Dometic RMD 8555 Refrigerator replacement

[tgoedken]

Originally Posted by ITSNO60

Have you tried bringing in a grounded (negative) test wire to check for 12V at each of the wires instead of going from wire to wire?

There has to be some 12 volt there to operate the board or the 3 way would not have worked on any setting, probably the smaller wires.

On the mystery wires can you ring them out for continuity? (Attach extension test wires onto the ends so you can reach both ends with your test leads).

Being a 3 way fridge there has to be a 12 volt circuit for the electronics and another heavier one for the element. If something has gone wrong with it can you get new wires in place?

You didn't forget to turn the battery switch on right?

Brian

Yep - battery switch is on for testing.

I checked continuity of the orphaned ground wire and it is good back to the refrigerator. I am not able on the second "brake" as I don't really know where that goes.

Back to the refridge.

I do have power and negative back to the old 3-way refrigerator electronics - power goes through a 2 amp fuse and uses 18 ga wire. I ASSUME the negative smaller wire (also 18 ga) was matched to this BUT IT IS NOT CONTAINED IN THE DIAGRAM SCHEMETIC. Question: Is it possible that AS used this ONE negative wire for BOTH the 12V connection as well as the electronics?

[ITSNO60]

Originally Posted by tgoedken

Brian

Yep - battery switch is on for testing.

I checked continuity of the orphaned ground wire and it is good back to the refrigerator. I am not able on the second "brake" as I don't really know where that goes.

Back to the refridge.

I do have power and negative back to the old 3-way refrigerator electronics - power goes through a 2 amp fuse and uses 18 ga wire. I ASSUME the negative smaller wire (also 18 ga) was matched to this BUT IT IS NOT CONTAINED IN THE DIAGRAM SCHEMETIC. Question: Is it possible that AS used this ONE negative wire for BOTH the 12V connection as well as the electronics?

Yes that is possible if I am understanding what you are saying, on mine (RML 8555) they grounded the 12 volt element wire (12 AWG) to the fridge chassis then grounded the electronics to the chassis, so only 1 negative wire. Now if you are asking about the 18 AWG, no that shouldn't be used as the negative on a 15 or 20 amp circuit, it's too small. The negative needs to be at least as large as the positive. (I have since disconnected my #12 hot and ran a pair of #8s directly off the battery to improve 12V performance)

[tgoedken]

Yep - I get that 18 GA would be too small to carry back the 15 AMP flow.

Question - the positive wire out is 10 GA. At the refridgerator the connecting with to the 12 V is 14 GA. The 10GA positive is overkill as it won't EVER deliver more than 15 AMP. Can I put an inline 12GA 15AMP fuse connector in between the 10GA and the 14GA wires?

[ITSNO60]

Originally Posted by tgoedken

Yep - I get that 18 GA would be too small to carry back the 15 AMP flow.

Question - the positive wire out is 10 GA. At the refridgerator the connecting with to the 12 V is 14 GA. The 10GA positive is overkill as it won't EVER deliver more than 15 AMP. Can I put an inline 12GA 15AMP fuse connector in between the 10GA and the 14GA wires?

Yes you can. The length of #10, even though overkill for the current, will help to reduce overall voltage drop which can be substantial in a 12 volt circuit. Of course your new NovaCool only be drawing what, 5 amps? At 10 feet of #14 that's a VD of 2.6%

[tgoedken]

Yep - at most 5 amps. That's what I will do!

Will post result

[tgoedken]

I went ahead and installed the in-line fuse - picture attached.

I also connected the "orphaned black wire" to the ground buss in the 12V DC panel (picture attached). I used that wire back at the refrigerator as the ground.

Note that these two wires do NOT go through the converter and are NOT shut off wity the supposed "battery disconnect" located in the entryway of the coach. The original refrigerator had a on/off panel that could be seen from the outside of the refrigerator. The new refridge has a "dial" on the inside. I WILL HAVE TO REMEMBER TO TURN THAT BABY OFF WHEN STORED OR MY BATTERIES ARE TOAST.

Or I may consider installing a true battery disconnect at the battery box.

I still have two wires that connected the old refrigerator electronics - the POS wire has that funky 2 amp fuse in the 12 V DC panel. I will remove the fuse so there is no power back there in the refrigerator area - although I may just "open" the fuse and tape it off.

Thx for the help!

[ITSNO60]

Originally Posted by tgoedken

I went ahead and installed the in-line fuse - picture attached.

