# Low Temp Freezer PC testing



## karma0013

So, I did a thing...

I've heard a-lot of people saying that you cannot put a PC in a freezer, and have seen quite a few try and fail.

So, I got my torches out and went shopping for materials to build an insulated box. Somewhere around the 300$ mark i saw a little chest freezer that was just about the size I wanted for 115$. Sold.

Well, to anyone interested, here's a PC in a freezer. Albeit heavily modified freezer* 

Gutted a freezer. Cut a hole in the top. Installed and sealed a viewport. Put a much bigger condenser on it. Put a much bigger evaporator in it. Put a bigger compressor in it (still quite a bit smaller than the ones I see people use from window AC's, about half the size in comparison).

Used cheap fans for the coils as I wasn't sure if they would have the static support to pull through the coils.
Turns out they are great. I will be buying some magnetic high static fans to replace these.

Tips and Tricks:
Fixed metering device is a no go and will only get you to one temp and will be inefficient to maintain.
Internally equalized TXV will be problematic at low temps (below freezing).
Use externally equalized TXV as this will balance the temps under various different loads. Get an adjustable one for the best refrigerant control.
For ultra-low temps, use a custom sub-cooler on your liquid line. Mine is ten 7/8" loops of 3/8" copper through 1-3/8" canister.
Use a suction line accumulator to protect the compressor from liquid refrigerant under various loads.
When balancing the charge in the system, bottles of hot water simulate a heat load very well.
PSU and HDD/SSD's go outside the unit.
Insulating foam and cork tape to seal penetrations.
Vacuum port to remove moisture.
Use Larger than 1/4" acrylic as the 1/4" will bend and buckle under 15" vacuum.
Use a solenoid in conjunction with a high pressure / low pressure cut out control. This will prevent warm refrigerant from migrating to the evaporator during off cycles and help the box retain low temps longer and fewer runs per hour.

**If you run the system with no cold storage, it will cycle constantly and fail to keep up under heavy load.
Currently 3 gallons of water in the bottom of the freezer. This is where the latent heat gets absorbed during normal operations and prevents the system from cycling constantly.

Testing with cold storage at -10c yesterday, the compressor would cycle 2 times an hour rather than the 6 I had allowed it. During CPU benchmarks (nzxt z73 surprised it's still pumping haha) the CPU will still get up into the 40's at 4.8ghz and into the low 60's at 5.4ghz. The GPU is still air cooled (custom low temp loop coming soon. sponsors?) and will get up to 68after repeated benchmarks and actually takes a bit to cool down where as the CPU returns to negative temps within seconds. With the CPU radiator in direct exchange with the evaporator (below the test bench) it takes a very long time to heat soak it. I am currently relying on a mobo probe and GPU probe that can read negative temps, so after the CPU or RAM are below 0c, its all a guess.

Pulling my cold storage down to -15c today my onboard SSD stopped reporting somewhere around -12c (I forgot it was still in there. It still works in the laptop, so only problematic at low temp.)

So there is is guys, a freezer PC. It is, the most expensive and impractical PC case I have ever built, but I dig it haha.
Charging and balancing the system to respond correctly under different loads had been, tedious, so if you're going to build one, pack patience.

Tons of pics and additional info for anyone interested. Hope at least a few of you get a kick out it, i got a kick out of building it.


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## The Pook

karma0013 said:


> Put a much bigger condenser on it. Put a much bigger evaporator in it. Put a bigger compressor in it.
> Internally equalized TXV will be problematic at low temps (below freezing).
> Use externally equalized TXV as this will balance the temps under various different loads.
> For ultra-low temps, use a custom sub-cooler on your liquid line.
> Use a suction line accumulator to protect the compressor from liquid refrigerant under various loads.
> Insulating foam and cork tape to seal penetrations.
> Vacuum port to remove moisture.
> Use a solenoid in conjunction with a high pressure / low pressure cut out control. This will prevent warm refrigerant from migrating to the evaporator
> If you run the system with no cold storage, it will cycle constantly
> This is where the latent heat gets absorbed during normal operations












very cool, but pretty sure the people that "tried and failed" in the past to put a PC in a fridge have just tried putting a PC in a fridge without gutting it and rebuilding it 🙃

why not just take the compressor and make a phase change cooler?


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## karma0013

I thought about phase change, but that has sort of already been figured out. I wanted to tackle something that I had seen some people struggling with. Additionally, I would happily let any pc run in one of these while I was at work all day and not worry about condensation, leaks, mechanical failure etc. Even if this experiences a compressor failure while I am away, the cold storage can maintain freezing for far more than 24 hours.


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## acoustic

Custom loop time!

Awesome work. Pics of the entire box? I wanna see your handiwork


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## Ichirou

I don't understand about any of the technical science here...
Is there any concern for condensation?


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## karma0013

acoustic said:


> Custom loop time!
> 
> Awesome work. Pics of the entire box? I wanna see your handiwork


To be honest, I don’t want to show either of the I/O sides just yet. I have not mounted any of the hard drives or other externals. I will clean things up soon to be more presentable.

for now.


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## karma0013

Ichirou said:


> I don't understand about any of the technical science here...
> Is there any concern for condensation?


None at all. The entire system exists in a below freezing temp. I put moisture absorbent in the bottom for times that I have to open the box. Outside of that, there is no place for condensation to come from.


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## Damage Inc

Good job. That r404a sticker brought tears to my eyes. Used to run VPC for years myself and the r404a was my all around favorite refrigerant and sometimes maybe r507a.


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## karma0013

Damage Inc said:


> Good job. That r404a sticker brought tears to my eyes. Used to run VPC for years myself and the r404a was my all around favorite refrigerant and sometimes maybe r507a.


I still work with both pretty often. 404 is my goto for any low temp projects


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## maltamonk

I think the sticker makes it. Don't think it would work without it.


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## karma0013

maltamonk said:


> I think the sticker makes it. Don't think it would work without it.


Correct. Without it, the box is actually a heater.


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## T.Sharp

Big props on the project, I love ridiculous overengineered stuff like this.😁

Would be awesome to do this with something like a mini-split AC condenser running outdoors 😃

I looked up the storage temp of Asetek coolers and it says the minimum is -20c, and I'd expect that it could go lower if the coolant is moving. But they do state the min operating temp as +5c, so idk. Maybe the plastic rotor becomes too brittle or the hoses become more permeable, maybe it doesn't matter 🤷‍♂️

Anyway, nice work m9, looking forward to more updates.


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## karma0013

T.Sharp said:


> Big props on the project, I love ridiculous overengineered stuff like this.😁
> 
> Would be awesome to do this with something like a mini-split AC condenser running outdoors 😃
> 
> I looked up the storage temp of Asetek coolers and it says the minimum is -20c, and I'd expect that it could go lower if the coolant is moving. But they do state the min operating temp as +5c, so idk. Maybe the plastic rotor becomes too brittle or the hoses become more permeable, maybe it doesn't matter 🤷‍♂️
> 
> Anyway, nice work m9, looking forward to more updates.


