How to Convert a mini fridge to a chest refrigerator

It's just awful that when I open my refrigerator, all the cold air falls out. This makes me sad. So, I turned my refrigerators word upside down, or at least 90 degrees. Now, when I open the door, more cold air stays inside and this makes me happy - it increases my quality of life in fact.


For the rest of you with a large refrigerator.... I, and my partner in crime have something cooking for you. But, it's going to take a month or so as I want data showing this big refrigerator modification works. As you read meters are whizzing and collecting :)

Step 1: Aquire Fridge

This particular model was discovered in the annals of the UCF dumpsters during dorm move-out. The funny thing is, it was found, in the dumpster, with ice inside.

Comments

[VadimS]

I know this is old, but I thought I should point out, no fridge uses suspended lubricant, they are all oil bath (any suspended lubricant would significantly reduce efficiency). That being said, the oil isn't that thick, and there's no need to leave it overnight, a couple hours will do nicely.
Also the reason for letting it sit is not so it doesn't run out of oil, but because if the lines get full of oil (as it's so much thicker then the gas) it could clog the expansion valve, and that could damage the compressor.

The small compressor on a fridge hold abought half a litter of (usually mineral) oil.

[VadimS]

Bit of a mistake.
r12 and r22 systems use mineral oil, r12 was banned in 1995, but r22 is still used (supposed to be phased out by 2020), but most companies favor r134a and it uses peg oil.

[EnterprisingRedHen]

Great Idea. thanks for the instructions. I want to apply this to my large family fridge. How did you go with your large fridge data and conversion. I could not find it on the site.

Have you posted anything further in relation to that?

thanks for your great contribution.

[whalenmd]

Thanks for the instructions. I build mine last night, and decided to take someone's advice by building a wood frame for it to sit on. I didn't have any shelves in it before, so I increased my capacity from about 14 to now over 50. Needless to say, I'm excited for the Super Bowl.

[whalenmd]

I decided that I needed some storage system for a warm beer "on deck" rack. This is what I came up with:

[Dr.Bill]

By the way. Where is the heat exchanger on your fridge? Mine is on the back and I'm wondering if it is possible to do my fridge this way.

[trebuchet03]

Potentially?

Here's what I've learned.... You need a  measuring device - like a Kill-a-Watt or similar.

1. Monitor power consumption during normal use - upright. Do this for at least a week to get smoother and potentially more reliable data (longer is better)
2. Reset the measurement and repeat for the same amount of time, but this time empty the fridge and throw in a 1 or 2 gallon jugs of water (to make up for missing volume) and DO NOT open the door.

Compare the consumption for these two tests.

At the end of the day, for this mini fridge - there was no difference :( It always consumed a LOT of power (nearly 1.5KwHrs/day - the same as our main apartment big fridge!)

My reasoning as to why this is the case? Thermal mass. Air doesn't have much mass compared to the rest of the cold objects and as a result doesn't carry much of the "coolness." For example, if there's .25 pounds of air* in the fridge, and 75 pounds of food and cold refrigerator mass, the air in that fridge makes up 0.5% of the chilled mass.... And that doesn't even take into consideration actual thermal mass (which is material dependent).

------
To answer your other question
Th condenser is in the skin ;) Should you ever take one apart - and I don't recommend it :p You'll find copper tubing behind the outside metal skin... Super inefficient - but extremely cost effective from an mfr perspective :p

------
At the end of the day, these small refrigerators aren't very energy efficient (your measurements may vary) :p

[Dr.Bill]

I've got one of these fridges But it has a heat exchanger on the back.

Can this still be done with what I got ?

[Randy Lahey]

letting it settle is definately a good idea.  the compressor itself sits in an oil bath as seen here http://www.youtube.com/watch?v=MxWoNjvLZWY&feature=related and that oil is what has to settle.

[Randy Lahey]

very good idea by the way.

