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Old 20-07-2016, 14:56   #16
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Re: Refigeration Amp Hour usage survey

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[Q UOTE=sailorchic34;2170775]Just for comparison, my cheap 120V fridge and inverter ($200), only 3.5 CF but has a small freezer, runs 60 ah a day. It's now 9 years old and still going strong.

Mind you it pulls 15 amps when running, but duty cycle is about 16%.
Your 120 v fridge runs only 16% of the time? light years ahead of anything I've ever owned. What brand is it and what Is the climate where you are[/QUOTE]

A cheap $120 magic chef. Temperatures in 85-90 degree cabin temps in the california delta. It runs about 2.5 minutes in 14 minutes or roughly 10 minutes an hour. More mid afternoon, but less at night. When it gets to 95 degrees it runs longer, but solar easily recovers my batterys by noonish in summer. The 2.5 minutes in 14 minutes was measured at 1PM.
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Old 20-07-2016, 15:10   #17
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Re: Refigeration Amp Hour usage survey

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It's almost too big, and too deep.
My plan is to eventually add insulation to the the inside of it and especially the floor and hopefully we won't need the stool to reach the bottom anymore, and cut down on energy consumption. It was an ice box, and I think the idea was you could put several days worth of ice in there, that would raise the bottom and still leave plenty of room for food.
I've been toying with getting an Engle or similar and using it as a freezer for when we are gone for months, but will likely wait and see if that is really needed or not.
I would examine if there are any coils at the bottom before adding the insulation! If there are, your freezer would not function properly as the coils would likely get too cold while the contents above your insulation get warm. I'd recommend either adding a plastic shelf or thermal mass.
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Old 20-07-2016, 15:40   #18
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Re: Refigeration Amp Hour usage survey

If you like Sailor Chic's solution, have room for a manufactured unit, and can spend a little more, and can access Euro appliances (geez, not a lot of caveats there), I'm a very satisfied (and completely unaffiliated) customer of Liebherr. Mine came with the boat, installed ~4 years ago, and runs flawlessly.

Their TP1434 is rated to use 253Wh/day under the standard Euro testing method (25C/77F ambient temperature, partially full, x openings per day). The "T" in the model denotes tropical design/use, rated for use up to 43C/110F. If you dig around you can find their energy curves, ours uses about 30-35Ah/day in the Pacific tropics, and that includes the inverter inefficiency.

The sister TP1486 freezer has very similar usage if you want a freezer. And usage ratings in Europe are at -18C/0F. Unopened it is rated to keep things frozen for 23h with no power (there are some top-opening Euro A+++ units that are >100 hours unopened).

The 1434 has a small freezer box, if all you want is fridge, the TP1720 is a fridge only, rated at 14Ah/day (actual use 20-25).

Any one of those would set you back ~US$500 + really good ~250-300W inverter to run them (they are sensitive to crap inverters). I've built any number of boxes on boats, with various cooling components and various insulation systems, and the only reason I can see to do that these days is if you have to fit an odd-shaped space and can't fit one of the super high efficiency manufactured units. You can get a 150 liter (5ft3) fridge and 100 liter (3.5ft3) freezer for under $1500 (including the inverter(s)) and still use 50-60Ah/day, with somewhat redundant units thrown in.
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Old 20-07-2016, 17:03   #19
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Re: Refigeration Amp Hour usage survey

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About a 10-12 cu ft freezer and a spillover bar sized fridge about 70 amps per day in the Bahamas (temp usually in the eighties). AB cold machine .
We're getting better. It took all of 10 posts this time before someone screwed up the "amps" v "amp hours' thing.
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Old 20-07-2016, 17:08   #20
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Re: Refigeration Amp Hour usage survey

in case anyone is interested, this is what I did to our fridge (wall on RHS of pic).

Two drawers, the black knobs twist to the right to open, slam locks to close, all home-made.
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Old 20-07-2016, 18:38   #21
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Re: Refigeration Amp Hour usage survey

9-10 cu ft box, 1.5-2 cu ft of that freezer.

Summer (FL with mid 90s daily highs) 45-50 amp hours/day
Winter (FL mid 70s daily high) 25-30 amp hours/day
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Old 20-07-2016, 19:09   #22
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Re: Refigeration Amp Hour usage survey

So waddaus all mean? For many, many years, 60ah per day (thanks again, Stu!) has been the norm for basic level operation.

So, you insulate the box.

Then you get a BETTER unit.

Your daily use gets cut down to 75% of what you started with.

That's great.

In the grand scheme of things, one has saved 25% of 60 ah = 15 ah per day.

That's good, but nothing a good solar system couldn't put up with if sized right, or, depending on where and how you boat, nothing a good sized alternator wouldn't deal with if you motor a lot.

Your boat, your choice.
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Old 20-07-2016, 19:33   #23
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Re: Refigeration Amp Hour usage survey

50 quart freezer into 50 quart fridge in a spillover configuration. About 1" of 27 year old insulation on the sides and 5 inches on the bottom.

New frigoboat keel cooled system with stainless lobster controller.

When filling fridge and freezer from warm it consumes about 100 Ah.

Average days are about 45 to 55 Ah.

Days when we barely open freezer maybe 25 to 35 Ah.


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Old 21-07-2016, 08:46   #24
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Re: Refigeration Amp Hour usage survey

It depends entirely on how many warm beers and bottles of tonic water we put in each day.

That thermal load aside, I think we average about 50 amp hours for our refrigerator and about 85 for our freezer. This is in the Caribbean, with daytime temps around 30 C.

Don't know the exact volumes, but would guess about 10 cu ft for the refer and about 8 for the freezer.

