mini cold box project.

I was reading a project that Dude had posted (https://www.homebrewtalk.com/showthread.php?t=14907&page=4) and thought about making a mini cold box...basically using a 1.7 cu ft. dorm fridge. The storage are would be just big enough to house 2 cornies (CO2 would be outside).

My question is...would this fridge this small be strong enough to bring 2 cornies down to the correct temprature?

Thanks,

Mike.

this is a tricky question. If the box can "maintain" you desired temperature when empty, than it is strong enough to keep anything you put inside it,(provided that this item is at target temperature) be It a huge block of lead or just air at your target temperature. Heat itself is what flows. cold dosent flow. to maintain a temperature lower than than the temperature outside the box, your fridge only has to compensate for the heat that flows through the insulation into the box from the warmer outside air. if what you put in the box is at or close to your taget temp, it will work fine.
Now if you put a large mass of warm or hot matter in the box, your fridge will still need to compenate for its own lacking insulation, and at the same time be burdoned with pumping out the heat of the added mass untill it reaches target temp. on a small fridge, this may cause the compressor to run for much longer than it;s designers ever intended. and the rate at wich it cools will probably be slower than what you intended.
my advice- cool it to as close to the target temperature and see what happens

I am hoping that I would be able to place a keg filled at room temprature and have the cold box cool it down to the 38 degrees. Presently, I have no other means of cooling the keg to the target temp.

I might just go ahead and try putting something together and see if I can get it to work. Once I give it a go, I'll post the results for anyone interested.

it would benefeit you to place a box fan blowing directly on the fridges condesor coil. (the hot snakelike tubing that zigzags across the back of the fridge). At least untill you get the keg down to temp. this will reduce the cooling time and reduce the load on the fridges compressor.

I did something like that years ago by attaching an apartment size fridge to a small chest freezer that didn't work anymore. I could easily get it down to the low 30's. Just make sure it's well insulated and sealed.

Thanks mcody2005 for the assistance and brewiz for the experience. Amy recommendations as to the type of insulation that should be used?

Check out this thread it may help.
http://homebrewtalk.com/showthread.php?t=11440

Brewiz said:

I did something like that years ago by attaching an apartment size fridge to a small chest freezer that didn't work anymore. I could easily get it down to the low 30's. Just make sure it's well insulated and sealed.

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That's a great idea. I see chest freezers as well as uprights and refrigerators that are in the large item trash pickup every once in awhile. I guess a 1.5-2.0 cu. ft. dorm size refrigerator might work?

That's what I used, it worked for about 10 yrs. I could replace the fridge part and use it to lager but I have a better idea I want to try using an full size fridge.

if you plan on building the cabinet yourself, your best bet would be Rigid Polyurethane Foam Board Insulation. this is the pink or blue sheets of foam found at home improvement stores. Pick the one with the highest "R-Value" this is the rating on how well the foam insulates. make sure that you dont use the insulation itself as the primary building material as this stuff is delicate, and dents and generale abuse will decrease its efficency. In other words, make sure the foam is sandwiched between a durable inside and outside layer( probably plywood). The smaller you make box the less surfice area it will have and the better it will work.
this project seems like it would be alot of fun, but you can grab an old chest cooler go for it! I know i would.

Thanks for all the advice, I am in the planning stages now and I making some preliminary drawings. Once I move along further I will post my progress with some pictures.

Thanks for all the help,

Mike.

Uncle Argyle said:

Thanks for all the advice, I am in the planning stages now and I making some preliminary drawings. Once I move along further I will post my progress with some pictures.

Click to expand...

Definitely do keep us posted, man. I'm a few pic's short of pulling the trigger on this project myself. If I see yours I might get jealous and just do it!!

