Convert new Dometic fridge from 220V to 110V

[HappyHapgood]

It’s a long story, but I recently purchased a new Dometic RMD 10.5XT refrigerator from England and had it shipped to the US. I then installed it in my 2015 LandYacht (replacing a dead 8-series 3-way fridge).

The new fridge works great on propane. It doesn’t work well on 12V, but it’s better than nothing.

I have not yet done anything to make it usable on AC power. Because I purchased it in England (there was no US version available 6 months ago) it is 220volts. I think I have a few options to get it to work on 110 volts here:

1. Use a step-up transformer. Simple, but most are not rated for use where it might get wet or hot (behind fridge where it normally plugs in). And it’s heavy (about 8 lbs).

2. Try to “convert” my unit to 110 volts. Of course, about 3 months after I paid a crazy amount of money buying one and shipping it to the Us, Dometic now lists the RMD10.5 on their US website. Do I need a new control box? Or can I just put a 110 3-prong plug on the existing cable and plug it in? Would I need a different heating element?

The electrical schematics for the British unit and the US unit appear to be identical, except the British plug ends in a WAGO fitting (for which Dometic sells an adapter to work with 3 prong outlets in England.

https://www.dometic.com/en-gb/uk/pro...adapt-_-206937

I measure the ohms on the existing AC heating element (211 ohms) but I did that with it still connected to the controller (couldn’t figure out how to disconnect the wiring block or wires from the control board and didn’t want to break it...

I can’t find a parts list to see if the British and US fridges share the same control board. Or heating element.

Anyone have any ideas or suggestions? Access to parts manuals? Or even how to unplug that connector block in the photo below??

Thanks,

Matt

[waninae39]

get a 1:2 step up transformer and keep it close to the fuse panel.
that is a dry area. the fridge motors are tied to local AC voltage. not easy to replace

[HappyHapgood]

I've considered that, but hate the idea of a 5-pound hunk of steel that adds 10-15% inefficiency. And there is no motor... it's simply a control board and heating element. And I'm not even convinced the control board actually uses the AC power...

Matt

Originally Posted by waninae39

get a 1:2 step up transformer and keep it close to the fuse panel.
that is a dry area. the fridge motors are tied to local AC voltage. not easy to replace

[nvestysly]

Originally Posted by HappyHapgood

I've considered that, but hate the idea of a 5-pound hunk of steel that adds 10-15% inefficiency. And there is no motor... it's simply a control board and heating element. And I'm not even convinced the control board actually uses the AC power...

Matt

I'm certainly not an expert but I think the control board operates on 12V. It seems like the only thing you need to replace is the heating element. Have you contacted Dometic?

Many of the items on RV refrigerators are the same (or very similar) from model to model. If Dometic is not helpful you might try contacting one of the Amish RV refrigerator manufacturers in northern Indiana. Maybe they have a part that will work.

[Rossue]

The RMD 10.5XT is now available in U.S. with 120V AC operation. One dealer that sells it is Dyer's RV Parts in Phoenix:
https://www.dyersonline.com

[HappyHapgood]

Thanks for the link Rossu. I wonder if they are able to access parts, and possibly tell me which parts I’d need to replace to switch mine to 120V operation.

[richard5933]

Seems like what you really need is a wiring schematic for your fridge. That will likely tell you which components need to be converted.

[Merlintiaga]

I would not worry too much about the power loss of the transformer. You’ll be on shore power so it won’t impact your batteries. Also, the 220V unit might have a motor that is physically smaller than the 110V so you’ll get the 5 pounds back in motor (compressor) size. the power output would be the same as 110v in a smaller package.

[HappyHapgood]

On the contrary I am almost never on shore power. 99% dispersed camping and rely on solar. Yes, propane is also an option, but on sunny days it’s nice to use free electricity. And the more efficient the appliance, the better!

My fridge doesn’t have a compressor.

Originally Posted by Merlintiaga

I would not worry too much about the power loss of the transformer. You’ll be on shore power so it won’t impact your batteries. Also, the 220V unit might have a motor that is physically smaller than the 110V so you’ll get the 5 pounds back in motor (compressor) size. the power output would be the same as 110v in a smaller package.

[HappyHapgood]

Good point.
Not sure if the manual has one… I think it doesn’t. But if it does and I can compare to the US version then I’ll at least know if the wiring is the same, though I won’t likely know if the parts are the same.

Originally Posted by richard5933

Seems like what you really need is a wiring schematic for your fridge. That will likely tell you which components need to be converted.

[Al and Missy]

Originally Posted by HappyHapgood

Good point.
Not sure if the manual has one… I think it doesn’t. But if it does and I can compare to the US version then I’ll at least know if the wiring is the same, though I won’t likely know if the parts are the same.

