Chest Refrigerator

Started by considerations, December 13, 2008, 11:50:15 PM

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pagan


Squirl

Thanks Pagan.  I was just considering one.  I am now leaning towards a small upright one.


pagan

Squirl,

In the future I'd go with an upright with a small freezer, something like the Sunfrost. We were looking at Sunfrost but we went with the Sundanzer because it is very efficient and cheaper than the Sunfrost, mainly because it has no freezer. It's difficult to say I regret the decision to go with the Sundanzer because we went four years with no refrigeration, so it's nice to have something. It's only after a year of having the Sundanzer that we're really starting to discover some of the flaws and things we do not like.

Whitlock

Sunfrost are no better than the Sundanzer I have had them >:( and you can read here-


http://www.windsun.com/General/Sunfrost.htm
Make Peace With Your Past So It Won't Screw Up The Present

MountainDon

Just because something has been done and has not failed, doesn't mean it is good design.


Freeholdfarm

When electricity goes to eighty cents per KwH, non-electric coolers might be the best way to go, at least in climates where they'll work (dry climates with cool nights even in the summer).  I've read, haven't tried it yet, that even in the summer in a climate like ours (Eastern Oregon high desert) that if you have an insulated box, put a container of water in it, close it up and keep it in the shade during the day and then open it and expose it to the night sky after sundown, that after a few days you can have ice in the water in the cooler.  (I really need to give this a try!)  So my thought is to somehow build the insulated box into the north wall of the house in such a way that you can slide it out at night and have it opened up to the clear sky.  It would need wire or something on the top to keep critters out.  Then in the morning slide it back inside under an insulated top.  Less complicated but a little more work would be to have the cooler on a covered porch and move it out from under the roof at night, taking the top off the cooler (and covering it with something to keep critters out).

There's also the evaporative camp cooler -- hang a wire cage with a couple of wire shelves in a shady spot.  Put a container of water on top of the unit, and hang burlap or cotton material around the sides of the unit with a wick to bring water to the fabric from the container on top.  You'd have to top off the water once in a while.  This one is a proven design.  My grandfather used it when camping in the summer.  It won't get things down to 40 degrees, but will keep them quite a bit cooler than the outside temperature.  Again, it's only for dry climates, though.  Won't work in high humidity.

Kathleen

Squirl

Thank you witlock. I didn't know this article existed.  It reinforces a lot of the same conclusions I was finding but was unsure if I was missing something.  

pagan

Whitlock,

Nice information, thanks.

Freeholdfarm,

I like the idea of a spring fed cooler.

RainDog

Quote from: Freeholdfarm on January 19, 2010, 04:10:51 PM
a climate like ours (Eastern Oregon high desert) that if you have an insulated box, put a container of water in it, close it up and keep it in the shade during the day and then open it and expose it to the night sky after sundown, that after a few days you can have ice in the water in the cooler.  

It freezes at night in the summer there? Wow.
NE OK


Freeholdfarm

Quote from: RainDog on January 19, 2010, 05:48:32 PM
Quote from: Freeholdfarm on January 19, 2010, 04:10:51 PM
a climate like ours (Eastern Oregon high desert) that if you have an insulated box, put a container of water in it, close it up and keep it in the shade during the day and then open it and expose it to the night sky after sundown, that after a few days you can have ice in the water in the cooler.  

It freezes at night in the summer there? Wow.

It does freeze at night in the summer here, sometimes.  But freezing temperatures aren't required to make this work, just significantly cooler temps than during the day.  Something about opening the box up to the night sky removes the heat from it, then you close it up during the day.  You have more heat loss overall than heat gain, so eventually it can get down to freezing inside the box.  Like I said, I haven't tried it yet, but I do plan to.  It makes sense, based on what I've seen here with animal water buckets in different locations.

Kathleen

Pritch

Has anybody tried using a Navacool with added insulation like suggested Backwoods Solar(and used in the Coyote Cabin)? 
"The problem with quotes from the internet is that they're not always accurate." -- Abraham Lincoln

RainDog

Quote from: Freeholdfarm on January 19, 2010, 06:52:34 PM

It does freeze at night in the summer here, sometimes.  But freezing temperatures aren't required to make this work, just significantly cooler temps than during the day.  Something about opening the box up to the night sky removes the heat from it, then you close it up during the day.  You have more heat loss overall than heat gain, so eventually it can get down to freezing inside the box.  Like I said, I haven't tried it yet, but I do plan to.  It makes sense, based on what I've seen here with animal water buckets in different locations.


  ;D
NE OK

Whitlock

Make Peace With Your Past So It Won't Screw Up The Present

Whitlock

Make Peace With Your Past So It Won't Screw Up The Present



Freeholdfarm

Quote from: Whitlock on January 19, 2010, 09:30:04 PM
Or this might be fun to try-

http://www.communicationagents.com/chris/2004/04/14/cool_fridge_without_using_electricity.htm

Or if you could find one of these-

http://aussiethings.biz/coolgardie-safe/

Or build one of these-

http://en.wikipedia.org/wiki/Qanat#Cooling

The coolgardie safe is like the camp cooler that my grandfather used to build.  The Qanat is pretty cool, pun intended, LOL!  I read a couple of pages about them; it sounds like the only reason some of them are no longer in use (in some areas) is because drilled wells lowered the water table too much. 