This is likely what the project will look like in the long term. A smaller, better insulated case with an evaporator inside of it and a low temp wine room condenser out at the side of the garage. Keep the noise outside. Under these conditions the ambient temp will sometimes be 120+(f) and the system will need a much more effective sub cooler to achieve the -20 to -40 goal. This is tricky because subcooler needs a couple of key things happening right at the same point the refrigerants are exchanging heat. Without designing the system in a lab, this can be…. Laborious. The box it the daunting part currently. I have the mechanical design of the system in mind but am turned off by the box building process 🤷🏼‍♂️ This will have to hold me over until I come up with a design I’m excited to build or find a box to buy (I’ve had my eye on a few)


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## Rei86

ah man this is some good stuff that I miss from reading forums.

Would love to see what's next and even step by step build process.


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## T.Sharp

karma0013 said:


> This is likely what the project will look like in the long term. A smaller, better insulated case with an evaporator inside of it and a low temp wine room condenser out at the side of the garage. Keep the noise outside. Under these conditions the ambient temp will sometimes be 120+(f) and the system will need a much more effective sub cooler to achieve the -20 to -40 goal. This is tricky because subcooler needs a couple of key things happening right at the same point the refrigerants are exchanging heat. Without designing the system in a lab, this can be…. Laborious. The box it the daunting part currently. I have the mechanical design of the system in mind but am turned off by the box building process 🤷🏼‍♂️ This will have to hold me over until I come up with a design I’m excited to build or find a box to buy (I’ve had my eye on a few)


Ahh, I didn't consider that, but it makes sense that you would need a 2 stage system to create such a large temp differential. That definitely complicates things. 

I wonder how how far you could push a single stage system if you add a water drip line or sprayer to the condenser.

If you do build a 2 stage system, could you use liquid coolant for the heat exchange between stages? As in ; evap and condenser in a food cooler or something, filled with antifreeze and a pump to circulate it.


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## karma0013

T.Sharp said:


> Ahh, I didn't consider that, but it makes sense that you would need a 2 stage system to create such a large temp differential. That definitely complicates things.
> 
> I wonder how how far you could push a single stage system if you add a water drip line or sprayer to the condenser.
> 
> If you do build a 2 stage system, could you use liquid coolant for the heat exchange between stages? As in ; evap and condenser in a food cooler or something, filled with antifreeze and a pump to circulate it.


The water drip over the condenser coil can be problematic for a couple of reasons. Controlling the flow to be consistent I nearly impossible unless you completely saturate / submerge the coil. Minerals in the water build up on the coil and destroy it physically.

there are water loop condensing coils, like those used in water source heat pumps and this would be an amazing and efficient condenser for this project. But, to use a water loop, you need a constant supply of water and a way to remove the heat from the water. Easy peasy. Cooling tower in the back yard. While they don’t make cooling towers small enough to make sense for this application, they are fairly easy to engineer and most of the materials for a small cooling tower would be available at Home Depot.
Still this would require a constant supply of water to account for evaporation, and now that I’m thinking about it and not completely against it, it is a looooot of work and material. Sounds like fun lol

picture a miniversion of a cooling tower from a nuclear plant next to the trash cans along side my house


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## karma0013

Cleaned up the wiring and externals a bit. 

A pic of the 2 circuit evaporator I used as a condenser.

the unwrapped canister is the accumulator

the wrapped canister is the subcooler / heat exchanger

Box with the top off. Did not want to tackle inside cable management tonight.

Yes, those are otter pops in my cold storage. I’d love to blame the kids, but they are mine.


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## karma0013




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## xmanrigger

Constructive criticism. I love creativity. I dont want to burst your bubble. I am sure I will get dumped on, but this is my observation.

For the expense and effort you went to, the temps dont look all that great. 60C? 5.4ghz on all cores I hope. Lots of people got to 5.4ghz with their CPUs with AIOs. But dont run them there much. Benching mostly. Hell, I have ran and benched my i7-3930K at 5.2ghz back in 2011. But I sure dont run it there 24/7. And yup, it will still do 5.2ghz, benching.

Also, where does the heat generated from the PC go? Over time the interior temp will reach an equilibrium. The system is hardly efficient in any aspect. That is likely why it never caught on. Just like systems submerged in non-conducting fluid back in the day. Even a submerged system needs an external heat exchanger of some sort. And as with your system, that air/heat would have to be exchanged in some fashion.

The only way I see this feasible is maybe in a commercial walk-in meat cooler in a butcher shop. You need the volume.

The noise alone. I hope it isnt in the same room as your monitor and keyboard.


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## karma0013

xmanrigger said:


> Constructive criticism. I love creativity. I dont want to burst your bubble. I am sure I will get dumped on, but this is my observation.
> 
> For the expense and effort you went to, the temps dont look all that great. 60C? 5.4ghz on all cores I hope. Lots of people got to 5.4ghz with their CPUs with AIOs. But dont run them there much. Benching mostly. Hell, I have ran and benched my i7-3930K at 5.2ghz back in 2011. But I sure dont run it there 24/7. And yup, it will still do 5.2ghz, benching.
> 
> Also, where does the heat generated from the PC go? Over time the interior temp will reach an equilibrium. The system is hardly efficient in any aspect. That is likely why it never caught on. Just like systems submerged in non-conducting fluid back in the day. Even a submerged system needs an external heat exchanger of some sort. And as with your system, that air/heat would have to be exchanged in some fashion.
> 
> The only way I see this feasible is maybe in a commercial walk-in meat cooler in a butcher shop. You need the volume.
> 
> The noise alone. I hope it isnt in the same room as your monitor and keyboard.


I had some of these initial concerns as well.

first, the performance. I am not aiming for extreme overclocking. I am aiming for 24/7 stable performance with lots of headroom to thermal.

the main function of this box is to run my VR training rig for my guys in my garage.

the garage at times can get very hot, and while I have the garage conditioned. The PC would still get very warm after long sessions and with certain titles would still experience thermal stress.

as far as the heat removal,when the system is not under stress, the condensing temperature is under 70°(f) this is due to the low side running at -20° and absorbing a lot of the latent heat from the liquid referigerant. It’s been in my garage for days and I have not turned on the AC in the garage yet asit’s still cool outside. Garage has never been over 72° and the box has been running about a week now.

when you first pull the box down from the &0°’s the condenser can be upwards of 90° but this only lasts a few min.

additionally, I don’t think the AIO I’m using is ideal for this and probably to blame for less than optimal cooling. It aslso failed testing the box at -20 last night. I ran a 3dmark cpu profile with a max temp of 11°. About 20 min after the test I noticed the CPU sitting at 40c. Tested the pump and it had failed.

so the box is in limp mode until my custom loop materials come in. I may put a fan on it in the interim to have a comparison of air over heat exchanger at low ambient temp vs water cooled at low ambient. The reason I consider this worth doing primarily is viscosity. Once your operating in lower temps, liquid all get thicker and less effective. I’m sure there is a point at very low temp where air would trump water as it has not viscosity and therefore won’t be restricted in its quest to remove heat.

while typing it, it feels necessary to point out that I understand that at conventional temps and I most applications, liquid is almost always more effective than air.

but if you start shopping for non corrosive fluid that retain low viscosity at -40°c, you’ll understand why I am considering that air may be more effective

and to your point, this is, effectively a meat locker, just much much smaller, you know, about the size it needs to be for a PC  Building and designing low temp systems and walk ins is what I do for a living.When you are removing heat at the -0 and below level, the waste heat is not like it is when you are removing heat from your home.

the reason others I’ve seen struggle with this is due to the refrigerant they are using, the lack of refrigerant control. Misuse of thermal energy still stored in the refrigerant during run cycles. When you run a window AC to cool a pic, it’s going to us a loooot of power and create a looooot of heat. this box at -20 draws 3.1 max amps. Decibel meter on my Apple Watch says 44 decibels but I question the accuracy, it does seem a bit louder, definitely louder than my enthoo case I was using prior. Fortunately, no one will ever hear it and it cannot be heard from inside the home.


