I like to think i am a jack of all trades but I still not a master and would love the more knowledgeable folks to add any info where I might be lacking. That being said, I started on a budget and found on so awesome ways to make things work better for me, one of the most useful things I have found is to modify deep freezers to hit much lower temps than from the factory. I would specifically like people to chime in and comment on how much more strain doing something like this will add to the alliance. I have had some of the most knowable say that it will not last long but since I have had one modified freezer for over 2.5 years and another for 1.5 years. So at $600 new for a 19 CF chest freezer, i think I have already gotten my money out of it. so let get started.
So you can use a multitude of different controllers that are already made and easy to use, I chose the Inkbird all purpose digital controller . This controller can heat and cool but we will only need the cool part to work. all the controller has to do it read the current temp and be able to be set at your desired temp. Now normal freezers were not designed to hit these ultra low temps so depending on the type of refrigerant used and the design of the compressor and evaporator different models will perform differently. I would like to find out what refrigerant is most suitable for hitting the lowest temp and while writing this I see another topic about just such thing and will add a link here… . So to add to what I read there, i bought a 19.8 CU. FT. Frigidaire-FFFC20M4TW CHEST FREEZER for $525 and have read temps as low as -50F with a thermal gun and -38F using the prob connected to the ink bird controller I wired in. This freezer preformed vary well and i have been more than happy with the overall performance. It should be said that doing these type of modifications will put excess load on the appliance will certainly void the warrantee. But I believe most of these freezers use scroll type compressors and I would think these style compressors are the best for this type of application. I say this bc the temp prob actually came out of the freezer at one point and it was probably several weeks of non stop running and still didn’t break after 1.5 years of modded use! I modded the first chest freezer a 6.9 CF Magic Cheff 2.5 years ago and that one dose not get as cold at -32F but it has also held up against time so far. I also took a page from home brewers and did the same mod a lot of them do for kegarators and added wood between the lid and base to give more hight but also to allow for lines to go in and out without cutting holes in the freezer itself. here is a link to build a Kegerator so you can do the same as i did if you don’t want to put holes in your freezer or need more hight. I will give more details about wiring such a mod if people need it in a bit when i have more time and hopefully can find some pics as well. Hope this may help some of you out and make get the topic of which refrigerant/alliance is best for these mods.
Hell Yes bring iT on make time
I hAve found -40 F/C a necesary temp for lab works and indeed achievable with household appliencess but All info is welcome and Yes pics
I’m super interested but not very clear on what you actually did to mod the freezer- just an inkbird temp controller placed before the power cord ? did you change refrigerant? I feel as though I am missing something.
So to add to what I read there, i bought a 19.8 CU. FT. Frigidaire-FFFC20M4TW CHEST FREEZER for $525 and have read temps as low as -50F with a thermal gun and -38F using the prob connected to the ink bird controller
So the newer chest freezers are capable of lower temps? Ill need to verify the refrigerant type in my craigslist find I could only get down to -30f with the compressor running balls to the wall
I just figured out how to post pictures, I will look to see if I took more detailed images from a while ago to show. But in a nutshell on most freezers there is a mechanical type of temp sensor that looks like a type of thermocouple to me which is attached to an adjustable thermostat type device allowing you to modify the range of temps the device turnes on and off from, similar type of mechanism to the old mercury thermostats switch’s used in old homes. The idea here is to basically cut the old control system out and replace with a more varable modern digital control device I.E. a inkbird. The inkbird is essentially a programmable thermostat with a temp prob on it. They come in several variants where the input voltage is either low (maybe 12-36 volts) or higher (most likely what you would want at 120v for a standard freezer). So then you essentially take apart the part of the freezer that has the adjustable dial for standard temp control and usually there is one posative AC wire that runs to this device and the device essentially acts as an on/off relay and cycles the freezer on at off at a given set Point, usually around 2F to -2F and that really receives input from the (usually a copper tube with a balb on the end) tempture sensing device located somewhere inside the freezer or buried in the freezer wall to sense the temp and send signal to turn on/off the freezer… this is the thing we want to study and take apart. We want to first connect the negative white wire to ground the inkbird before any other step. Then take the black posative wire connected to the old thermostat and run this wire to power the inkbird at one connection and then jumper that to the positive side of the “cool” relay a few spaces away on the inkbird. You then want to find the other black or red wire going to power on/off the compressor and connect that to the other “cool” relay. After doing all this you need to make sure thedevice powers on properly and run the new thermostat wire from the inkbird to the freezer so it can accurately detect the interior temp. Next you just need to program the inkbird to the desired temp.
Ive been meaning to do this…as a broke ass hobbiest these tricks are key. Thank you for going through the trouble of posting, you’ve made my job much easier. I hadnt realized it was that simple with the temp control switch being so accessible…
they are bypassing the oem thermocouple so the freezer thinks its not as cold as it is. or they use a 3rd party controller to run the compressor. both options essentially run the compressor at a much higher duty cycle to get the freezer down to a lower temp.
there are ways to squeeze a few more degrees colder by using a different refrigerant or blends but it will need to be something pretty close to the same bp/pressure curve or else you will need to modify the expansion valve sizing or more. ive had thoughts about swapping in a larger 24k btu compressor with a modified regulating valve and run propane as a refrigerant in a used chest freezer but i would need to talk with a hvac buddy about it. the chest freezer would need more insulation as well. the r value of the standard freezer isnt meant for much cooler than sub zero temps.
Yeah that’s what I did to mine it will get down to -30 f but it takes quite a while to get that low and if you open it enclose it it can take many more hours to get back down to that temp it’s certainly not very efficient
If you could fill the empty void spaces with some fluid that can hold the temperature it might make it a lot more efficient
Probably just water bottles full of water would do the trick just fine
Maybe increase the insulation around the the box itself but don’t constrict compressor airflow im really high but i built a 4x5x10 foot oven for powdercoating and increasing the r value of the heated or cooled device, I made Small access doors and large doors to prevent losing all your time earned energy in seconds lol
bwahahah toO hIgh… was trying to say if you increase the r value you simply decrease losses that have to be accounted for with energy from the heating or cooling source
I been playing with this idea myself but i might just break down and pay like 1700 2000 on ebay lol lot easier but I really appreciate someone is working on this! Bad ass of you guys to make a move on this !
propane for the win