Depending on the equipment in the fridge, you might need more than a step up transformer. The standard line frequency in the US is 60 Hz, in the UK it is 50 Hz. That may make a difference, or it may not. Check the specs on the UK unit to see what the required frequency range is.


Edit: Installation Manual gives a schematic.
https://www.dometic.com/en-us/outdoo...-10.5xt-205131


Looks like the AC goes to the controller and best guess is everything except AC heating element is DC from there on. Wow! 170 watts on DC, 250 on AC. About 3 times the Vitrifrigo on DC.


Different heating elements for AC and DC. Substantially more heat on AC. That is probably why it doesn't cool very well on Dc.

[richard5933]

Originally Posted by Al and Missy

Depending on the equipment in the fridge, you might need more than a step up transformer. The standard line frequency in the US is 60 Hz, in the UK it is 50 Hz. That may make a difference, or it may not. Check the specs on the UK unit to see what the required frequency range is.


Edit: Installation Manual gives a schematic.
https://www.dometic.com/en-us/outdoo...-10.5xt-205131


Looks like the AC goes to the controller and best guess is everything except AC heating element is DC from there on. Wow! 170 watts on DC, 250 on AC. About 3 times the Vitrifrigo on DC.


Different heating elements for AC and DC. Substantially more heat on AC. That is probably why it doesn't cool very well on Dc.

Is this a 3-way fridge? As in one that can make cold with nothing running except the 12v power supply? If so, then that would explain the high draw possible on 12v.

No 3-way propane fridge is efficient on 12v only, as powering the heating element on 12v takes a lot of effort.

[Farmer Dan]

I am installing a Dometic RMD 10.5XT in my 2019 27' Globetrotter. It's replacing an RMD 8555 that is unreliable. The wiring is different on the RMD 10.5. It has a connector with 8 spades in a plastic connector. The old fridge had only 4 wires going into the block on the back of fridge. These 4 wires came from the RV. How do I make the new one work ??

Dan

[ITSNO60]

Originally Posted by Farmer Dan

I am installing a Dometic RMD 10.5XT in my 2019 27' Globetrotter. It's replacing an RMD 8555 that is unreliable. The wiring is different on the RMD 10.5. It has a connector with 8 spades in a plastic connector. The old fridge had only 4 wires going into the block on the back of fridge. These 4 wires came from the RV. How do I make the new one work ??

Dan

On the 8555 two of the 12 volt wires are fed from a 3 amp or a 5 amp fuse and they power the board. You can tell which pair this is because they go to the terminal block with the tiny wires on the other side and one is colored violet. There is also a small jumper going from the ground wire to the cabinet
The other 12 volt pair is fed by a 20 amp fuse and goes to the 12 volt heating element and has brown wires coming off the back side of the terminal block.
Now you just need to look at the documentation on the new fridge to see which terminals do what. The extra terminals could be for the a 12 volt relay which gets power only when 12 volts is being detected from the vehicle so it can engage the 12 volt elements, I don't know how this is accomplished on your new fridge but on the 8555 the relay is screwed onto the back of the fridge and the wires go directly to it.
Wish you were closer, I'd take that 8555 off your hands. I've got mine running perfect but parts are real hard to come by.
Here's a copy of the RM8 series service manual with wiring diagrams:

[Bill M.]

Is it an absorption fridge? Probably does not have a compressor or motor. So a wiring diagram might tell all. If no motor but just heat functions the frequency might not matter,. If it has a motor then that will add additional problems, Hopefully you have a friend that is good at this sort of thing. I think, but do not know, that our absorption fridges work better on 110 than propane. For a pure heat function and free electricity the step up transformer might be a decent solution. I do not know how expensive they are. I expect pricy to carry that much load. Maybe somebody that works on boats at a good marina would know how to work around this.

[mrdes8]

I hope this will be of help, recently (6 months) bought a dometic CRX110 on ebay for a great price. I was pretty sure from the description that it would be a 12v/220v Australian version but I didn't care because I've had one for 4 years that runs all the time on 12v. Came with a 220 cord. Then out of the blue the seller sent me 110v cord, just a standard plugin power cord like a computer, said he had talked to Dometic who said basically the unit senses the voltage and runs accordingly. Plugged it in and it worked great. I have not installed it yet so I have no long term results. Think maybe of how a Victron solar controller does either 12 or 24v???
Good luck, Mark D

[Farmer Dan]

The RMD 10.5XT is an absorption fridge. And it is 110V. I'll check the wiring diagrams that Brian sent. Then I will contact Dometic for advice, as well. I've heard good things about tech support from them. Thanks for your responses.

Dan