[trebuchet03]

Thanks :)

As it turns out, it really doesn't matter in this modification - just as long as the compressor is upright during operation....

Why?

Looking at the orientation of the evaporator (and condenser) - gravity isn't going to allow anything to get back into the casing...

Oil shouldn't be able to get out of the HP side... and most compressors have a muffler connected to the suction inlet - so I'm not worried :) Even if some does escape via the suction side, it's going to get pulled through fairly quickly :)

This is mind, I didn't wait to fire up this refrigerator - and the compressor worked quite well until I stopped using it due to it being superfluous :)

[goiden]

Hi we bought a thermostat of ebay to convert a chest freezer  into a refrigerator and it works fantastic, the motor hardly ever runs and it stays icy cold, we live off solar power so we needed a large chest  fridge that would hardly use any electricity as we use it for storing  milk and fresh produce.    
it only took 5 minutes to change the thermostat over and we didnt have to modify anything just swapped the thermostat as it looked the same as the thermostat we pulled out , we looked at other ways to do a freezer into a fridge conversion and  this was by far the easiest way  
we bought it off    freezer2fridge  in Australia
http://cgi.ebay.com.au/Turn-a-Freezer-into-a-Fridge-Thermostat-Kegerator-Solar_W0QQitemZ160372777342QQcmdZViewItemQQptZAU_Home_Appliances?hash=item2556f6617e

[stgagnon]

Hey, this is a great project. Thanks for posting it.. Does anyone know if a similar technique could be used to turn an upright freezer into a chest freezer? Also, is there any news about turning a standard sized fridge into a chest fridge? Thanks, if anyone is still listening.. Suz.

[contest]

You can check this link out - http://mtbest.net/chest_fridge.html -
Great efficiency for the chest frig!

[withalligators]

Quick question...Do you mean face the top of the compressor towards what will be the new top (ie opening) side of the fridge? You state to face it towards the bottom. I just want to clarify. Thanks!

[x2percentmilk]

Finally some nice simple instuctions. Thanks :) But I do ahve one question. On the inside-back of my mini fridge (or what will be the inside-bottom, im making a chest ferezer) I have a what looks like a smiple pc-style fan and behind that some type of opening. I assuming thats to flush the cold air into the fridge, and covering it up with boxes of frozen food doesnt sound like a good idea. Anyone have any ideas?

[overhyped]

you've probably got a peltier based minifridge - these are nice, but not as powerful. You will need to provide good ventilation space (add legs or something). peltier frridges "pump" the heat out - hence the fan, and (assuming there is one in there) a heatsink. --- or atleast thats what I thinks going on hope that helps! ---

[x2percentmilk]

Awesome, Thanks for the info =)

[spamattakky]

What you really need is to add more insulation. You need to know where all the cold and heat panels so not to cover them and insulate what you can. I have a solar power chest refrigerator and it has 10cm of insulation. Now only if I can find a way to wick the moisture out, since it stays in. Any suggestions?

[nate12680]

Spamattakky, maybe to help with the moisture those packets that come in shoe boxes and beef jerky packs that say "do not eat". They are for moisture control I think. Dont know if this is bad for your health though.

[NobodyInParticular]

By the way, the white silica gel desiccant packs are usually totally nontoxic. They consist of something like extremely fine glass dust compressed into beads. The non-food ones may have some insignificant amount of fungicide added. Of course, if you ate a few pounds, I suppose the gel could swell uncomfortably in your gut.

[benner81]

It is definitely a good idea to let the compressor sit upright for a few hours to make sure liquid refrigerant settles where it's supposed to be. If you turn it on right away, it can be hard on the compressor.

[zipperboy]

Nice job. As saites2001 says air circulation means better more efficent cooling. If I build one of these, and it is likely at some point. I would add PVC legs and bring it up off the floor to a level to allow grabbing a beer by the neck with the arm hanging down in a relaxed manner. This would also provide a storage area for empty cases. For the fussy for looks crowd, a curtain of mesh fabric could be added to hide the cases from view while allowing air to circulate.

