with cooling. I wish I would have done this along time ago, but I wanted to try and make what we paid a lot of money for work the way it is supposed to. I did my best and got the Dometic working reasonably well but I worried about it constantly. While we were driving today everytime I opened the Refrigerator the temperature gauge on the door was constant at 38 degrees. Love it!  Sorry I don't have my usual picture tutorial but I didn't have time plus this is an advanced project, once you start the demo there is no going back! I guess I'll have to keep my Unity for a few more years! :smirk::
 

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Gamma1966

2013 Chassis /14 Unity MB
Congrats on moving away from the Tri-Fuel to a compressor based refrigeration system.
I also made the change to a NovaKool 2 summers ago, and have never been happier.
As usual you have provide us on the forum with insight to the approach you used, which may help others DIY'ers do a similar conversion.
 

RandyJohnson

2018 Unity TB
Gamma1966...

Did you install the RFU6800? If so what have you done to eliminate the possibility of the fridge going upwards of 50 degrees?

We have the RFU6800 installed but noticed as of late that the during 90+ degree days can sometime wander above 40 degrees.

Thanks in advance...

Randy
 

Gamma1966

2013 Chassis /14 Unity MB
I have added a pair of 12 v PC fans in the space behind the microwave and above the evaporator coil of the NovaKool. I have a temp controller; which runs these fans when the temp in the air space behind the NovaKool exceeds 90 Deg. the fans exhaust air out the top side ventilation opening on the side of the Unity. The NovaKool has its own fan near the motor; which I paired with another pair of 12 V PC fans to "push air up " the evaporator space. So the evaporator air space is generally a "cool 85 to 90 Deg" when running.

I set the inside temp setting of the NovaKool to 5 or 6 and get pretty consistent 40 Deg in upper compartment and -5 to + 5 in the freezer compartment. I just did a search on a previous posting show more details on the rear fans, but I cannot find it... the search on this forum is marginal at best.

Here is a recent posting on monitoring temps in the battery compartment(s) and the refrigerator space(s) .

If you have any questions PM me and I will be glad to help.
 

jmoone

New member
With the NovaKool are you using your batteries or mostly plugged in. I'm researching on which brand NovaKool or Isotherm, then I will need to find a reputable company to install it. I understand that adding insulation is the key and perhaps a fan?
 

Gamma1966

2013 Chassis /14 Unity MB
When on Shore power I have a dedicated 120 Vac to 12 vdc "Power Block" and relay that supplies 12 Vdc to the NOvakool. Other wise it is on battery 12 volt power,
I typically use about 50 amps of 12 vdc power to run the refrigerator over 24 hour period.

I would buy the combo Ac / DC model of the Novakool if I would do it again, versus the DC ONLY model I bought.
 

SSTraveler

2014 LTV Unity Murphy Bed
With the NovaKool are you using your batteries or mostly plugged in. I'm researching on which brand NovaKool or Isotherm, then I will need to find a reputable company to install it. I understand that adding insulation is the key and perhaps a fan?
Here is a Refrigerator size comparison chart that you might find useful, https://www.suremarineservice.com/Galley/Refrigeration-Size-Comparison/. As you can see the NovaKool RFU6200, RFU6800, and the Isotherm Criuse 165 can fit the Dometic 8555 opening. NovaKool also makes an RFU6400 that fits but is not listed on the chart. I mentioned the 6400 for those who have the ability to simply close off the outside, cap the propane, and then want an easy plug and play electrical connection. The 6400 has a different compressor/fan placement that appears to offer better compressor ventilation. It certainly seems like it would have no compressor cooling airflow issues like others report with the 6800.

I wanted a larger 2 door Refrigerator with a smaller freezer so I decided to completely remodel my microwave/Refrigerator cabinet so I could install the larger Isotherm Cruise 219 and changed out the microwave/convection oven to a smaller microwave only. I really like my Isotherm Refrigerator, it works exactly as I was hoping for. Similar to the NovaKool my Isotherm uses between 40-60ah per day depending on the outside temperatures and how often the compressor runs. My AGM batteries can easily handle running the Refrigerator for 10 hours if you have a roadside emergency or when boondocking (dark hours until the solar comes online again).
 

