Using a small chest freezer as a fridge
 

Saw an article one day about a guy in Australia that uses a small chest freezer as a super efficient fridge by using a bypass thermostat to cut it off when the temps get down to 38-40. He claimed the electrical use got down to 100watt/hrs per day....which is about 1/20th of the typical conventional upright fridge that uses about 2kw/hrs day ( 2000watt/hrs ).....of course, he was using a 7-9 cubic foot model, but still, that's DANG impressive if true.....and would give many folks a way to run some refrigeration with a small amount of solar power....a single 150w panel ( w/battery/inverter/charge controller ) would be all that was needed, ( assuming 4 hrs of sun at least every 3-4 days ) instead of a BUNCH of panels...

So I ordered an external bypass type thermostat from a beer making site ( they do the same thing with a small freezer to hold beer/wine cold)

http://kegman.net/images/9025.jpg

http://kegman.net/9025.html

It's a real simple deal....you just plug it in the freezer outlet, then plug the freezer into the double plug, and stick the thermostat bulb in the freezer, and set the dial on the unit for the temperature you want. All it does is kill the power to the freezer at the desired temp, and turn it back on when it rises.

SO, I had this thing sitting on the shelf, along with a Kil-a-Watt meter, for recording wattage on a single receptacle, and been meaning to try it for a while, when Armed Peasant was over at the house one day and we got to talking. He jut picked up another small chest freezer (7cuft)to add to his "collection" and he was interested in trying this too....so he took both to his house to run some real world tests for a week or two.

He sent me the numbers yesterday, and I tried to get him to write this up, but I guess he's busy doing that rain dance due to the drought at his house......ahahaaaa....

So here's the figures:

( He ran 72 hour tests.....3 days.....so you have to divide by 3 on the watt hours to get a daily figure )

All of these runs were at an average ambient temperature of 70 F.

1. 8 cubic foot freezer at 40 F. 72 hours with start up (started with freezer Temp. of 70 F.) and did not open freezer for the 72 hours used 0.57 kwh over the 72 hours. ( 190 watt/hrs/day )

2. 8 cubic foot freezer at 40 F. with no start up (started with freezer temp of 40F.) did not open freezer for the 72 hours used 0.51 kwh over 72 hours.
(170watt/hrs/day )

3. 8 cubic foot freezer running as a freezer at 0 F. no start up (started at freezer temp. of 0 F.) did not open freezer for the 72 hours used 2.88 kwh over 72 hours. (960 watt/hrs/day)

4. 8 cubic freezer at 40 F. no start up (started at freezer Temp. of 40 F.) normal use opened freezer 3 times a day just long enough to put food in or take food out. Used 0.89 kwh over 72 hours. (297watt/hrs/day)

5. Small dorm size refrigerator at 40 F. no start up (started with Ref. Temp. of 40 F.) normal use opened sames as above freezer run. Used 1.78 kwh over 72 hours. (593 watt/hrs/day)


4 and 5 were the most interesting to me. #4 shows the way you would "typically" use fridge....open, close, etc. This model ran 3 times what the Aussie guy claims, but STILL very impressive compared to a normal fridge in terms of power consumption.

#5 is also very interesting, considering the small freezer is probably twice the capacity of the little dorm style fridge, but the dorm fridge used almost twice the power.

So, there you have it.

Any questions, ask Armed Peasant.

Re: Using a small chest freezer as a fridge
 

Andy

Had a thought that may come into play
Australia uses 220 volts and as you know if you double the voltage you half the amps.
So the author's figure may be right for him.

If a device uses say 20 amps at 120v, it will use 10 amps at 220v
likewise the reverse is true.

The bypass device looks like it cuts power usage by a bunch of watts.
And that add up to a great savings over time.

Just a thought.

Re: Using a small chest freezer as a fridge
 

Hey Andy, thanks for the info, I'll try to understand this very simple application into my non electrical pointy little head and also print out this stuff for future reference...whew! that only took 5 minutes to type...
Once again thanks my old friend...

Re: Using a small chest freezer as a fridge
 

This would be really handy during a extended power outage situation. That wattage is something attainable with a few batteries, inverter and a couple decent solar panels.

hmmmmmm

May have to add to my list.

Right now i am trying to accumulate parts for a water storage system utlizing an rv type 12 volt pressure pump, a whole house filter, and a 300-500 gallon tank.

Re: Using a small chest freezer as a fridge
 

Watts are watts.

Amps x volts = watts

20amps times 120v = 2400 watts
10amps times 220v = 2400 watts

Only thing higher voltage does is allow you to run smaller wire/fusing......you will use the same amount of energy no matter which way you go.

Re: Using a small chest freezer as a fridge
 

Don't you hate those early morning

BRAIN FARTS?????
I know I do...:biggrin:

Thanks Andy..

Re: Using a small chest freezer as a fridge
 

All,

There is only 1 reason for power consumption....and that is "loss or cooling"....which in thermodynamics really means freezer/fridge gaining heat. Heat flow goes from hot to cold.....

