DIY temperature controller for freezer/keezer

by Daniel on May 20, 2012

kegerator temperature controller, using STC-1000 aquarium controller

finished digital keezer temperature controller

Whether you’re just starting out with kegging or you’ve been doing it a while and are looking for more capacity by getting a chest freezer, this DIY project to build a temperature controller (using an STC-1000) for a chest freezer is perfect for you.  For about $40 you can build this controller to instantly convert your freezer into a kegerator (“keezer”) without modifying the freezer itself!

Keezers are great because they have the capacity for multiple corny kegs and when opened, the cool air stays inside.  Personally I wanted the simple, fast, and inexpensive project with the option to pimp out later.  Currently my freezer has the CO2 and kegs inside, hooked up to cobra picnic taps rather than going elaborate with tap lines and all that.

Keezer/Kegerator Temperature Controller Parts, using STC-1000 aquarium controller

parts for keezer temp controller

Without some kind of temperature controller, a chest freezer will get too cold for your beer.  This DIY temp controller solves that problem and cuts the cost in half compared to buying one new.  The nice thing too is that this is a dual stage temperature controller, so it can control both a heating & cooling element, so you can also use it for a fermentation chamber if you want!  Are you ready to take the leap?

This project has been done by many people.  However, there are some things that aren’t completely clear in the assembly, so here’s everything step-by-step starting with what you need:

    1. 110V AC version of the “Mini Digital Temperature Controller” STC-1000 (for an aquarium)
      • Amazon: $16.95 & Amazon Prime shipping
      • eBay: $15-20 shipped.  Most of these are shipped from Hong Kong, so be prepared for a long wait & check estimated delivery date before you choose this option.  If my eBay link doesn’t work, search “digital temperature controller 110v”, and SEE BELOW:
      • Check before you buy:
      • Product specs: Make sure to get the 110V AC version.  If it doesn’t say, it’s probably the 110V standard version, but if it says 220V AC or 12V DC you’re getting the wrong one and it won’t work properly.
      • Shipping cost and estimated delivery – most of these come from Hong Kong with cheap/free shipping, but some can take a while to arrive.
      • Warning:  If your chest freezer’s load rating is higher than 10A at 250V it might be too much for the STC-1000 to handle and could damage the unit or blow a fuse in it!
    2. 15-25ft extension cord – $7  – (OR get a computer power cord for free) – need one that has a ground wire (3 prongs)
      • Thanks to a poster on reddit.com who had this great idea: If you work for a medium/large company, go to the IT department and ask them for a computer power cable – they’ll likely be happy to get rid of one because it saves them paying for recycling.
    3. (6) 8 inch length pieces of wire, cut from the extension cord (see below)
    4. 7″x5″x3″ project box (from Radio Shack) – $7
    5. 2-socket electrical outlet & wall plate – $2
    6. Screw-on wire joining cap – $0.50
    7. Wire cutter/stripper
    8. Dremel cutting tool or small saw to cut holes in the project box
Project Box for Temperature Controller

holy project box!

First, trace out the outline of the temp controller & electrical outlet on the project box.  Then use whatever tool you have to cut out holes in the box – you’ll also need two small round holes, one for the entering extension cord, and one for the exiting temperature sensor from the digital controller.  Next, prep the extension cord by cutting off the female end and exposing 24 inches or so of the 3 wires, green, white, and black.  Cut all three off in two 8 inch sections, leaving 8 inches coming out of the cord, and giving you six pieces of 8 inch wires.  Use a wire stripper to strip the ends off both ends of your 6 wires & the ends from the extension cord.  Next, take a look at your 2-socket outlet – on one side you’ll see two silver screws going into a silver plate.  On the other side are gold screws and a gold plate.  There are tabs on either side of the outlet connecting each of the two plates, silver & gold.

breaking the tab

With needle nose pliers, break off the tab on the gold side.  This will allow the temperature controller to send power to one outlet at a time – one for cold, and one for heat.  You will likely only need the cold side, which is where you will plug in your freezer, unless you want to use this device as a fermentation chamber controller with heat & cooling elements.  Now you’re ready to wire this all together!

The STC-1000 temperature controller comes with a wiring diagram telling you what each of the 8 terminals on the back represents.  Use this diagram along with my description & pictures to do the STC-1ooo wiring.  Please note that I am not an electrician nor do I have formal training in electrical work.  You’re doing this at your own risk, just like me – I take no liability for anything that may happen to you or your property.

