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Old 09-01-2012, 00:47   #61
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Re: Can a Household Refrigerator Work on a Sailboat?

1.6 Amps AC from the power label on the back of my dorm size refrig.
1.6 amps AC X 115 volts AC = 184 watts Amps X Volts = Watts ?
As I said my math might be wrong - kind of hoping it is as those refrigerators are everywhere for around 100 dollars US. If I could make it work on my boat for non-shore power I would be glade to add extra insulation for more efficency.
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Old 09-01-2012, 01:14   #62
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Re: Can a Household Refrigerator Work on a Sailboat?

My comparison revealed that most state-of-the-art, cheapish "eco label" fridges in the eu are just as efficient as boaty fridges
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Old 09-01-2012, 06:30   #63
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Re: Can a Household Refrigerator Work on a Sailboat?

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Originally Posted by idpnd View Post
My comparison revealed that most state-of-the-art, cheapish "eco label" fridges in the eu are just as efficient as boaty fridges
Yes but in which climate? I mean if you go North enough it will run less than a minute a day and be very efficient. But that changes once you reach the tropics. Also, you can't avoid the 5% or so loss of the inverter, so it can never be "just as efficient".

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Old 10-01-2012, 12:53   #64
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Re: Can a Household Refrigerator Work on a Sailboat?

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Yes but in which climate?
44cc is in a similar climate to me, a bit further north so arguably warmer still.
Weather for today is toasty with a Max of 36 degC
Brisbane Forecast

as I type this @ 5:45am I have 28.3 degC inside

Quote:
I mean if you go North enough it will run less than a minute a day and be very efficient. But that changes once you reach the tropics.
I go north to reach the tropics, but I know what you mean but like I have said previously, people living in Asian climates which have two weather patterns, Hot and Fken hot, manage to have refrigeration.
A couple or even a few extra panels will be cheaper than the 12v fridge alternative and surely take care of extra power used.
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Old 10-01-2012, 13:34   #65
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Re: Can a Household Refrigerator Work on a Sailboat?

That was my reasoning: Marine fridges are expensive and unreliable. Extremely expensive to fix. Domestic fridges are usually very reliable and very cheap to replace.

(If a household fridge failed in less than 10 years you'd be pretty dissapointed with it, if a marine fridge ran for 10 years with no problem you'd feel pretty lucky)

So I spent SOME of the price difference on more solar panels - which usually are good for 20 or more years trouble free.

For cloudy periods I have a 1 kva portable genset and a 50 amp charger. Which haven't been run for quite a while now.


The fridges you buy here are usually "tropical rated" whatever that means. I'd assume it meant a bit better insulation.

I used this website: Refrigerator/Freezer - AS/NZS 4474.2

To help select my freezer.
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Old 10-01-2012, 17:18   #66
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Okay I understand the reasoning, but doubt the reliability figures. I think household fridges have Danfoss compressors too, and the same aluminium evaporators.

I have been on some of these "mega yachts" that have the domestic freezers and he crews always complain; often the freezer hardly freezes etc.

North = tropics... Check. I don't understand how you guys manage to live upside down

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Old 10-01-2012, 17:48   #67
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Re: Can a Household Refrigerator Work on a Sailboat?

A quick look around some forums shows plenty of people having problems with marine refrigeration.

Getting this stuff fixed costs plenty. I could probably replace my 240 volt freezer for the cost of just getting a fridge mechanic out to my boat. Or less.

Can't see why they wouldn't work in hot climates. Not everybody in Aus has aircon - we only had our bedrooms A/C'd, but fridges and freezers worked fine there. (Subtropical Qld.)

All of mainland Aus sees high temps at some times. In fact generally the tropics don't see the peaks the more "temperate" regions get to. ie 45'c is not unheard of in western Sydney or Perth, Adelaide or even Melbourne. Lots of houses without AC whose fridges and freezers keep working.

Anyway, we're not a megayacht, but our freezer freezes hard. Icecream is too hard to eat. Runs easily off solar - on a sunny day we'll be in absorbtion mode by lunchtime, and float mode most of the afternoon.

And we run watermaker lights, radio etc as well.
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Old 10-01-2012, 17:54   #68
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Re: Can a Household Refrigerator Work on a Sailboat?

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Originally Posted by 44'cruisingcat View Post
A quick look around some forums shows plenty of people having problems with marine refrigeration.

Getting this stuff fixed costs plenty. I could probably replace my 240 volt freezer for the cost of just getting a fridge mechanic out to my boat. Or less.

Can't see why they wouldn't work in hot climates. Not everybody in Aus has aircon - we only had our bedrooms A/C'd, but fridges and freezers worked fine there. (Subtropical Qld.)