Ever think of making a super insulated chest freezer?

Biuld a nice wooden surround - but make sure there is a way for the heat exchanger to reject heat out of the surround. Also a well insulated lid/cover. even fill the walls between the surround and the metal freezer with foam....

The existing freezer chest wall is only a few inches thick....it needs more insulation....

You might be able to cut power needs to a very small ftaction.....down to just 20% or even less?

I once thought about making a super insulated walk-in...with 2 foot thick walls floors, ceiling.....adding a bunch of thermal mass - like barrels of brine, or my 7 tons of copper pennies.....barrels of fresh water.....open it up to the outdoors on the few cold winter nights in Michigan where we get below zero.....get everything nice and cold and try to make it all summer. Like an "Icehouse" but I would not have to cut/haul ice from a lake.

If it was well insulated enough I might be able to keep it cool with a small freezer hooked into the wall and open to the cold room. The back of the little freezer cooling the big room would have to be well insulated - as mentioned above.

Let me do some calculations on how many tons of water at say 0F I'd have to hoard away in my cold room using some basic power assumptions......I'll be back in a bit.

Re: Using a small chest freezer as a fridge
 

I noticed quite by accident if I placed a sheetof 3/4 extruded polystyrene foam on the lid of my freezer that after a few hours passed, if I put my hand between the foam and the lid, the lid seemed VERY cold.

I am now accumulating adhesive magnets and plan to make a 3/4 inch 'stick on' blanket for my freezer. cheap, easy, and doesn't look too bad.

>>Oh and for everyone else, during an extended power outage, put as many blankets on top of and around your freezer as possible. This REALLY helps keep things frozen. (learned during IKE when our genset went splat)

Re: Using a small chest freezer as a fridge
 

QWAK,ruprick,I turned a 1902 "ICE BOX" in to a modern refrigerator about 30 years ago. Worked fine BUT the DOOR gaskets on the oak wood box were never totaly air tight :452: and It would have been better with 2" more foam!:yes:

Still got IT too :yes: I need to resolder a refrigerent line that broke moving it down 3 floors and back up 3 floors back in Chicago. One of my "Round to it projects"! :wink:

The main diference in the efficiency of freezers is in the thickness of the foam insolation :yes: I bought a cheep small freezer at Lows 2 years ago and recently noticed that the TOP is some times cool enough to have condensation so OBVIOUSLY not enough insolation. I will likely just cut a piece of 2" high dencity foam insolation to place on top to increase efficiency -- another "ROUND TO IT " project! :yes::4_1_72:

the DUCK :15_1_70v:

Re: Using a small chest freezer as a fridge
 

Re: Using a small chest freezer as a fridge
 

not that most don't already know this ;

opening the fridge door let's the cold air fall out, as opposed to a chest type fridge/freezer. a bigger factor than most think.

Re: Using a small chest freezer as a fridge
 

I cycle in water jugs when the freezers get a little empty. Just a touch of insurance for a bad power day.
I've often wondered about gluing insulating foam board (structural foam?) to a freezer for S&G's. Haven't found anybody who's done it and taken readings to see if it is worth the effort and expense.

Re: Using a small chest freezer as a fridge
 

Blue Ice,

Not really about dollars and cents savings....you'd have to be doing an apples to apples comparison of the same cubic foot upright fridge to this chest freezer.....and even then, I suspect from a current dollar cost, you'd never come out. Say you saved 500 watt hours over a small conventional upright.....that's 1/2 a KwHr per day.....about 5-10 cents/day most places in the US......you'd probably never even pay for that separate thermostat, much less buying a freezer.

But a dollars and sense savings is NOT the point of this experiment......

The point is: IF the S-were-to-hit-the-fan, and grid electricity subject to rolling blackouts, or be gone entirely.....you COULD have some basic refrigeration with a minimal amount of solar or wind electrical production....

At that point, being able to keep food cool would be PRICELESS.

Re: Using a small chest freezer as a fridge
 

At 10 cents a day that's 36.50 a year with a life of 6 years ($219) you could pay for the chest freezer and thermostat.
With the foam padding payback could be sooner?

Re: Using a small chest freezer as a fridge
 

Buddy of mine did just this mod.

I forget how much it cost, but reasonable enough for
him to turn a small freezer into a beer cooler in his
home. A small keg nicely fits right inside. He also
nitrogen charges the ale for that creamy draw.


Warning, make sure you call the manufacturer of
the freezer to learn where the coils are in the lid
before drilling for the tap.

Re: Using a small chest freezer as a fridge
 

Haven't had the occasion to test or rely upon them in the real world as yet, but earlier this year I purchased for my personal use these units:

Engel MT 60-Combi

Viking Odin

Not cheap (a little over $4600), but in my overall preparedness budget, a worthwhile line item. Both are robust and versatile, not to mention portable.