Wiring for Keezer/Kegerator Temperature Controller, using STC-1000
STC-1000 wiring for the keezer temp controller – gold screws closest to temp controller box

First I’ll explain the wires coming out of the extension cord.  The green wire is your ground wire.  Attach this to the (usually) green screw on the corner on the back of your outlet.  The white cord is the power return (completes the circuit).  Attach this on the silver side as shown in the picture (which is the same side as the outlet that will be the “cooling” outlet.  The black (power) wire you will leave for now, you are going to be joining this with three other wires at the end.

Now for the 6 wires that go into the back of the digital controller unit.  In the picture above, you see eight slots for wires to go into, divided into four pairs of two.  I used all black and white wires, but there is no rhyme or reason for which I used for which spot.  From left to right in the image, they are: Power, Temp Sensor, Heating, Cooling.  Take 3 of your free wires, and put one of them in the first of each of the paired slots for Power, Heating, & Cooling.  After these 3 wires are screwed into the temp controller, join/twist the free ends with the black wire from the extension cord with the screw-on wire joining cap.  Only 3 wires to go!  Put the remaining three wires in the second of each of the paired slots for Power, Heating, & Cooling.  The one from the power slot goes to the silver side of the outlet, on the side of the for the “heating” outlet.  The one from the heating slot goes on the gold side, also on the side of the “heating” outlet.  The one from cooling goes to the other outlet on the gold side.  Finally, hook up both ends of the temperature sensor into it’s slots on the unit, and run the sensor end out of the box.  Tuck all your wires into the box, screw the box shut, and you’re done!  Now you have a fully functioning dual stage temperature controller to use for whatever meets your needs.  Remember – check the load rating of your chest freezer ahead of time – a savvy reader pointed out to me that some older units could push beyond the rating of the STC-1000 (10A @ 250V) and damage it or blow a fuse when trying to kick in the compressor.  However, this build has now been working solidly for my chest freezer that fits 3 corny kegs for more than two years — also, for those interested, see below about what you can do to prevent this problem by adding an external relay.

Check out my other easy DIY projects here, or visit other categories or my most popular posts in the sidebar for brewing tips and more.  Don’t forget t0 subscribe to my blog with your email on my side bar for updates!

ADDENDUM for those interested in adding an external relay:  I have received a few comments regarding whether the way I have the temperature controller wired could damage it due to it directly mounted to the current of the freezer (see comments section).  A helpful reader Gary was kind enough to put together a diagram (below), and had the following to say in an email which I will quote since he knows way more than me on the subject!  This is the type of relay he recommended:  http://www.hottubworks.com/part-2-G4B-item-spa-electrical-relays.php

The 3/16″ pinouts(stakons) are the 120 vac magnetic coil and the 1/4″ stakons are for the dry contacts, the contacts that will bear the load of the fridge or freezer’s compressor and fan.  I will find a minute to send you a simple circuit drawing. Clearly, one has to choose a relay that not only has the similar specs, but also will fit into the control box. You will see that the drawing emulates exactly what you have already done with the addition of the extra relay.  Remember that the current (amps) while the compressor runs can generate heat sufficient to destroy that nice little controller of yours.  If you add the relay as drawn, any heat build-up will be handled there instead of at  the controller.”

External Relay for Temp Controller

{ 86 comments… read them below or add one }

Pedactyl May 20, 2012 at 2:02 pm

Excellent build. Very clean and organized.

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Spencer August 29, 2012 at 12:54 pm

So, you do not need to do any electrical work on the outlet your chest freezer is currently plugged into?

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Daniel August 29, 2012 at 3:47 pm

Spencer, thank you for the question. You are correct. You actually plug this unit into your wall outlet, and then plug your chest freezer into this unit only, so that it has complete control over the power to the freezer.

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Mike September 27, 2012 at 6:24 pm

Is the temperature readout in C or F or both?

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Daniel September 27, 2012 at 10:46 pm

Thanks for the question Mike. The temperature readout is in C only. My solution was to make a chart in excel that has the temperature in C with the corresponding temp in F and printed it out and taped it on the side of my keezer. I keep mine at about 4 degrees Celsius which is 39.2 F. You can just put the equation into excel and use the “Fill Down” function to populate all the columns. I have 0-20 C and then just use the equation (C*9/5 + 32) to calculate the corresponding temps in F, which gives me a range of 32-68 F.

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Jeff Jones October 2, 2012 at 12:09 am

Thanks man! I got my keezer rocking tonight because of your write up. Big props!

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Daniel October 2, 2012 at 8:53 pm

Rock on Jeff! Glad to hear it’s working great for you :) I’d love to see photos of your successful project, just email me. Now that winter’s coming, you might want to check out my project for a quick and easy fermentation chamber – consisting of a garbage can and aquarium heater to keep your fermenting beer at a nice consistent temp that you can set and forget. See “DIY Fermentation Chamber Heater” in the Most Popular Posts section of the sidebar.