Hey Uncle Argyle,
If you built the cold box yourself, the local big box shops Home Crapot and Lower Quality didn't have the 2 inch extruded polystyrene. I called a couple of insulation places and located the 2" stuff for about $25/sheet. One sheet was just enough for a 6.5 gallon fermenter and 6-1 gallon jugs of ice if that gives any idea of what mileage you can get from a single sheet. The 2" stuff is fairly durable and very easy to work with but I do like the idea of using 1/4 plywood for greater integrity. In my flippin' hot as hades garage in central Texas, the box would maintain a temp in the mid 60's for 2-3 days between ice changes. I imagine with a little 1.7-2.0 cu. ft. refrigerator the temp would be easily maintained at what you want. Good luck.

this thread has been tuning the gears in my head for days. Im gonna go down the the local estate sale flee market on friday and see if i can pick up a small fride with good guts. they usually have a lot crap like this for aroud 15 buck or so. the "quick and dirty" cooler i just built to lager my beer may be going into the dumpster...

It's funny that you mention Home depot not having that type of insulation. I went to their website and couldn't find insulation of any kind...

I am going to have to look around locally and see if I can track down that 2" foam board.

I will keep you all posted. Thanks for the advice.

When I built my walk-in cooler, I chose a 3/4" R5 foam board over the thicker 2" R7.8 board. You can stack it to 4 layers for R20 in 3" thickness where the other board is only going to give you R15.6 in 4". Also, don't skimp on insulating the floor as cold decends.

The cold box (the cooling area attached to the fridge and not the entire external dimensions of the kegerator) that I am thinking about is only going to be 6 cu ft. with the internal dimensions about 14"D x 24"W x 30"H. This gives about 2" space between the kegs for circulation and keeps space to a minimum.

My questions are...is this too little space? Doesn't seem it would be, given the internal dimensions of a sanyo refigerator.

Also, given this size...would I need to have 3" to 4" of insulation? I am trying to keep the external dimensions as small as possible.

Thanks again.

OK, I stopped at Home Depot for kicks and found the following
1 7/8" R12.2
1" R6.5
2" R10
1 1/2" R7.5
3/4" R4

Keeping mind that I want to keep external dimensions to a minimum, would 4 sheets of 3/4" R4 be my best bet? That would be R16 at 3 " and is the most cost effcient to purchase as well. Is there an R value that I should be shooting for?

I think that 4 sheets woul be overkillfor your small project. it makes more cense on a large walk in type for energy saving$. r-10 should be more than enough on a small box like yours. spend the extra time and dough thinking about how to get a good air tight seal between the box and the door because this area will be much more penetrable from outside heat than the rest of your box.

mcody2005 said:

I think that 4 sheets woul be overkillfor your small project. it makes more cense on a large walk in type for energy saving$. r-10 should be more than enough on a small box like yours. spend the extra time and dough thinking about how to get a good air tight seal between the box and the door because this area will be much more penetrable from outside heat than the rest of your box.

Click to expand...

I was more pointing out that layering the thinner higher R-value board can you more insulation is less thickness... I don't know his planned R-value, but the higher the better, obviously.

I have been using a freeware 3D program (Wings 3D) to help plan the design for mini-coldbox. I hope these images show up...first time posting pics.

The cube in the pics is a 1.7 cu ft. dorm fridge.

Uncle Argyle said:

I have been using a freeware 3D program (Wings 3D) to help plan the design for mini-coldbox. I hope these images show up...first time posting pics.

The cube in the pics is a 1.7 cu ft. dorm fridge.

Click to expand...

Wow...that looks eerily similar! Nice job!

I've scanned this thread--you are on the right track I think. Plan for a fan inside the cold box--I'm having trouble keeping mine under 45° without one.

Thanks. I was going to put a fan at the entrance to the freezer tray...but I'm not sure how to control it's operation...or if I even need to. Should I let it run all the time, get a timer, wire to run with the compressor or some sort of temprature controller (more money than I would want to spend I think at this time).

Thanks again for the inspiration Dude! How did you seal the door? Can you describe or post a close up pic of the hinge and seal?

why not just place the C02 canister inside the cooler?

I was trying to keep the amount of space that required cooling to a minimum...wasn't sure the power of the fridge.