Kathleen

pagan

Whitlock,

The spring fed cooler will work best for me as I have a deep spring on my land with water coming out of the ground at 38 degrees F., even on the hottest days of summer. Thanks for the links.

Dave Sparks

This is fairly new but it comes very close (now testing) to the holy grail!
The grail being a unit that can run only when the sun is out or have holding capacity for 20 hours. It will happen someday!

http://www.stecasolar.com/index.php?main%7Ccat465bf98204a48_0%7C2
"we go where the power lines don't"

Squirl

Quote from: pagancelt on January 20, 2010, 08:35:03 AM
Whitlock,

The spring fed cooler will work best for me as I have a deep spring on my land with water coming out of the ground at 38 degrees F., even on the hottest days of summer. Thanks for the links.

In the old days, people built a spring house.  They put food in Jars in a shallow trough that the spring ran though. 

pagan

I've been running some numbers on our Sundanzer. The literature claims the 5.8 cubic foot refrigerator will use 90 watts or 3.2 amps per day. This is empty with an outside ambient temperature of 70 degrees Fahrenheit. Our Sundanzer is full, but everything has been cooled and it was not opened while tracking run times. The house was kept close to 70 degrees.

First off, since this is a DC unit, I have no method of finding out what it's really using when it runs. Last Sunday, Feb. 5, we were at float and it was very sunny so there were no amps coming in from our panels. The refrigerator came on and the charge controller registered 3 amps, actually it was bouncing between 3 and 4 amps and when the fridge shut off the incoming amps returned to zero. This leads me to believe when running the Sundanzer is consuming 3 to 4 amps per hour. I just used 3 amps for calculating consumption, so it's probably slightly higher in reality than what I've calculated.

OK, the Sundanzer runs from between 39 minutes to 35 minutes 4 times in a twelve hour period. It's strange because it will be off for 1 hour 53 minutes, then run for 37 minutes, then it'll be off for 3 hours 32 minutes, then run for 39 minutes, and then be off for 1 hour 46 minutes. The times for running and off change by a few minutes each cycle, however the short off...long off...short off cycle is consistent. I've been watching the fridge for the last week and this cycling is consistent. The interior temperature of our house varies slightly but I try to keep it between 68 and 72 degrees when I'm tracking the fridge and it's fairly easy to keep the house reasonably consistent while I'm at home. These temperatures aren't too far off from Sundanzer's ambient outside temperature for their literature. In twelve hours it runs 4 times for 39: 37: 36: 37 minutes each time. Since I don't want to stay up 24 hours I've just doubled these numbers for a full day.

Using these numbers I've calculated our Sundanzer uses about .05 amps per minute while running, which means it uses 7.45 amps in a twelve hour period, and 14.9 amps daily. Our system is 24 volts which means our Sundanzer is using 357.6 watts per day and 130.52 kw per year. Not even close to the 3.2 amps/90 watts daily consumption Sundanzer claims.

Our Sundanzer performs far better than most refrigerators currently on the market, although it's difficult to quantify as most refrigerators also have a freezer and we do not, but it's still a far cry from what Sundanzer claims.

These are real world numbers and not what can be produced in a factory laboratory by engineers. Hope this helps some of you.


MountainDon

You piqued my curiosity when I noticed some of your terminology was used incorrectly. What caught my eye was the reference to using 90 watts or 3.2 amps per day. The figures of 90 watts or 3.2 amps as a measure of power use is incomplete without a time reference, as in watt-hours or amp-hours.  Referring to the Sundanzer website one sees that they rate your model at a daily energy consumption of 77Whrs / 6.5AH. That is 77 Watt-hours or 6.5 Amp-Hours at a rated 12 volts. That 90 Watt-hours figure belongs to the larger model refrigerator.

Your statement "Sundanzer uses about .05 amps per minute while running" also threw me. The number of amps used is a constant. So I wondered if your methodology was faulty. I got out my paper, pencil and calculator.

It is important to note that WATTS are a unit of power and WATT-HOURS are a measure of energy consumption.

Okay, there's no argument about the time though. You measured the time the unit was on at 39 + 37 + 36 + 37 = 149 minutes in a 12 hour period. It's safe to say that in a 24 hour period the use would be 149 x 2 = 298 minutes. Divide that by 60 and we have 4.9666 hours. Close enough to call it 5 hours run time in a 24  hour period.

