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ThermoStar® Dual-Mode Digital Temperature Controller


SKU# U41264

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The first dual-mode digital temperature controller to go from -50°F to 300°F—and back again—with the flip of a switch. The low-profile, ultra-mountable design is perfect for any fermentation situation.

With a responsive dual-color LED display and modular probe that eliminates the need for a thermowell, perfect homebrew has never been so effortless.

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ThermoStar™ Dual-Mode Digital Temperature Controller

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  • ThermoStar® Dual-Mode Digital Temperature Controller
  • ThermoStar® Dual-Mode Digital Temperature Controller
  • ThermoStar® Dual-Mode Digital Temperature Controller
  • ThermoStar® Dual-Mode Digital Temperature Controller
  • ThermoStar® Dual-Mode Digital Temperature Controller
  • ThermoStar® Dual-Mode Digital Temperature Controller


Product Details

No longer is an advanced degree in electrical engineering required to achieve flexibility in fermentation temperature control. With ThermoStar®, switching from heating to cooling is not only easier than ever with the simple push of a button, it is instantly recognizable with an LED screen that displays the target temperature in blue when the unit is in cooling mode and red when it is in heating mode. You will never need to unscrew the unit to make changes or internal adjustments.

A low-profile design outfitted with multiple mounting options—everything from magnetic to suction to nail hooks—ThermoStar® delivers superb, reliable control even in the smallest of fermentation spaces.

Ideal for serving kegged beer at the perfect temperature. Mount it to the side of your fridge/kegerator or directly to the collar on your keezer build. 

Upgrade the modular stainless steel probe to our longer 12” model and monitor the actual internal fermentation temperature of your wort without the need for a thermowell. Designed to work perfectly with our Big Mouth Bubblers and their Dual Port Lid option.

