Repair or replace Dometic NDR 1292 with residential

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garyb1st

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So after thinking about this for two days, there are many things to consider.  It's possible that replacing the cooling unit with an Amish unit might be the most cost effective option.  The Amish unit including shipping is available on line for about $1250. 

A small no frills residential refrigerator can be purchased for probably $5-600.  But a residential will likely require two more 6v batteries.  It might also require an inverter upgrade.  Current inverter is a 1000 amp pure sine wave AIMS.  If a larger inverter is required and possibly some solar, the cost goes way up.  But we like to boon dock and I've been thinking of more batteries, an inverter charger and solar anyway. 

Another possible option is a 12 volt refrigerator.  Costco sells this one for $999.99.  https://www.costco.com/Unique-9.0-CuFt-Solar-Powered-DC-Refrigerator---UGP-260L-W-.product.100362122.html.  This looks like an option that's too good to be true.  Anyone have any experience with a solar powered fridge?

In looking for the most energy efficient residential, I've found a 14.5 cu ft top freezer with no ice maker uses 336 kWh a year.  By comparison an 18 cu ft 3 door bottom freezer Samsung residential uses 594kWh.  Not sure how meaningful the kWh per year measure is in an RV but I have to believe the smaller unit uses considerably less battery amp hours. 

Limitations that need to be factored in.  The big one is weight.  Space is another.  The smaller residential is about 50 lbs lighter than the Samsung which helps.  But then we may need to add two batteries.  We have two under the entry steps.  There is not enough room for two more.  So where do we put two more?  Lithium solves the size and weight issues but at a price. 
 
If you boondock, go with the Amish unit or you're going to have to spend some serious coin on batteries, solar, monitors etc
 
Scott, without solar and more batteries, it's either the 5500 Onan or the 2000i Honda that's burning through gas.  The Onan is used whenever Maria uses the microwave, rice cooker or toaster.  I use it whenever I make coffee.  For the 8 days we were at KOFA, we burned about 17 gallons of gas with the Onan and maybe another 2 or 3 with the Honda.  At California prices, that's $50-60 for gas.  I've been thinking of a small portable solar array to charge the batteries, but finding a place to store it when traveling, the possibility of theft when we leave for a few hours and just setting them up and taking them down each time we use them seems like a lot of hassle.  That said, I haven't determined the cost of solar yet.  Sticker shock might get me thinking I can live with the hassle.  ;)
 
I have been doing some reading about the Nova Kool 12v units. They use the same Dan Foss compressor as the Costco unit you linked to. According to the spec sheet on their website they draw about 5.2 amps. So for 24 hours of run time that would be about 125 amps. If it ran for 80% of the time over a 24 hour period that would be about 100 amps. I believe they are used a lot in marine applications. One plus is they are sized to be drop in replacement for Norcold/Dometic units.

Backwoods Solar lists the RFU9000 at $1876 on the website. They also state that adding 2? of rigid foam insulation on the rear wall cuts the power consumption in half.

I have four 220 amp hour batteries and currently have very low electric usage. So I think I could run this on my 4 batteries. I don?t think I would try it with 2 batteries.

I would be interested in hearing if anyone has firsthand experience with the Nova Kool.
 
Gary, it sounds like you use a fair amount of 120V aside what the fridge would use, so I gather part of the solar equation for you is simply trying to get away from the genset to a degree. Because it doesn't sound like you're ready to put a full-fledged 7-900 ish watt system on the roof (plus 4 batteries, a 2000+ watt inverter and a battery monitor) I still think a gas fridge is the answer. At least you don't have the fridge sucking 100AH/day, and you can address your other power usage with a much smaller system. Plus you can get the fridge working now, and address the rest without the pressure of needing an immediate solution. That said, even with a big solar system, you're going to need some genset time for charging based on your usage (but much less).
 
Debra, thanks for the response.  I'll take a look at the Nova Kool.  But at $1876, it's almost twice as much as the Unique being sold by Costco.  I'd sure like to know why they're so much more. 

