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As I mentioned before, I recently acquired an immersion circulator. I had been thinking about them for a while, but there was no way I was going to shell out $1000 for one. In fact, I probably wouldn't have shelled out $200 either. I love traditional roasting, sauteeing, searing, braising, etc., and I could do without sous vide cookery. If I were opening a restaurant, yes, I would definitely have gotten a couple immersion circulators. But I cook at home, in a normal-sized apartment kitchen. An immersion circulator was not a necessary.

But then it occurred to me what a boon it would be for dinner parties. Yes, I can do all the interesting sous vide cooking stuff, but what really impressed me was mise en place. So I started thinking a little harder about them. Eventually, I started to really want one. And here's my road to how I got one:

After some thought, and a decent amount of research into the going rates for used equipment, I concluded that I'd never be able to afford one. So then it occurred to me that I might be able to build one. After all, it's basically just a pump + heating coil + thermocouple + microcontroller. Throw on some electrical wiring, program the microcontroller, and you've got yourself an immersion circulator. Of course, it likely wouldn't be nearly as accurate as the pro models. But for most culinary uses, it needn't be.

Some of the Polyscience immersion circulators (the standard in the culinary world) control temperature to within +-0.05 degrees Celsius! That degree of precision, while nice, is unnecessary. So I figured if I could build one that maintained the temperature of a water bath to within +-1 degree Celsius of the target temperature, that would definitely be sufficient for my purposes.

I sent some emails to a couple of my more technical friends. My college dorm mate Daniel was a huge help. We started to discuss plans for buying parts. But then, while doing some additional research, I happened upon a singular find!

On eBay, I was looking at other temperature control devices, and went to a manufacturer's website. They mentioned something called a "thermoregulator"--not an immersion circulator. I looked into it, and it sounded like it was the same as an immersion circulator. But I couldn't find much information about them. I discovered that several companies had "thermoregulators," and they all sounded and looked just like the immersion circulators I'd seen. They listed similar specs, and described similar uses. I just never saw anything that said "thermoregulator = immersion circulator."

And then I found one on eBay.

It was listed as a "Buy It Now" auction, at $500. Closer to my price range, but still not there. But this was an awesome immersion circulator, if that's what it was. An Omega HCTB-3040, it was another order of magnitude more accurate than the Polyscience models, and had a much broader range (up to 250 degrees Celsius). It retailed for over $2000. And no one had bid. No one was looking for "thermoregulators."

So I used the "Make an offer" feature. I initially made a low-ball offer of $250, excepting them to reject it outright or perhaps make a counteroffer. But they didn't. They accepted it!

The listing promised that it was in good working order, though used. When it arrived, a week or two later, it was not in good working order. During shipping, a piece that acts as a float level indicator (basically just a metal bobber) had gone missing. And, more gravely, it wouldn't turn on.

When I say it wouldn't turn on, what I really mean is that when I turned it on, every time I turned it on, it immediately emitted a giant and dangerous-looking electrical spark and promptly blew a fuse in my apartment. I went through three fuses that first night before concluding definitively that there was a short circuit.

Now that I knew there was a problem, I contacted the eBay seller. He was very nice and offered to pay for the reasonable cost of repairs to the device. The problem is that I called the company, and the repairs would not have been reasonable. They wanted around $200 just to look at it, and then would charge parts and labor on top of that. So I asked the seller for permission to attempt to repair it myself, reserving the right to return it if the repairs didn't work. And then I dug in.

I must have spent three hours just getting the casing open that first time. There was much ado about a stripped screw, some hidden screws, and some very tiny ones that were nevertheless inserted with a lot of torque. Once I had the casing open, I was presented with a bunch of parts and wiring. And then I stared at it. And stared at it. And stared at it.

And then, finally, I spotted something that looked amiss. Two wires appeared to have been soldered together quite loosely, and the connection hadn't been wrapped (see detail at right). So I played with them a bit, and followed the wires to their ends. I spend another hour or two just formulating an idea of what each of the wires did. I brought out the multimeter that I hadn't used since Digital Logic class in my sophomore year of college at Vanderbilt.

Eventually, I concluded that two wires were not meant to be soldered together, but each had snapped away from the location to which it had been soldered, and had somehow gotten tangled in the other's loose wires. The two wires weren't soldered together, there was just residual solder on them from their previous connections. So I drew out some schematics, stared a lot more, and then broke out the soldering gun and went to it. A few minutes later I had an immersion circulator that powered on!

I replaced the housing, and went to try it out in a giant stockpot. And promptly dropped the entire immersion circulator into the stockpot full of water (when it was powered off). I again feared for its life.

So, I again removed the housing in order to dry it as best I could. I was afraid excess water would remain. So I waited patiently for it to dry. For three days, I left it out on a table with its casing removed, a large fan blowing directly on it, risking kitty interference the entire time. But finally, after three days, I decided to try it again, hoping there was no residual water in it, lest the thermoregulator shock me, or, worse yet, blow out its electrical system, rendering it useless.

But I got it all set up and tried it out. It powered on. No explosion. No short circuit. But the LCD display wasn't giving a temperature reading. Instead it said an error code: "LLL." So I checked in the manual and discovered that it was a "low liquid level" reading. But why? It had plenty of water. And then I realized that it had arrived missing a part! The aforementioned little flotation ball that attached the to end of the float level indicator was gone. And so I did what I have done a lot of whenever I set the immersion circulator up: improvised.