Product Specs

Setpoint Temperature Range -50°F to 300°F
Differential Adjustment +/- 2°F
UL Listed Yes
Body Dimensions
Width (at widest point) 68mm
Height/Thickness 40mm
Length 120mm
Temperature Sensor
Standard Probe Length 2 inches
Extended Probe Length 12 inches
Cord Length 8 feet
Additional Information
Support Documents: ThermoStar® Instructions
4.3 / 5.0
41 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
Unreliable and Not Durable
The first controller I received was malfunctioning out of the box. Northern Brewer replaced it. The replacement unit just died after less than 18 months. It went off in the middle of a hot Arizona night and I nearly lost the 15 gallons of beer that were in my keezer. I am switching to Inkbird. These controllers cost half as much, so I can afford to keep backups on hand.
September 26, 2016
Response from Northern Brewer
Customer service is always happy to help with any product issues.
November 21, 2016
Northern Brewer N
Works as described - excellent purchase.
My basement has an average temp of 63/64 degrees. The controller keeps my fermenter +/- 1 degree of my desired temp. Obviously you need to purchase a heating mat, band or wrap separately. It is worth the $$ for peace of mind. It illuminates in Red for heating, blue for cooling and has a compressor cycle safeguard. Great stuff. On a side note - it would be great if it could accommodate dual heating/cooling systems - I have heard this accomplished with a plug splitter using one thermometer probe (if you want two carboys set at same temp.)
February 22, 2016
Must have for better fermentation.
I feel that the Thermostar temperature controller is a must have for people wanting to improve their beers. It has often been said that fermentation is one if the top things a Brewer needs to control for the best tasting beer. And I agree. The three batches that I have brewed since my purchase are superior compared to previous batches. Ester profiles, attenuation, and lack of off flavors are some of the improvements. The temperature controller gives amazing control over temperature and has so many features that even the NB description doesn't do it justice. First of all it has a large display which can be dimmed. A simple flick of a switch turn it from heating, bypass, and cooling. The display even changes color according to the above designation. Adjusting the temperature is also very easy. Just follow the diagram map in the manual. The display will show the actual temperature and with a push of a button will show the "set" temp.. Where it really shines is in its advanced features. There is a lock option to lock or unlock access to advanced options. A temperature band option. An example of this is if you want the temperature to be 62 and set the band at 2 then the cooler will not turn on till it reaches 64. The range is between 0.1-20 degrees. A compressor protection delay that can be set from 1-60 min. A display brightness setting. A decimal setting to set up as whole degrees like 65 or an even more accurate tenth of a degree like 65.3 degrees. It also has a temperature offset function which I have not had to use. I am very satisfied withe the controller and my beer has improved because of it. Mike
March 24, 2016
Awesome Temperature Controller upgrade!
Was working with an old Johnson temp. controller. Was very inaccurate as the probe was too big for a thermowell and had to be in a container full of liquid measuring it's temp., not the fermentation temp., from inside my fermenting freezer. With the ThermoStar controller, I can tape the probe on the side of my glass big mouth bubbler, insulating it with a few paper towels and painters tape. Because of the sensitivity of the ThermoStar probe I can now pinpoint my target fermentation temps. What a revelation!
October 15, 2015
Nice "plug & play" Temp. Control.
Bought this from Northern back in April and wanted to get some solid use out of it before commenting. So far, I've done 4 batches (A Bohem. Pils and a couple of Ales and a Stout) using it to control my brew-fridge and it's worked just fine. I gave it a day to adjust before brewing my Pils and, once 54* , it held it steady through both fermentations. After the pils, I ramped it up to 65 and did both ales. It adjusted quickly and held temp with no issues. It's extremely easy to set and even comes preset in a couple of settings to avoid over-cycling your compressor. I haven't used it to control a heat source yet but I'm thinking that since I'm down in the Houston, Tx area, that ability might not come into play for quite a while. It does have a 15A max (output ) on it so, theoretically, it COULD be used to control an element like a 1000w / 8.3A or a 1500W / 12.5A to hold an HLT at temp. or to bring up to strike temp overnight I suppose. I may try this later down the line just to experiment and will update when /if I do. As far as just using it to control a fridge, It works like a charm and is a HECK of a lot easier to set than Inkbord or other PID controller. Id recommend and would
August 7, 2016
Thermostar dual mode digital temperature controller
Nice product, quick shipping, easy to use. Would have given it 5 stars except instead of a +/- 1 degree variance, I'm experiencing a 3.5 - 4 degree variance.
September 22, 2016
Could use improvement
I just received this item and plugged it in, so I do not have a review for prolonged use. There are several improvements I think this product could make to be more convenient. (1) The setting for cooling is not very intuitive, as you set the temperature that you want to cool to, rather than the temperature that you want to call the freezer on. For example, I want to have the freezer turn on at 66, and off at 63. I have to set the freezer to 63 then select a swing/hysteresis of 3. If i want to adjust swing, I then have to adjust the setpoint to maintain my max temp. (2) Having the output A/C socket directly on the unit is troublesome for a couple of reasons. First, it limits the adapter you can attach directly to the unit (3-outlet if you want the controller to initiate the freezer, and one/two fans). You could connect an extension cord, but the controller becomes awkward since there are already cords coming off the bottom, and now you have one coming off the side. Further, attaching either of these two to the unit makes it heavy, and it's integral magnets are not strong enough to prevent it from sliding down the side of the freezer. (3) Magnets are not strong enough to provide a reliable hold. If the controller had a temp setting that called on the freezer, had a cord leaving the unit rather than the outlet built in, and the magnets were stronger, this would be a great product. As it is, the product is OK, but the only advantage it has over the Johnson A419 is the easier ability to switch to heating mode without opening up the controller.