Are your batteries 6 volt?  If so, you have a total of 440 amp hours at 12 volts.  According to the Unique website, the one advertised by Costco runs on less than 100 amp hours a day.  That would discharge our two 6 volt batteries quite a bit and we wouldn't have much left for computing or watching TV.  So it might work on two but four is what I'd want.  The site also says, 200 to 250 watts of permanent solar is the minimum to keep it powered. 

Unless I get some positive feedback on 12 volt fridges, I'll continue looking at the residential. 

 
Gary, for what it's worth - back when dinosaurs roamed the earth - our first motorhome refrigerators had three energy sources: propane, 110 and 12 volts.  We don't recall the 12 volt part as being very impressive.  We used it when there was no other alternative.  Does the 12 volt refrigerator have a compressor?  If it does, Jerry thinks it would take more generator power (and/or solar) to generate enough heat to run the compressor.  You'd have to find out more about that.  There's a reason the manufacturers moved away from 12 volt and I suspect it's because they weren't that great and people stopped wanting them.  Propane is probably a lot more efficient and cools better than 12 volt.

ArdraF
 
Ardra, it has a DC Danfoss/Secop compressor.  At least according to their website, the best one made.  How that compares to compressors back in the day I can't say. 
 
BTW, I meant to say sorry that you and Maria are having the issue with the fridge. It is a bummer when a big expense like that comes up.

My batteries are 6v agm. I have 520 watts of solar and a 2000w Samlex pure sine wave inverter. That?s a lot for a trailer my size. But I don?t have a generator so I wanted plenty of cushion since I boondock/dry camp about 85% of the time. On a sunny day I can have the tv on all day, use my coffee grinder and Mr Coffee in the morning, my laptop on all day, charging devices, run the microwave a few minutes and my batteries will stay at 100% SOC. I hardly ever go below 90% even when it?s cloudy. If you wanted to go with the 12v, you could probably get by with 400 watts of solar and 4 batteries. Especially since you do have the generator as backup.

If you want to boondock, the residential is going to require the generator use. That?s the big drawback in my mind. I like that the Costco unit has the same compressor as the Nova Kool. I think the Nova Kool has had more use in marine applications than in RVs but it has been around awhile. If you have the room for the free standing unit I think that would be worth serious consideration. I don?t really have room for that in my little trailer. The Nova Kool I could drop into the same space as the Norcold I have now. If I ever have trouble with mine I?m definitely going to consider the Nova Kool.

I?m hoping someone will weigh in on the 12v. It seems like a good option for those who want to get away from the absorption refer but don?t want the high electrical consumption of a residential unit.
 
Gary,

Where do you want to be with the RV 3 or 5 years from now?  If a residential fridge is part of that view, then now is the time to do it.  Use the genny to power it until batteries and solar catch up with power demands.  The 12 V vs 120 V unit debate will continue.

If a residential fridge is NOT part of that view, just fix what you have with the Amish unit.

Ardra, back in the day, that 12V / 120V / propane fridge was an absorption unit, so it used LOTS of 12 V power to heat the system.  The current 12V fridge uses a high efficiency compressor, so it is MUCH more efficient than the old 3 way power units.
 
Thanks, Grashley.  It's nice to have an update on that.

ArdraF
 
I think you are over-estimating the daily power consumption of a residential, but much depends on how you use the fridge (frequency door opens, how long, etc).  336 KWH per year is about 0.9 KWH per day.  From a 12 battery, that about 80 AH.

Modern Energy Star fridges have high efficiency 120v compressors.  The only advantage of a 12v compressor is simply avoiding inverter overhead, the power lost in the conversion from 12vdc to 120avac. We usually figure about 10% loss.


The 1000W AIMS runs a fridge handily. I used one with a 14.5 cu ft GE residential and it hardly noticed the load (180W-240W). But if you are also using it to run a microwave or coffeemaker, then it may come up short on total capacity.