I also connected the "orphaned black wire" to the ground buss in the 12V DC panel (picture attached). I used that wire back at the refrigerator as the ground.

Note that these two wires do NOT go through the converter and are NOT shut off wity the supposed "battery disconnect" located in the entryway of the coach. The original refrigerator had a on/off panel that could be seen from the outside of the refrigerator. The new refridge has a "dial" on the inside. I WILL HAVE TO REMEMBER TO TURN THAT BABY OFF WHEN STORED OR MY BATTERIES ARE TOAST.

Or I may consider installing a true battery disconnect at the battery box.

I still have two wires that connected the old refrigerator electronics - the POS wire has that funky 2 amp fuse in the 12 V DC panel. I will remove the fuse so there is no power back there in the refrigerator area - although I may just "open" the fuse and tape it off.

Thx for the help!

You could set up a N/O relay with the fridge power running thru it and connect the small wire to the house side of the battery disconnect and use it to trigger the relay, this way the fridge can only work when the battery switch is on. Or really just connect the relay trigger to any source that is hot when the battery switch is on.

[Revedream]

posting some questions to those who've been there done that on the isotherm cruise 195 install

I'm removing the dometic RMD 8555 (deleting the propane option) on a 2020 globetrotter 27

1) Venting - as propane is going away, did anyone vent into the inside (essentially sealing of the upper and lower vents). I hadnt considered this but saw someone else do just that. My plan is to seal the unit with foam on the sides and top (much like the dometic was) to keep the inside and outside separate, modify the top shelf (shorten to 14" and raise so bottom of shelf is 53.5"). Also, is it necessary to leave the "wood" wall in place as well or simply remove it for more airspace. the only function I can see is that it may protect the 120v outlet...thoughts on that?

2) 12v power - I found that the 10ga 12v power send comes straight from the 12v junction up front (has a connector as well) but is outside the "shutoff" as noted in prior posts. I assume I can tie both fridge and freezer 12v +/- leads to the orange/white. i did see some folks adding a fuse but not sure why that is necessary if it was not there for the dometic??

3) 120v power - thinking of adding and additional plug AND installing a double 15 breaker so I can run dedicated 14/2 wire to both...is that overkill. I will need to add a double 15 AND a new GFCI which will go to the fridge outlets. I bit of work but my breaker box is below the fridge so not a lot of work to do

4) Fridge securing - my box is 21" wide which is 3/8" LESS than the 195's width WITHOUT the front frame. My goal is to remove the frame and use 2" FLAT kickplate on the left and right secured with countersunk screws to the fridge's side just like the stock frame. My hope is this prevents any cabinet modes and I keep the curtain.

Am taking picture as I go to post at the end so anyone doing the same will have the benefits of the steps taken and all the beg borrowing stealing to make it as best as I can.

let me know your thoughts!

Thanks

Bob

[richard5933]

Originally Posted by Revedream

3) 120v power - thinking of adding and additional plug AND installing a double 15 breaker so I can run dedicated 14/2 wire to both...is that overkill. I will need to add a double 15 AND a new GFCI which will go to the fridge outlets. I bit of work but my breaker box is below the fridge so not a lot of work to do

4) Fridge securing - my box is 21" wide which is 3/8" LESS than the 195's width WITHOUT the front frame. My goal is to remove the frame and use 2" FLAT kickplate on the left and right secured with countersunk screws to the fridge's side just like the stock frame. My hope is this prevents any cabinet modes and I keep the curtain.

3) When I installed the 12vdc compressor fridge in my motorhome I ended up not using the 120v plug at all and just used it on 12vdc all the time. There is no advantage to using the 120v option at all unless your trailer's converter is underpowered. The 12vdc fridges run natively off 12vdc, so when you're using the 120v option there is a small converter running inside the fridge to make the 12vdc power.

The fridges don't draw that much 12vdc amperage and my 45-amp converter was easily able to handle the load of the fridge and still get my 780Ah FLA battery bank recharged without a problem.

4) The Vitrifrigo I installed was also slightly smaller than the propane fridge it replaced. I had a local fabrication shop make a new mounting flange for it which I painted to match the cabinets. It screwed to the rear of the new fridge's mounting flange and then to the opening where the old fridge was mounted. Made everything look like I belonged there and cost me less than $100.

Here's a photo of what it looked like. You can see the added flange painted brown around the fridge.