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Hippie Joe November 12, 2012 at 4:09 pm

Probably an awfully obvious question, but how did you run the sensor wire into the freezer? Did you close the door on it, look for or make an opening somewhere else? I assume this is a requirement, and was wondering if there were any tricks, pictures of your final configuration? Great write up! If it helps, I am trying to make a Keezer via a vintage 50’s stand-up Westinghouse.

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Daniel November 12, 2012 at 9:29 pm

Thanks for the question. I just closed the lid on the sensor wire :) It’s so thin it didn’t break the seal of the door at all. Not really any tricks to it. I put the sensor into a little jar with some water in it inside the keezer. That way the temperature reading doesn’t fluctuate as much as if it was just free in the air and gives better accuracy.

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Rob January 5, 2013 at 5:06 pm

Thanks for the write-up. Question about the outlet tabs. I went too fast and removed the tabs on both sides before seeing the instructions said just the gold side.

Will this still work or can you explain why only the gold side should be removed? From what i’m reading online (im a newb), I think you would only break one side if you wanted the other outlet to always be running. I don’t want both the heater and cooler running at the same time though right?

Let me know your thoughts! Thanks!
Rob

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Daniel January 5, 2013 at 10:28 pm

Hi Rob, I am certainly not an expert on circuitry–so take this with a grain of salt. However, the other tab is the “neutral” side, so it’s not going to be feeding “hot” electricity to the other outlet. Plus, the STC-1000 itself it only going to send power to one or the other outlet based one the temperature inside your freezer – it won’t have both on at once. I tested this when I first used my finished product: If I plug my freezer into the outlet designated “heat” and the the temp controller turns on the “cool” side because it’s too warm inside, the freezer doesn’t get any power, so the temp controller will just keep trying to run power to the other outlet without avail. I would just buy a new outlet and break just the gold tab. Like I said, I’m no expert, but I did read from a couple places online where people (who were not talking about temp controllers but residential two-plug outlets) mentioned potential dangers that might arise from having both tabs broken if you’re not careful and don’t know what you’re doing. I wouldn’t risk it to avoid buying a replacement $2 part.

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Rob January 6, 2013 at 5:42 pm

Thanks, i got myself a new outlet today and i’m all set up. Thanks for the article!

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JC January 8, 2013 at 7:22 pm

I can’t afford a ready to use one…….I want to try this. Is yours still working? Can you really connect a regular sized frig to it? Thank you and great job!

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Daniel January 8, 2013 at 8:27 pm

Hi JC, thanks for your interest. Mine is absolutely still working, and you can really connect a regular sized refrigerator! I’ve got a good sized chest freezer hooked up and it’s been running like a dream! Let me know how it goes for you.

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Todd January 21, 2013 at 6:44 pm

Thanks for posting such detailed instructions Daniel. Built mine today using your design and instructions. Will test it tomorrow once I get the keezer put together.

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Daniel January 21, 2013 at 7:40 pm

Thanks Todd, let me know how it turns out!

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Nick February 16, 2013 at 3:49 pm

Daniel awesome build. I also just built a keezer and was using a Johnson Controls analog temperature controller. I have had nothing but issues with it and after reading your post I ordered the STC-1000. I am having problems where the thermostat on the Johnson is letting the keezer get too cold (20F) or too warm (48F).
As for my question… what do you have the thermostat on your freezer set to? You know the little dial that they build into the refrigerators and freezers to control temp? Or does it not matter?

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Daniel February 16, 2013 at 4:12 pm

Thanks for the question Nick–I like your blog, you’ve got a nice keezer build! I left my freezer on the factory setting. It seems that since your freezer is capable of reaching the 20F mark that it probably isn’t the problem. Theoretically I’m thinking that as long as the freezer “wants” to get colder than the setting on the STC-1000 (which is all the time since the STC is set above freezing and the freezer typically below), then the STC will completely regulate temperature. I hadn’t thought of the scenario until you brought it up that maybe if this were hooked up to a refrigerator with a factory setting higher than what you set on the STC (or a freezer that was getting too warm) that it might not kick in when the STC tried to turn it on because of its own thermostat. I would think turning it down to as cold as it will go would fix that problem if that indeed was causing a conflict. I have not had a single problem with my DIY temp controller and it’s been running for 9 solid months and the temperature has always been kept within the range I set. If you use the STC and it ends up having the same problem as your Johnson controller, then the issue is your freezer OR the way you have the controller’s sensor inside the freezer. I can’t quite see in the picture on your blog how you have the sensor set up inside your keezer. However, I recommend having the sensor in a cup/jar of water if you don’t already, as it helps reduce big swings in temperature from your controller overreacting to air temp changes inside (say from opening & closing). I hope that the STC-1000 solves your problem. If not, email me and we can troubleshoot together!

