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Old 01-10-2012, 12:59   #31
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Re: Non Marine Fridge - 11 Watt

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Originally Posted by sailorchic34 View Post
The edgestar is a 2 CF refrigerator or freezer that costs oh $560 ish. Really my fridge is 3.5 cf and includes a small freezer. The 3.5 CF fridge is 1.75 times the edgestar volume. Oddly enough factor in the increased volume and the energy usage is about the same per CF as the edgestar....
I'm not saying what you are doing is not an option as obviously it is working for you and others. Just putting out some other info. The EdgeStar is 2.3 cu. ft. (from measurements of the inside of ours) and I agree that the portables are not as efficient as a good built in fridge but still think at 3 1/2 amps running 25% to 40% of the time are somewhat better than the dorm type fridge and one might give up a little interior volume for less total amp/hr usage per day. If so then one of the portables might be an option.

We lucked out on ours and got it on a Christmas sale for a little over $400 and free freight a couple years ago. Since all of the portables have gone up in price. Still not as inexpensive as yours .

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Old 01-10-2012, 13:23   #32
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Re: Non Marine Fridge - 11 Watt

These are expensive (but not as expensive as many boat systems) and heavy but are used in marine installations, they are the most energy efficient systems available on a non custom basis, but the heavy weight makes them less desirable for boats, I use several in off grid situations. I applaud Europe as they are moving to energy efficiency.

Sun Frost Refrigerator specifications


The R10 refrig only with 258 lt uses 13 amp hr daily, I have one in a cabin and its better as our temps are lower than the 75F they use. My 200lt water cooled boat system uses 60-75 amp hr daily.
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Old 01-10-2012, 13:34   #33
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Re: Non Marine Fridge - 11 Watt

Agreed that smaller storage volumes use less energy. Though the overall efficiency between the $400 edgestar and the $140 magic chef is the same. The 120V uses more power because it has more volume to cool/freeze, not because its less efficient then a 12V unit.

A BTU is a BTU weather 12V or 120V

I did look at the edgestar and engel too. Along with norcold and sundazer.

Norcold and Sundazer make a 12V 4CF fridge for about $1000. It uses 720 watts a day where my $140 120V fridge uses 750 watts a day including inverter loss.

Engels are nice. but way too spendy for what you get.



The only real improvement is using additional insulation where possible.
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Old 01-10-2012, 13:50   #34
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Re: Non Marine Fridge - 11 Watt

Dsanduril, this data is indeed very valuable, thank you!
I think with this we can calculate that in a tropical area, where at least 35 deg C are realistic, not 25 as defined by the European standards, the consumption of the 11W fridge goes up by 16.7W. So we have a total of 28W plus about 7W from limited DC/AC converter efficiency. So we are at 35W mean consumption in the tropics (equals to 70 Amp hours per day) for a price of 400 EUR (plus converter).
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Old 01-10-2012, 19:43   #35
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Re: Non Marine Fridge - 11 Watt

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Originally Posted by sailorchic34 View Post
Agreed that smaller storage volumes use less energy. Though the overall efficiency between the $400 edgestar and the $140 magic chef is the same. The 120V uses more power because it has more volume to cool/freeze, not because its less efficient then a 12V unit.

A BTU is a BTU weather 12V or 120V

I did look at the edgestar and engel too. Along with norcold and sundazer.

Norcold and Sundazer make a 12V 4CF fridge for about $1000. It uses 720 watts a day where my $140 120V fridge uses 750 watts a day including inverter loss.

Engels are nice. but way too spendy for what you get.



The only real improvement is using additional insulation where possible.
Yeah, I've often come to the same conclusion. It WOULD be nice if someone did a head to head comparison of 12v vs the average new 120v small unit for sure. Everytime this comes up on the forum, there are 3 pages of people crunching numbers and questioning other's numbers. In the Caribe my boat at anchor needed 100-110 amps a day replenished. 12v fridge with a small box was mostly all that... I would estimate 80-90 amps. My previous boat with vacuum panel insulation and a small box used about the same. Wouldnt it be nice if a $120 fridge worked nearly as well!
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Old 01-10-2012, 20:24   #36
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Re: Non Marine Fridge - 11 Watt

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With solar panels being so much less expensive nowadays. It may sometimes be easier just adding another panel then to add 2-3 more inches of insulation to an already small icebox.
Just offering a slightly different look at the issues.
Thats how I am looking at things now.

