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Old 17-03-2017, 13:53   #46
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Refrigerator: AC vs. DC

A regular marine conversion fridge just can't really be tested because they very most important part of it efficiency wise, is the part the boat came with. The ice box it's going into.
While the AC house type fridge may be an option for some, for many it is not. It just would not fit in my boat, not without a lot of modification that I am unwilling to do.
However while you can get probably close to the efficiency of a good ice box conversion unit, you I do not think can match it. Reason is a couple of fold, one is insulation. A proper built in can have tremendous insulation value, far beyond what is possible with a home unit as no home unit I have ever seen has 6" or more insulation. And secondly to achieve peak efficiency, you pretty much have to have a top opening system, air has little mass so a front opener is not a killer, but you do let a lot of heat in when you open the whole side of a fridge.

However for those that have room to fit acres of Solar panels and or regularly run the generator and have the room in the boat, a house type fridge is I think a viable option.
Great in big Cats, big powerboats and house boats I'd think, not so much average mono hull sailboat.
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Old 17-03-2017, 20:46   #47
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Re: Refrigerator: AC vs. DC

Quote:
Originally Posted by Fuss View Post
Actually, you have to ask yourself just one question. Why do the marine magazines never do a comparison test between marine stand alone fridges and energy star A++++ fridges.
...
Example....Household A+++ fridge freezer. Bosch Model KGE36DW40 uses 149kwh per year, keeps food for 35 hrs with the power off.
Oh we don't have to read magazines, we are lucky enough to have a professional on the forum

Quote:
Originally Posted by ColdEh Marine
Your average home fridge 2.5kwh a day or 912.5kwh a year !
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Old 17-03-2017, 23:45   #48
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Re: Refrigerator: AC vs. DC

10 years ago I needed a fridge on the boat. I looked that the $900 12V AB units and thought to myself, they seem a bit spendy. But I'm also an engineer who sometimes plays with refrigeration. Though generally in the 500-1500 ton range (1 ton =12,000 btu's). So I knew voltage has little to do with energy efficiency.

While all the Marine folks said using a 120V fridge would never work, I decided for $130, lets give it a go. So I installed a cheap $130 fridge that lasted 9-1/2 years running a good part of the time on a $40 msw inverter with 240 watts of solar.

Now I have a nice new two compartment fridge and a fancy smancy PSW inverter, that saves me a additional 20 ah per day over the old cheap one fridge. Sure i could have spent $1500-$2000 on a fancy marine fridge. Oh wait, I'm a poor sailor and have not had even $1000 to spend. So I did what I always do, Find a way to make it work with the $$$ on hand.

Is it perfect, no.

But it works well for a singlehanded sailor for not alot of money. Oddly my stove and fridge combined was less then $700. So I probably saved at least $2000 compared to the 'marine" versions. The nice thingy is if it breaks I can buy another $200 fridge or $250 RV stove and still be WAY ahead of the game.

No it's not for everyone. But it does work pretty well for me. At least I'm pretty happy with being able to have ice cream aboard finally.
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Old 17-03-2017, 23:54   #49
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Re: Refrigerator: AC vs. DC

Quote:
Originally Posted by a64pilot View Post
However for those that have room to fit acres of Solar panels and or regularly run the generator and have the room in the boat, a house type fridge is I think a viable option.
Great in big Cats, big powerboats and house boats I'd think, not so much average mono hull sailboat.
It took 240 watts of solar panels (2 12V panels) to keep the old fridge happy. So not lots of SF required. I took one of the salon berths and made it a short berth (cat food storage) and fridge. It works pretty well and the new fridge is very energy efficient. If the fridge had 3 inches more insulation I would be ecstatic, but then again, it would not fit through the main hatch then either.
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Old 18-03-2017, 17:32   #50
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Re: Refrigerator: AC vs. DC

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Originally Posted by darylat8750 View Post
"For example, without an inverter (a situation), we would have had to fire up the genset to power an AC-only fridge while underway or at anchor. Whereas with an AC/DC model, we could flip a few breakers, fridges run while underway and at anchor, nose wet. Lots of folks don't have an inverter."

Chris, I would suggest that if you need to replace your current fridge that when shopping you consider the cost of a domestic (apartment sized?) unit and the cost of a suitable inverter. I think that the savings will amaze you and the power draw will be a very small increase over the current unit. In fact depending on the age of your current unit you may even see a slight decrease in electrical consumption. Also still no need to run the genset under way. I did this and even though I had to do a little cabinet work to make the new unit fit (I now have at least 30 percent more refrigerator space and 50% more freezer space) five years later I am still very happy with the results.
Thanks,I'm aware of the options, and advantages/disadvantages. I'm good, for now, but reckon to compare with current factoids at the time... should it come up.

We have to fire up the genset to cook, 2x/day, and that's not going to change... so our fridges' power consumption is low priority... at least for now.

-Chris
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Old 18-03-2017, 20:01   #51
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Refrigerator: AC vs. DC

Quote:
Originally Posted by sailorchic34 View Post
It took 240 watts of solar panels (2 12V panels) to keep the old fridge happy. So not lots of SF required. I took one of the salon berths and made it a short berth (cat food storage) and fridge. It works pretty well and the new fridge is very energy efficient. If the fridge had 3 inches more insulation I would be ecstatic, but then again, it would not fit through the main hatch then either.


