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Old 04-09-2021, 07:32 PM   #1
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Multiple Refers vs Full Size Refer

I have read the forums and am still confused as to the right direction to go. Have had several boats most with inadequate refrigeration. In our new project boat we have a full size ac refrigerator. We were excited about having the capacity. Of course it dies 2 weeks into owning it. We have a 26” doorway to get the thing in the galley which minimizes options. We spend a lot of time on the hook and want to run genny 2-4 hours per day. We prefer to have ice. 8 6v house bank on Maxum inverter. I have plenty of room to install multiple smaller dc fridges, replace the large fridge, or install smaller fridge and freezer. What is the most efficient way to go? I have solar to top off the bank as well but are in PNW so sun is out when we cruise but not the tropics.

Does anyone have any recommendations from their own experience? We were always super annoyed with our smaller refers on the other boats. I have seen drawers that seemed like a good way to go. I also am tired of hauling ice all of the time for the cooler but like to have cold pop, wine, etc... it would be great to have an ice maker.

Thanks ahead!
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Old 04-09-2021, 07:55 PM   #2
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Many will say the dedicated 12v fridges are more efficient. However, a 50l Engel will draw about 50ah per day or about 1/2 a kWh. My 400l inverter fridge at home draws about 1 kWh. Where I am, a new Engel is ~A$1000, my fridge was $800.

Let's not mention the Admiral's passionate hatred for top load fridge/freezers.

Obviously, if your one fridge dies then you are eating canned food until you get home.

Sure there are inverter losses yada yada yada but you do the math. 😁
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Old 04-09-2021, 08:41 PM   #3
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I run a large refer and 2 freezers with my inverter. I run a generator a couple hours every 2 -3 days when I make water, charge, laundry, etc. With a good inverter and a decent battery bank, AC 24/7 is no problem.
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Old 04-09-2021, 08:52 PM   #4
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If the large fridge is in the boat now, why not just have it repaired?
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Old 04-09-2021, 09:29 PM   #5
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Other aspect to consider between a large fridge and multiple smaller one is efficiency.
When you open your fridge you basically leave cold air out and warm air in. Smaller the volume, less energy needed to bring it back cold. On the other hand multiple unit means multiple compressors running.
Would be very interesting to see measured differences in energy consumption between the two cases when you properly sort you items so to have all the most used in the same unit so not to open multiple ones for nothing.
Interesting experience.

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Old 04-09-2021, 10:18 PM   #6
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I have a smaller 3.5 cubic foot fridge/freezer and a dedicated 3.5 freezer both 12 volts. I like having the two separated as on shorter trips I won't bother firing up dedicated freezer, used pretty much exclusively for longer trips. The fridge/freezer will be turned on until roughly mid-November beginning in a week or so. I keep it fairly well stocked up with food so I can decided at a moments notice to go our for a couple of days without having to do any shopping. So when I'm at anchor for a couple of days I'm just running the fridge/freezer and not both units
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Old 04-10-2021, 05:45 AM   #7
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"If the large fridge is in the boat now, why not just have it repaired?"

Instead of repairing the AC setup, pull all the outdated junk and install a modern DC system.

To find out if unit DC would be large enough purchase a block of ice.

Put the ice block on a shelf for 24 hours and then weigh it,
wait 24 or better 48 hours and weigh the ice block again, under 5 lbs of melt per 24 hours means DC will work OK.

Anything you can do to the old box ,like better door seals or added insulation glued on outside will lower the battery power requirements.

Mount the compressor in a well vented location.
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Old 04-10-2021, 12:31 PM   #8
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PS: in refit, I had an inch of foam added around the fridge/freezer. This addition definitely improved the performance of the fridge. If you would have asked me about the fridge pre-foam I would have said its okay. Post foam addition the fridge works really well. Nothing dripping down, etc.

There was space under my helm seat so when I had the old held seat and frame removed I replaced it with a box with one inch insulation inside of it to accept a freezer. Now I sit on top of my freezer.

I can't report as to how much energy the insulation saved me on my fridge as pre-refit there was no electrical monitor so my guess would be just that. I have since added a Victron monitor. But from a performance point of view, I really recommend the insulation. In my case I have no generator so any power saved is a good thing.
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Old 04-10-2021, 12:39 PM   #9
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We have a full-size Bosch fridge and a top loading chest freezer. This will keep the two of us fed for up to 6 weeks in the Bahamas with the occasional stop to buy salad and vegetables.
We have an all electric galley and run a generator 3 to 5 hours a day to cook, launder and make water. That keeps the battery bank fully charged too.
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Old 04-10-2021, 12:53 PM   #10
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I have a large double door refrigerator/freezer in my dirt home. It is standard size and with the doors removed (a very simple process) the unit is just about 28 inches thick. I can't believe that you can't find a refrig that will pass through a 26 inch door.

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Old 04-10-2021, 04:37 PM   #11
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Keep a full size, home type refrigerator freezer, mostly refrigerator. You can find ones that will fit through the door with their doors removed. Then put drawers that can be used mainly as freezers anywhere you have space. Don't think just galley.
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Old 04-10-2021, 04:45 PM   #12
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Without a lot more info it is kind of hard to say what would be better.