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Nick February 16, 2013 at 4:27 pm

I hope so too! Thanks for the prompt reply too.
I actually had mine in water as well too, but I stopped doing that once it became a brick of ice!
I will post back once I finish the STC-1000 build.

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Smitty February 23, 2013 at 8:01 am

Fantastic post and overall site. If I wanted to mount the controller so that it is visible on the front of the keezer collar I think the wiring instructions would be the same, correct? I would insert a switch plate on the back of the collar. I understand I will need to account for wires back from the controller to power and the plate. Might encase them in some type of wire run. Point being, do you see any problems with your design by splitting the controller and plate with in collar mounts?

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Daniel February 24, 2013 at 6:02 pm

Thank you, Smitty, and great question! You’re absolutely right, the wiring will be the same layout, except that you’ll need extra length for some of the connections in order to allow you to have the STC-1000 mounted through your collar and then pass the wires outside the keezer through the back of the collar (if I understand your plan correctly) to your seperately enclosed switch plate. I would definitely recommend encasing the wires. I do not see any problems with splitting the controller & plate. Best of luck, and I’d love it if you emailed me some pictures of what you end up doing!

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LiveCulture February 27, 2013 at 10:22 am

Hi Daniel,

Thanks for the clear descriptions and photos. Yesterday I built up the temperature controller, plugged in my keezer-in-progress, and the whole thing worked perfectly… until this morning. Now it looks like the temp controller is not getting any power. I have checked all of the connections (multiple times) and everything seems tight… same as yesterday. Any ideas about what might be happening?

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Daniel February 27, 2013 at 9:06 pm

Hi LiveCulture, I’m sorry to hear that the controller isn’t working for you after a day. You’re the first person I’ve heard have an issue. Here’s a couple possibilities that can quickly begin your process of elimination as to what might be the problem and where that problem might be along your circuit:

1.) Make sure the unit you purchased is the 110V AC version – sometimes the ebay description can be confusing and you might have ended up with the incorrect version, leading to a short or something.
2.) Try disconnecting everything and connecting the main power (first two slots) directly to the extension cord wires to see if that might get power to it – I believe it would be the black wire to the first slot, and the white wire to the 2nd (but try another combo if at first that doesn’t work because I’m no electrician). If that does not work, then likely the unit is a dud or had some sort of failure and now it’s busted. That would be the worst case scenario, but perhaps you’d be able to get a new one sent from the seller? The good news is, if this does work, then that means the problem is somewhere else in your wiring/connections. Of course, it’s possible if it’s not working it could be the extension cord, but that’s pretty unlikely.

Those two options cover the two biggest possibilities and quickly start your process of elimination. I really hope it’s not a dud temp controller. If the direct power thing works (I know you checked all your connections already), then the first place I would go to is the screw cap connector as those things can easily have problems with little stray wires causing shorts. If that’s not it, look at all your individual gates and make sure there’s not a single stray frayed wire that’s bumping into something and causing a short. Email me and let me know what you find out and I’m happy to try and help further if you find the unit is not a dud but something is still not working after you try all the other stuff above.

Best of luck!

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Outofhand April 9, 2013 at 8:34 pm

My temperature controller has my freezer on at all times with this wiring setup. Any idea what I did wrong? Temperature is test set to 15.5 C or around 60F.

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Daniel April 10, 2013 at 1:40 am

Good question. My first thought which you might have already checked is that you have the freezer plugged into the outlet that’s actually the “heat element” outlet, which in this setup for a keezer isn’t used. So it actually matters which of the two plugs your freezer is plugged into as one outlet is the “cooling element,” and one is for heat which we’re not using. If you’re plugged in to the heat outlet, the temp controller will correctly read the temperature inside, but as the temperature drops, it will turn on the heat element to try to raise the temperature, not knowing that it’s continuing to drop the temperature. If that isn’t the problem, then I would re-check that all of the wires are hooked up exactly as I described, as it’s easy to make a mistake there.

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Outofhand April 10, 2013 at 5:02 pm

Ya, I tried both of the plugs. They are both active. I removed the little bracket thing as well. :/ I’d assume our wire colors mean the same thing since mine is black white and teal-ish too. I’ll take and upload a picture of my box later. Working on a paper for class.