September 18, 2014
Great product!
The unit works great, and was super easy to set up. I like that the unit is magnetized, and can be put right on the side of my keezer.
March 23, 2017
6 months ago
Look no further
Got my chest freezer, plugged in my Thermostar and set it up in less than 2 minutes, had frosty beer about an hour later. I love it when things come together.
March 24, 2016
ThermoStar Digital Temp Controller
Using this on my newly built Keezer and so far it is working flawlessly and will purchase another one when I get an old refrigerator for doing Lagers.
January 11, 2016
Start typing your question and we'll check if it was already asked and answered. Learn More
Browse 29 questions Browse 29 questions and 80 answers
What happens if the main power source goes out and then comes back on? Will the Thermostar Controller resume its control where it left off - or will it have to be reprogrammed again?
A shopper on Dec 7, 2016
BEST ANSWER: In my experience, the controller does not need to be reset if the power is interrupted for a short time. I haven't had a loss of power for more than a few minutes though, so I can't speak to expended periods of time.
Can the probe be immersed in liquids like wort?
G R on Sep 27, 2015
BEST ANSWER: At least the metal portion of the probe can be placed in liquid. I bought the 12" probe specifically for this purpose, as it is able to go through a stopper and into the wort in a carboy. This way I get the temperature of the wort and not the air nearby. I am not sure it should be immersed such that the cable and joint between cable and metal probe gets wet, however.
Do I need an appliance, or can this heat and cool on its own?
A shopper on Apr 12, 2017
BEST ANSWER: This is the controller, you need a hat wrap to make it warm up your wort or you need a refrigerator to cool the wort. You can only do one thing at a time. Northern Brewer sells a heat wrap, and I also Redmond the longer prob. If your cooling you plug the refridgerator into the unit and it then turns it in and off to maintain your desired temp, use it for lagering.
Will this work ok on a plastic 7 gal fermentation bucket in a room with ambient temperature of 64 degrees F? If used with the Thermostar temp controller, could I tape the temp probe to the outside of the bucket and get ok results (bucket lid has a single small hole only for the air lock)?
Michael C on Apr 4, 2017
ThermoStar® Dual-Mode Digital Temperature Controller
ThermoStar® Dual-Mode Digital Temperature Controller
FermoTemp™ - Electric Fermentation Heater
FermoTemp™ - Electric Fermentation Heater
BEST ANSWER: I've used in and open area in my basement. However I had the foam insert from some box that held the carboy almost perfectly about an inch off the floor. I then used masking tape to hold the sensor to the bottom of the carboy away from the heating element. I put another piece of foam under it to insulate the sensor from the floor at it is always pretty cool. I successfully used this set uo or five or six batches until I got a cheap 5 cu. ft. freezer and started making lagers. I use the heating side when it gets pretty cold here in Western New York to even maintain 38 degrees. I think if you just keep the sensor away for the heating element and maybe back it up with some insulation you should be good.
Will this work on the freezer side of a side by side without affecting the fridge? I want to use the freezer side for my kegerator while using my fridge side as usual.
A shopper on Mar 1, 2017
BEST ANSWER: I'm not sure. You might be able to set it up to keep both sides cold. But much experimentation would be needed. The fridge plugs into the controller, then controller into outlet. The temp probe would be put in the freezer side. It would keep the freezer side at the requested temp, not sure what the fridge side would cool to.
Buy a small chest freezer. Super easy and convenient. Then make that keggreater/fridge. Hope this helps.
I understand this is more than likely a horrible question, that being said; does this just monitor the temperate and activate another source to alter the set abiant temperature? Or does this device alone actually heat up? Winter time and just looking for a solid way to hold a healthy temp . Thanks in advance.
jack S on Nov 23, 2016
BEST ANSWER: This device is only a controller that operates either a heater or refrigeration device. The unit has a built in temp sensor to monitor the temp. I taped the temp sensor to my carboy and used one of those sheet heaters to warm the carboy. The controller turned the poser on and off as necessary to maintain the temperature. The temperature hysteresis is adjustable so you can control the high and lower temps.
Looking to use this in conjunction with a recently purchased refrigerator. Does the fridge just plug into the temp controller and kick on when temp rises above my desired fermentation temperature? Thanks for any insight - I'm not particularly electrical-savvy.
S H on Jan 14, 2016
BEST ANSWER: Yes, it hard breaks the electrical connection until the temp set on the controller is passed. It then allows power to the fridge unit allowing it to cool until it get back below your set threshold. You will set a range of usually +/- 2-3 degrees. so for example 33F to 39F if you set it at 36F ideal temp. When it passed 39F it kicks on until it is 33F then cuts the main power back off. It needs this window of temps to keep the cycle time long enough to not over stress the compressor in the main unit which would cause it to wear out very fast.
Have had the unit in monitor mode for about a month. When I set it to cool today the temperature readout says 80 but I have frozen beer in my keezer?
A shopper on Jun 18, 2017
BEST ANSWER: The temperature probe should be in a fluid or taped to the side of your keg and covered to insulate it. If it is hanging around loosely it is essentially monitoring ambient air inside the keezer.

