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Old 17-06-2020, 23:52   #1
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12 volt or mains power fridge?

Hi cruisers, I need to replace my fridge, (aprox 100 litre capacity)
"Marine" 12 volt units are expensive and there are few brands to choose from, compact mains power units are made in lots of different brands and are cheap (by comparison) so, would it be worthwhile to use a mains power fridge with an inverter as opposed to a dedicated 12volt unit ?? I am not overly concerned by corrosion, what other things should I consider?
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Old 18-06-2020, 23:02   #2
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Re: 12 volt or mains power fridge?

Residential fridges might have the condenser, in the side skin of the fridge, meaning they will not be happy constrained in a cabinet, or allow for extra insulation which can greatly reduce electrical consumption.

The inverter needs to run 24/7. My inverter turned on, powering nothing consumes more hourly, more than my fridge does, 90% of the time.

Residential fridges might have defrosters, basically a heater and run regularly and can greatly increase battery capacity required. Turning off this feature might not be possible.

The start up surge will be 10x of the running wattage, perhaps more. Many reports of people needing a 1200 watt inverter just to run a 50 liter dorm fridge that consumes only 65 watts after the start up surge.

Residential fridges might not allow a good ergonomic way to keep the door closed.

They might not handle boat vibrations very well.

There's ways to mitigate some of these potential issues, which bring the price closer to that of a Danfoss/Secop powered 12v fridge designed to work in boats.

I've read reports from those that have pulled it off claiming good average AH consumed on a 24 hour basis, and some who tried it and then ponied up for the DC fridge when they became stressed over their batteries constant state of undercharge and short lifespan.
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Old 18-06-2020, 23:34   #3
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Re: 12 volt or mains power fridge?

Thanks, all good points, I will need to do more homework.
Cheers!
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Old 19-06-2020, 00:45   #4
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Re: 12 volt or mains power fridge?

This and a few other posts by Sailorchic on her fridge experiments are worth a read. She is an engineer so digs into the calculations too.

https://www.cruisersforum.com/forums...ge-180007.html
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Old 19-06-2020, 09:07   #5
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Re: 12 volt or mains power fridge?

Opposite question: I've noticed that marine fridges in 12v-only versions are cheaper than dual voltage. Why spend the money on dual voltage? When you have shore power your batteries are always charging anyway.
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Old 19-06-2020, 09:16   #6
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Re: 12 volt or mains power fridge?

For about $850 USD you can have the best (worst) of both: Dual Voltage Marine Fridge. We have a 110v mini-fridge in our boat, but the ones we looked at do not fill the space well. (22" wide space, but fridge is only 17" wide...) Marine fridges seem to fill the space better and are dual voltage, but as you said are very expensive.
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Old 19-06-2020, 09:47   #7
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Re: 12 volt or mains power fridge?

Front opening fridges are much less efficient than top opening one as you let out all the cold air when you open the door. I found a portable compressor fridge mounted on a slide works very well. Max size is 60 or 80 L though. One possibility would be a 60l fridge paired with a 40l freezer. Might be worth a look.
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Old 19-06-2020, 09:56   #8
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Re: 12 volt or mains power fridge?

This question has come up before. We use a 220V household fridge and freezer run off a dedicated 350W inverter. Even with all the inverter losses we find the total electrical usage lower than any 12V fridge we've had, the temperature control better, and the volume greater.

The trick is getting one of the European A+++ energy rated fridges. Anything less and you'll start to chew up the Ah, but the A+++ units really sip the energy (and there are several that are designed for cabinet/undercounter installation).
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Old 19-06-2020, 10:10   #9
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Re: 12 volt or mains power fridge?

My question is what extra value does the 110v have? Looking at sources like Defender many of the marine fridges come in either 12v only or 12/110v. The latter are often pricier. What is the value of having the 110v rather than just 12v?
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Old 19-06-2020, 10:15   #10
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Re: 12 volt or mains power fridge?

No one here has ever reported results of trying the new inverter technology AC refrigerators on a boat using a smaller dedicated sine wave inverter. I was going to try it. Bought a 300 watt morningstar suresine and was going to get a smaller inverter fridge. They sell smaller sizes of these in Mexico, Central America, and probably most of the world. (have only seen full size ones in the US). Circuit board failure is a possible drawback in a marine environment. Inverter technology refrigerators and split ac systems have been around a while now. They have low start up draw and use variable speed compressors. Another option using a dedicated inverter would be to wire the fridge thermostat to the inverter trigger so that the inverter itself will turn on and off as the fridge cycles. I think that the A+++ rating fridges are inverter technology. By the way, "inverter technology" is just a marketing term not to be confused with the term "inverter" as we know it. They use circuitry to produce a 3 phase current to run the variable speed compressor. The multi voltage marine units basically do the same thing but these home units are now mass produced, and have nice cabinets but most of them are a bit large for most boats.
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Old 19-06-2020, 10:19   #11
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Re: 12 volt or mains power fridge?

Quote:
Originally Posted by flagatorclearwa View Post
My question is what extra value does the 110v have? Looking at sources like Defender many of the marine fridges come in either 12v only or 12/110v. The latter are often pricier. What is the value of having the 110v rather than just 12v?
It gives you the option of not having to cycle your batteries when the boat is plugged in.
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Old 19-06-2020, 10:21   #12
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Re: 12 volt or mains power fridge?

After having used the marine units from Frigoboat for many years, we have now switched to SnoMaster Expedition units.

The biggest unit is 95 Liters one compartment or 85 liters two compartments (each with itís own thermostat). These can be set as fridge or freezer
https://www.snomasterusa.com/product...fridgefreezer/
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Old 19-06-2020, 10:26   #13
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Re: 12 volt or mains power fridge?

I believe my Dometic (previously Adler Barbor) control unit and compressor uses 3-phase current and variable speed to save energy, yet they have not applied the "inverter" marketing term.

Generally people looking to install home refrigerators are doing so because they don't want to spend the money on a marine unit and it's installation. That approach, extended to all sorts of essential boat equipment, is generally short sighted. Basically, boats are expensive and those short cuts only delay the inevitable: You need to go back to work and make some more money.
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Old 19-06-2020, 10:26   #14
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Re: 12 volt or mains power fridge?

We have been running our 150l fridge and 104l freezer on a small, good inverter for 3 years, and have reported it here on several threads. Both units are A+++ and use inverter technology for low draw. We used to run both units on a 180W inverter, but every once in a while if they both started up at the same time they would trip the inverter. We moved up to a 350W inverter and have never looked back. We keep the freezer at -18C (0F) and the fridge at 4C (39F) year-round whether in the tropics or here in the PNW.

The full voltage units provide more energy efficiency (selection is critical) and are less expensive than marine units. The downside is that you have to be able to fit a consumer sized product - they only come in certain sizes.
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Old 19-06-2020, 10:29   #15
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Re: 12 volt or mains power fridge?

I bought this after reading about sailorchic: https://www.edgestar.com/edgestar-co...rs/CRF321.html

Haven't cared since. The thing uses about the same amount of power as my dead 12v units, is about the same level of noise, and gets the job done at a quarter of the price of the 12v units and at a 10th of the price of replacing my old reefer units.
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