On the roof up top I can easily accommodate 10 x 200w panels if needed with no shaded areas.
I am tempted to have a go running my samsung 434L household fridge which I very recently bought new and am loathed to get rid of.
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Old 01-10-2012, 20:36   #37
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Re: Non Marine Fridge - 11 Watt

Well everyone said you could not use a 120v fridge on a sailboat. I had read that alot. But being blonde and having an engineering background, I decided to buy the cheap 120V fridge and try it out. After all a BTU is a BTU. Plus if it did not work out I could get the better 12V system later.

Yes at first blush the 120V fridge uses way too much amperage. But I found by sitting and actually timing the on/off cycle one hot summer day in the delta that my little 120V fridge only ran about 2-1/2 minutes then had 10-12 ish minutes off. I checked several cycles over a few days of 90+ degree days.

I was surprised to find that my energy hog 120V refrig. actually only used about 2.5 amps an hour (including inverter loss) during the heat of the day.

The other issue some raised was oil starvation. But the basic compressor design is the same between the 12V and 120V systems. Nothing special with the 12V. Matter of fact the 12V compressor has an AC motor with a DC to AC drive (the mysterious black box).

After 5 years of sailing (admittedly not that much sailing for the first 2-3 years). But I've logged over a 1000 miles in 2011 and its going to be over that for 2012. OK Not long distance cruising yet.. (That's next year ) But with the boat sailing in the brisk San Francisco winds, its been doing fine. Even healed over 25 degrees or more.

To me looking at the different refrigeration systems on the market, its seems there is not really any real world difference between power consumption on 12V compressors and 120V comressors on a per hour usage. Its true that the 120V fridge will use more amps when it runs. But it runs only 1/6th the time, compared to 1/3 to 1/2 or more for a marine 12V compressor.

Its sort of like which heating element uses more energy to heat 40 gallons of water, a 4KW or a 40KW. The answer is they both use exactly the same amount of power, just that one heats the water much faster.

The main difference in energy savings comes in the amount of insulation "R" factor the cold box has. That's about the only real savings you get. More insulation means less run time on the compressor. Besides that the basic 12V and 120V hermetic compressors will use the same energy to cool a given size box.

Oh sure water cooling will give a little more bang for the buck. But only where the water temperature is much cooler then the air temp. In the Sea of Cortez in the summer a water cooled compressor will be working pretty hard too.

The joy of the $140 fridge is when it goes out, you toss it away and get another one for less then a service call from a marine AC tech. So far mines been working fine for 5 years running and me being a full time liveaboard cruiser.
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Old 02-10-2012, 08:21   #38
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Re: Non Marine Fridge - 11 Watt

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Well everyone said you could not use a 120v fridge on a sailboat. I had read that alot. But being blonde and having an engineering background...
I remember the very first day in my very first engineering class in college. The professor said that the most important rule in engineering is "if it works, use it." Doesn't matter what anyone says, doesn't matter if the math seems right or not, doesn't matter if it agrees with anything else that you've learned... If it works, use it!
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Old 02-10-2012, 09:30   #39
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Re: Non Marine Fridge - 11 Watt

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Originally Posted by sailorchic34 View Post
Well everyone said you could not use a 120v fridge on a sailboat. I had read that alot. But being blonde and having an engineering background, I decided to buy the cheap 120V fridge and try it out. After all a BTU is a BTU. Plus if it did not work out I could get the better 12V system later.

Yes at first blush the 120V fridge uses way too much amperage. But I found by sitting and actually timing the on/off cycle one hot summer day in the delta that my little 120V fridge only ran about 2-1/2 minutes then had 10-12 ish minutes off. I checked several cycles over a few days of 90+ degree days.

I was surprised to find that my energy hog 120V refrig. actually only used about 2.5 amps an hour (including inverter loss) during the heat of the day.

The other issue some raised was oil starvation. But the basic compressor design is the same between the 12V and 120V systems. Nothing special with the 12V. Matter of fact the 12V compressor has an AC motor with a DC to AC drive (the mysterious black box).