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Outofhand April 11, 2013 at 12:00 am

I have rewired it, exactly like yours with heating and cooling. It switches on heating correctly, but even when it switches on the heating circuit the cooling circuit stays on, which I tested with a night light…

I think the relay might be fried. I am going to sit and listen for it to see if it clicks in or not. Heating does click, audibly. Confirmed when I threw the probe in my freezer that has been running all night, thankfully empty. :)

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James April 16, 2013 at 6:22 pm

Awesome! Thanks for doing all the hard work. I am making mine tonight, I will let you know how it goes.

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Daniel April 16, 2013 at 10:11 pm

Thanks James, I look forward to hearing how it works out!

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James April 17, 2013 at 2:49 pm

Works like a charm! The wife was interested in what I was doing so I just pieced it together and am going to build a customized box with dual outlets; one heating and the other cooling this weekend or next. Going to teach the wife to solder and make it look like it was retailed. I am also thinking about doing a dual setup (2 outlets and 2 controllers) as I actually have two beer fridges, one for my kegs and one for my lagering and bottles of brews. It will be nice to have them both ‘controlled.’ What do you have your difference value at? I had left mine at the default .5 but am thinking of bumping that up a few degrees. I just don’t want to keep fluctuating the temperature of my beer and also having the power turn off and on continuously. Whats your opinion?

Once again thanks and Cheers!

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Daniel April 19, 2013 at 4:46 pm

Glad to hear it’s working James! I kept the sensitivity at 0.5 as well and find that it works well for me and doesn’t have to turn on too often. I keep mine in the basement which also helps as it doesn’t fluctuate in temperature very much. If you have yours inside your house, it may change a bit more depending on the programming of your thermostat, but that’s just a guess. I think leaving it at 0.5 or increasing to 1.0 would be just fine for your keg fridge. However, for lagering I might suggest leaving it at 0.5, because the 1.0 technically can result in a 2.0 Celcius swing in temperature prior to it turning on and bringing the temp back down by 2.0C again. That might cause more stress to your yeast and lead to off flavors in your beer than the 1.0C swing of the 0.5 sensitivity setting.

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Jeremy May 12, 2013 at 12:38 am

Thanks for writing this. I am wiring this up now. My question is what if you don’t plan on doing any heating? Should I still break the tab or just leave it alone? Thanks again.

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Daniel May 12, 2013 at 3:37 pm

Thanks Jeremy, you don’t have to break the tab if you don’t plan on doing any heating. Let me know how it goes!

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Jeremy May 12, 2013 at 9:26 pm

Thanks again. I followed to the letter but am not getting power to the receptacle. Got power to the thermometer. Not sure what the problem is. I even tried a different receptacle.

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Daniel May 14, 2013 at 11:00 pm

Hmmm, you might as well try breaking the tab, then make sure it’s plugged in to the right plug of the two (the cooling side). Am I to assume that your unit is correctly reading the temperature, and that it turns on the indication light that it is trying to feed power to the cooling unit? Also, did you double-check that you purchased the 110V version? I’ve heard a few people have problems because they got the wrong voltage version, so you might want to check that as well. Let me know!

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Johannes Beeby June 13, 2013 at 12:11 pm

Great Build! Unfortunately we are having the same problem as some previous replies. Thought maybe we bought the wrong voltage model but it definitely says power supply 110VAC on temp sensor. Temp controller is powered on and showing cooling outlet should be on but no power is going there. I found on another site that the wiring diagram on the temp sensor may be incorrect and that the hot and cold are switched on some temp controller models. Check 1:55 into video.

http://www.youtube.com/watch?v=30TvX1Zz1-Y

Going to try and switch wires around tonight. Will let you know if this fixes the problem fingers crossed.

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Daniel June 16, 2013 at 11:35 pm

Thanks for the heads up Johannes. I will look into it and see if I got it wrong so I can fix the possible mix-up!

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Matt June 21, 2013 at 10:08 am

Thanks for taking the time to create and post this. I know it’s over a year ago. I wish I would’ve seen it before I bought my controller. I bought one that does cooling OR heating, not both. Anyway, it’ll work for my keezer. All is good as long as it keeps my kegs cool (and it does). Great info and much appreciated.

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Travis July 13, 2013 at 12:08 am

Thanks for the post. It was easier to follow than a wiring diagram. Just finished my temp controller using your instructions and some posts on homebrewtalk.

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Olan Suddeth July 20, 2013 at 6:32 pm

This is one of the best tutorials I have seen anywhere for building a temperature controller. You make it very easy to understand. Awesome job, I will be using this when I build mine next week!