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## karma0013

This is the reason for the high and low pressure controls me the condensing temp will at times run a bit lower than the garages ambient temp (meaning the condenser has a cooling affect on the ambient air. If the ambient in the garage drops below 40f the system will run in very low pressure and likely ruin the compressor. The pressure controls are to help manage the pressures under various circumstances. Hot garage, cold garage, hot box, cold box etc this in conjunction with the externally equalized TXV is where all the magic happens that most others that attempted similar builds simply did not have an adequate understanding of refrigerant dynamics and control.


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## karma0013

Dimms 2 and 3 have been consistently 2-3c warmer during testing. Added a lil fan I had lying around and they are about .3c warmer than the outside 2 now


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## xmanrigger

karma0013 said:


> so the box is in limp mode until my custom loop materials come in. I may put a fan on it in the interim to have a comparison of air over heat exchanger at low ambient temp vs water cooled at low ambient. The reason I consider this worth doing primarily is viscosity. *Once your operating in lower temps, liquid all get thicker and less effective. I’m sure there is a point at very low temp where air would trump water* as it has not viscosity and therefore won’t be restricted in its quest to remove heat.
> 
> while typing it, it feels necessary to point out that I understand that at conventional temps and I most applications, liquid is almost always more effective than air.
> 
> but if you start shopping for non corrosive fluid that retain low viscosity at -40°c, you’ll understand why I am considering that air may be more effective



"*Once your operating in lower temps, liquid all get thicker and less effective"*
This is very true. The higher the viscosity, the less effective. Even sub zero liquid cooling I have a 240mm fan blasting directly into CPU and VRMs. I was using distilled water with just enough glycol to keep it fluid. I wanted to try using winter windshield wash as coolant, but havent had the time. It is good for -40C to -50C. Lowest ambient I have benched at is -38C to -40C. And yes, the coolant get very sluggish at those temps.

"*I’m sure there is a point at very low temp where air would trump water"*
I agree as well. I have done a ton of sub zero clocking. And from what I have experienced, I have to agree with this point as well. I have clocked video cards further on air than with liquid cooling.

If you can look back (2012-2013) and find the score boards for Realbench at ROG Forums, you will see that 5.2hgz-5.3ghz on all six cores was very doable even back then. Albeit, benchmarking, not 24/7 operation. I have a few scores there with clocks at 5.2ghz. I actually held top score for a bit at one point. Usually in the top 5.
My point being is that it seems strange that it took this long for mainstream clocks of 5.0ghz and above. But still, not on all cores. Sad part is that unless the CPU is manually tuned, it will never reach it's full potential. But this has been the case for some time.


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## karma0013

xmanrigger said:


> "*Once your operating in lower temps, liquid all get thicker and less effective"*
> This is very true. The higher the viscosity, the less effective. Even sub zero liquid cooling I have a 240mm fan blasting directly into CPU and VRMs. I was using distilled water with just enough glycol to keep it fluid. I wanted to try using winter windshield wash as coolant, but havent had the time. It is good for -40C to -50C. Lowest ambient I have benched at is -38C to -40C. And yes, the coolant get very sluggish at those temps.
> 
> "*I’m sure there is a point at very low temp where air would trump water"*
> I agree as well. I have done a ton of sub zero clocking. And from what I have experienced, I have to agree with this point as well. I have clocked video cards further on air than with liquid cooling.
> 
> If you can look back (2012-2013) and find the score boards for Realbench at ROG Forums, you will see that 5.2hgz-5.3ghz on all six cores was very doable even back then. Albeit, benchmarking, not 24/7 operation. I have a few scores there with clocks at 5.2ghz. I actually held top score for a bit at one point. Usually in the top 5.
> My point being is that it seems strange that it took this long for mainstream clocks of 5.0ghz and above. But still, not on all cores. Sad part is that unless the CPU is manually tuned, it will never reach it's full potential. But this has been the case for some time.


This is why The cpu is not really my concern. The system has plenty of processing power without breaching thermal. If I need more processing power, it’s as easy as upgrading to 12900k. I don’t have much desire to spend hours adjusting clocks that I’ll never use in regular application. The GPU on the other hand gets maxed quite often during training sessions and the goal here is to have a system run reliably, 24/7 in sub ambient temps low enough to stress the GPU for long periods without approaching thermal limiters.
CPU fan should be here in the AM and I’m still picking parts for custom loop so I will have time to thoroughly test air over applications at different temps to compare against the custom loop when it’s complete.

long term I will likely run the cpu at 4.8/5.0 and the GPU with a conservative Air cooled over clock. As stated above. The goal of this is to create an environment for my GPU to operate in subzero temps for long periods to avoid interruptions or inconsistencies in my training sessions.


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## karma0013

Some pics during the build process. The original compressor before it was trashed. The evaporator coil after install without the test bench in the way. Wiring for all of the controls. Evap under normal light. And the condenser on its first startup.


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## karma0013

Basic mechanical design for anyone interested.
High pressure cut out set to 350 psi at point “A”
Low pressure cut out set to -15psi at point “E”
Subcooler must be installed to conjoin along point “B” and point “D”
Accumulator must be installed at point “E”
Solenoid installed between point “B” and point “F”
Metering device between point “F” and point “C”
Sensing Bulb and equalizing tube at point “D”


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## karma0013

A couple of pictures of the subcooler / heat exchanger in action. At the time of this picture the box was at 5°f. Suction line (blue) temp was -15°f. Liquid saturation temp 92°. Actual liquid temp after subcooler 40°f.


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## karma0013

Suction line accumulator after protecting the compressor for a 4 hour 80°f to 0°f stress test. 

The dark spot under it is from the little puddle it leaves when it defrosts. 

It is a looooot of mass to freeze that way and I’ve only seen it build frost like this on the initial run down to 0° And todays stress test. During the normal tests I ran over the last week it never ran long enough to build up any significant frost.

Needless to say, it has done its job in protecting the compressor under various loads.


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## karma0013

Some decibel readings from the condenser and the compressor. For comparison, when I went back to listening to my podcast at 70% through my phone, volume of the phone was between 70-78 decibels.


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## karma0013

Some refrigerant data from todays stress test.
Blue circle is the evaporator coil temp.
Red circle is the actual liquid temp.
Purple circle is the subcooling.
Yellow circle is the box temp.
All diagnostic temps are Fahrenheit.
Test was run from 80°f to 0°f and took just over 4 hours with around 3 gallons of 80° water in the cold storage. PC was running regular ops during this time. Web browsing, Netflix, and steam, no heavy loads.