[Revedream]

Thanks Richard

Biggest focus was on you Ah....at 400ah, sounds like I'm in trouble so will move that to the front of the line (thinking 3 EPOCH 300ah to replace my 4 Lifeblue 100ah). will make sure my converter will keep up.

On the 120v, never thought of that but it makes sense...even when on shore power, suppose the only downside is battery cycling

Also, I see you have a vent below and above your unit...assume your install is completely sealed from the outside, correct? (eg no venting of the heat to the outside?)

[Revedream]

ok, with focus on venting.....

it appears all of the new airstreams have 2 stage (ac/dc) only fridges and NO external venting. I've searched the web for pics. It's clear the side vent flap is gone but couldn't determine if the roof vent was gone either. Viewed an AM solar vid and its clear the 2023 27 globetrotter they were outfitting did not have either the side or the roof vent.

So, on the side vent, I will simply extend the "wood wall" board so that external opening is sealed and I can use it for small storage. With respect to the roof vent, I will need to either

1) seal it from below and add a drain tube to prevent trapping water (complicated)
2) remove it from above and add a stainless patch (not the best look)
3) leave it as is and use it to vent from internal to external (easiest for sure but doesnt seal external from internal like the new models)

any thoughts on those or other options?

[richard5933]

Originally Posted by Revedream

Thanks Richard

Biggest focus was on you Ah....at 400ah, sounds like I'm in trouble so will move that to the front of the line (thinking 3 EPOCH 300ah to replace my 4 Lifeblue 100ah). will make sure my converter will keep up.

On the 120v, never thought of that but it makes sense...even when on shore power, suppose the only downside is battery cycling

Also, I see you have a vent below and above your unit...assume your install is completely sealed from the outside, correct? (eg no venting of the heat to the outside?)

The install in the photo is atypical. The unit above the fridge is actually the air intake for the air conditioning unit. The whole cabinet behind the fridge is part of the intake so when the a/c was running the fridge was easily kept cool.

But, when the a/c was not running there was a problem with ventilation. That's why you see the bottom vent that I added. I also added a second pancake fan on the condenser under the fridge to help it shed heat. There was one from the factory, but the control box had enough current to the fan terminal to run two of them easily. In the heat of summer I had the second fan wired to a separate toggle switch so it could be left on to run continuously instead of just when the compressor cycled. I thought it would help remove residual heat but no real way to know for sure.

If we didn't have the a/c intake over the fridge I probably would have opted to vent the cabinet to the outside. If yours already is vented I'm not sure what the advantage is to closing that up. There is a potential upside to keeping it though, as the airflow through the cabinet via natural convection will help the fridge shed heat.

We had 780 Ah of FLA battery capacity, which gave us about 390 Ah of usable capacity. We could easily go 3-4 days running the fridge, the roof fans, lights, and water pump before we hit 50% SOC on our battery bank. If we deployed our portable solar panels we could go indefinitely. If you have 400 Ah of lithium you should be good to go unless you regularly dry camp for more than a 3-day weekend.

RE battery cycling...It's my understanding that if your batteries are at 100% they won't actually be affected at all by the converter supplying power to the fridge (or anything else that's running off 12vdc). Batteries at 100% SOC can't take on any more charge, so the converter just provides enough current to supply devices being used - at least that's the way it appeared to my via the Cerbo I had installed on that rig. Your mileage may vary depending on the particulars of your configuration.

[Revedream]

12v DC best practice for Isotherm 195?

The Dometic 8555 being replaced had 10ga (+/-) and 14ga (+/-). I know to orphan the 14ga circuit but not sure on the 10ga. The isotherm 195 appears to be two distinct units that operate independently (each have their own 120vAC and 12vDC hookups.)
120vAC – I installed a new 15amp 120v circuit for dedicated supply and shutoff from the main power box to power both. No issues there as the AC circuit in the AS is straight forward (note a single 15amp AC circuit using 14ga romex to cover both compressors)

12vDC – It’s clear the Dometic 10ga comes directly from the DC Junction box (eg. It’s not affected by the on/off switch that kills the DC coming from the AC/DC enclosure (for good reason as you don’t want to shutoff your fridge every time you hit that switch). So, question is, can I tie both of the Iso’s Fridge and Freezer DC connections to this 10ga OR do I need to run another dedicated 10ga (+/-) run from the DC junction box?

