Homemade Sous Vide Immersion Circulator

One great thing about a parent at Evergreen, the school where my children go, is the number of parents with very intense hobbies and interests, that they pursue to the extreme, and enjoy talking about. Some of them, in particular, are foodies and pursue their efforts with almost ludicrous intensity.

These are people who read Charcuterie, then go out and build a sausage curing house, with temperature and humidity control, or spend hours at a time standing next to a Barbecue for a full 24 hours to make sure the brisket is just right. I have my own ridiculous foodie attributes as well, like making pizza dough that takes 5 days, maintaining 4 sourdough cultures, and going to ridiculous lengths to brew beer that could just as easily have been brewed with a bucket and a few parts from the toilet.

But, I have gone a step further into geekiness now. After making my complicated beer brewing setup, I started to feel very comfortable with electricity. I think it was one of my friends from Evergreen that taught me about Sous Vide cooking. Sous vice, for those who do not know what it is, is a method of cooking food in a temperature controlled water bath, vacuum sealed in a plastic bag. Sounds kind of gross, really. But with it, it is possible to do some things that are difficult or impossible to do in any other way. You can make amazing textured eggs with this, PERFECTLY cooked steaks from edge to edge, no matter how thick, and you can turn a piece of $2.99/lb chuck steak into essentially filet minon, but with FLAVOR. Pork Belly confit is unbelievable with this.

Originally, as my friend did, I built a sous vide machine based on plans from
Seattle Food Geek and was pretty happy with it. After building it, I became concerned about a few things-- first, it was not properly grounded, second, the holes I made were, shall we say, imperfect, so there was some condensation inside even after sealing with silicone, and the heaters stuck down a short distance only, so of any evaporation occurred, the elements would go dry and burn out. This was not a modular design in which components would be easily replaceable if they burned out. In addition, there had been several web accounts of the thing getting so hot that it melted the plastic housing. Finally, the small, yet cheap, pumps that run the device will melt if the temperature gets above 150 degrees. This is fine for most meat, but you can’t do vegetables and you can’t do confit.

As I enjoy my life, and don’t want it to end too early, I decided I would try something new. I decided to design and build a modular, grounded immersion circulator, with easily and cheaply available replacement parts, with quality components and a higher maximum temperature. Since I wanted both the water and container (if metal) and the actual device itself grounded, and with GFCI on the cord so it will be safer anywhere it is plugged in, even a non-GFCI outlet.

I designed the immersion circulator out of aluminum tubes and plates, available at onlinemetals.com, and a few rubber mats to waterproof the connections. To the right are the schematics for the box construction and the general design. It is basically a 5x5x5 aluminum box (0.25” thick) with a 3x4x8 inch aluminum tube below it, and a plate welded into the tube to separate the wet side from the dry side. The most difficult part, I think, is the cutting of holes in 1/4” thick aluminum and trying to fit and braze a plate into the bottom, water containing tube. Ultimately, I gave up on brazing and just used JB weld. The heating element just needs a hole in the plate that is tapped for 1” NPT threads, and the other two holes in this plate are 1/4” NPT tapped holes to hold a RTD temperature sensor and a 1/4” NPT compression fitting, to waterproof the electrical cord going from the wet side to the dry side of the box. For a full sized PDF of the diagram, click on the picture and it will open a new window.

The pump I am using is a Rule il200p. It is good to 176˚F and rated for continuous duty, and pumps 200 gallons an hour, providing plenty of power. The heating element is a simple and cheap Camco 1500 watt water heater element. Inside the dry part I have two Auber instruments PIDs- one to control the water temperature, and another hooked to a detachable needle style k-type thermocouple for monitoring the temperature of what you cook. The thin probe can be inserted directly into the bag through a piece of closed cell foam tape, and it does not break the vacuum. Because I could not find an adequate pump that works on 120v, I had to buy a 5 amp 12 volt power supply through ebay that was incredibly tiny. This is the only power supply that could fit inside and still provide enough power for the pump and to drive the cooling fan. As a matter of fact, when I slightly scaled up the power of the fan, the whole thing crashed. Since it is all metal, and screwed together, there is no electrical resistance throughout the entire body, connecting the internals, the water, and the pot to which the unit is clipped to the ground wire, and the GFCI outlet makes it so if there is a current leak, it will shut off within milliseconds. For the outlet, I included a 1/2” NPT threaded hole, so that depending on how much water I want to circulate and with how much force, I can screw in various sized NPT hose barb adapters depending on the application it is being used for. And lastly, because of the design, the chamber containing the heating element will trap air above the outlet. As electric elements should never run dry, I included a push button air purge valve in the upper part of the box. When starting up the machine, it has to be purged of air before it starts firing the element. Also, as I may want to have notification if the temperature fluctuates more than 1 degree, or if the meat gets to its internal temperature, I placed an audible alarm on the unit as well.

Now, one thing I am not is an electrician, specifically, not an electrical engineer, and I am not very good at drawing electrical plans. So, I have made the below diagram to show how it all ties together, but it is pretty ugly.


After cutting the holes and drilling and tapping holes necessary to hook the thing together, it worked PERFECTLY. That is until I tested the boundaries at 180 degrees for 36 hours. After about 24 the pump AND the fan had failed. I changed the design slightly afterwards to externalize the fan, which makes it much more spacious inside and allows it to be changed without having to open up the entire body. It is working flawlessness again, but I will now keep within the stated maximum temperature of the pump.

Here are a few shots of the finished project

Lastly, I have a video of the machine running, but it is HUGE! I will place a link to it
HERE. Sorry, all I have is my iPhone for movies and I am not sure how to scale down, so this is a full 1080p HD quicktime movie.

If anyone has any questions, please feel free to contact me! I would love to help you build something like this. It is, I believe, as functional as the professional immersion circulators with a much lower cost ASSUMING YOU ALREADY HAVE THE TOOLS. It requires a drill press, a bunch of drills and taps, and a good quality metal file, as coarse as you can get. The total cost of the project was less than 200 dollars. Once built, it is very easy to replace anything that breaks, and it does not require sending the unit to a repairman, and therefore is quite inexpensive to fix if something goes wrong.