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SSTraveler

2014 LTV Unity Murphy Bed
This is the first full summer I have been using my Isotherm Cruise 219 Refrigerator and with +100° temperatures it performs flawlessly. Freezer stays between -5 - 10° and the Refrigerator is 35 (near back wall) - 41 degrees (on the door). With all that's going on we are staying closer to h8me this year and just using the Unity to checkout SC and Ga State Parks, so the outdoor temperatures are near 100 with a real feel as high as 110° and the performance never waivers. I have my thermostat dial marked so I put it on the same setting every trip. I start it up about 4 hours on the morning we are leaving, load it with food and go. The one thing I would change is rather than installing a 120mm fan and switch, to help exhaust and pull cooler air from the back space of the Refrigerator, I should have used a small 80mm fan and direct wired it to 12v so it runs continuously. It would be easier than remembering to switch on the 120mm fan. The Isotherm has a 120mm fan that runs when the compressor is running, and it dissipates it's heat, but if the sun is shining on the Refrigerator wall and it's 95+ outside, the temperature of that exterior wall gets upto 120°. So I switch on the fan to draw cooler air into the back. Just having a small fan run constantly would probably be a good thing just to keep the air moving behind the Refrigerator all the time. The only problem I thought I solved but didn't was keeping the food from moving and pushing open the doors when driving. I was using Camco Refrigerator bars to try and keep the food from moving past the door openings but still on a couple of sharp or uneven right turns my ice bucket and a large jar of olives sent the doors swinging. So I found this Refrigerator latch, that is really for an 10.7cuft 2 door Whirlpool compressor Refrigerator, that I was able to modify to work great as a travel door latch. I found this latch at Total Value RV in Elkhart, IN. 574-262-4460 and ask for the parts department. The gentleman I talked to said the latch is really a Whirlpool Refrigerator part with the part number #0315479. I told him that I didn't have a Whirlpool Refrigerator but I wanted to try and fit this for use on my Isotherm and I recognize I may have to drill a new hole or two. He took my information and CC and said it would be $21.67, including tax and shipping. I got it in about 5 days. I used the existing door reversing screw holes and drilled new holes to get the latch placement correct. It moves between the doors, so it just flips out of the way to the side of the doors when not in use. With you flip around to the front of the doors, the rubber tips keep the doors from flying open. I found the little rubber tips weren't quite large enough to actually apply pressure to keep the doors pressed closed, so the doors could still pop open a little bit. I found a pair of silicone brake lever covers (https://www.amazon.com/Mantain-Bicycle-Silicone-Anti-Slip-Protection/dp/B07QSTXXDS/ref=sr_1_6?crid=2Q9UZFVA5KW65&dchild=1&keywords=silicone+brake+lever+cover&qid=1595843542&sprefix=Silicaone+brake+lev,aps,226&sr=8-6) in my junk drawer and cut about an 1" of the ends off to use as new tips. I pushed them on over the rubber tips and that did the trick. The shape and none slip material the silicone brake covers, with a little bend to them, works perfectly to grab onto the corners of the doors and hold them secure. I still use the Camco rods to keep things on each shelf from sliding forward, but now it's just so I don't have stuff falling out on me when I open the doors on the road or after a day of driving.
 

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SSTraveler

2014 LTV Unity Murphy Bed
Isotherm does send you latches (They include 2 of these, https://www.amazon.com/Dreambaby-L1...ream+refrigerator+latch&qid=1595877526&sr=8-3) but they just stick on and you have to manipulate them every time you want to open the doors. I didn't like them so I didn't install. TampaSteve installed his but he said at least one fell off, so they don't seem to work. I came up with a couple of ideas but I thought this would work best, and it does work as I envisioned so l'm very happy .
 

SSTraveler

2014 LTV Unity Murphy Bed
I saw this post on Facebook where a Leisure Wonder Owner is installing a NovaKool RFU6404D, 2 compressor model Refrigerator/freezer. I never could find that NK makes a 2 compressor model that would fit as a replacement. Evidently you have to call NK to special order it. NK uses DanFoss BD35F compressors and it's just undersized for their 2 door models like the RFU6800. If I was going with NK I would definitely select this 2 compressor 6404 model. Isotherm uses a BD50F in their Cruise 165 and 219 models, this larger displacement compressor works great in our very hot summer temperatures. So the NK with 2 smaller displacement compressor should work equally as well. I hope Gmillerok1 reports back here as well, about his NK Refrigerator install.

20200728_081127.jpg
 

gmillerok1

New member
I saw this post on Facebook where a Leisure Wonder Owner is installing a NovaKool RFU6404D, 2 compressor model Refrigerator/freezer. I never could find that NK makes a 2 compressor model that would fit as a replacement. Evidently you have to call NK to special order it. NK uses DanFoss BD35F compressors and it's just undersized for their 2 door models like the RFU6800. If I was going with NK I would definitely select this 2 compressor 6404 model. Isotherm uses a BD50F in their Cruise 165 and 219 models, this larger displacement compressor works great in our very hot summer temperatures. So the NK with 2 smaller displacement compressor should work equally as well. I hope Gmillerok1 reports back here as well, about his NK Refrigerator install.

