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Skyward View Drop Down
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Joined: 10 Mar 2014
Location: Pahrump NV
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Posts: 16 		Direct Link To This Post Topic: Computer board refrigerator
    Posted: 11 Jun 2019 at 10:01am
Our Dometic refrigerator is only 4 years old, like our Rpod. It works ok on hookup, but not at all on gas.  We were told by our local dealer that the computer board has to be replaced, or a whole new fridge. I thought Dometic was the highest quality around! A call to their offices-no recourse for us, it’s out of warranty. Has anyone else encountered this problem? Thanks!
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Posts: 6128 		Direct Link To This Post Posted: 11 Jun 2019 at 1:11pm
Did they tell you that, or did they troubleshoot and decide that?

Dometic products are fine, but, just like anything else, they can break. Rolls Royce has a warranty department.
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Posts: 31 		Direct Link To This Post Posted: 11 Jun 2019 at 1:23pm
I have the same problem with my 2015 179. It doesn't work on gas or 12v. My RV repair guy is going to replace it this Thursday. The part is $376 and the labor is $125.  What can you do?
Rick and Melanie
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Posts: 966 		Direct Link To This Post Posted: 11 Jun 2019 at 1:59pm
Not that I want my fridge to stop working, but a failure after 4 years or a $500 repair would be all the excuse I would need to replace it with a 12v compressor fridge.
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Posts: 2702 		Direct Link To This Post Posted: 11 Jun 2019 at 2:55pm
What's the ballpark energy consumption on a 12V compressor fridge? Amps or watts.
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Posts: 5290 		Direct Link To This Post Posted: 11 Jun 2019 at 6:43pm
The danfoss/secop compressor uses around about 5a when running. That’s not counting any condenser fans. So ithe total load is going to depend on the compressor duty cycle. My guess is that two compressors would be required to have adequate capacity for the existing poorly insulated fridge box.
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Posts: 966 		Direct Link To This Post Posted: 11 Jun 2019 at 6:55pm
Different models have different power requirements, but usually low enough to work well on 100-200 watts of solar and 100 ah of battery in most cases for the 1 to 4 cu ft units.
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Posts: 5290 		Direct Link To This Post Posted: 11 Jun 2019 at 7:29pm
A 1 ft3 unit and a 4 ft3 unit aren’t going to have the same energy consumption. The existing rpod fridge is about 4 ft3. And its front not top opening and the insulation is thin. If you wanted to replace the cooling system for that you’d need to plan on at least 60 ah per day, and that’s just to maintain temp not to cool things or to handle a lot of door openings. You’d probably need significantly more. So, realistically probably 350-400 watts solar.

That’s still only about $200-300 at today’s prices so not a big deal in the overall budget. The hard part is going to be to do the retrofit or build a new fridge box that would fit in the opening and look good. Might be easier and much cheaper to install a good quality energy efficient dorm fridge and an inverter to run it. It would use maybe 10% more energy, not that big a deal, and you could run it on 120vac when in hookups.
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podwerkz View Drop Down
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Posts: 966 		Direct Link To This Post Posted: 11 Jun 2019 at 9:57pm
Lots of variables. 

Flat, roof-mounted, non-tilting panels produce less, on average, so you need more of them...300-400 watts would be about right to run a 4 cu ft front-opening fridge (like a Nova-Cool or a Truck-Fridge) and several other 12v devices.

But a 100 watt portable panel (moved to catch sunlight all day) will power a 1 cu ft top loading 12v compressor fridge with power to spare IF it has no other significant loads. 

You only need to calculate amp-hour draw at night (when running on batteries) since during the day the fridge is running more or less directly from the panels...unless of course the panel is under-producing due to cloudy/rainy/shaded conditions.

BTW, a 2 cu ft chest-style compressor fridge has about as much usable interior storage space as a 4 cu ft front-loading absorption fridge. 

And, most 12v compressor fridges can run on 120v directly, AND sip energy when on 12v so the converter in the trailer, or your vehicle auxiliary 12v line will have no problem powering the fridge when you aren't using solar. 

Of course, they dont run on propane at all, and average service life (running 24/7) seems to be about 2-5 years, so they are not suitable for everyone.
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Posts: 5290 		Direct Link To This Post Posted: 12 Jun 2019 at 11:15am
Originally posted by podwerkz

Lots of variables. 


Yep, lots of variables, This is my field, been designing PV systems for 40 years, including lots of refrigeration systems. Kinda like the solar equivalent of having a calibrated hand for checking brake temps LOL

First, the difference in output between a tracked and a horizontal fixed orientation solar system is only about 15 percent in summer conditions. Manually moving a module is a form of tracking, just not as good as an automatic system. So, feel free to move your modules around during the day, its something to do while camping I guess. Myself, I'd rather go hiking. 

Second, I agree that 100 watts would maintain a well insulated  1 ft3 fridge on a sunny day. If you put warm stuff in then that's a different story. But what we're talking about here is a replacement for the "big" front loading fridges in our rPods. Most folks aren't going to want a  little 1 ft3 fridge underfoot as an alternative. 

Third, if you want to run autonomously on solar you can't just add load without adding battery capacity.  There are always variables in PV performance based on weather. Batteries average that out. You should have at least 2-3 days autonomy for your total system load to keep from having to run backup power systems frequently. So if you have say a 60 amp hour daily fridge load you should add 120-180 AH of usable battery capacity to your system, or plan on frequent recharging from a generator.

The performance metric for refrigeration compressors is coefficient of performance (COP). For the Danfoss/Secop compressor COP is around 2 for typical evap temps. For residential refrigerators the COP is also.....around 2. Thermodynamics doesn't care what voltage the compressor runs at.  So, there is no magic bullet because the Danfoss unit runs on 12V. It sips energy because its a small compressor. 

If you want to build or retrofit your own Danfoss based fridge (cruising sailboat owners do it all the time) then there are kits for that and setup procedures for refrigerant charge and electrical settings to go through. Those make for nice systems but they are heavily insulated (reducing fridge space), aren't cheap,  and are best setup by someone with expertise.

That's why I'm suggesting that replacing the existing fridge with the highest efficiency front loading dorm size fridge available might be the best way to go. You can get one that will fit in the existing space and it should be about as efficient as a Danfoss/Secop 12V one would be using the same fridge box. 

The difference in overall efficiency would be the 10% or so inverter losses you'd need to account for when running it from 12Vdc. For the cost you'll pay for a new dometic propane fridge you ought to be able to buy a good dorm fridge, a 350 watt PV module which can be roof mounted,  a charge controller, and an inverter. The additional battery capacity is more problematic, getting above 2 GC2 lead acid batteries poses a placement and weight problem and swapping for Li batteries will blow the budget. Depends on what else you're running on 12V while boondocking and how frequently you're willing to run a backup genny.  
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