The charge controller was indicating 3 to 4 amps being pushed through to the batteries and whatever devices were running off the batteries. For simplicity let's say that the refrigerator is using 3.0 amps; the same figure you used. We will assume that current draw is even. There may be a surge when the compressor motor starts but we'll ignore that. Something else we'll have to ignore is the variable speed nature of the Danfoss compressor. There is an electronic control that can vary the motor speed; that would cause the actual power used to be higher or lower at certain operational times. That sort of confuses the issue. Nowhere in the Sundanzer info can I find an actual power rating on the compressor, other than there claim of so many watt-hours or amp-hours per day of energy consumption.

Note: some test meters have a 0 - 10 amp range for measuring current use. If you were to hook up such a meter in one of the power feed wires you could measure the actual amps used. The meter would be inserted in series in one of the power leads. All power used would pass through the meter and be measured. That would provide more accurate actual power use figures.

If we assume your Dandanzer is using 3 amps at 24 volts that is equivalent to 3 x 24 = 72 watts. It runs for 5 hours per 24 hour day. That comes out to an energy consumption of 360 Watt-Hours, which is much the same as the figure you came up with, except your terminology was simple "watts", no time factor included.

I am surprised to see such a large discrepancy in the factory numbers and your test. It would not surprise me to see some variance, but to see 4.6 times more energy used than their rating does seem to be a bit on the outlandish side. What was the interior refrigerator temperature? Sundanzers STC has the interior at a reasonable 38 degrees. Was yours significantly colder? I think that is unlikely. So that leaves the amp reading as suspect. 

My thought is that using the current indication on the charge controller is wrong. I believe that is not indicating the actual number of amps being used by the Sundanzer, but is inflated somehow because of the batteries being there in the circuit. One would think that if the charge system is sitting there on float with the refrigerator off, that the charge controller meter would indicate the correct power actually used. Perhaps that is not a correct assumption.

OR the only other conclusion must be that Sundanzer has been totally fraudulent in their representation of the actual power use. It's too bad the Energy Star tests do not include DC model refrigeration. At least there the test conditions used are the same for all the rated units. But they only test 120 VAC.


It would be most interesting to see the actual amperage draw on a test meter hooked into the power line to the refrigerator. If you have the means to make that measurement you could remove any doubts from your test.


Oh, I found a discrepancy in the Sundanzer info. Their residential system sizing PDF download shows an energy consumption of 117 watt-hours per day on that refrigerator, at 70 degrees room temp. Using that you're estimated use is better, but still a long ways off. That is 3.08 times as much energy as they state.


So in closing, you came up with the same answer as I did, but used terminology that was confusing.



Just because something has been done and has not failed, doesn't mean it is good design.

pagan

Don,

Thanks for responding to my post, I was hoping I would get some input from you or Glenn. After I hit submit I saw I had not put in the "hours" for my amps and watts. I was just too lazy to go back and correct my post, sorry about that. It's supposed to use 77 watt hours or 3.2 amp hours at 24 volts dc daily and because my numbers are so vastly divergent from Sundanzer's literature I'm questioning my methodology. My assumption is that if at float with no amps coming in from the panels the only draw would be the fridge, and when the fridge shut off the charge controller returned to zero amps coming in from the panels so another assumption is nothing else was drawing electricity to affect the amp reading on the controller. There were no other loads at the time I was checking the charge controller and the Sundanzer is the only DC appliance we have. The interior temp is roughly 38 degrees. Slight variances in temperature should not account for such a huge discrepancy, however, so I'm thinking, like you, the amp reading through my charge controller is inflated. I have an amp meter at home so I'll try that to get an accurate reading on what the fridge uses when running. Should I just clip it to the positive and negative power lines for the fridge and wait for it to come on to get my actual 24 vdc consumption?

MountainDon

Hook up with the meter would be something like this. If the meter has provision for measuring amps there will be terminals for that use.  One terminal may be marked COM  and the other 10A or 10ADC. Something like that. If the polarity is connected wrong asome meters won't work, other will auto sense and set themselves.

Just because something has been done and has not failed, doesn't mean it is good design.

pagan

Thanks Don. I'm pretty sure my meter has a setting for amps. Hopefully I can get to this tonight. If not it might be a few days, but I'll post my findings.

pagan

Sorry this took so long, but I found out my Craftsman multi-meter had a blown fuse and I had no spares. Couldn't get one locally, even at the Sears store, so had to wait until I was in Williston. Even then I got the last fuse set the Sears there had in stock.

Enough of my problems. Thanks Don for all of your help and insights. Here are the numbers.

When it initially starts it will surge to 2.4 amps, but this is for 1 second or so, really just enough to actually see it on the meter. After the surge it comes down to 1.6 to 1.8 amps. It will hold steady at 1.7 amps for 10 to 15 seconds at a time, so this is the number I'm going with.

1.7 amps while running.
5 hours per day run time.
8.5 amp hours daily consumption.
24 volt system.
204 watt hours daily.

It looks like the numbers I was using from the charge controller must have some system losses in it, or it was trickling some into the battery bank. Either way I'm much closer to what Sundanzer provides for consumption, however I'm still using more energy, just not as much as I initially thought. This difference could easily be attributed to my house being a little bit warmer than Sundanzer's test conditions.

Does this look about right, Don?