The Iso specs 10amp draw with both compressors running. It also limits the 10ga wire feed to 19ft (so good there). Separately a 20ft 10ga wire should allow for 15amps….so my conclusion is that this original 10ga +/- should meet the spec to drive both in DC but would like to hear opinions on that path.
Thanks

[hyrax]

Howdy all - We are on our second 12V refer in a two year old pottery barn. The 'old' one just plain quit getting cold top and bottom...red control panel light showed red indicating the unit was powered, but the compressor would not run. The mobile RV fixer said the only thing was to replace the refrigerator. Fortunately, the extended warranty paid the majority but gee, I sure hated seeing a basically new $1500 refer disappearing off down the road in the back of the tech's truck!

[richard5933]

Originally Posted by hyrax

Howdy all - We are on our second 12V refer in a two year old pottery barn. The 'old' one just plain quit getting cold top and bottom...red control panel light showed red indicating the unit was powered, but the compressor would not run. The mobile RV fixer said the only thing was to replace the refrigerator. Fortunately, the extended warranty paid the majority but gee, I sure hated seeing a basically new $1500 refer disappearing off down the road in the back of the tech's truck!

Likely it could have been fixed by swapping out the control box - they're only a couple hundred.

When our Vitrifrigo went out that was the cause. The root cause was a failure of the circuits that switch from 12vdc to 120vac. When I installed the new control box (sent to us under warranty from Vitrifrigo) I only connected to the 12vdc power supply and never had a problem again.

[F Broostin]

So, my 2018 GT refrigerator did not cool well. I made a few easy changes that seems to have fixed it. First, I noticed that the two fans on backside that cool coils were not running. They are controlled by a thermo switch on the coolant line. I tested it and it never made contact so fans never ran. I installed a small toggle switch that I manually turn on when I want to use the refrigerator. Fans then run 24/7 but load is small so don’t care.
Second, there is another thermo switch on the gas burner housing. Safety cutoff I think. The connections to that were intermittent so I put a little no-ox-ide on the terminals to fix that.
This is about a $10 set of solutions that worked for me. I had frozen food stay frozen in freezer for 8 days of 90F weather on recent trip.

[10Smiles]

From all the discussions above, I don't see anything regarding what people have done about the outside vent door and the roof chimney. We are probably going to be replacing our Dometic absorption fridge with a compressor fridge. Is it possible to turn the side vent into a solid door and have a small storage compartment? I suspect the upper aluminum chimney can be removed and the hole covered with a piece of aluminum.

[richard5933]

Originally Posted by 10Smiles

From all the discussions above, I don't see anything regarding what people have done about the outside vent door and the roof chimney. We are probably going to be replacing our Dometic absorption fridge with a compressor fridge. Is it possible to turn the side vent into a solid door and have a small storage compartment? I suspect the upper aluminum chimney can be removed and the hole covered with a piece of aluminum.

That upper opening is a great weatherproof way to run wiring to/from solar panels and other roof mounted devices. Rather than removing it and blocking it off permanently, I'd suggest doing something to stop the airflow from the inside without removing it.

You will still benefit from having access to the back of the compressor fridge, more or less depending on the model and setup. The one I had in my previous rig had the compressor and associated stuff in the rear and it would have been nice to have access to it from the outside.

[10Smiles]

Originally Posted by richard5933

That upper opening is a great weatherproof way to run wiring to/from solar panels and other roof mounted devices. Rather than removing it and blocking it off permanently, I'd suggest doing something to stop the airflow from the inside without removing it.

You will still benefit from having access to the back of the compressor fridge, more or less depending on the model and setup. The one I had in my previous rig had the compressor and associated stuff in the rear and it would have been nice to have access to it from the outside.

Yeah, I've thought about that, but I think I would rather cover the hole with an aluminum skin and mount some kind of a weather tight junction box on the patch for running wires into the trailer from the roof. We'll see, your idea is good, thank you.

[richard5933]

Originally Posted by 10Smiles

Yeah, I've thought about that, but I think I would rather cover the hole with an aluminum skin and mount some kind of a weather tight junction box on the patch for running wires into the trailer from the roof. We'll see, your idea is good, thank you.

It is also a good idea to consider using the existing ventilation chimney for providing a good supply of air to the compressor fridge. Even though there is no flame that needs to be vented, the basic operation of the fridge still means taking heat from inside the fridge and throwing it to the outside via the coils on the back of the fridge. Compressor fridges work more efficiently when they have proper ventilation and this natural convection chimney is just that.

If you are planning to camp in cold weather then you might consider installing removable air blocks top and bottom for the winter months, but otherwise there would be no need and you could just let it vent.