Cheers, zipperboy

[icemachete]

My dad made one of these.

[saites2001]

Very nicely done. I have a similar fridge, and I've always thought about the design seeming rather poor. Since I have a microwave on top of mine, I won't convert mine, but I'll keep it in mind when I have more space. I would imagine you would want to add spacers whether or not it fit back in, as doing so would allow air to move freely. In the instruction manual for my fridge, it recommended keeping the fridge a certain distance from any other objects for this purpose. Good job, once again.

[trebuchet03]

I would imagine you would want to add spacers whether or not it fit back in, as doing so would allow air to move freely.
I've considered adding a fan to the compressor area - to blow off some heat as it does get rather toasty.

it recommended keeping the fridge a certain distance from any other objects for this purpose.

I've taken apart refrigerators like this -- and found that the condenser is located on the top and sides of the refrigerator. And what really sucks is that the condenser is just copper tubing - not very efficient from a heat transfer standpoint. BUT, putting these things back together after taking them apart is pretty much impossible - so modification isn't a viable option :/

[codmac]

ACTUALLY, COPPER TUBING IS A PREFERRED FOR THE CONDENSER BECAUSE OH ITS HIGH COEFFICIENT OH HEAT TRANSFER. THE CHEAPER UNITS USE STEEL TUBING, IMPROVING ITS HEAT TRANSFER RATE BY SPOT WELDING TABS TO THE TUBING AND STEEL SIDE COVER. UNFORTUNATELY, THE SPOT WELDS SHOW THROUGH THE SKIN, REQUITING ADDITIONAL FINISHING STEPS.

[trebuchet03]

Copper does have good thermal conductivity - but good thermal conductivity is not the only factor that makes a good heat exchanger. Really, the only refrigeration device I can think of that has such a primitive heat exchanger/condenser is a modern mini fridge (older ones are even a step up with bar finned external condensers).

Here's a nice write up on heat transfer with the introduction of fins - [http://www.tech.plym.ac.uk%2Fsme%2FTHER205-web%2FHeatxs3-fins.PDF&ei=GL_NSLeSGJXmvQWl64DVAw&usg=AFQjCNFgYd7qKSsMrJq0PLBx993l4A-JZQ&sig2=Dlc-7rUPFvXDleahLxqwbg PDF Link].

All that and you should really turn caps lock off ;)

[Esmagamus]

Now that you've got a nice place for your booze, I'll suggest some modifications I'd make if I had a freezer of my own: -Add a 12V transformer and relay set-up. -Pull a line from the transformer to the inside of the refrigerator and place a 80 or 120 mm, high-speed computer fan pushing hot air to the inside of the evaporator, so as to get some very cold air flowing inside at high speed. It seems that beneath the control box would be a nice place. -Pull another line from the transformer and use a relay connected to the motor. Place a fan blowing the hot air away from the condenser outside, so as to make your refrigerator work twice as better (at least mine does, since I've made that mod). The relay will switch the 12V fan only when the 110/220 V motor is running (this way you don't need two transformers). -Add a drain plug. This way, spills are easier to clean and you can also partially fill your Booze Chest with brine, that makes heat transfer way faster than air. Just make it with about 26% salt. That stops it from freezing down to -20ºC. -Last: add more booze and have a party. And have a beer for all of us!

[trebuchet03]

Here's what I've done on your modifications list... -12V power - check (well, 7V actually, the fans are more quiet and they're still effective despite the lower cfm) -80mm fan inside and outside - check Can't really do much about the condenser - it's built into the sidewalls. From prior mini fridge disassemble, there's not way to get at them without destructive means. The mfr's build the fridge, place the shell over it and then inject expanding foam. It's decent for insulation, and cheap, but it locks everything into place :/ The fan I have outside is to blow air over the compressor and away from the fridge, which does get hot. Other mods... I unplugged the thing and stopped using it. I stored groceries in there for awhile, but the power usage of the mini fridge is almost the same as the full sized apartment one when used normally.