All of mainland Aus sees high temps at some times. In fact generally the tropics don't see the peaks the more "temperate" regions get to. ie 45'c is not unheard of in western Sydney or Perth, Adelaide or even Melbourne. Lots of houses without AC whose fridges and freezers keep working.

Anyway, we're not a megayacht, but our freezer freezes hard. Icecream is too hard to eat. Runs easily off solar - on a sunny day we'll be in absorbtion mode by lunchtime, and float mode most of the afternoon.

And we run watermaker lights, radio etc as well.

Last week Adelaide had heat wave - over 40C for days.
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Old 10-01-2012, 18:02   #69
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Ah yes when you need to call men to come fix your things... on the other hand, dumping old and buying new is not considered very environment friendly today...

For performance in the tropics, there are some factors at play. The insulation value of the box is he most important. There is no cheap domestic freezer that can match something anywhere near the insulation that I built into my box (I build all myself). The compressors have not malfunctioned ever since I installed them 7 years ago.

I bet that most trouble you read about for marine refrigeration is caused by incorrect installation. We have Richard Kohlman as member here who could write books about that I think

ciao!
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Old 10-01-2012, 18:20   #70
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Re: Can a Household Refrigerator Work on a Sailboat?

Now doubt properly built/insulated refrig using danfoss 12 v is efficient, effective and long lasting.

In case of 44c and catmando building from scratch their own vessels using adapting household refrigeration will get them on the water faster and initially cheaper and with ability to mount solar on their cats effective as 44c is proving.

I don't doubt they may even consider building some refrig in down the track if they find the time and energy for a refit down the track as you have recently done with your refrigeration, Nick.

Seems both options can work, and there is no doubt of improved effeciency and cost of better insulation.
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Old 10-01-2012, 20:04   #71
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Re: Can a Household Refrigerator Work on a Sailboat?

I posted this elsewhere, but here it is again. My 3.5 CF magic chef 120V fridge. pulls 1.4 amps at 120V (measured). Converting that to a 12V inverter makes it about 15 amps. But it does not run 50 percent of the time or even 25 percent of the time. I've timed it and it runs about 2-1/2 minutes in 15 minutes, or about 10 minutes per hour. It runs a little less on the bay and a little more in the delta during summer (95+ degrees F).


Weather 12V or 120V the amount of heat rejected from the box would be the same. A 12V fridge runs 1/3 to 1/2 of the time. My 120V fridge on inverter runs 1/6th of the time, or about 2.5 amps per hour. Which give or take is about the same amount of energy a 12V compressor would use.

The energy required to cool a ice box / fridge is the same for a given size / insulation. etc.

Some goes for heating btw. A 10 gallon water heater with a 1.2 kw element uses the same amount of KW/ power (ignoring standby heat loss) as a 10 gallon water heater with a 10kw element. One just gets it done faster then the other.
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Old 10-01-2012, 20:32   #72
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Re: Can a Household Refrigerator Work on a Sailboat?

Yes. Nobody is claiming a 240 or 110 volt domestic fridge will be more efficient. But the OP's question was "Can it work?"

It can work and it does.
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Old 10-01-2012, 20:53   #73
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Re: Can a Household Refrigerator Work on a Sailboat?

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Seems both options can work, and there is no doubt of improved effeciency and cost of better insulation.
Which gets us back to another blast from the past:
Why cant I take 50-100mm blue styrofoam and stick it on the outer of my domestic fridge?
Surely this will increase foam thickness and efficiency.
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Old 10-01-2012, 21:20   #74
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Re: Can a Household Refrigerator Work on a Sailboat?

Wading through this article now

Quote:
Calculating Energy Rating of Domestic Refrigerators
Through Laboratory Heat Transfer Measurements
and Computer Simulations


http://www.inive.org/members_area/me...997%5CP284.pdf

Quote:
As shown later in this paper, the results indi-cated that about 87% of the energy exchange in the refrigerator took place through the walls of the unit. The remaining heat transfer (ie, 13%) was assumed to have occurred mostly through the doors’ gaskets.
snipped
These experiments were per-formed twice, once all the measurements were taken with the refrigerator in its as manu-factured condition, and then with an additional layer of a 30-mm polystyrene insulation added to all the walls.
snipped
It was found that the power consumption of the refrigerator dropped by 11% and 17% respectively when 30 mm and 60 mm of polystyrene insula-tion was added to the walls of the refrigerator [18].
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Old 10-01-2012, 22:27   #75
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Re: Can a Household Refrigerator Work on a Sailboat?

Just a note that if your refrigerator does not have a external condenser on the back of the fridge, then its built into the walls of the fridge. Mine is that way so no insulation can be added to the sides. Next time I'll look for one with a external condenser...
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