DC Refrigerator Conversion

[badandy]

I'm 95% sure all those Samsung inverter fridges run on 5v and 15v DC inside. You could hack up the power supply part of the main board in there and connect your own 5 and 15vdc and be happy. But all that screwing around gains you only a few watt-hours over an inverter running it. You also have to consider that you need a good 15v boost converter. The DC supply built into the fridge is probably 95% efficient.

The CPAP wall wart is wasting lots of power. It takes more power to run that CPAP then 2+ full sized Samsung fridges.

[Kiwi3]

Originally Posted by rshrimp

My thing is to not do excess conversions. All conversions waste energy.
Why take 12v, run Inverter to make 110v just to convert it back to some DC voltage?
That's whay I am asking about the Samsung Fridge. WHat voltage does it really run on? Why not just supply that?

You would have to ask Samsung about that. But I would imagine that doing so would void your warranty.

But the ability to wire the fridge directly into DC is why I'm interested in the JC conversion. I don't really need a bigger refrigerator since I eat Keto. Amazing how much room all those carbs take up in the fridge and cupboards.

[rshrimp]

The warranty is voided the moment you stick it through the door of an RV. I do like the idea of the conversion. Especially for the smaller (less than 4 door) Dometic's and Norcolds.
I would do that 100 times over a new Absorption cooling unit.

[K Ridley]

My absorption fridge went out about 4 years ago. After researching the various options I decided that a Nova Cool with the Danfoss 12 volt compressor fit my needs best. I think it's one of the best upgrades I've done.

[GregOC]

I see you have a 94ptwb. I got one in 2003 and sold it in 2013.My floorplan put the refer on a 45deg angle. nice set up but...... I fought with the refer for the first 7 years. until I pulled the refer to update the ammonia guts with a Amish built system just to give that a try. When I went to reinstall I found the OEM install instructions which dictated no more than 1 inch of clearance between the backwall and the coil fins. ***. NO More Than. I decided to build a false wall with sheet metal to mimic a backwall and life was good. unbelievable cold diet pepsi. Not sure if the fix was the new Amish cooling system or the proper back wall. the problem with extra space in the back is you confuse convection and heated air does not drift up and out. Ended up doing the samsung thing a year later because we leave the refer on electric when parked and a test revealed the cost to make cold from a electric heater is more than a grand a year.

[rshrimp]

"confuse the convection"
While I agree, and it does describe the condition well, it is only the second time in my life that I have heard that term (apparently is was memorable)

A roofer once told me I had too many roof vents and it would "Confuse the Air" in the attic!

[Randy Dupree]

Originally Posted by rshrimp

"confuse the convection"
While I agree, and it does describe the condition well, it is only the second time in my life that I have heard that term (apparently is was memorable)

A roofer once told me I had too many roof vents and it would "Confuse the Air" in the attic!

Air flow is a funny thing,it does not always do what you think it should.
Mike Magrau has a great understanding of air flow in ducts etc.
Interesting stuff.

[NoGas]

For a Samsung RF18, some have added a dedicated low watt pure sine (PS) inverter as a backup to their big “inefficient” modified sine wave model. My updated Magnum MS2812 pure sine inverter is advertised as 90% efficient and 30 watts (2.5 amps DC) consumption under no load ie refer compressor off. Worst case mid-winter that’s 45 amps total overhead overnight (18 hrs) for running the big inverter, and solar can easily replace that in just a few minutes the next day. A small inverter would presumably create some standby load as well, so the difference is probably less. Like Andy, I have lots of Ah available off-grid so using the big Magnum as opposed to a smaller dedicated inverter OR hacking into the Samsung power supply to eliminate the inverter all-together is not worth the effort.

When I installed the Sammy I did not need to modify the cabinet, although I did raise the platform it sits on. The refer box fits completely flush in the cabinet, as-is and “convection” is not a factor .

(Pics below show install w/o cabinet doors top & bottom):

[Kiwi3]

I contacted them to check on prices. This is for a Dometic RM70030 two door.

Converts your existing fridge to a residential fridge, (which eliminates your Lp gas) this cooling unit is built with a compressor system and not only do you get to keep your same fridge and controls you are used to but there is no need to remove the windshield or window to get the old fridge out and the new in nor the hassle of cutting or redoing the cabinets to make a new fridge fit. There is also no need to have your coach level anymore for the fridge, since this unit will have a compressor. * It pulls .08 A on the AC Compressor and will run off a 600W inverter (does not require pure sign wave) and is pulling only a fraction of Amps that a regular residential fridge would pull. Or we can also do a DC 12V Compressor off the 12V wires behind fridge with a 5.5A draw. This cooling unit is designed to withstand hot humid temps and will keep your ice-cream hard. This unit comes with a 3 year warranty with the option to buy an additional 3 years for $125, it is very user friendly to work on in the field should it need it down the road. We can ship to you truck freight for $175 business or $225 residential drop, have it factory installed for $400.

AC Compressor $895.00 / DC Compressor $1095.00

This unit comes with: foam sealant, thermal mastic, foil tape, self-taping screws, LP gas plug, glass fuse, interior fin fan, basically everything needed to do the install


* There is always the question of how much power it really takes or how long the battery will last on a charge........ You need to multiply your amp hr on your battery by how many batteries then multiply by 60% for amps available, then divide by either 8 for the AC compressor or 5.5 for the DC Compressor. But to keep it simple you can run this unit 24hrs on 1 battery full time without a charge, but since it will only run approx. 40% of the time that can be extended

[badandy]

A residential fridge, even the small cheap ones like Haier, use the same amount of current once cooled down. They cool down farther and faster, however. They are equally as efficient (arguably more) as this conversion. Don't let their doublespeak fool you about that.