[Esmagamus]

Pitty... Condensers on the outside give much more improvement possibilities. The suggestion of using 12V was based on the fact that 12V transformers are easy to come by. There's even the new solid state 60W 12V transformers that are much more energy efficient. Still, you've got a nice refrigerator for any party you want to make. Have fun.

[erwin]

I always thought that if the compressor of a fridge is laid sideways, the oil may not be circulated the right way and the compressor will burn out. I only would try this with a really old spare unit.

[trebuchet03]

Reading is fundamental.... Step 3 covers that and it's very visible in the pictures in step 5... etc. etc.

[gbots]

I live half-time in a remote area of Central America on solar. I thought about this idea as a but wanted to include removing the coils from the back, submerging them in water to help with heat dissipation and adding a bunch of insulation too. Can anyone give me an educated opinion of the potential effectiveness /ineffectiveness of this idea?

[Mr. Smart Kid]

cool idea / use

[LancePenney]

This sounds like a good idea, I'll definitely try this if I come across a cheap mini fridge. BTW: You do have to wait to plug in a fridge after its been tipped over. I blew the compressor on my deep freeze once after I tipped it to clean it out. I herd you should wait at least 24 hours.

[LowEnergy]

It would be interesting to see the results of your power monitoring. But how will you know whether it made an improvement? (I'm assuming you don't have data from before the mod.) I suppose you could simply wave a piece of cardboard around to blow the cold air out to simulate the effect of opening the door, and compare that to the performance without doing that.

[trebuchet03]

In my want to "do" a project/make something... I did not get baseline data :/ I can report, however, that after 23 hours and 54 minutes... The unit has consumed .74kWh of energy - including start up power. I've read elsewhere that these refrigerators tend to consume about 1.5kWh per day (not sure on the validity, but this seems reasonable). I believe that the more you use the refrigerator, the more efficient it will be. That is, if you keep it closed all the time, you're not going to see much difference. But, if you're using it frequently, it should shine as the more efficient configuration. Perhaps I should take the beer out and put groceries in :p

[kill-a-watt]

Oddly enough, with my own Kill-a-watt and my own dumpstered mini-fridge, I found that total power consumed exceeded the total power used to keep my standard sized fridge cold. Let me restate that. The mini-fridge filled with a reasonable amount of canned soda cost more to run than my full sized fridge (filled with standard food too). Sorry, I've misplaced the data, but I'll rerun the experiment when I get my meter back from my brother. Oh and the reason why you wait before plugging back in a fridge is that you don't want the compressor trying to compress a stroke full of oil. Liquids generally don't like to compressed and you don't want to experience hydro lock. I'd also like to experiment with total watts used when one tries to beef up the outside with insulation, say with 1" pink foam board

[kill-a-watt]

item			raw KWH		raw HH:MM	KWH per 24 hoursfull-sized fridge	2.32		26:15		2.12dumpstered mini-fridge	1.67		23:51		1.68

Mini fridge was tested by loading with 18, 500ml bottles of water and running fridge for about 24 hours prior to test. Mini fridge was opened maybe once or twice during test. Full sized fridge contained my food and was opened a reasonable amount of time during the day. No A/C, mean temps for both days was about 76 °F

Although the smaller fridge did not use as much power, it used almost 80% as much as the full-sized one. It's very likely to match the larger one when it is used like a main fridge and opened throughout the day and used to pre-chill room temperature items. It's also worth noting that the mini-fridge is less than a third the size.

The larger fridge (that came with the house) is on the bottom of the energy efficency scale, but I think I calculated that for a new energy efficient fridge would have a break-even point of several decades.

trebuchet03, how's the hacked fridge doing?