I think though that usually people that bring up the house type fridge are literally talking full size double door fridge. You know the kind with heated gaskets and are frost free, not the dorm type of fridge that I think you have.
Your not going to run those off of a couple of hundred watts of panels, but that's OK, cause the type of boat that will usually accept a full size house fridge, likely either has a lot more panels or regularly runs a generator.

Of course I may be wrong.
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Old 18-03-2017, 20:13   #52
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Re: Refrigerator: AC vs. DC

Quote:
Originally Posted by a64pilot View Post
I think though that usually people that bring up the house type fridge are literally talking full size double door fridge. You know the kind with heated gaskets and are frost free, not the dorm type of fridge that I think you have.
Your not going to run those off of a couple of hundred watts of panels, but that's OK, cause the type of boat that will usually accept a full size house fridge, likely either has a lot more panels or regularly runs a generator.

Of course I may be wrong.
I do think in terms of larger than Salorchic, as in apt sized. However, when looking for efficient refrigerators one really needs to be aware of things that will use energy. Frost free is a killer of watts. Also through the door ice or any built in ice maker.
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Old 19-03-2017, 12:26   #53
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Re: Refrigerator: AC vs. DC

A good full size 15-19 cf fridge/freezer might use 1.5 KW per day if one picks a low energy usage one. Which for the size of the box is not too bad. It really is a function of heat gain through the box, so a bigger box will need more power to offset heat gain. I would disable the gasket heater and the frost free mode with is just a resistance heater anyway.

Most with that size fridge will have a boat with either a kw of panels or a 7+kw genset and a pile of $$ for fuel Lots of power boats go in that direction.
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Old 19-03-2017, 13:58   #54
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Re: Refrigerator: AC vs. DC

Quote:
Originally Posted by sailorchic34 View Post
10 years ago I needed a fridge on the boat. I looked that the $900 12V AB units and thought to myself, they seem a bit spendy. But I'm also an engineer who sometimes plays with refrigeration. Though generally in the 500-1500 ton range (1 ton =12,000 btu's). So I knew voltage has little to do with energy efficiency.

While all the Marine folks said using a 120V fridge would never work, I decided for $130, lets give it a go. So I installed a cheap $130 fridge that lasted 9-1/2 years running a good part of the time on a $40 msw inverter with 240 watts of solar.

Now I have a nice new two compartment fridge and a fancy smancy PSW inverter, that saves me a additional 20 ah per day over the old cheap one fridge. Sure i could have spent $1500-$2000 on a fancy marine fridge. Oh wait, I'm a poor sailor and have not had even $1000 to spend. So I did what I always do, Find a way to make it work with the $$$ on hand.

Is it perfect, no.

But it works well for a singlehanded sailor for not alot of money. Oddly my stove and fridge combined was less then $700. So I probably saved at least $2000 compared to the 'marine" versions. The nice thingy is if it breaks I can buy another $200 fridge or $250 RV stove and still be WAY ahead of the game.

No it's not for everyone. But it does work pretty well for me. At least I'm pretty happy with being able to have ice cream aboard finally.
I admire your ingenuity and desire to get things you need for your boat without worrying about what others in the sailing community think or say. I wouldn't buy one of those $1,200-$2,000 marine refrigerators if they were half that cost. And lets face it. Building yourself a good frige/freezer set up marine style is very costly.

I tried the household frige way, but found that no matter how efficient the house refrigerator / freezers were that they were difficult to keep up with because of the power they used. Not because they were power hungry while running mind you, but because they run all of the time due to crappy non efficient box construction. I mean they are now wrapping the condenser units around the 1.5" of insulation they have before putting on the tin on so that it's hidden and looks better. Who cares if it runs all the time as long as it looks good.

So I found a Grape Solar 4.7 Cu. Ft. 12V/120 volt frige/ freezer online through Home Depot for $400. and bought it. I figured this was the ticket as it only consumed 3.4 amp hours DC while running. I thought wrong. During the summer months in the Caribbean, it ran more than it didn't run, and came on every time you opened it no matter how fast you closed the door.
Thats when it dawned on me that insulation is the key.

So my next step was to tear apart the Grape Solar fridge, separate the wrap around condenser from the insulation and add insulation to it so it wouldn't run all of the time. I built a waxed wood box around the frige, and used polyurethane foam to increase the insulation to 3" all the way around. I also split the door, and increased the insulation there to 3". (3" is the best I could do with what I had to work with). This modification worked well, and it cut my run time down by half which now allowed us to own a frige on the boat that we could use. We used this set up for 5 years before I had issues with the thing not cooling. Plugged up capillary was the cause, and I would be doing major surgery in order to fix it.

The decision was made to head over to SXM and buy a well insulated 120 volt chest style freezer. A top loader that used R134a and had an externally located condenser. I found an "Ocean Brand" made in Portugal that fit the bill nicely. Bought it for $225.00, took it back to the boat, removed all of the 120 volt electrical and compressor and installed my 12 volt compressor on it. I also had to buy a 12 volt DC digital thermostat controller that cost me $34.00 that would take the place of the freezers thermostat. It works great and runs 4.5 minutes approximately every 40 minutes @ 3.4 amp hours at a temperature setting of 35 degrees on, and 28 degrees off. Very happy with it. I did have to redo my wifes galley counter top to allow for the top to open and close, but I chose corian in a color she liked and mounted it directly to the lid of our new fridge and she loves her new galley.
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