It might have a harder time initially cooling the cooler but it will not have to work as hard in the long run with the additional mass.

FYI, I'll PM you a copy of my Zymurgy article... might have some useful tips.

Just a thought, why dont you mount the fridge at the top of the cold box insted of the bottom? after all heat riases and cold falls..

That's an interesting idea MadWeezel...I'll give that some thought.

OK, I suck as a carpenter...but, all in all, it's coming together OK. The fridge fits better than it looks in the picture.

Next, I am going to start cutting the foam board and fitting it in place. I've aleady filled a lot of seams with Great Stuff foam filler. I will keep posting as I go...

Advice is always welcome!

looking good.

neato :rockin:

I am posting a pic of the part that worried me the most, the cold box area. I have completed the framing and the foam...it came out as well as could be expected (for my skill level anyway). I added some liquid foam to fill in the seams...still need to secure the fridge and seal that up as well.

Next I have to clean up the edges and build the door. This part has me stumped a little...I think I am going to go with a piano hinge and hasp on the other side...i need to make sure I have a good seal with door, so I may have to spend some time mulling this one over. Any suggestions??

Is there a foam strip that I can use as the door seal? Like a 1/4" thick 2 to 3" wide foam like tape strip?

home supply store (lowes, menards, hd) should have door seals for house doors. ya buy it in strips or rolls and cut to length

I wonder if it would be possible to ditch the fridge box and use just the cooling parts from it on your keg sized box... call me crazy

Argyle, are you going to put a shelf up above for bottled beers? Seems like some wasted space up there.....

eriklupust, thanks for the comments. I went to Home Depot for ideas and ended up looking at rubber weather stripping...seemed very similar to the material on fridge doors. They claimed they didn't have replacement fridge door stripping, this was the closest thing I found.

Daburban...you're crazy! ;-) I had thought about removing the guts of the fridge, but I had no idea how to even start something like that...and most likely would've ended up breaking a something...this seemed easier.

Dude, I'm not sure what space you are referring to. There isn't enough space above the kegs and the space above the fridge will be outside of the cold box area. I didn't want to expand the cold box area beyond the size required for the kegs as I believe I will be pushing the limits of this dorm fridge as it is.

Thanks for all the questions and help,

Uncle Argyle

long time no post, but it's good to see you have made so much progress!. my idea for a door seal uses magnetic tape. it's available at craft stores. i think most fridge seals use flexible magnetic tape inside the extruded rubber gasket. TEST- close your fridge door slowly while watching the gap between the seal and the steel fridge shell, at a certain distance, the seal will attract the door and allmost instantly cling to it!
I wouldn't waste my time trying to feed a thin magnetic strip through the hollow of a rubber/foam seal, but what if you put them side by side, so that the magnetic strip clenches to the door or cabinet just as seal compresses enough to seal the door? kinda complex and precise, but it's just an idea.

Daburban said:

I wonder if it would be possible to ditch the fridge box and use just the cooling parts from it on your keg sized box... call me crazy

Click to expand...

Possible maybe, difficult yes. Most conventional refrigeration systems will have the compressor, an expansion valve, compressor coils and evaporative coils. Removing all of those without causing a leak would be tough but I guess possible. I'd like to know if anyone has been successful but I'm certainly too afraid to try it.

After coming across a great deal on a 4.9 cu.ft. Kenmore Elite, I've decided to abandon this project. I got to a point where I was starting to spend money on a lot of little things and figured that I'd rather spend a few more and have a nice working unit. I still have no idea how well this would have worked...

Having said that, if anyone is interested in continuing this project I will glady let them take it off my hands (fridge included!). It will save me having to take it apart and throw it away.

I can deliver in the central MA area, although it has to be after dark as I have a out-of-date inspection sticker on the truck ;-)

Thanks to all that have offered advice and support...I have an odd feeling that I am letting someone down...LOL!

PM me if you're interested.

Mike ~ Uncle Argyle