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KoRy M July 21, 2013 at 7:11 pm

Hey this is an awesome article, Just got everything today to start the project. My question is the additional wires you used to connect everything, The 6 black and white ones, are they just harvested from the extention cord? or should I go out an purchase some additional wires?

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Daniel July 23, 2013 at 2:06 am

Thanks KoRy! You’re correct, I just took additional length off the extension cord for the additional 6 wires to save material.

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Bill July 26, 2013 at 4:47 pm

Great post, thanks for the write up.

One thing I haven’t seen mentioned here is the load rating of the freezer/refrigerator. The STC-1000 relays are rated at 10A @ 250V

Just be sure your units do not pull more than this when they start up or you could damage the unit or blow a fuse.

Older units can get close to this due to compressor loads.

Happy Brewing.

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Daniel July 27, 2013 at 4:00 am

Hey Bill, thanks for the tip! I did not know that and will add that to my post as I think there are some people that have run into that exact issue!

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KoRy July 27, 2013 at 12:21 pm

Is there a way to tell how much the freezer pulls?
The chest freezer that I have it pretty old so this freezer pulling more than the unit can handle is quite a possibility

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Daniel July 28, 2013 at 7:03 pm

Kill-a-watt can be purchased for cheap or borrowed (many libraries have them). They can tell you exactly how much power a fridge will pull. Good luck!

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Rob August 1, 2013 at 1:14 am

Is there any danger of blowing out your compressor by this unit constantly starting and stopping it? How long is the delay, is it adjustable?

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Daniel August 1, 2013 at 2:56 am

Good questions Rob. All I can say to the first is that there are lots of people that have done this build and I haven’t heard that problem crop up, and mine has been working fine. The delay I believe is 1 minute by default, but you can adjust it – although I didn’t.

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Glenton August 9, 2013 at 1:02 pm

Hi. Great instructions. Thanks very much – works perfectly. I’m still working on the brewing, but found another use for the temperature controller, which is sous vide cooking. My blog post on the subject is here if you’re interested: http://drxorile.tumblr.com/post/57801069277/sous-vide-cooking

I’m going to build a second one so I can do both!

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Daniel August 10, 2013 at 9:35 pm

Thanks Glenton for the comment, that’s awesome that you’re using it for sous vide cooking!

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Tim August 15, 2013 at 2:24 pm

Hi Daniel,

If I understand this right, there is one outlet for heating and one for cooling? If so, would it be wise to label the appropriate outlets? If I use it for heat, assuming I unplug the freezer and plug it into the other outlet, do I then have to wire something else to heat the freezer to the proper temp?

Thanks so much! Going to collect parts today and get my STC-1000 ordered!

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Daniel August 16, 2013 at 1:48 am

Hi Tim, you are correct, it’s a good idea to label which is which. I haven’t unplugged mine from the cold outlet ever since I started it, so I never really labeled it myself. I’m not sure if I completely understand what you’re asking about the heating portion, but hopefully I’m guessing right. What most people use it for would be if they are using the freezer as a fermentation chamber, therefore maintaining the temperature at whatever warmer temperature for fermentation/lagering. In this arrangement, you still have the freezer plugged into the cooling outlet, and then put a heating element (many people just use a light bulb) into the heating outlet, and place that inside the freezer. That way your freezer will be kept at a VERY precise temperature for good fermentation control. Just make sure you have your time delay set on the STC-1000 to a longer delay so it’s not constantly cycling the freezer on and off and fighting the light bulb. If you’re only using the heating outlet and not the cold (such as for an aquarium), you just plug your aquarium heater into the heating outlet.

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Tim August 20, 2013 at 3:33 pm

Thanks Daniel – you answered my question perfectly! I was having a mental block on the whole heating side of this build, but someone in the Homebrewtalk forum made it crystal clear for me. I hope to recreate your DIY on that forum with the pics I took during my process. I couldn’t have built mine without your help – thanks so much! Great step by step…

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Chris Childers August 16, 2013 at 3:13 pm

If I wanted to use this on a larger 23 cu ft chest freezer is it going to pull to much current for the STC-1000? Is there a larger option I could buy?

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Daniel August 21, 2013 at 2:22 am

Hi Chris, the STC-1000 relays are rated at 10A @ 250V, so if your 23 cu ft is going to pull more than that, you may want to look into other options as you described. As to what those are, I’m not sure myself but I would love to hear what you find if you do need a different solution.