Insulation is 4-5 inches, with well-gasketed and insulated lids.
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Old 21-07-2016, 08:55   #25
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Re: Refigeration Amp Hour usage survey

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Originally Posted by SV DestinyAscen View Post
I would examine if there are any coils at the bottom before adding the insulation! If there are, your freezer would not function properly as the coils would likely get too cold while the contents above your insulation get warm. I'd recommend either adding a plastic shelf or thermal mass.

It has cold plates, I put them in, no coils under the floor.
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Old 21-07-2016, 09:18   #26
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Re: Refigeration Amp Hour usage survey

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Hi Everyone.

Thought I would put it out there , how many Amp Hours is your 12v DC refrigeration using in any given day (24hrs) on average ?

You can include size of fridge , ambient temperatures, amount and kind of insulation , make of equipment , and what ever else you can think of, if you like .

But Amp Hour usage is the main point.

I will start . I use 28 amp hrs on average.

Ambient temps are 87 during the day and 70 at night

Box is 7.7 square feet ,
5 inches of Polyisocyanurate insulation and 1 inch of polystyrene (blueboard)

Built my own condensing unit using a Danfoss BD35 using thermostatic expansion valve with a rollbond evaporator plate 16" x 32" in size .

Regards
Wow, that is amazingly low usage. For my boxes , usually less than 2 cu ft, it was likely 80-90+ ah per day in the tropics. Factory insulation. One had vacuum panels but not much better results.
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Old 21-07-2016, 09:24   #27
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Re: Refigeration Amp Hour usage survey

I don't feel so bad now with my 100+
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Old 21-07-2016, 09:43   #28
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Re: Refigeration Amp Hour usage survey

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Originally Posted by sailorchic34 View Post
Just for comparison, my cheap 120V fridge and inverter ($200), only 3.5 CF but has a small freezer, runs 60 ah a day. It's now 9 years old and still going strong.

Mind you it pulls 15 amps when running, but duty cycle is about 16%.
An important point I'm discovering now that I know my new charger will trip my old 15 amp AC breaker. Luckily, Ohm's Law tells me the upgrade.
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Old 21-07-2016, 09:56   #29
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Re: Refigeration Amp Hour usage survey

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Wow, that is amazingly low usage. For my boxes , usually less than 2 cu ft, it was likely 80-90+ ah per day in the tropics. Factory insulation. One had vacuum panels but not much better results.

Thanks , I should add that I took out the 134a and replaced it with "RED TEK" R12a, also changed out all the oil in the system and used theres but it wasn't required . This is a hydrocarbon refrigerant. Much more efficient . This lowered my head pressure to 75 psi in a cold box . This translated to my BD 35 running at low speed drawing around 2.5 amps .

I also built my own condensing unit using a thermostatic expansion valve instead of a capillary tube .

Regards


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Old 21-07-2016, 11:10   #30
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Re: Refigeration Amp Hour usage survey

There are many other threads about my system, which defies all expecations...

I have a custom built box (2005 or so) which replaced the 'double decker coffin' 19CF icebox (we cut it out and started from the bulkhead, the only remaining wall).

It's 6" of extruded polystyrene covered in epoxy as it went in, then epoxied again, and fiberglassed into a box. The lid (same) went on last. I double gasketed both doors, which are made from the same insulation and method.

The freezer is ~3.5CF and the reefer is ~6.5CF. I never measured the previous Frigoboat Danforth50 keel-cooled installation's draw, but it ran on low, based on the SSC bars showing. I estimate that it would have used perhaps an average of 3-4A, resulting in 75-100AH/day.

That system failure is documented elsewhere on CF, so I'll save you the story. It was replaced with a Sea Frost BD80, air and water cooled, and the freezer got three evaporator plates of about the same area as the previous Frigoboat plate.

We measure our draw overnight, where there is no entry, from a cold start (doors never opened for hours beforehand), to keep plate temp cycle point to zero F, with a 6 degree hysteresis - which works out to about a box variance of 2F, the same as with the Frigoboat, yielding a freezer temp of about 15 or so. The original FB Carel electronic thermostat keeps the reefer at 32-34F very reliably.

The draw goes up in approximate tandem with the outside temp leading number. 40F gets an average of about 4A. 80-90F, with similar water, gets about 8A average. That is, if I look at the difference in AH consumed overnight, no wind or sun to help, currently I'm seeing 8-9A average.

I've done delta testing of the exterior of the box (how much colder is the exterior than the ambient air around it); it is mostly 1 but at most 1.5 degrees. From that experts have opined that my insulation is effective. But I still eat electrons voraciously in order to get my cold.

That works out to 200-225 or thereabouts AH/Day, assuming we don't ever open the doors, and it doesn't get any hotter during the day. Of course, overnight temps are only 80 or less, so the number is higher during the day, and likely I have even more draw than that.

I'm impressed and insanely jealous of those with similar boxes (there are at least several who chimed in on the other threads) with 50-75AH daily use.

No amount of fiddling (at least yet) has made it better. To the best of my knowledge, the system is working to its best level; the frost line ends about 1/2" shy of the exit hole. The installer, who expected to be able to make it work with air only, finally gave up after replacing presumed defective constant-pressure valve and thermo probes, and installed (using a Tee on my salt water washdown, which disabled it, dammit) the water line and pump.

The system, in current Vero Beach temps, will run continuously on low, and never cycle. Higher speeds (the controller can be L/M/H or auto, computer driven to establish a 32/16 minute cycle) cycle the freezer.

So, aside from the outrageous cost in amps, we're pleased with the system...
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