As the low side temp drops below freezing and starts to freeze the subcooler you can see a drop in liquid temp and rise in subcooling. This additional subcooling is what makes sustaining very low temps a non issue regardless of the units outside ambient temp.


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## xmanrigger

Again, just my observations. Like I said, I love creativity. Prove me wrong. I am in no way trying to discourage you.

Would the test show more integrity if there was some sort of a constant controlled source of heat inside during the stress test? This would simulate having an active system inside. Would give you a better idea of how it would operate under load. Would have to be a static temp for accuracy and calculations.

Your test only demonstrated it's ability to lower the temperature of a mass. The function of any freezer. But in your case, a super freezer. You didnt monitor and maintain any kind of inside temperature with an active heat source inside. That should be your next test. Maintain a constant (+/- 5C) inside acceptable temp with a controlled heat source. 5C is a big variable when sub zero overclocking, so should I would shoot for something in that range to start. If you can achieve that, you got something.

I think it would take an exceptionally powerful cooler to achieve what you want to do, if even possible. Even the cost alone of the electricity to run it if it worked. I believe your biggest downfall is volume. There just isnt enough volume inside that freezer to dissipate the heat generated while maintaining a worthwhile temp, without overloading the cooler. Like I said in the other post, equilibrium. I believe physics says the temperature will reach an equilibrium. That harmonious temperature might be lower than what is of any usefulness.
It might be fine for a few hours benchmarking, but I dont think it would serve for an extended period of time.

Just food for thought. This might give you an idea of what you would want to achieve. I will use my i7-3930K as an example. Say at -35C outside ambient and PC outside. Pumping close to 1.6V into it and running it at 5.2ghz, it maintained a CPU core temp of about -10C*. That is with distilled water/glycol for fluid, and a 240mm fan blowing on it as well. There is no way any mainstream or abstract cooling system short of Ln2 or helium would achieve anything lower. Anything practical for that matter.
That was pretty much an absolute constant -35C to -40C total environment. So unless you can maintain temps close to that, I dont see much usefulness. If you can, you got a money maker. Otherwise, far more economic and practical solutions are available.

So if all this works.... great.

If it dont...... mod it further and you got yourself one bad-ass phase change unit. Pump that **** thru a cold plate.

Go Hard or Go Home!

EDIT: The CPU core temp of -10C I mentioned above was reported by my Asus Rampage IV Formula motherboard. The Rampage mobo series will report sub zero temps.


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## J7SC

karma0013 said:


> View attachment 2556706
> View attachment 2556707
> View attachment 2556708
> View attachment 2556709
> View attachment 2556710
> 
> View attachment 2556711
> 
> 
> Some refrigerant data from todays stress test.
> Blue circle is the evaporator coil temp.
> Red circle is the actual liquid temp.
> Purple circle is the subcooling.
> Yellow circle is the box temp.
> All diagnostic temps are Fahrenheit.
> Test was run from 80°f to 0°f and took just over 4 hours with around 3 gallons of 80° water in the cold storage. PC was running regular ops during this time. Web browsing, Netflix, and steam, no heavy loads.
> 
> As the low side temp drops below freezing and starts to freeze the subcooler you can see a drop in liquid temp and rise in subcooling. This additional subcooling is what makes sustaining very low temps a non issue regardless of the units outside ambient temp.


 
This is a really 'cool' project you're doing. 

Something to consider down the line  :


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## karma0013

xmanrigger said:


> Again, just my observations. Like I said, I love creativity. Prove me wrong. I am in no way trying to discourage you.
> 
> Would the test show more integrity if there was some sort of a constant controlled source of heat inside during the stress test? This would simulate having an active system inside. Would give you a better idea of how it would operate under load. Would have to be a static temp for accuracy and calculations.
> 
> Your test only demonstrated it's ability to lower the temperature of a mass. The function of any freezer. But in your case, a super freezer. You didnt monitor and maintain any kind of inside temperature with an active heat source inside. That should be your next test. Maintain a constant (+/- 5C) inside acceptable temp with a controlled heat source. 5C is a big variable when sub zero overclocking, so should I would shoot for something in that range to start. If you can achieve that, you got something.
> 
> I think it would take an exceptionally powerful cooler to achieve what you want to do, if even possible. Even the cost alone of the electricity to run it if it worked. I believe your biggest downfall is volume. There just isnt enough volume inside that freezer to dissipate the heat generated while maintaining a worthwhile temp, without overloading the cooler. Like I said in the other post, equilibrium. I believe physics says the temperature will reach an equilibrium. That harmonious temperature might be lower than what is of any usefulness.
> It might be fine for a few hours benchmarking, but I dont think it would serve for an extended period of time.
> 
> Just food for thought. This might give you an idea of what you would want to achieve. I will use my i7-3930K as an example. Say at -35C outside ambient and PC outside. Pumping close to 1.6V into it and running it at 5.2ghz, it maintained a CPU core temp of about -10C*. That is with distilled water/glycol for fluid, and a 240mm fan blowing on it as well. There is no way any mainstream or abstract cooling system short of Ln2 or helium would achieve anything lower. Anything practical for that matter.
> That was pretty much an absolute constant -35C to -40C total environment. So unless you can maintain temps close to that, I dont see much usefulness. If you can, you got a money maker. Otherwise, far more economic and practical solutions are available.
> 
> So if all this works.... great.
> 
> If it dont...... mod it further and you got yourself one bad-ass phase change unit. Pump that **** thru a cold plate.
> 
> Go Hard or Go Home!
> 
> EDIT: The CPU core temp of -10C I mentioned above was reported by my Asus Rampage IV Formula motherboard. The Rampage mobo series will report sub zero temps.


I have been stress testing the system with benchmarks all week. Yesterdays stress test was to see how long cold storage would take to pull down as it is a significantly greater load on the system than a benchmark.

benchmark and heavy load stress tests are a non issue. Even using the 3090 for mining over a 4 hour period only raised my cold storage temp by 3°. Although my cold storage was not under -20f at this time, I expect it would have held up better if it had hardened.

Again when you speak to not having enough “volume” I believe this is because you don’t understand the dynamics of refrigerant adequately, or perhaps have not considered the capacity of the evaporator coil.

-5c under heavy load was achieved day 1 lol I’ve been shooting for -20 to -40 c as water takes a hardened state at this point and will absorb much more heat before changing state. The balancing of the system has been figuring out how to get enough low temp refrigerant into the coil at -30c to handle the heat off put by the GPU and CPU. This is about the point it starts to get difficult. At -5°c there is plenty of refrigerant in the coil to absorb this heat and maintain box temp. As the temp lowers, the metering device restricts the flow of refrigerant to lower the temp more. My “problem” threshold has been -25c. There is simply too little refrigerant in the coil at this point to maintain and after a long run will bring the box back up to the -15c range. During the build, this is when I introduced the cold storage, as even if I lose control of the box temp, if I have a “battery” of cold mass to absorb excess heat, the compressor will have less work to get the box back to -25.