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Mic August 23, 2013 at 12:19 am

This is an amazing instructional. I am getting ready to start working on my controller over the next couple of weeks but have a couple questions first.
1) can I damage, in any way, a freezer by raising the temperatures to ~68°. I am wanting to start out using the one I have as a ferm chamber for now until I start kegging and make it into a keezer.
2) if I do use it as a ferm chamber, do I need to check or so anything special to it to adjust the temps from freezing/cooling to fermenting?
Thanks again for showing us your build. I believe this will be my main point of reference as I build.

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Daniel August 28, 2013 at 2:35 am

Hi Mic, sorry for the delayed reply. 1.) Although I’m not a freezer expert, I don’t believe that you can in any way damage your freezer – that’s what’s great about this setup, and FYI I do know people that have used this with great success with a chest freezer as a fermentation chamber. The key is it only turns the freezer on when it needs to cool the temperature when it rises above your set range, so it won’t put too much strain on the freezer at all – and the time delay prevents it from cycling on and off too often, which is really the only opportunity to wear out your freezer – so set it how you like it. 2.) No. The STC-1000 covers a very large range of temperatures making it useful for many applications. All you have to do is set your desired temperature on the controller (converted to Celsius), which the instructions that come with the STC-1000 tell you how to do.

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bryan September 3, 2013 at 12:06 am

Thanks for the info…. I’m building mine this week and have a question for you. For my keezer I will not be needing the heating side. However, I might like to have one of the 2 outlets always on for a poss fan in the keezer. Any ideas how to have one foor cooling and the other to always be on??

Thanks in advance for your reply…

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Daniel September 3, 2013 at 6:40 pm

Hi Bryan, that’s an excellent question and a good idea. The easiest solution would be to add a second dual outlet unit to the design. Then you tie on two wires to the main power from the extension cord on it’s way in the box. Attach one of these to the new separate outlet (which would then be always on), then the other go into the temp controller and original outlet to be wired as usual. If you want to get really fancy, there’s a guy on HomeBrewTalk that did something similar, but had an entire outlet for cooling, another for heating, and another for always on. At least from his picture you can get an idea of what I’m talking about and design yours how you choose. Just make sure both (or all) outlet units are grounded! I hope this helps, and I’d love to hear from you how it goes when you’re finished.

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Benjamin September 23, 2013 at 7:50 pm

Just finished testing my temp controller. Works beautifully. Thank you so much for the tutorial. I stepped it up a little by adding a light switch to control power to the whole unit. There isn’t really any reason for it except that I built it in a 3 switch electrical box so I had a slot to fill. One of the most enjoyable tinkering days I’ve had in a long time, and I’m one step closer to finishing my 6 keg keezer. Once again thank you for the tutorial and cheers!

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Daniel September 24, 2013 at 12:02 am

Hi Benjamin, thanks so much! I’m glad to hear it’s working well. Happy brewing!

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JC September 27, 2013 at 6:01 pm

Awesome!!! Can you use this for turning off/on a heat blanket inside some kind of cooler? What about a full size refrigerator and not a keezer? Thanks!

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Bill Krahmer October 21, 2013 at 10:40 am

Thanks for the write-up and materials list. I thought I’d share a small bit of feedback. The 7″x5″x3″ project box from Radio Shack did not fit the full depth of my STC-1000 if installed in the top of the project box, so I had to install the STC-1000 into the (narrower) side of the project box. I kept the A/C outlet on top on the other side from the STC-1000. No big deal, but I am wondering how you fit yours, maybe a different revision of the STC-1000?

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Daniel October 22, 2013 at 2:54 am

Hey Bill, good question! Although it was a little while ago, I do recall removing a plastic plate off of the back (in the wiring picture which shows the back of the STC-1000 you can see where the screw for the plate goes in). Removing that, I believe, gave me the space I needed to fit it in the way I did. It was a very close fit, but it did fit. If that is no the answer to your question, then perhaps they have changed the STC-1000, but I would be surprised.

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scott putnam November 19, 2013 at 12:17 pm

thanks for your post, very helpful. I do have one question though…how do i get the temp sensor inside the fridge? do i just lay it in there do i drill a hole or what?

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Daniel November 22, 2013 at 1:10 am

I just put the sensor wire (which is very thin) under the lid – does it compromise the seal from the gasket? I don’t think so. Good luck!

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scott putnam November 19, 2013 at 8:02 pm

hey, I just read all the other comments and my question was already answered….thanks again for this awesome post!

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Dbj November 21, 2013 at 7:12 pm

Nice write up, just wondering how you secured the outlet in the box.

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Daniel November 22, 2013 at 1:11 am

I actually still need to do that, I’ve just been so lazy and since it just sits around and doesn’t get moved I haven’t bothered with it yet. I’ll probably screw it in.