I'm not trying to talk you into residential over the Amish replacement, but wanted you to have accurate information on the table.
 
If our AIMS 1000 will run a 15 cu ft residential with two 6 volt batteries, then that's probably what we're going to do.  We will use the generator as necessary to top off the batteries and run the more power hungry appliances.  Going forward, if we decide to keep the Pace Arrow, then we'll think about more batteries and solar.  We like the motorhome and other than driving through the 75+ miles of the greater Los Angeles area to get to open road, it's a pleasure to drive. 

Gordon, that's the 64,000 question.  The wife and I aren't planners.  Other than possibly watching the grandsons in February, I couldn't tell you where we're going to be next week.  ;)
 
There is no question that the AIMS will run it; the only consideration is how long the batteries can power it under YOUR typical operating conditions. Another pair of 6v's would certainly be welcome for the additional amp-hour capacity. Or change over to 12v deep cycles and use 3 x Group 27 or 31 to get more boondock capacity.
 
What Gary said! I'm now convinced that a modern high efficiency residential refrigerator is saving me on the close order of $60 per month as compared with a smaller (volume) RV type running on electric. Since I replaced the RV type, I've had three consecutive electric Bill's of $60-65  where I had not seen a bill under $100 over a period of five years during the winter season; more typical was $140.

Ernie
 
Ernie, that's a good point.  Never thought about the amount of energy a 3-way refrigerator uses on 120 power.  While that's not a consideration for now, it's possible that if we ever purchased a lot and built an RV garage/residence, it could be a major factor. 

Agree on adding two batteries Gary.  Only question is where.  Ours are in the steps and there's not enough space for a third. The only option I can think of is a new tray in the bay next to the stairwell.  If that require any significant cash outlay, I'll look at Lithium batteries. 
 
Gary, this refrigerator looks very nice!  I've been waiting to see something like this.

The Danfoss compressor uses a permanent magnet motor, which automatically cuts it's power consumption by close to 50% compared to a conventional compressor.

A conventional motor uses electric current to create opposing magnetism in both the armature and in the field windings of the motor.  The Danfoss compressor uses permanent magnets in the armature, eliminating that half of the electrical consumption.

This makes it's electrical draw about half that of a similar sized refrigerator, even the Energy Star models. The smaller refrigerator you mentioned uses about 900 watt-hours a day (0.9 KwH)

Unique's published consumption rate of 574 watt-hours a day is indeed slightly more than half of that. 

A pair of 220 amp-hour golf cart batteries stores about 2640 watt-hours, or 1320 watt-hours if you don't draw them below 50%.

At 574 watt-hours a day, a pair of golf cart batteries will run this fridge 2 1/3 days before drawing the batteries down to the 50% level.  Two sets (4 batteries) will run it for almost 5 days (4 2/3 days). 

That's without any offsetting solar or generator charging and is exclusive of your other electrical uses. 

If you have 6 hours of full solar a day, an additional 4 amps of solar charging (48 amp-hours) will handle the fridge's usage.  One extra solar panel will be close to break-even, two extra panels will more than cover it.

Here's a link to more information about the fridge including the Owner's Manual, from the manufacturer:

http://uniqueoffgrid.com/product/solar-powered-dc-fridge-2/
 
While I do not have any experience with a "Solar powered" fridge I do have a high efficiency all electric (Danfoss class compressor) Compressor freezer.  Very pleased
So far the only thing I have done to it in 25 years is DEFROST and once I took it out and blew the dust out of the "Outside" parts (Compressed air jet.. Painter's mask).

Only problems I've had with it were "External" (Issues with the wires feeding it 12vdc)
13 years old and still cold.. Have used on both 120 and 12 volt  36 watts.

Dometic and Norcold both made units like this less than 50 watts running.
 
To the O.P.......why did you want to upgrade the NDR1292......because you like to boondock ?  We have the same model, S/N 20300046 and it came with our 2003 M/H when we bought it in 2012.  Is it a 2003 fridge ?
 
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