View attachment 148076
Yep, that's me. I've attached a write up I posted on that group. I have nothing but good things to say about the 6406D. The Novakool 6406D ACDC model got to 0F in the freezer and kept the fridge section 36-38F. The first day was rough-and a good test, as I drove in the Texas panhandle with record highs in the 106F+ range. It never got higher than about 45 as it tried to cool everything down. By the next day, however, it stayed at 36F and I actually had to turn up the thermostate to about a 4.5 out of 7 to keep the fridge section from going below 32F. The freezer got down to 0F, and would have stayed there, but I raised it up a bit to get it to around 10-15 or so. It's very quiet and sips energy. It's a direct replacement for the Dometic 8555 and RMD10 series (it's a bit shorter and narrower so a 1/4" shim on each side and a 2" rail on the bottom is needed). This is not a special order model, but like any Novakool, they make them to order. Mine came in two weeks (I was told it takes up to seven). Since it does have two Secop BD35 compressors, it is more expensive than the single compressor models. Any questions, please let me know.

I discussed the RFU6800 cooling issue with the Novakool folks and asked them if they would build me one with the BD50. The response was that the BD35 is adequate as long as there is 60sq. in. of ventilation as specified on their website and that the BD50 was not needed for the RFU6800. With that being said, the 6406D has about twice the cooling power than the RFU6800 obviously, since it has two of them. Another thing RFU6800 owners should try is to increase the compressor speed as Novakool defaults these to about a little of half full speed. A simple resistor change is all that is needed.
 

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SSTraveler

2014 LTV Unity Murphy Bed
Nice install, It's fortunate that you went with the 2 compressor NovaKool RFU6406D, it should work well with those 2 smaller compressors. I would expect your Refrigerator to use more power simply because it's running 2 compressors. But certainly well within the ability of any type battery to supply for a few hours (overnight) when not on Solar/Shore/Generator power. I'm glad you are seeing good cooling results. IMHO, the issues with the NK RFU6800 simply boil down to the compressor being undersized. I think people who camp in summer climates of less than 85° might be satisfied with the NK6800, but for those who camp in high summer temps like +100° the Single compressor NovaKool will always be disappointing. I live in SC and most of the summer is +100° and I see 120° on the exterior wall when the hot afternoon sun shines on it. I have seen interior wall temps of 95°, and since the compressor puts off +90° when operating it's imperative to exhaust the space behind the Refrigerator under that condition. The Isotherm has a larger compressor (BD50F) which produces the extra amount of cooling needed to overcome higher exterior temperatures and a powerful fan to exhaust the compressor heat. Based on my experience, I would advise anyone interested in the NovaKool Refrigerator, to only get a 2 compressor model.

Another observation, the Isotherm Cruise 165 (direct replacement for the Dometic 8555 or RMD10) and Isotherm Cruise 219 (the model I choose to install) use a 50 (BD50F DanFoss compressor) sized displacement compressor and the NK6406D essential has a 70 (2-DanFoss BD35Fs) equivalent size. DiverBob just had JC Refrigeration convert his Dometic to a compressor Refrigerator using a 65 sized compressor and did not close off the exterior vents. He has said he's very happy so far with his Refrigerator performance. So it's possible the NK6406D could perform well without modification to the exterior vents. If I were selecting the NK6406D I would certainly try the install with no modifications to close off the exterior vents first and see if it performs satisfactorily. It may surprise and function equally well as DiverBob's new Refrigerator conversion. I probably would add 1 or 2- 120mm fans to the top vent and have them run constantly to exhaust heat from that exterior space but that's easy. It's certainly worth a try before you go to the extra effort of closing off the vents. Something to consider, and it might turn out to be easiest, readily available, plug and play Dometic Refrigerator replacement option yet.
 
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TampaSteve

2018/2019 Unity CB
Great to see a 6 year old thread still going strong. I installed the cruise 219 also. I'm satisfied with it but I don't seem to be getting quite the spectacular results that @SSTraveler did. I insulated very well, and added auxiliary fans.

On this trip it has performed adequately, maintaining a door temp around 39 to 40 and a rear wall temp around 37. That's way better than I ever got with Dometic.

My complaint is severe frosting. I had a substantial layer within 12 hours and doubt I could go more than 5 days without a defrost.

Other issue is it runs near continuously.

The freezer is always around -3.

In fairness we have it way overloaded this trip and we are in the deep south with high humidity.

So it's still a work in progress. My wife already calls me the food police, and I am going to crack down on food volume on the return.

Not sure that is related though as all food was loaded cold.

At least even with my complaints it is working acceptably.
 