I can tell from your last two openers that you probably get a lot of kick back from your posts on forums.

Some advice:

It’s much easier to ask questions or ask how something works as opposed to making assumptions with incomplete data. You’ll get better results. 👍

If I didn’t know better, I would almost accuse you of posturing to know MORE about the design of a refrigerant circuit than I, so please, if you have improvement suggestions, please make them. I love new ideas.

Note* this isn’t a money maker. Anyone silly enough to spend this kind of money on a pc case should have their head examined. I do HVAC for a living and intend to use the boxboth for practical training on refrigerant theory and as a VR training rig. The box is probably only valuable to me and a handful of HVAC nerds or trainers. If anyone here asked me to build them one, they would laugh me out of the forums when I told them the cost haha

I still am not sure if you even have a question or just here to flex brain cells. If you do have a question, I would be happy to answer it. If your just here to flex, I’ll be back after my coffee 👍 🍻


----------



## karma0013

J7SC said:


> This is a really 'cool' project you're doing.
> 
> Something to consider down the line  :


This is super rad!! I am trying to stay away from condensation inside the box though and I believe even with the box at -20, I will still get condensation issues if I use LN2. I think there would be a balance point where the loop would actually help cool the box and once the two met a fair equilibrium, the concern would go away.

But, I’d have to hurt someone if they ever opened the box, it would ruin everything.

Currently, I can be have one of the kids play horizon 5, open the box at -10, grab a few otter pops and close the box. The differential is not great enough currently to worry about short term exposure.

The temps with LN2 would make that a scary situation lol I could see myself diving at one of the kids as I see them reaching for the freezer lol

“NOOOOOOOOOOOOO”


----------



## karma0013

The evaporator coil. About 140x140x360mm as a water radiator, it would be awesome! For refrigerant, in this circuit, it is perfect 👍 The depth of it is really what makes it shine in this application. If you can see, I had to add plexiglass panels on top and bottom to make sure the air would be drawn across the entire coil. Because the Evap is so deep, the air spends a lot of time in contact with very low temp refrigerant making it very effective at absorbing heat.

Single circuit evaporator coil (this has proven to be semi problematic, and if I had it do do again I would have used a dual or quad circuit coil)
This was taken from a failed unit and repurposed for this project. It’s intended for use in a low temp box around 10x larger than my freezer. This is why I chose to use low airflow PC fans instead of a high rpm refrigeration fan. High airflow would have led to short cycles and it would operate more like a freezer and less like a pc cooler.

This entire coil will be the temperature indicated in the blue circle in each of the pics. When this coil is at -15f, I cannot generate an amount of heat inside the box that the refrigerant cannot absorb. As I add heat to the box, the TXV increases the flow of refrigerant to account for the additional heat and keeps the box at temp.

with cold storage at -20f run cycles are even fewer that I had expected.

there were no heavy load stress tests yesterday as it’s still running with the failed kraken cooler. Air over fan should arrive today and I can get back to testing.

It’s worth noting that in a low temp design like this with a solenoid and pressure cut outs, the compressor does not need to run for the evaporator to absorb heat.

When the air in the box reaches the set temp, the solenoid closes and pumps all of the refrigerant into the condensing coil to cool it down before the next run cycle. This is where a lot of the efficiency comes from. When it does it, it prevents the warm refrigerant from migrating back into the evaporator and equalizing the box temp. Instead, the evaporator coil remains at a lower temp than when it was running, allowing it to continue to absorb heat. The cold storage acts like a battery during this period and helps the box maintain it low temp in the off cycle for much longer. Once the box temp comes up, the solenoid opens and once the system reaches operational pressures the compressor re-engages and pumps the evaporator coil back down to the temp it needs to be to accommodate the box temp.


----------



## karma0013

The dynamics of 404a are really what make this system functional beyond those designed by others. It’s capacity to absorb heat at the temps that one would want to to cool a PC make it perfect. Most other refrigerants have much higher target temps in mind, making them more effective at high temps but much less effective at low temps like the ones I want to achieve. Outside of exotic refrigerant blends, 404a is perfect.

Here’s a spreadsheet on the dynamics of 404a. Anyone with a pocket calculator can run some numbers and tell you that it does not take much 404a to absorb a massive amount of heat at the temps I am aiming for.

it does, like I stated, leave a bit to be desired below the -25c mark and I do wish I was knowledgeable enough to create a consistent blend myself (not off the table) to maintain higher pressure at lower temp. But, to be honest, I knew going in that I would have a threshold around the -20 to -30c mark that I wasn’t exactly sure I would be able to overcome. I do know now that from testing, I would have much more capacity at the -25c mark if I had used a dual or quad circuit coil for the Evap like i did for the condenser. And is not really necessary to overcome. The box can currently maintain below freezing under all different workloads and operations. And that really is what I wanted to achieve with it.



https://www.freon.com/en/-/media/files/freon/freon-404a--thermodynamic-properties-si.pdf?rev=616c710021d149b0a6798d738cccee7e


----------



## karma0013

The capacity curve of the system is worth noting as well due to the use of 404a refrigerant.

If you use the data in the spreadsheet to run your numbers for capacity, you will notice that there is a “sweet” spot for 404a and it’s right below freezing. Perfect 👍

the problem here is, what happens if the box is warm already? The refrigerant does NOT have the capacity to absorb the heat from an 80°f box as well as the system under full load.

once you get the box temp down into the 20°f range, it starts to meet the capacity requirements of the box and the system under full load.

with the box at 0°f it runs optimally and has a significant greater capacity than is necessary to maintain the system under full load.

then again as you near the -20 mark, the refrigerant is capable of absorbing heat, there is simply much less of the refrigerant present at this temp to absorb heat, this is where you start going backwards.

introduce, custom made subcooler, suction line accumulator, and cold storage, these additions are there to combat the issues I knew I would have at certain temps.

will I be able to achieve a -40 box under load? Not likely with 404a. But it can idle at -40 and I’ll be much happier after a long training session to see the pc sitting at -15c rather than the 60’s and 70’s it would constantly run at previously.


----------



## cneuhauser

karma0013 said:


> View attachment 2556026
> 
> View attachment 2556027
> View attachment 2556028
> View attachment 2556029
> View attachment 2556030
> 
> 
> So, I did a thing...
> 
> I've heard a-lot of people saying that you cannot put a PC in a freezer, and have seen quite a few try and fail.
> 
> So, I got my torches out and went shopping for materials to build an insulated box. Somewhere around the 300$ mark i saw a little chest freezer that was just about the size I wanted for 115$. Sold.
> 
> Well, to anyone interested, here's a PC in a freezer. Albeit heavily modified freezer*
> 
> Gutted a freezer. Cut a hole in the top. Installed and sealed a viewport. Put a much bigger condenser on it. Put a much bigger evaporator in it. Put a bigger compressor in it (still quite a bit smaller than the ones I see people use from window AC's, about half the size in comparison).
> 
> Used cheap fans for the coils as I wasn't sure if they would have the static support to pull through the coils.
> Turns out they are great. I will be buying some magnetic high static fans to replace these.
> 
> Tips and Tricks:
> Fixed metering device is a no go and will only get you to one temp and will be inefficient to maintain.
> Internally equalized TXV will be problematic at low temps (below freezing).
> Use externally equalized TXV as this will balance the temps under various different loads. Get an adjustable one for the best refrigerant control.
> For ultra-low temps, use a custom sub-cooler on your liquid line. Mine is ten 7/8" loops of 3/8" copper through 1-3/8" canister.
> Use a suction line accumulator to protect the compressor from liquid refrigerant under various loads.
> When balancing the charge in the system, bottles of hot water simulate a heat load very well.
> PSU and HDD/SSD's go outside the unit.
> Insulating foam and cork tape to seal penetrations.
> Vacuum port to remove moisture.
> Use Larger than 1/4" acrylic as the 1/4" will bend and buckle under 15" vacuum.
> Use a solenoid in conjunction with a high pressure / low pressure cut out control. This will prevent warm refrigerant from migrating to the evaporator during off cycles and help the box retain low temps longer and fewer runs per hour.
> 
> **If you run the system with no cold storage, it will cycle constantly and fail to keep up under heavy load.
> Currently 3 gallons of water in the bottom of the freezer. This is where the latent heat gets absorbed during normal operations and prevents the system from cycling constantly.
> 
> Testing with cold storage at -10c yesterday, the compressor would cycle 2 times an hour rather than the 6 I had allowed it. During CPU benchmarks (nzxt z73 surprised it's still pumping haha) the CPU will still get up into the 40's at 4.8ghz and into the low 60's at 5.4ghz. The GPU is still air cooled (custom low temp loop coming soon. sponsors?) and will get up to 68after repeated benchmarks and actually takes a bit to cool down where as the CPU returns to negative temps within seconds. With the CPU radiator in direct exchange with the evaporator (below the test bench) it takes a very long time to heat soak it. I am currently relying on a mobo probe and GPU probe that can read negative temps, so after the CPU or RAM are below 0c, its all a guess.
> 
> Pulling my cold storage down to -15c today my onboard SSD stopped reporting somewhere around -12c (I forgot it was still in there. It still works in the laptop, so only problematic at low temp.)
> 
> So there is is guys, a freezer PC. It is, the most expensive and impractical PC case I have ever built, but I dig it haha.
> Charging and balancing the system to respond correctly under different loads had been, tedious, so if you're going to build one, pack patience.
> 
> Tons of pics and additional info for anyone interested. Hope at least a few of you get a kick out it, i got a kick out of building it.
> View attachment 2556036


You sir... are awesome... I will hold your beer any day!


----------



## karma0013

The principal and practice is the same as if someone were to call me and tell me they were converting a 20,000 sq ft warehouse to a call center. Give me a floor plan and get an idea of how many people, computers and lights there will be. Calculate capacity.

Or if they were turning an old 1800 sq ft insurance office into a pizza kitchen. Account for the extra capacity from the ovens and walk in and done.

If it’s a grow facility that needs 100,000 sq ft conditioned and humidified and dehumidified simultaneously….And they want a chiller that will cool large masses of material from 220°F+ to -80f quickly, you get out your pad and paper and you run the numbers carefully.

This is easy. When you know exactly the potential heat of each component in the system. Math math math = capacity.

If someone can use a r410a/134a window ac to cool a bunch of glycol and cool their PC, Its no doubt one would obtain much better performance much more efficiently with a 404a circuit.

Another important note for comparisons, when comparing to water or glycol cooling (cooling glycol first then pumping it to the PC) with that method the glycol is simply a carrier to absorb and transfer heat to your cooler. The longer it has to travel and the energy used needs to be accounted for. And neither glycol, nor water are bad at absorbing heat, but in comparison with direct refrigerant contact, they simply to not compare and cannot remove heat quickly enough to sustain high loads.

In Hvac, your typical water loop or glycol system will show you about 10° change on an efficient loop. The reason they are used is because they are not expected to remove heat quickly and they can simply run on a pump continuously rather than an expensive compressor.

When you work with refrigerant loops you can expect temperature changes up to 60° In different applications.

All that matters is capacity. How much heat do you need to remove? Put that much refrigerant through your system. Know the rate at which you will gain this heat? Match the airflow to your heat load.

In all practicality, this is a phase change system, just much more efficient, no worry for condensation, where it lacks is the direct refrigerant contact with the cpu so it will not achieve sustained low core temps. The core temps throughout testing have made it up to the 60°c range regularly with little to no effect on the box temp. The highest liquid temp I recorded during testing while the cracken was still running at -10°f was 1°c. So the liquid would be a bit warmer than the box with no real effect on the box, I blame this primarily on whatever fluid they use in the kracken. The GPU tests had a bigger impact on the box than the CPU did actually bringing my cold storage temp up over long tests


----------



## xmanrigger

karma0013 said:


> I have been stress testing the system with benchmarks all week. Yesterdays stress test was to see how long cold storage would take to pull down as it is a significantly greater load on the system than a benchmark.
> 
> benchmark and heavy load stress tests are a non issue. Even using the 3090 for mining over a 4 hour period only raised my cold storage temp by 3°. Although my cold storage was not under -20f at this time, I expect it would have held up better if it had hardened.
> 
> Again when you speak to not having enough “volume” I believe this is because you don’t understand the dynamics of refrigerant adequately, or perhaps have not considered the capacity of the evaporator coil.
> 
> -5c under heavy load was achieved day 1 lol I’ve been shooting for -20 to -40 c as water takes a hardened state at this point and will absorb much more heat before changing state. The balancing of the system has been figuring out how to get enough low temp refrigerant into the coil at -30c to handle the heat off put by the GPU and CPU. This is about the point it starts to get difficult. At -5°c there is plenty of refrigerant in the coil to absorb this heat and maintain box temp. As the temp lowers, the metering device restricts the flow of refrigerant to lower the temp more. My “problem” threshold has been -25c. There is simply too little refrigerant in the coil at this point to maintain and after a long run will bring the box back up to the -15c range. During the build, this is when I introduced the cold storage, as even if I lose control of the box temp, if I have a “battery” of cold mass to absorb excess heat, the compressor will have less work to get the box back to -25.
> 
> I can tell from your last two openers that you probably get a lot of kick back from your posts on forums.
> 
> Some advice:
> 
> It’s much easier to ask questions or ask how something works as opposed to making assumptions with incomplete data. You’ll get better results. 👍
> 
> If I didn’t know better, I would almost accuse you of posturing to know MORE about the design of a refrigerant circuit than I, so please, if you have improvement suggestions, please make them. I love new ideas.
> 
> Note* this isn’t a money maker. Anyone silly enough to spend this kind of money on a pc case should have their head examined. I do HVAC for a living and intend to use the boxboth for practical training on refrigerant theory and as a VR training rig. The box is probably only valuable to me and a handful of HVAC nerds or trainers. If anyone here asked me to build them one, they would laugh me out of the forums when I told them the cost haha
> 
> I still am not sure if you even have a question or just here to flex brain cells. If you do have a question, I would be happy to answer it. If your just here to flex, I’ll be back after my coffee 👍 🍻


Dont get you panties in a knot. Constructive criticism from somebody that has been around this industry for 25+ years. Nothing more. I have seen a lot of different ideas on cooling PCs. A PC inside a freezer is nothing new. One that is user friendly, doesnt exceed the cost of the system it is cooling, efficient, not a colossal, and cost effective, is new.