It is possible temperature variances can occur with a keezer, being that freezers aren't designed to be kegerators.

But if you think your probe has malfunctioned test freezing temperatures with a glass of ice and boiling temperatures with a fresh boiled glass of water. Also, if you have a reliable spare digital thermometer, you can compare. If there is a problem comma call the Northern Brewer staff. I can attest to their excellent customer service. Good luck.
Can this temp. control unit be used on a manual up-right freezer? I usually maintain a temp. of 55-58 degrees.
Steve C on May 4, 2016
BEST ANSWER: If it is manual as in an analog thermostat on the freezer, this controller would certainly work. You plug the controller into the wall then the freezer in the controller and there is a temperature probe that goes into the freezer. The controller controls when the freezer turns on based on the temperature reading from the probe. Let us know if you have any further questions!
Can I run 2 fermentation wrap heaters at the same time? Assuming the carboys are sitting next to each other and the 12" probe is in one.
H A on Feb 14, 2016
BEST ANSWER: No, I'm afraid you would need two temperature controllers to control two fermentation wraps. You can attempt to tape a wrap against two fermenting vessels in a way that the wrap is partially in contact with both vessels. This way, however, would not be effective in properly heating both vessels as in using an independent fermentation wrap per vessel because of less surface area in contact with the heater wrap. Also, monitoring one vessels temperature does not guarantee that an adjacent vessel's temperature is the same. Cheers!
I just bought one of these, but cannot figure how to set the cooling differential to less than two degrees. For example, when I set it to 60F, it won't turn on until it reaches 62F. I know how to view the temp menu settings, but can't change any of those value?
A shopper on Feb 25, 2017
BEST ANSWER: Press the up arrow and SET buttons at the same time and hold for 3 seconds. This will take you to the advanced settings. Second, unlock the controller by setting the lock code to 18 and pressing SET to permanently set it. Next, scroll with the arrow buttons until you get to the HY (Hysteresis) option. That sets the time between the set temperature and when the controller turns your cooling system's compressor back on. Press SET to change this setting. You will also need to set the T (Compressor Protection Delay Time) option to less than the default setting, 2.