Gamma1966

2013 Chassis /14 Unity MB
For those who might be interested, the following table shows the compressor speed that runs when a resistor is placed in series with the "Control Circuit" of the Danfross BDF35 unit. I found that the BDF35 Starter that controls the Compressor has its own pre-programmed speed control. So even if you put a 1523 Ohm resistor in the circuit ( Factory Default ) the compressor actually starts out at about 2500 rpm and then over time, as pressure in the refrigerant line increases, it will step up the rpm's. Bottom line, just take the factory default resistor, and let the Thermostat determine the desired temp in the upper refrigerator compartment. My recently added digital temp control system provides for pretty accurate temperature control of the NovaKool upper refrigerated compartment. I did also reduce the amount of Frost build-up, by using an auxillary heating pad and recirculation fan in the upper refrigerator compartment. Unfortunately, the freezer compartment follows along with the temp in the upper compartment. Without the Aux heating pad the freezer was generally 10 to 15 degrees colder than the upper compartment. Adding the auxillary heating pad only provide about 10 to 12 degrees colder temperature in the freezer compartment. When I am ready to remove my existing NovaKool refrigerator from the RV, I will probably install this new double compressor model from NovaKool. (Note: The Auxillary heating pad draws about as much watts from the battery as the BDF35 compressor; so it would be like the dual compressor unit, in terms of power consumption. However, I would be able to achieve Zero or Sub-Zero temps in the freezer; which I cannot achieve with the current NovaKool unit.

Danfross Compressor
Ohms @ Trpm'swatts
152335000.25
69230000.25
29725000.25
021580.25
 

gmillerok1

New member
For those who might be interested, the following table shows the compressor speed that runs when a resistor is placed in series with the "Control Circuit" of the Danfross BDF35 unit. I found that the BDF35 Starter that controls the Compressor has its own pre-programmed speed control. So even if you put a 1523 Ohm resistor in the circuit ( Factory Default ) the compressor actually starts out at about 2500 rpm and then over time, as pressure in the refrigerant line increases, it will step up the rpm's. Bottom line, just take the factory default resistor, and let the Thermostat determine the desired temp in the upper refrigerator compartment. My recently added digital temp control system provides for pretty accurate temperature control of the NovaKool upper refrigerated compartment. I did also reduce the amount of Frost build-up, by using an auxillary heating pad and recirculation fan in the upper refrigerator compartment. Unfortunately, the freezer compartment follows along with the temp in the upper compartment. Without the Aux heating pad the freezer was generally 10 to 15 degrees colder than the upper compartment. Adding the auxillary heating pad only provide about 10 to 12 degrees colder temperature in the freezer compartment. When I am ready to remove my existing NovaKool refrigerator from the RV, I will probably install this new double compressor model from NovaKool. (Note: The Auxillary heating pad draws about as much watts from the battery as the BDF35 compressor; so it would be like the dual compressor unit, in terms of power consumption. However, I would be able to achieve Zero or Sub-Zero temps in the freezer; which I cannot achieve with the current NovaKool unit.

Danfross Compressor
Ohms @ Trpm'swatts
152335000.25
69230000.25
29725000.25
021580.25
Thanks. It doesn't look like the Merlin II really helped that much. I was thinking of adding that but what's the point? Also, what is so critical about zero degrees in the freezer? I know that is the recommended temperature for long term storage, but unless users are full times it would seem anything below 20F would be fine and would save a bit of energy as well.
 
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SSTraveler

2014 LTV Unity Murphy Bed
Great to see a 6 year old thread still going strong. I installed the cruise 219 also. I'm satisfied with it but I don't seem to be getting quite the spectacular results that @SSTraveler did. I insulated very well, and added auxiliary fans.

On this trip it has performed adequately, maintaining a door temp around 39 to 40 and a rear wall temp around 37. That's way better than I ever got with Dometic.

My complaint is severe frosting. I had a substantial layer within 12 hours and doubt I could go more than 5 days without a defrost.

Other issue is it runs near continuously.

The freezer is always around -3.

In fairness we have it way overloaded this trip and we are in the deep south with high humidity.

So it's still a work in progress. My wife already calls me the food police, and I am going to crack down on food volume on the return.

Not sure that is related though as all food was loaded cold.

At least even with my complaints it is working acceptably.
The only thing that was different about our Isotherm 219 installs is that I didn't add the temperature controller like you did. Installing that required drilling a hole into the refrigerator box to add the temperature controller sensor inside. Maybe there is warm air leaking in some how. I don't get any frost in my refrigerator area and only small amounts in the freezer but not for a couple of weeks into a trip. In fact I've never had to defrost once on a trip yet. It sounds like warm air is coming in either through the seal or the temperature sensor hole. You might want to check the door seal and make sure it's good. If you can't find any leaks then possibly adding some internal circulation fans would help. I hate to even suggest this, but removing the temperature controller maybe the best thing to do. I keep my setting at about 3.25 and my door temperature is 41°, but the interior temperature ranges from 32° on the back wall to 38° at the front of the shelf. In fact I still find some food items just starting to freeze when I go to use them. If anything sits on the back wall it will freeze solid, even more than on gallon of milk/juices. My compressor runs less than 4 times per hour, particularly at night. It may only run once an hour through the night. I guess a lesson s learned is try the stock Isotherm before you think about adding the digital temperature controller.
 
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