After 5 years of sailing (admittedly not that much sailing for the first 2-3 years). But I've logged over a 1000 miles in 2011 and its going to be over that for 2012. OK Not long distance cruising yet.. (That's next year ) But with the boat sailing in the brisk San Francisco winds, its been doing fine. Even healed over 25 degrees or more.

To me looking at the different refrigeration systems on the market, its seems there is not really any real world difference between power consumption on 12V compressors and 120V comressors on a per hour usage. Its true that the 120V fridge will use more amps when it runs. But it runs only 1/6th the time, compared to 1/3 to 1/2 or more for a marine 12V compressor.

Its sort of like which heating element uses more energy to heat 40 gallons of water, a 4KW or a 40KW. The answer is they both use exactly the same amount of power, just that one heats the water much faster.

The main difference in energy savings comes in the amount of insulation "R" factor the cold box has. That's about the only real savings you get. More insulation means less run time on the compressor. Besides that the basic 12V and 120V hermetic compressors will use the same energy to cool a given size box.

Oh sure water cooling will give a little more bang for the buck. But only where the water temperature is much cooler then the air temp. In the Sea of Cortez in the summer a water cooled compressor will be working pretty hard too.

The joy of the $140 fridge is when it goes out, you toss it away and get another one for less then a service call from a marine AC tech. So far mines been working fine for 5 years running and me being a full time liveaboard cruiser.
THAT IS LESS POWER THEN MY 12V NORCOLD USES
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Old 02-10-2012, 13:40   #40
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Re: Non Marine Fridge - 11 Watt

Yes it is. Not intuitive at all, even surprised me. But I did check the actually running amps on AC, so my numbers are good.

Part of the reason is the condenser coil for the magic chef is embedded in the metal sides of the fridge. So there is about 10 CF of heat rejection area for the condenser. I think the Norcold, uses a smaller condenser coil with less then half the surface area. Same applies to the 12V AB systems too. Though the condenser fans help that nicely

The down side to the magic chef is the sides need clearance around them and additional insulation can not be added. Plus one must choose care where to attach mounting brackets to it... It would be more then annoying to puncture the condenser coil
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Old 30-09-2017, 12:43   #41
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Re: Non Marine Fridge - 11 Watt

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Dsanduril, this data is indeed very valuable, thank you!
I think with this we can calculate that in a tropical area, where at least 35 deg C are realistic, not 25 as defined by the European standards, the consumption of the 11W fridge goes up by 16.7W. So we have a total of 28W plus about 7W from limited DC/AC converter efficiency. So we are at 35W mean consumption in the tropics (equals to 70 Amp hours per day) for a price of 400 EUR (plus converter).
Its a long time ago now, but I like to add, that I finally did a measurement with this fridge in tropical Panama and ended up with an average total consumption of 15W which equals 30 amp per day. So quite a bit less than estimated above and still nice for a 130 liter fridge (4.6 cubic feet), made in 2012.

Meanwhile, technology has made further progress in Europe:
I just checked the latest models and I see a dramatic additional reduction of power consumption. While the fridge above was specified with 100kWh per year you can now get a state-of-the-art model from 2017 consuming just 65 kWh per year and offering even more volume: This is the IKP1660-20 with 165 liters of space.
So the additional energy saving achieved between 2012-2017 is 35% or, when calculated per internal volume about 50%!
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Old 30-09-2017, 13:36   #42
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Re: Non Marine Fridge - 11 Watt

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I remember the very first day in my very first engineering class in college. The professor said that the most important rule in engineering is "if it works, use it." Doesn't matter what anyone says, doesn't matter if the math seems right or not, doesn't matter if it agrees with anything else that you've learned... If it works, use it!
We have the usual undercounter Norcold fridge/freezer in a addition we built a 3cu.ft. freezer box with 4" of polyiso insulation on all sides and a well gasketed aluminum framed door(also with 4" polyiso) running off a swing compressor. I have ice cream on the boat for the first time in 23 years.

Couldn't give a damn about the numbers, Six months at a time on anchor and still have to run my 2400Watt Yamaha only every four days for 4hrs. Just like before I installed the freezer.

It works and it's all the space I had..... Statistics, damned statistics.
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