A bit of warning. Setting these values lower than the default setting of 2.0 seconds will diminish the life of your compressor. Hope this helps
My Thermostar digital readout is flashing between what I assume is the actual temperature and the number 0. I currently have it set to heat and am using a ceramic heat bulb to warm my fermenter up to 68 degrees. Has anyone seen this error?
A shopper on Feb 15, 2017
BEST ANSWER: I'd try unplugging it and also re-attaching the temp probe to it, it may be getting an intermittent signal from the probe. Make sure the mode switch is in the correct spot, and that the other settings are properly entered. If you cannot get this to read right, there may be a short in the probe wire, and that part may need to be replaced. Please let us know if you are unable to get it working correctly!
What is the diameter of the probe?
J A on Aug 26, 2016
BEST ANSWER: Just shy of 1/4", designed to fit through a standard drilled stopper.
After reading the description of this unit I figured that my fermentation temperature problems were solved as I could now turn my beer dispenser into a controlled fermentation unit. This weekend I tried the unit for the first time, on my kegerator, however the the unit does not bypass the kegerators temperature control, actually nothing happens other than the temperature continues to rise. Any suggestions what I can do? the kegerator is a Danby DAR163BLDP
R R on Aug 7, 2016
BEST ANSWER: I wonder if it's set up correctly. If set up right, the temp controller will be shutting off the power to the kegerator, and only turning it on enough to bring the temp down to the desired temp it has been set to. If it's set to, say, 58 degrees, it will turn on the kegerator, and it will shut off when the temp is a few degrees below 58. It will slowly let the temp rise, to a few degrees above 58, then it will turn on again. It will work in a cycle like this, to hold the inside temp at the temperature it's been set to. The temp probe of the unit should be set up somewhere in the kegerator so it's measuring the air temp inside the unit, and so it's not touching any cold walls or cold kegs. If it is touching the cold kegs or walls, it will be giving incorrect readings, and so, not working right. - Mike W, Northern Brewer
In the user manual for this controller, under "Technical Specifications," it says "Output Relay Rating (Max): 15A/240VAC, normally open" - does this mean I have to use a 240V, 15A rated heating cable/mat? The outlet is a normal 120V/15A outlet, right? So I'm confused! Thanks!
A N on Jun 5, 2016
BEST ANSWER: No, that means that 15A/240 VAC is the VERY MOST that can be run through the unit's relay. It will perform well with a "regular" ( for the US ) 120 VAC heat mat or heat unit. This could be used in higher voltage applications, if the power cords were rewired. -Mike W, Northern Brewer
When upgrading to the 12" probe will you receive the 2" probe also.
J S on May 18, 2016
BEST ANSWER: Yes, the 12" Thermostar probe is a separate item, so you'd still get the regular, smaller probe with the Thermostar unit. -Mike W, Northern Brewer

We purchased one of these controllers recently and are a bit puzzled at how it should work with a chest freezer. When setting the desired temp at a higher range like 53F, the controller kicks on the freezer compressor and the temperature goes into lower ranges of 20 something F. Certainly not the desired effect. Would it help to shut the built in freezer controller off? Or are we missing the point on something?
N E on Feb 29, 2016
BEST ANSWER: Sorry to hear about a possible issue. I would make sure it is set at that temperature and is in cooling. The probe should be in the freezer either free hanging near the top or attached to the object that you want to be at a specific temperature, like a fermentor. How are you seeing the temp get that low, like with a thermometer setting in the freezer? Not sure if the freezer has some sort of controller - you want to set it on its coldest dial setting and unless it has its own temperature controller - the unit should over ride the freezer...as long as it set up correctly. If having issues, maybe send photos of how you have everything set up and make sure to review the instructions on getting the unit set correctly. Cheers!
Will I be able to connect this to a heating element in my HLT to control mash and sparge temperatures? Will the probe function well in a bed of grain and hot wort (I assume I will need the 12" probe for that)?
Gregory B on Feb 14, 2016

Yes, I believe you can use the thermostar for mash temps as well as fermentation control.
Can you connect both a cooling unit and heating unit at the same time with this unit? Will the unit be able to distinguish between the two and initiate the heating or cooling unit when necessary?
N B on Nov 18, 2015
BEST ANSWER: The ThermoStar will only heat or cool at one time. It has one socket to plug in a refrigerator/freezer or fermenter heater. There is a switch to change between cooling, heating or sole temperature monitoring. You would need two temp. controls to do what you?d like.

