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Old 14-10-2010, 17:57   #1
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Powering Full-Size 21 cu ft Refrigerator by Inverter

Does any one have first hand experience powering a full size refrigerator 21cu ft refrigerator from a inverter, solar panel, battery? not looking for guestimates, prefer yes i am using blank blank blank and works fine brand new refer (energy star)
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Old 14-10-2010, 20:41   #2
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Just look at manufacturers specs and see how much power it uses. I would take what the maximum power draw and add at least 25% if that's all the inverter is going to do...
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Old 15-10-2010, 15:55   #3
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I can answer part of your question...I supplied the power for a 21 cu. ft. household refrigerator (new at the time) from a bank of 12 Trojan T-105 batteries in the usual series parallel configuration to provide 1320 Ahr capacity at 12 VDC. Note that usable capacity (50% Rule) was 660 Ahr.

The inverter/charge is a venerable Xantrex Freedom 25 (2.5 kW) modified sine wave.

With nominal household loads, including coffee by a Mr. Coffee in the morning, we used 550 Ahr every 24 hours. This was replenished by a Balmar APC (no longer manufactured) which consists of a Kubota 6 hp engine directly coupled to a Balmar large case 190 amp alternator. We replenished to 95% full in about 5.5 hours.

We used this set up while we cruised the Eastern Caribbean for 3+ years and it worked flawlessly.

Regarding solar panels...Doing the math, you will need 550 Ahrs x 14.2 VDC = 7810 Whrs. of power generated by solar panels during approximately six hours. The newest monocrystalline panels in the current West are rated at 3.62 A.
3.62 A x 14.2 VDC x 6 hrs = 308 Whrs so you would need 25 panels. Not practical.

Charlie
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Old 15-10-2010, 16:59   #4
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G'day, Mate. Excellent analysis, CharlieJ. I have lived aboard now over 12 years running our large fridge/freezer one day using the inverter and the next day running it off the genset (and charging the batteries back up from the amps removed the previous day). Agreed solar panels are not the practical solution to these large energy requirements. Cheers.
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Old 15-10-2010, 19:10   #5
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Thank you ALL so much for the knowlegeable input, we presently have 13kw of generator and are typically hooked to an embilical (shore Power) We wanted to do some hook time down island,tyring to avoid running generator that often. Thank's again for the wisdom
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Old 15-10-2010, 22:03   #6
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G'day, mate. Agreed, always the goal to "avoid running the generator that often". Since your new fridge probably doesn't have holding plates, like the typical household model, it's going to want to cycle on an off during the day. Since you're not going to want to run the generator every time it cycles, the inverter will be critical.

You will just have to get a handle on your total daily kilowatt usage for all your systems to help manage your battery banks and minimize that genset time. To maximize your fuel efficiency you will also want to run your generator in the "sweet spot", roughly 6 to 10 kw for your 13 kw unit. So if you have a watermaker, make water while you running the genset. Also helps to get all the "noisy" stuff done at once.

And if you have a couple of solar panels they will help to maintain the life of your batteries. It's not practical to run the genset until you get every last amp back in the batteries, so the panels scan greatly assist there.

Have a great time living on the hook down island. Cheers.
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Old 16-10-2010, 07:50   #7
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We run two 7 cu ft freezer that are top loading, use one as a refer by switching two large jugs of ice and just run the one as a freezer. Works great.
Two things:
top loaders are much more efficient as the cold air does not pour out when you open the door
these units need clear space around them to disperse heat
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Old 16-10-2010, 13:56   #8
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Another comment--

I installed an 8.5 Summit fridge this summer and trash canned the older NOrcold. The Summit is just unbelievable for its performance, I cannot hear it running. I decided to power the fridge from a 1KW true sinewave Xantrex inverter. The fridge uses less than 200 watts/hr when it is running.

I oversized the inverter, if I was doing it over, I would go even larger. There are two things that are important, the first which is often overlooked is the defroster. That uses between 6-700 watt/hr but only operates for a few minutes. And yes, I highly recommend a self defrost unit. There is also a start up surge that could trip your inverter. You would not even know it until the fridge was opened. You do not want surprises.

I wired mine so the fridge operates (via a 120vac relay) from dock power...ie-- the relay is energized making the circuit complete. Away from the dock or during a power outage, the AC powered realy remains unenergized so the AC needed power comes from the inverter.

Foggy
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Old 16-10-2010, 14:05   #9
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Quote:
Originally Posted by lorenzo b View Post
We run two 7 cu ft freezer that are top loading, use one as a refer by switching two large jugs of ice and just run the one as a freezer. Works great.
Two things:
top loaders are much more efficient as the cold air does not pour out when you open the door
these units need clear space around them to disperse heat

I agree that cold air will tumble out when the door is opened but a top loader has disadvantages. I had a top loader in my old sailboat. Getting at anything required removing everything.

And yes, the air does tumble out. But the mass of the air is negligible compared to the food stuff. The major heat loss is from the top, bottom & sides and is a factor of amount of insulation present and the temperature difference between the inside and outside of the fridge.

Foggy
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