Re: Using a small chest freezer as a fridge
 

A FYI, the foam insulation with the highest performance per inch thickness is extruded polystyrene (as opposed to expanded polystyrene aka 'Styrofoam' or beadboard, the same stuff you see coffee cups or throw away ice chests made of). The two manufacturers of extruded polystyrene are Dow (the blue sheet aka 'blueboard') and Owen Corning (the pink sheet). R value of extruded polystyrene is ~7 per inch. If you want to wrap your freezer or fridge with insulation, extruded polystyrene is your best option. IMO you'd be wasting your time with anything else.

There's also another high performance foam insulation available in board form called poly-isocyanurate. When manufactured it has a R value of ~7 per inch, but within a year or two it will experience thermal drift where the R value drops to about 5 or 6 per inch.

There are other high performance foam insulation options but they are not practical for a freezer or fridge as they are sprayed on and unless one has a buddy who's in the business it would be cost prohibitive anyway.

Re: Using a small chest freezer as a fridge
 

A very important thing to remember when trying to add insulation to a chest style freezer, or even some other refrigerators.
The refrigeration cycle has a low pressure/cold side, and a high pressure/warm or hot side.
The condensing units on many of these chest freezers, are just under the outer skin of unit, and you can determine if this is the case by running your hand on the outside painted surface around the box while it's running. If you feel "warm" spots, then this is the style you have. you cannot add insulation to these types on the outside, as it will not be able to reject the heat to the surrounding air. The compressor relies on being able to reject that heat, or the "head pressure" inside the refrigeration cycle (refrigerant pressure) will become too high, the compressor will draw too many amps, keep heating up and toast itself prematurely, It's called a "burnout" in refrigeration land. The compressors rely on some relative amount of cooling effect from the refrigerant on the suction side of the compressor, coming back from the evaporator.
Similarily the evaporator side (cold) can be built much the same just under the metal or plastic liner inside the box. So if you add insulation, you could hinder the performance of the freezer, where it cannot pick up the heat.
it might be ok to add the extra insulation where there are no evaporator or condenser tubes under the skins of the box, however keep in mind the tubes under the skin are touching the metal skin on the outside, and rely on heat transfer of metal outer skin to reject the heat to the surrounding air, in other words, the painted metal skin is essentially the large surface area to reject the heat gathered inside the box.
You can determine if you have an imbedded condenser too, by looking at the mechanical compressor device, and see if there are any coils etc that reject the heat (remember old refrigerators had those black wires and tubes on the back that got warm?) If there are no external condenser coils showing, and the "discharge line" (hot one while compressor is running, almost too hot to touch) of the compressor is going back into the box somewhere, it probably has an embeded condenser.
I would avoid adding extra insulation in the manners talked about here. You are already winning by a factor of 10 to 20 over an upright, and this is pretty good.

Great idea on using the chest feezer with bypass stat to keep it "warmer" than freezer temp. One of the greatest advantages of chest refrigeration or freezing is that "cold air is heavier than warm" you do not lose your "Cold air" each time the lid is open. upright freezers or refrigerators are horrible in this regard because the cold air spills out each time you open it.
Maybe this is covered above, but I didn't get to read the whole thread. Keep in mind too, that starting load amp draw on a refrigeration compressor is usually very high, and yes if you average the run time/watts ratio out over time it's very good, but you will still need 120v power plus some number of amps to start the comp. Maybe it's assumed when you use solar that you have a battery bank, but I just wanted to get a little clarification from TNAndy about that.

Re: Using a small chest freezer as a fridge
 

high density polystyrene min R-5 --max R-5.4 per/in
low density is significantly lower

poly Iso new min R-6.8 per/in
aged min R-5.5 per/in

I just wanted to clear up your implications that poly Iso age's to a R factor below comperable polystyrene, at no point does poly iso underperform same thickness polystyrene

the actual stats above are from wiki

Re: Using a small chest freezer as a fridge
 

Yes, you will need a battery bank, and enough of an inverter to handle the start up of the compressor......can't skimp there.....but my point was you won't need TOO much solar panel space to provide the power thru the battery bank compared to a conventional upright.

Re: Using a small chest freezer as a fridge
 

lessoil is 100% correct on this one, it's the style of fridge, chest versus upright that gives you 90% of your efficiency savings. The heavy cold air sits in the bottom of a chest freezer/fridge where it belongs. The insulation only counts more if you never open it. (Not too likely in real world situations.)

Re: Using a small chest freezer as a fridge
 

http://goldismoney.info/forums/showthread.php?t=390259

Re: Using a small chest freezer as a fridge
 

Good information Andy. Thanks.

Re: Using a small chest freezer as a fridge
 

one other quick note regarding freezer/refrigerator modifications.

I've seen a few units ruined when customers in my plant tried to screw into the sidewall of a freezer/refrigerator, and pierced the condensor line just under the sheet metal. Keep this in mind, be sure you determine which type you have.
There is no good way to fix a problem like this, as most of these devices have a hermetically sealed compressor/refrigeration circuit. It would cost way more to repair this type damage than to just buy new.