# Making a Chest Freezer Super Cold???



## waterboy865 (Dec 2, 2016)

I want to make my chest freezer SUPER COLD(-30F to -40F). 1. Is this possible on a DIY level? 2. If yes to #1, How do I do this? 3. Thank you for your expertise and input. Your knowledge is valued.


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## de-nagorg (Feb 23, 2014)

WHY?

I think that on it's best setting should be cold enough to suffice for most uses.


ED


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## Bondo (Dec 8, 2007)

Ayuh,.... option #1,... turn the freezer dial to as low as it'll go,.....

option #2,.... put whatever ya want that cold, outside my house in February,....


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## Bret86844 (Mar 16, 2016)

What temperature is the freezer normally rated for? The refrigerant only gets so cold, so all you can do is put a different thermostat in that makes it run longer.


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## waterboy865 (Dec 2, 2016)

de-nagorg said:


> WHY?
> 
> I think that on it's best setting should be cold enough to suffice for most uses.
> 
> ...


Everything I've read on DIY freeze drying food states having your freezer at -30 to -40 F


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## sgenks (Mar 9, 2015)

Research cascade refrigeration, not really a DIY project, but will achieve the temps you're looking for. Most standard household freezers will not achieve t these deep freeze temps. The refrigerant, probably 134a, isn't designed for that low if temp range 

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## user_12345a (Nov 23, 2014)

The information you've been given is inaccurate.

A refrigerant can be run at any temperature, just a question of the operating pressure.

R134a like others can be run in a vacuum and get a very low saturation temperature or boiling point. In fact certain machines actually do run the evaporator in a vacuum, generally using R11 or R123 refrigerant.

Typically in a freezer r134a will run at no more than 5psi in a 0f freezer.

After 0 psig or atmospheric pressure, there's another 14.7 psi to go, granted no machines will run near 14.7.

boiling point of refrigerants vs. pressure...









Some compressors may not run well in a vacuum and you do risk getting liquid back to the compressor if the freezer is too cold.

The operating temperature and pressure of the evaporator coil is in part determined by the load on it -> in your case, freezer temperature.

The colder the freezer, the lower the evaporator pressure will be.

You can rig the t-stat and get it below 0f; the lowest temp will be determined by the unit's capacity vs heat gain.

Unit's capacity goes down as the freezer gets colder and heat gain goes up, at some point it will have to run constantly to keep up.

I don't think you'll get anywhere near -30f, if you can get to -10f you're doing really well.

Compressor life could be shortened and energy use will be high.

Why do you need to maintain -30f or lower?


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## user_12345a (Nov 23, 2014)

The he cascade refrigeration concept is interesting, using two circuits to step down the temperature and maintain a reasonable compression ratio.

first i've heard of it and had the urge to google it.










The challenge is really maintaining a high compression ratio rather than how low the evap pressure has to be.

With a fixed metering device it would be tough to get the compression ratio low enough to do really cold temps.

something experienced with refrigeration could change out the metering device of a freezer and maybe put in a higher capacity compressor to get the evap cold enough to pull far below 0f.


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## beenthere (Oct 11, 2008)

R 11 and R123 are low pressure gasses, and are used in centrifugal compressors. They are not suitable for use in a recip, rotary, or scroll compressor.

Running recip, rotary, or scroll compressors in a vacuum increases the risk of an electrical short in the compressor windings. 

R134A is a poor refrigerant for low temps.


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## 123pugsy (Oct 6, 2012)

waterboy865 said:


> Everything I've read on DIY freeze drying food states having your freezer at -30 to -40 F


Ahhh, freeze dried foods.

And here I was thinking you had to transport a frozen body a great distance and didn't want it thawing until you got there.....


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## ZZZZZ (Oct 1, 2014)

A simple solution to a super cold freezer might be to drop in some chunks of dry ice.

Not sure if this really is a good idea or if it really works, but apparently you can make your own dry ice at home. 

http://www.enkivillage.com/how-to-make-dry-ice.html
.
.


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## beenthere (Oct 11, 2008)

*Re: Adding electrical baseboard*

Dry Ice cost about a buck a pound when bought in small quantities.


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## sgenks (Mar 9, 2015)

user_12345a said:


> The information you've been given is inaccurate.
> 
> A refrigerant can be run at any temperature, just a question of the operating pressure.
> 
> ...


Temperature and pressure go hand in hand, that small tin can will not handle that low of a temp, i.e. pressures, running in a vac for extended period of times. As someone has also mentioned, the cap tube will also not allow it to go that low, if cost allows, look I to buying a used small scientific fridge that goes that low in temp. I do cascade work, a small residential style unit will not go that low. Unless you change the whole refrigeration package. 



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## user_12345a (Nov 23, 2014)

never said it would get down to -30.

the energy consumption and operating cost of ultra-cold freezers must be through the roof. probably not worth it for the op.

why freeze dry anyhow? there are dehydrators out there - not sure if the results are the same.


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## beenthere (Oct 11, 2008)

user_12345a said:


> never said it would get down to -30.
> 
> the energy consumption and operating cost of ultra-cold freezers must be through the roof. probably not worth it for the op.
> 
> why freeze dry anyhow? there are dehydrators out there - not sure if the results are the same.


Freeze dried food last longer, and taste fresher when used.


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## supers05 (May 23, 2015)

sgenks said:


> Temperature and pressure go hand in hand, that small tin can will not handle that low of a temp, i.e. pressures, running in a vac for extended period of times. As someone has also mentioned, the cap tube will also not allow it to go that low, if cost allows, look I to buying a used small scientific fridge that goes that low in temp. I do cascade work, a small residential style unit will not go that low. Unless you change the whole refrigeration package.
> 
> 
> 
> Sent from my XT1585 using Tapatalk


After all you've mentioned.... Even if the OP could get out to work.... The btu capacity would be severely limited at the higher compression ratio. (it wasn't designed for it) The insulation of the chest would bleed too much heat through and the thing would likely never keep up. I seriously doubt it could do a hot pull down in any reasonable time. 

You'd also have to put it on a demand defrost system as the timed systems would take it offline too long and too often for the limited capacity. The frost build up will be irratic as items are added or left for a long while. 

Possible? Yes.... Plausible? No. I do like the dry ice idea though. 

Cheers!


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