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Old 23-08-2016, 08:29   #46
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Re: House hold refrigerator off inverter

Just some data:
Our lab testing shows a 27% difference in energy usage between a top open and front opening fridge/freezer box. Door opened for 7-8 one minute intervals per 24hr period. As you can imagine...the freezer front opener accounted for the bulk of that efficiency loss due to the larger delta T.

I have a front opening refrigerator and top opening freezer.
The refrigerator is not ideal...but it's a Boat...nothing is Perfect and I'm not going to rip up the galley to fix it. Ripping up the teak decks is damn enough for me!
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Old 23-08-2016, 08:50   #47
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Re: House hold refrigerator off inverter

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Originally Posted by SV THIRD DAY View Post
Just some data:
Our lab testing shows a 27% difference in energy usage between a top open and front opening fridge/freezer box. Door opened for 7-8 one minute intervals per 24hr period.
For those without teenagers, the amount of time the door is opened is a lot less. Me about 5-10 second per door opening, so about a minute a day. It would be interesting what the energy use would be for 2 minutes a day. Probably more like 7%.

So the engineer in me has to ask was the insulation of equal thickness between the top loading and side loading fridge.
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Old 23-08-2016, 09:00   #48
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Re: House hold refrigerator off inverter

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Originally Posted by sailorchic34 View Post
For those without teenagers, the amount of time the door is opened is a lot less. Me about 5-10 second per door opening, so about a minute a day. It would be interesting what the energy use would be for 2 minutes a day. Probably more like 7%.

So the engineer in me has to ask was the insulation of equal thickness between the top loading and side loading fridge.
Boy is that the truth.
I catch my kids just holding the door open staring in like something will magically appear that was not there the last time they looked 10 minutes ago...ha ha ha .

Regarding the test, we made exact duplicate boxes out of 4.5" of Polyiso. One had a front doors cut out that accessed both freezer and refrigerator sections and then the other had only a top more standard single lid that gave access to both the freezer and refrigerator. If I could do the test over again, I think a better test would be to have a top opening freezer and then a front opening refrigerator, rather than a combined freezer/refrigerator. I think that would be more "common" and make the numbers not as bad. One thing we noticed in the test is the frost growth on the plate. The front opening box has a 4X rate of frost growth and if not scraped off or defrosted will dramatically cut down the heat transfer rate from the box to the evaporation plate, giving higher box temps and longer compressor runs times. THIS I think was a bigger factor in the loss of efficiency than the opening door. I need to do this test again and scrape the evaporator daily but time is hard for me these days to get for playing around in the lab. But I do miss it....
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Old 23-08-2016, 09:12   #49
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Re: House hold refrigerator off inverter

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The front opening box has a 4X rate of frost growth and if not scraped off or defrosted will dramatically cut down the heat transfer rate from the box to the evaporation plate, giving higher box temps and longer compressor runs times. THIS I think was a bigger factor in the loss of efficiency than the opening door. I need to do this test again and scrape the evaporator daily but time is hard for me these days to get for playing around in the lab. But I do miss it....
I remember my brother doing the fridge stare for minutes at a time. I of course, never did that ...

The Tayana 37 I sailed on had a combo top and front, well side loading ice box. That was the best , cough, of both worlds. An energy pig.

Yes Ice on the evaporator is a huge issue. I defrost mine about every two weeks (coincides with a provisioning run). A 1/4" on the evaporator will raise temperatures in the fridge over 10 degrees F, and cause far more energy usage.

A front opening box would have more air exchange, so yea, more moisture.
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Old 23-08-2016, 09:14   #50
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Re: House hold refrigerator off inverter

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Originally Posted by sailorchic34 View Post
A 1/4" on the evaporator will raise temperatures in the fridge over 10 degrees F, and cause far more energy usage.
Absolutely...this is a GREAT Point for folks to remember.
Defrost that evaporator and do it often!
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Old 08-09-2016, 09:08   #51
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Re: House hold refrigerator off inverter

My magic chef 4.4 cu ft Household unit was $169 at Lowe's. So $35 per cuft? I have a Freedom 2000 inverter, with Heart monitor. Inverter consumes 48ah per day just being on. Fridge about 75ah at 80degF daytime temps. Everything else about 25ah. If I had a 12v fridge I could turn off the inverter most of the time, so refrigeration cost 125AH each day at anchor. The newer Norcold $1500, wouldn't fit and it was time to leave the dock on our 42ft trawler. Been working reasonably for 2 years on the freedom squareish wave inverter. It works better/colder on shore power. 90minutes of generator morning and evening will keep me good forever, or just 90 minutes once a day for just a few days on the hook prior to a solid recharge on shore or an 8 hour run somewhere with the mains. Needs defrosted about every 2 weeks or so, so we time that to a marina visit where we fire up the Kenmore freezer.

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