My set-up involves a steel meter stick threaded through the handles of a stockpot. The circulator rests on the side of the pot and the meter stick. Twine secures the meter stick in place. A nail through a bracket on the immersion circulator ensures it doesn't slide off the meter stick. In order to replace the flotation ball, I pressed a cork onto the float level indicator. The first time I also used a bunch of packing peanuts. They did the trick. Then, because I don't have a bath, but only a giant pot, and I'm worried about bags getting stuck next to the heating coil and melting, I've been using binder clips to clip the bags to the other side of the pot. It all looks extremely ghetto, but it works!

So after $250, a very helpful geeky friend, a decent number of hours with a very tiny sliver of electrical engineering expertise, and some ingenuity, I had myself an immersion circulator. If you are looking for one, I suggest you try searching for "thermoregulator."

Posted by Barzelay on 2009/01/14 @ 3:17 | Comments (15) | Equipment, Science, Technology


That's so funny. We used something similar in one of my old labs for water baths.

Posted by: lsmsrbls at January 14, 2009 10:47 AM

You didn't explain why you had to open up the housing the second time, after you put it in the water. Obviously it didn't work but what happened?

Posted by: sygyzy at January 14, 2009 11:25 AM

P.S. Please blank out the secret word you used to search ebay auctions. I don't need more competition!

Posted by: sygyzy at January 14, 2009 11:28 AM

Christ-y! I didn't even realize you were still reading this blog. Hello! And yeah, these are made for labs, not for kitchens. But the same principles apply!

sygyzy, after I dropped it in the water, I didn't even attempt to turn it on. You NEVER want electronics on when they've gotten wet. I opened up the housing just to let the inside dry out better.

And I've already given you enough of a headstart on eBaying "thermoregulators."

Posted by: Barzelay at January 14, 2009 11:34 AM

Hello! Yes, I've been one of your faithful readers who've kept up with the blog ever since the start.

When I got to "pump + heating coil + thermocouple + microcontroller," I was like, I know that! And then with the increased precision I figured your omega thing was more for labs.

It seems kinda odd to me that old lab equipment is cheaper than used cooking equipment. I guess there's more demand for cooking supplies, but scientific equipment is usually so expensive. But then again, how many companies would buy used?

Posted by: lsmsrbls at January 14, 2009 1:36 PM

Oh, the Polyscience ones are also lab equipment. But that company became aware that their products were being used for culinary purposes, so they started marketing them for that purpose in addition to their lab purpose. The one I got was only cheaper because the seller didn't know to use the words "immersion circulator" in the listing. I found it by chance.

It's been ages since you've left a comment. When no one comments or emails or chats about it, I assume they're no longer reading. Which is why I assume that maybe like 10 people read this blog. Maybe there are more. Who knows? I need to check Google Analytics, I just always forget.

Posted by: Barzelay at January 14, 2009 1:58 PM

It sounds like even if the flotation ball had arrived, you'd still need the meter stick setup. Is the machine always supposed to teeter on the rim of the pot like that? Or are you supposed to use it with a special tank rather than an ordinary, round pot?

Also, if you google "immersion circulator", this post is number five.

Posted by: Brendon at January 14, 2009 4:29 PM

Yeah, I'm afraid I don't often have much to add. I figured you knew I was was still watching because I assumed you kept up with IP addresses, and my domain would sometimes show up as nasa.gov.

Posted by: lsmsrbls at January 14, 2009 5:22 PM

Brendon, yeah, I'd still need that set-up. I could make something more permanent and attractive for it, but I'm looking into getting a water bath. It's not built for use in pots. It's built for these rectangular laboratory tanks. They sell as an accessory this bracket that mounts it to the water baths. Oh, and I'm shocked that this post is so high in the Google rankings. Weird.

Posted by: Barzelay at January 15, 2009 1:04 PM


Posted by: Food Rockz Man at January 22, 2009 4:18 PM

you lucky bastard you got the only one on ebay. I could used it on the pigs head im about to cook... ill post pics soon, sans SV equipment... old school it is!

Posted by: Patrick at January 29, 2009 11:04 AM

Thanks for this post. This the first time I hear about Omega trademark for an immersion circulator. I'll complete the list I made as this one seems to be price competitive (Approx. USD 850). This immersion circulator looks strangely like the Techne USA ones.
By the way we were informed yesterday about of a new company called Addélice that announced to have designed and manufactured their own immersion circulator. Addélice says the price of their equipment will be price competitive and the machine will be released mid-August 2009.


Posted by: Stan at June 23, 2009 1:56 PM

FYI, addélice designs, manufactures and distributes high quality immersion cirulators dedicated to sous vide cooking. Our main product called "swid" will be launched early September 2009 at EUR 489 incl VAT and shipping. Introductory price will be EUR 449 for the first 100 swids!

Should you have any questions feel free to contact us.

Addélice Team

Posted by: Jean-François at August 22, 2009 7:20 AM

Shridhan Automation is a Manufactures, Exporters & Suppliers a wide variety of Level switches, Level switches for liquids and Level Transmitters for liquids in India.

Posted by: shridhan at December 21, 2009 8:49 PM

I am very much frank to you that your writing skill about Immersion Circulator it help me a lot to find out my problem.you rock and do a beautiful job.

Posted by: Thermo circulator at May 27, 2011 7:58 PM