_"I have been stress testing the system with benchmarks all week."_
You never mentioned this testing before, or I missed it. That is why I suggested a static controlled heat source inside during testing. If the inside heat source isnt static and controlled, how could you possibley have accurate data if no control numbers? There has to be a constant somewhere.

_"because you don’t understand the dynamics of refrigerant adequately"_
I wont lie. No, I dont have the refrigerant dynamics understanding you have. I do have a basic understanding though. And a little knowledge of physics. Also, I have been around this industry long enough to see and know what works and what doesnt. You arent the first to try this nor will you be the last. I am sure some of those who have attempted this, have your level of knowledge and some greater.

_"-5c under heavy load was achieved day 1 lol"_
I was suggesting for integrity, the inside temp cant vary more than +/- 5C. Not maintain -5C. A variation of 5 degrees at sub zero is huge when overclocking. This I know for fact. Binderdundat.

_"I can tell from your last two openers that you probably get a lot of kick back from your posts on forums."_
History will tell. Yes, I have been somewhat of an ******* in some forums in the past. But in this case, I am simply offering my observations. Is your ego so big that you beleive you are on a level above all and nobody can offer any insight?


_"It’s much easier to ask questions or ask how something works as opposed to making assumptions with incomplete data."_
If I had a question, I would ask. As I said, I simply offered observations from a different view. Take it as you wish. Dont get too high on yourself.

See, historically I have been an *******. People change. I managed to get through this reply civilly. I am kinda proud of myself. LOL

No more comments from here. Good luck.


----------



## karma0013

Got the new fan installed. Stole the fans from the Kracken and added a couple of additional fans to circulate air downwards. Since it is all air over now, circulating the warm air downwards will be more important than it was with a liquid cooler.

Also made a custom sensor panel for Aida and added a 10”lcd touch panel to monitor the system without having to be at the keyboard / monitor. Sadly I made it the wrong resolution, or cannot correct the screens aspect ratio so I will have to remake the sensor panel. Amazon said it was 1024x600 so I made a panel that size and windows says it’s 1024x768 ugh back to the drawing board.


----------



## karma0013

xmanrigger said:


> Dont get you panties in a knot. Constructive criticism from somebody that has been around this industry for 25+ years. Nothing more. I have seen a lot of different ideas on cooling PCs. A PC inside a freezer is nothing new. One that is user friendly, doesnt exceed the cost of the system it is cooling, efficient, not a colossal, and cost effective, is new.
> 
> _"I have been stress testing the system with benchmarks all week."_
> You never mentioned this testing before, or I missed it. That is why I suggested a static controlled heat source inside during testing. If the inside heat source isnt static and controlled, how could you possibley have accurate data if no control numbers? There has to be a constant somewhere.
> 
> _"because you don’t understand the dynamics of refrigerant adequately"_
> I wont lie. No, I dont have the refrigerant dynamics understanding you have. I do have a basic understanding though. And a little knowledge of physics. Also, I have been around this industry long enough to see and know what works and what doesnt. You arent the first to try this nor will you be the last. I am sure some of those who have attempted this, have your level of knowledge and some greater.
> 
> _"-5c under heavy load was achieved day 1 lol"_
> I was suggesting for integrity, the inside temp cant vary more than +/- 5C. Not maintain -5C. A variation of 5 degrees at sub zero is huge when overclocking. This I know for fact. Binderdundat.
> 
> _"I can tell from your last two openers that you probably get a lot of kick back from your posts on forums."_
> History will tell. Yes, I have been somewhat of an ***** in some forums in the past. But in this case, I am simply offering my observations. Is your ego so big that you beleive you are on a level above all and nobody can offer any insight?
> 
> 
> _"It’s much easier to ask questions or ask how something works as opposed to making assumptions with incomplete data."_
> If I had a question, I would ask. As I said, I simply offered observations from a different view. Take it as you wish. Dont get too high on yourself.
> 
> See, historically I have been an *****. People change. I managed to get through this reply civilly. I am kinda proud of myself. LOL
> 
> No more comments from here. Good luck.


I appreciate your civil reply, I will untangle my panties at my first opportunity. I do get irritable when people make assumptions with incomplete data. It’s an easy path to misunderstanding, miscommunication and typically, failure to execute.

The box holds 0°f to -15°f very well under load. Games, benchmarks, VR, mining, etc. I tested all of that before I brought pics and build info here.

Under -15f it struggles to maintain temp and I have been testing cold storage to push temps lower for longer with fewer run times. This has proven problematic under -20f so far. But, testing is not complete and I have confidence 👍

I apologize if I appear to have an ego issue, I do not intend to come off that way. It’s likely because the refrigeration dynamics we are talking about are things that I discuss everyday.

My background, before HVAC controls and refrigeration near 20 years ago now was in PC hardware engineering, so, I’m not exactly new to the PC world.

I will assure you,I’m not going to have any world record benchmarks or overclocks with this box, and won’t be trying. What I will have, is something cool to engage my newer techs and teach them about the dynamics of refrigerant and how to use it effectively. And then they can play games on it. Its sure to pique Some interest.


----------



## karma0013

Updated the sensor panel to fit the screen.

After watching the system with a thermal camera for a few min, I positioned the kracken fans to push air down into the refrigerant coil and the other 2 fans to pull air up from below to circulate over the top and across the cpu.

Anyways, I think I’m done playing with it for the night. I’ll run some tests on it tomorrow.


----------



## Logic11

Nice! 


I'm wondering if you aren't freezing the cooling liquid in the CPU cooler's heatpipes, leading to high temps!??
Sounds crazy right!  Bear with me:

Heatpipes work be boiling off liquid at the heat source (CPU)
The steam then flows to the cold side due to the suction caused by its condensing there, then the liquid flows back to the heat source by capillary action.
But
If the cold side is too cold; all the liquid will freeze there and capillary action will stop.
On the hot side there simply wont be any liquid to boil off.

That would explain your observations pretty well wouldn't it..?


Maybe a stock loop (Glycol excepted) is the better option...
The water volume will add to your 'Cold Battery'...
I'd add and extra pump or 2, in series, to keep the sludge moving/ impinging on the WB base.
Perhaps water in direct contact with end part of the evap is a better option than a stock rad..?
"end part":
You want to keep the air @ a lower temp than the water, just in case of condensation on the WB...

Oh ye;
I think moving the air is more important than you realize:
You want to reduce boundary layer thickness (aerodynamics), hence the fans on CPU coolers, rather than just relying on case airflow...
(That reminds me; Try a bigger fan on the DRAM and increase TREF a lot!)

The HVAC rule of thumb is to never have a fan closer to a perpendicular to airflow surface than the fan's diameter.
That means your evap rad is a bit too close to 'the wall' for optimal airflow through it.
Lets say said air is only in contact with the evap rad for half the time, but it'll be 'in contact' twice as often...