I think FF had a good idea. If the old fridge is still suitable then get it repaired, at least get a figure for the repair. I am assuming the original fridge is 120Vac. You may find that the newer compressors are more efficient than the old. It may be possible to convert the old fridge to use a Danfoss compressor and run from 12 or 24Vdc.

Then get a chest type freezer for the longer term frozen stuff.

A point that occurred to me but I don't have the means to prove it one way or the other is one larger unit is likely more efficient electrically than multiple smaller ones and likely as far as heat loss is concerned also.

I have two friends who love their 12V ice makers
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Old 04-10-2021, 05:16 PM   #13
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Look for a counter depth refrigerator. With doors removed should be 24” or less. My GE cafe is 22” without doors
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Old 04-10-2021, 10:30 PM   #14
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Fridge threads! Now more numerous than anchor threads!

DC rules. Danfoss compressors (I have 2) consume 3 amps or less when running. Duty cycles will be dependent upon outside temperatures and the depth of insulation.
AC fridges will consume roughly twice as much for the same size box.
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Old 04-10-2021, 11:11 PM   #15
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AC fridges will consume roughly twice as much for the same size box.
True but only because the small bar/dorm sized AC fridges are inefficient relay controlled units rather than the inverter controlled like modern, full sized, domestic ones.

If the OP is looking for a full sized fridge/freezer he will struggle to find 4 or 5 DC units to give the same volume but less power draw than a single inverter AC model.

A major benefit to us of AC units is that they can take a major provisioning run and actually cool the staples/freeze the meats relatively quickly. Small DC units do struggle here as they prefer to maintain already cold supplies vs actually cool/freeze them from ambient temps. Within the context of the original question shorter periods at full power has a major effect on power draw (as well as convenience).
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Old 04-11-2021, 05:40 AM   #16
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Quote:
Originally Posted by koliver View Post
AC fridges will consume roughly twice as much for the same size box.
An urban myth, but prove me wrong.
A comparison of energy consumption of AC fridges is here: https://www.energystar.gov/productfi...rators/results

EnergyStar is a voluntary program, and none of the 12V fridge manufactures have submitted their units for testing, and I don't know of anyone else who have tested them either.

Click on "buying Guidance" for some useful hints if you decide to buy a new fridge.
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Old 04-11-2021, 05:49 AM   #17
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There are RV fridges that are built for efficiency , thicker insulation in the walls , so no heater is required to dry the insulation or door seals.

One brand blows the compressor heated air into the cabin , so no vent path needs to be constructed.

The new DC units learn what energy it takes to pull heat from the box , and will adjust their on pattern to a long slow process rather than hammer away at full bore all the time.

Also some use a voltage measuring concept, high (charge) voltage means the engine is on or your plugged in to a power source , so switch back to cool as quickly as possible.

As a guess there are probably 100 times as many RV as boat fridges , so innovation comes from demand ,not the ability to mark up just because its a "boat" part.
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Old 04-11-2021, 09:33 AM   #18
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Quote:
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An urban myth, but prove me wrong.
A comparison of energy consumption of AC fridges is here: https://www.energystar.gov/productfi...rators/results

EnergyStar is a voluntary program, and none of the 12V fridge manufactures have submitted their units for testing, and I don't know of anyone else who have tested them either.

Click on "buying Guidance" for some useful hints if you decide to buy a new fridge.
Curious, I checked the first that I recognized as a top quality boat unit, the Fisher Paykel drawer fridge. It rates at 150kW/annum. That is a good comparative to the Danfoss DC fridge, and only ignores inverter losses, so is quite good comparing AC units to DC.
Too bad we don't have a good way to actually compare power consumption before making our choices.
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Old 04-11-2021, 10:11 AM   #19
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Have dealt with this for decades. Current thinking is
Top loading freezer in bilge. Opened I to 2 times per week. As emptied replace voids with ice cubes in bags. A full container is easier to keep cool. Air is a good thermal insulator.
Two DC drawers for daily use. One set as frig. The other freezer. Alternate function periodically so wear evens out. I like each being independent. It’s on its own danfoss, thermostat, coolant loop. I like heat dump outside the boat with keel coolers. Even in tropical waters usually more effective than than air cooled. I like easy defrost but no automatic defrosting.
So far Frigoboat is my favorite. Although the newer draws from several companies seem quite good. Frigoboat parts are everywhere. Only issue is to be anal about getting the right gas and putting in a desiccant/ particulate filter when installed. Believe most troubles are
Wrong coolant or at wrong pressure.
Dirt or water in coolant. Even after a nitrogen purge and a refill.
Very pleased with danfoss compressors. Seem bulletproof. proof
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Old 04-11-2021, 10:20 AM   #20
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Two DC drawers for daily use. One set as frig. The other freezer. Alternate function periodically so wear evens out. I like each being independent. It’s on its own danfoss, thermostat, coolant loop. I like heat dump outside the boat with keel coolers. Even in tropical waters usually more effective than than air cooled. I like easy defrost but no automatic defrosting.
So far Frigoboat is my favorite. Although the newer draws from several companies seem quite look.

If you go for a custom or semi custom setup, I'd plan on one being a permanent fridge, the other being a permanent freezer. You can gain some efficiency by optimizing compressor, evap, condenser, etc. sizing to the desired temperature range, rather than having it be a jack of all trades.
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