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Gary Perez November 28, 2013 at 11:09 pm

Very useful arrangement. You should be aware that those type of controllers, including PID and auto-tuning type temperature controllers are used principally for pilot duty and seldom is it wise to expose the tiny and fragile board mounted relay to the current of a fridge or freezer. The solution is to use your controller’s relay output to drive an external relay or contactor, having a coil voltage of 120 vac and a more robust contact rating such as 15 amps at 120 vac, and carry the fridge or freezer load current through the dry contacts of the external relay. This adds about 15$ cost and 1/2 hour of benchwork to your project and, more importantly, lengthens the life of the fragile controller. If you are interested in a schematic drawing, email me.
Good project.. and happy homebrewing. PS-have 12 gallons in secondary ..
should be bottling up on the weekend.

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Daniel November 30, 2013 at 1:32 pm

Thank you for the heads up Gary, I appreciate you taking the time to explain this, as I do not have a good understanding of electronics at that level. I’ll email you about a schematic. So far I have been fortunate to not have any issues with my controller for the last year and a half. Good luck bottling this weekend!

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Jeremy January 3, 2014 at 1:01 pm

Hey, was gonna use this design to try and keep a pot of water at a steady 110 degrees. Will this switch allow my skillet to stay on until reaching the desired temps then cut it off, and then allow it to turn back on when temps drops x amount?

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Daniel January 3, 2014 at 8:46 pm

Hi Jeremy, yes, it should be able to do that. Just make sure you have the thermometer in the water in the skillet in some way that it doesn’t get scorched or melted on an edge.

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Lawrence February 14, 2014 at 7:04 pm

I am assuming this controller will work with a refrigerator as well?

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Daniel February 16, 2014 at 1:21 pm

Yes it will Lawrence!

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Lawrence February 14, 2014 at 9:46 pm

Forgot to mention…Be nice to see the loose wires you used in this build added to the parts list…gauge, sources, etc…Just sayin’

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Daniel February 17, 2014 at 12:23 am

Sorry I don’t remember the gauge. I included in the description after the list that I just took extra wire from the extension cord I purchased. It works great for the purpose, and then you don’t have to buy anything separately!

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David April 21, 2014 at 9:44 pm

Just finished making one and I want to use it with my freezer as a fermenter. What settings should I have it on and should I plug it into the heating or cooling? Thanks for all the cool info!

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Daniel April 28, 2014 at 2:12 am

Thanks David! You want it plugged into the cooling. As for settings, you decide, but I believe I have mine set to be within 1 degree Celsius, that way it’s not cycling on and off all the time putting too much strain on the freezer.

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Nate June 14, 2014 at 11:38 pm

Daniel,

I can’t thank you enough for this excellent writeup. There are plenty of other instructional pages on these temperature controllers, but yours is the best. The word description was key as I can’t understand most people’s wiring diagrams, but could understand you talking through the wiring connections.

I use mine as an aquarium controller; The STC-1000 is plenty accurate for sure.

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Daniel June 17, 2014 at 2:20 am

Thank you Nate, I’m so glad you found it helpful!

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Shaun Lippy June 25, 2014 at 1:58 pm

Built the controller over the weekend (took about 90 minutes total) and got ‘er running today – works like a charm! Great piece, Daniel!

NOTE: for anybody else who gets stuck, like I did, with a slightly different controller when ordering from Hong Kong on ebay, don’t fret – there are instructions out there for the wiring if you just do a quick web search. I ordered the STC-1000 but received the WH-7016C, which is a very similar unit but different enough that the wiring instructions in this article will not work. If anybody gets the WH-7016C unit and has trouble with the wiring, let me know and I can steer you in the right direction!

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Darren July 7, 2014 at 10:44 am

Daniel,

I have a quick question about this wiring, did you add a icecube relay to handle the inrush of the freezer. I seems like this may damage the controller. Maybe I’m just over thinking this.

Darren

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Daniel July 8, 2014 at 1:14 am

Thanks for your question Darren. I’ll be the first to admit I’m no expert on circuits & electronics. However, if you look above through the comments, a very helpful guy named Gary addressed the same issue and emailed me a diagram which I never got around to posting until now (see the end of the post). I have been using this temperature controller for over 2 years now, mostly non-stop, and it has done just fine. However I guess theoretically the arrangement I have can put some wear and tear on the controller.

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Neil October 14, 2014 at 2:33 pm

Any chance there are more detailed instructions for adding the relay? I’m even less of an electronics guy than you (based on you already putting this together). I’m not sure where the wires all attach based on the diagram.

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Daniel October 15, 2014 at 1:52 am

Hi Neil, unfortunately, the best I could do is what I posted!

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