----------



## karma0013

Logic11 said:


> Nice!
> 
> 
> I'm wondering if you aren't freezing the cooling liquid in the CPU cooler's heatpipes, leading to high temps!??
> Sounds crazy right!  Bear with me:
> 
> Heatpipes work be boiling off liquid at the heat source (CPU)
> The steam then flows to the cold side due to the suction caused by its condensing there, then the liquid flows back to the heat source by capillary action.
> But
> If the cold side is too cold; all the liquid will freeze there and capillary action will stop.
> On the hot side there simply wont be any liquid to boil off.
> 
> That would explain your observations pretty well wouldn't it..?
> 
> 
> Maybe a stock loop (Glycol excepted) is the better option...
> The water volume will add to your 'Cold Battery'...
> I'd add and extra pump or 2, in series, to keep the sludge moving/ impinging on the WB base.
> Perhaps water in direct contact with end part of the evap is a better option than a stock rad..?
> "end part":
> You want to keep the air @ a lower temp than the water, just in case of condensation on the WB...
> 
> Oh ye;
> I think moving the air is more important than you realize:
> You want to reduce boundary layer thickness (aerodynamics), hence the fans on CPU coolers, rather than just relying on case airflow...
> (That reminds me; Try a bigger fan on the DRAM and increase TREF a lot!)
> 
> The HVAC rule of thumb is to never have a fan closer to a perpendicular to airflow surface than the fan's diameter.
> That means your evap rad is a bit too close to 'the wall' for optimal airflow through it.
> Lets say said air is only in contact with the evap rad for half the time, but it'll be 'in contact' twice as often...


While I’m waiting on my custom loop components and tinkering with a full air over system, air movement became much more important.

when I was cooling liquid, I was ok with a 5° split as it would keep up with the slow change of liquid temp.

the air over configuration required much more airflow across the Evap to maintain low temps longer.

still hit a wall at about -30c (-22f) where there simply is not enough refrigerant in the circuit to absorb the heat if the components all ramp up to 100. The txv will lose control and regain it around the -10 mark and draw the box back down to -15.

for the custom loop, I will be reducing airflow back to normal, using 3 rads and I’m planning on placing my reservoir down in the cold storage.

also ordered some noctua industrial fans for more consistent airflow once it is complete.

I’ll add some pics when I get home, but you are correct about increasing airflow with allair over system. The space behind the Evap is adequate,but I made changes that I think you’ll approve 👍 pics to come


----------



## karma0013

Some updates and pics:

for air over testing air movement across the coil needs to be equal to or greater than air moving over the heat source or remove heat at a greater rate.

Again with 404a and this setup this becomes problematic at -20f. Not enough refrigerant in the circuit to make a maintain the temp.

With liquid, the change in box temp is much slower allowing much more of the radiant heat to be absorbed by the cold storage. This is not the case with air over cooling.

this required some minor modifications to be able to achieve and maintain -20f box temps without issue.

pics from bottom up:
Minor updates to sensor panel. CPU temp is cpu package temp (it is the only one that reports negative and is typically warmer anyways) GPU temp is GPU hotspot as this is the only temp that will report in Aida under -10c and is typically 10-15c hotter as well. Some graphic updates.

Top acrylic panel has been removed from the evaporator coil. NZXT fans installed on top of coil in “push” position. Front coil fans still in “pull” position. Bottom coil acrylic panel still in place. TXV adjusted to accommodate additional airflow.

all surrounding case fans are pulling the air from below to circulate the air across the cpu/GPU.

snapshot of afterburner when I got home today. Pretty “cool” coming home to my GPU idling at -25c.

so far the box has been very reliable and has only really posed issues when pushing it beyond its expected physical limitations (-40c I bust!!!)

I didn’t get to mess with it much today so it’s on just over a day uptime with no issues. (Since I’ve built it I’m typically restarting it a couple of times a day to make changes or tweak things.) longest uptime so far. Box set to -15°f with 3° differential and has maintained that with no variance. This is to be expected as the system is only at idle most of this time. But, uptime and reliability is important if I’m going to let this thing run 24/7 so it’s a good thing to see


----------



## karma0013

A few things came in.
PWM 4 pin powered fan hub. (No longer using salvaged case fan controller to power interior fans. Also ditched some spliced wires I had hidden 😬)

external NVMe drive housing (for the SSD that froze to death, she’s working well now although currently plugged into a usb 3.0 port) I didn’t know these even existed. Pretty handy and comes with both usb-c and usb 3.0 cables.

HDMI male to female extensions (red). The HDMI by the back of the box (by itself) is from the onboard HDMI out which will be used for the sensor panel.

Display port male to female extensions (gray)

I shut the box down and opened it up to work on it for about 25 min. I took some pics of what happens when you break vacuum and expose the components to ambient air. Frost accumulated instantly on the GPU and CPU (pictured above). Sealed everything back up. Pulled the box back into vacuum and started it up no issues.

The ssd drive on the video input side of the box will eventually move once I decide on a thunderbolt hub that suits the box best.

Also, having a hard time choosing a pump/ pumps for the custom loop setup. Just not very familiar with the different brands and reliability. I’m looking for 2 D5 PWM pumps that will be reliable in -30c environment. Any recommendation’s or suggestions are appreciated, especially if you run your pumps below freezing, let me know if you’ve had any issues.


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## karma0013

Temp sensors came in. I plugged them into w_in and w_out headers on the motherboard. I placed one near the return air of the evaporator coil (box temp) and one near the supply fans on the evaporator For a Delta temp.

Bios was able to read them in the negative no issue. After some frustration I found that asus’ AI suite will read these sensors in the negative. so now I have a software reference of the delta temp in the box.

Currently running Xmp II with core ratio on auto. CPU-x reference vs 10900k. The difference isn’t huge but it’s a reference point to how much better the cpu performs at stock settings in the box.


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## Logic11

Looking good! 

I shoulda warned you the *SSD* would die.
They like to be hot while writing data and cold while storing it.
Most practical is to move the ctlr chip heat to the NAND with a heat pipe, then cool that end of the pipe with fins.

You want to go server *U.2* as USB ads a lot of latency which kills random 4K performance.
R4K is over 60% of Windows I/O. The large sequential #s advertisers wave around are less than 1% of Windows I/O.

So you want a M.2 to U.2 adapter and cable, then U.2 to M.2 adapter to put the SSD outside the cold box.

*If you stay with USB yo want to go UASP.*
The ctlr chip in the external enclosure needs to be UASP capable.
Yours may be already.
You can check for SCSI driver in Device Manager.


*DRAM Refresh:*
As DRAM is a grid of nano capacitors, like normal caps, they discharge MUCH slower at low temps.
ie: DRAM remains usable for much longer before the data needs refreshing where its unusable for the duration of the refresh.
That means you can get a LARGE perf boost by *increasing* the intervals between refreshes.
Used to be called TREF. It's called something else (similar) now.

*Charge times* will also be a bit lower, so you should be able to decrease most all those.

*DRAM termination values:*
My thinking is that cold should decrease those termination resistances, leading to signal bounce errors.
So perhaps increase those if you go all out on the DRAM tweaking. (worth it @ low temps: BIG perf increase)


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