That said, I ferment in a chest freezer in my garage. If I desire cooling, I ferment in my freezer and plug the freezer into the ThermoStar. If it?s too cold outside for the desired fermentation temp, I ferment in the freezer, wrap a heater around my fermenting vessel and cover it with a towel. I find that the freezer is an efficient environment for fermenting since it?s insulated and dark.
The control is not maintaining desired range? I set my desired temperature around 50F, i have used the heat and cooling elements have seen the range jump from 28F to 67F in the fridge. I have used the lock feature, turned the fridge temp control off, and to its lowest setting nothing has work to maintain the temperature range. It is a old fridge but that shouldn't matter.
thomas b on Feb 2, 2017
BEST ANSWER: Does the fridge maintain a normal temp when just turned on without the controller? I would make sure the probe is attached to the side well to get an accurate reading of the ferment.
I'm having a hard time understanding on how to this device works, I have set the the temp to be around 55F for primary lager fermentation, i have seen temps ranging from 38to 67F. What am i missing? i have tried using the heating mode and cooling mode.
A shopper on Feb 1, 2017
BEST ANSWER: The first thing is to look at the cooling device. Most set them on their coldest setting to ensure the unit cools quickly. The next thing is the probe itself. You either want a long probe or thermowell to go into the liquid or be sure the 2" probe is contacting the fermentor, with some tape and some paper towel/cardboard to hold it in place and get good contact.
After purchasing this unit and reading the manual and reviews I'm a little disappointed. From what can gather this doesn't have a ssr relay.? .. Which would not have the issue of wearing out.
A shopper on Jan 18, 2017
BEST ANSWER: It does not come with a Solid State Relay. However these controllers are rated for a lifespan in excess of 1 million cycles. As an example scenario, turning on and off once every 15 minutes in constant operation, 1 million cycles is approximately 13.5 years.
Im trying to out if there is a way to re-calibrate these. I noticed a difference in readings on my internal fridge thermometer and the temp my ThermoStar is now reading... ( reading 56* instead of 66* ) After testing / comparing it with my glass lab thermometer, I found it's consistently reading anywhere from 9 to 11* COOLER than actual temps on several tests. Any help here would be greatly appreciated?
John A on Jan 16, 2017
BEST ANSWER: Hi there,
You can correct temperature offset from the advance options menu. Cheers!
Can the probe be used inside RIMS tube thermowall and still accurately measure the mash temperature?
A C on Aug 7, 2016
BEST ANSWER: We have not tried using this controller with a RIMS or HERMS setup. While the optional 12" stainless steel probe can be immersed, and mash temps are within the normal operating range for this controller, the cycle time is not necessarily optimized for brewing operations (intended more for fermentation).

Additionally, this controller is rated for a maximum of 15 amps.
Will this work with a Fast Ferment conical fermentor
M I on Jun 6, 2016
BEST ANSWER: It can work in a few different ways. The probe can be inserted to the thermowell with some teflon tape to hold it in place or just taped to the side of the fermentor.
Is there a way to waterproof the shorter sensor? Alternately, are there third party sensors or probes that will work with the plug on the controller? I already have the longer 12" probe, but want to use this in my mash tun directly in the mash to get the most accurate result. I think even the longer probe will get wet.
Y U on Mar 28, 2016
BEST ANSWER: You can use a thermowell made of plastic or metal.
Will this support a 120v AC 1500 watt heating element 12.5 amps
P W on Feb 22, 2016
BEST ANSWER: Yes, it would. The output relay on this unit is rated for 15 amps maximum. -Mike W, Northern Brewer
It says that with the 12'' probe you don't have to use a thermowell. How do you get the probe into the beer if you're not using a thermowell? I ferment in 6 gallon carboys.
J A on Sep 18, 2015
BEST ANSWER: A carboy cap is a fine option

or a two hole stopper. The probe is waterproof and long enough to reach the liquid so no thermowell is needed but you do need a second hole in the cover to insert it.
Can this be used in a fridge to control the temp?
B R on Sep 7, 2015

it can be used with a fridge or freezer to set and control the desired temperature.

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