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ThermoStar® Dual-Mode Digital Temperature Controller


SKU# U41264

Flat Rate Shipping only $7.99 only from Northern Brewer
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 Digital Temperature Controller   +$79.99
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Get it in Ashburn by Wed May 30.
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 ListedYes
Body Dimensions
Width (at widest point)68mm
Temperature Sensor
Standard Probe Length2 inches
Extended Probe Length12 inches
Cord Length8 feet
Additional Information
Support Documents:ThermoStar® Instructions
4.2 / 5.0
52 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
Tstat saved the day!
This product worked perfectly. My refrigerator broke and I did not want to spend $300 on a repair. The product was simple to install and to program. The instructions were not completely clear, but setting it up was not hard. I am using it to control a refrigerator, and the two degree swing around the set point is probably closer control than what I had with the original factor controller.
May 20, 2018
1 month ago
Excellent temperature control for both warming from ambient temp (combined with FermoTemp Carnot warmer), as well as colder than ambient temp as controller for chest freezer. Allows perfect fermentation temps as well as lagering temps. Love the control.
March 27, 2018
1 year ago
A snap to setup and use
First off, setting and adjusting the temperature is a snap. Perhaps they have changed how this is done because previous reviews complained about this. The heater does not completely go around my fermentation bucket or bubbler. With a second person, we put the heater on the fermentation bucket, then wrapped the heater and bucket with a towel and then secured it with bungee cords. The towel also acts as insulation. The long temperature probe works well, but you will need a way to have it inserted into the liquid. So I bought a two hole lid for the 6.5 gallon bubbler. For the fermentation bucket (used for wine) I drilled an additional hole and added a grommet that I also purchased from Northern Brewer. The heater and controller maintain a fermentation temp of 72-75 and greatly enhanced the fermentation. I highly recommend this kit.
March 26, 2018
2 months ago
Perfectly regulates temperature
This purchase was for use in my keezer, and it is much simpler to control than my other temperature controllers, and seems to be very durable. I only gave it 3 stars b/c the velcro attachment is weak.
Attached to the side of my keezer.
Attached to the side of my keezer.
January 26, 2018
6 months ago
Very short life
I loved being able to control the temp of my fermentation. I got tired of lugging carboys from the basement to upstairs and back again to try and keep the temperature in range. The =/- on the set temp was a little wide but it was still worth it.

Less than two years later I plugged it in and nothing. It just doesn't work anymore. At that price I would expect it to last longer. There's not even a way to open it up and try to fix it. Guess I just toss it in the trash. Disappointment.
December 25, 2017
Great and easy to use
Arrived in a timely matter, excellent product so far. Very easy to set up and currently brewing a lager and keeping my chest freezer at the exact temp i want. Temp probe is attached to the outside of my fermenter. Worth the price
November 9, 2017
7 months ago
Don't waste your money
I purchased this device November 2016. I didn't get a chance to use it until March 2017. Once we had it all set up, we included two other thermometers to ensure that it was reading and setting the temperature properly. It was about 10 degrees off - obviously that's a big deal. I called up customer service and they were extremely helpful. They sent me out a brand new one asap, but the brand new one is doing it now too. We even tried it on a different refrigerator.
September 22, 2017
Easy to set up and performs as advertised - solid product!
September 12, 2017
9 months ago
Worked for awhile
This temperature controller worked for about 2 years and it started failing after 1.5 years. The switch no longer turns on the outlet. For the price, I would have expected it to last longer than 1.5 years.
August 7, 2017
Worth every penny
I live in Houston and no matter where I tried to put my fermenter in the summary the temp just wouldn't stay in range. I now have complete control with thermostar. Step up took all of about 20 seconds.
August 4, 2017
10 months ago
Start typing your question and we'll check if it was already asked and answered. Learn More
Browse 36 questions Browse 36 questions and 94 answers
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.
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 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!
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.
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.
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 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.
Will this controller handle a heating element that is rated 1500W ?
A shopper on Sep 23, 2017
BEST ANSWER: No. I am using a 30 amp contactor with a 115 volt coil. I use the temp controller to pull in the coil of the contactor, that uses next to zero current and i have a second plug that feeds the primary input side of the contactor. Then an outlet wired to the secondary output side of my contactor. I can now switch anything up to whatever my circuit can handle up to 30 amps.
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.
I have a 3-gal carboy with stopper. Is there a way to adapt stopper to handle both airlock and the temperature sensor so the sensor can go down into the wort?
A shopper on Dec 8, 2017
BEST ANSWER: Yes, I’ve done it a couple ways. I have a stopper with two holes in it so the airlock or blow-off hose goes in one and my thermowell for the temp sensor goes in the other. The other way I’ve done it is to cut the stems off one of those orange carboy caps and I stick the airlock in one and thermowell for the sensor in the other. Finally, if you ever end up with a bubbler, they make a lid with two holes for two separate stoppers. Hope that helps.
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!
Is my Thermostar fixable? Have had it for about 2 years to control my keezer with no problems.Now the temp reading is all over the place, showing temps well over 200 degrees F. This of course, has frozen all my beer due to the incorrect temp readings. Is this a probe malfunction, or is the whole device useless now? The connections all look fine, as does the temp probe, and wire, with no visible cracks or anything.
A shopper on Feb 10, 2018
BEST ANSWER: It sounds like your thermocouple (temp sensor) died. It needs to be replaced without replacing the entire unit.
Has anybody used one of these to make a refrigerator with a window AC unit? Thoughts about the idea?
A shopper on Sep 25, 2017
BEST ANSWER: Hi, have not tried to use with a window AC unit, but do not see why not. The Temp controller cycles off and on based on the temp at the sensor. Probably much like the sensor in the AC unit. I imagine if you couple with an AC unit, you should crank the AC until as high as you can and allow the Thermostar to control the temp., just like when using it with a freezer. Hope this helps. It is a good unit.
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
Robert F 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.
Is my Thermostar fixable? I have been using it for roughly two years to control the temp for my keezer. Out of the blue the temp readings are now all over the place, ranging very high, usually 120-250 degrees F. All connections look good. I restarted the device, but same problem recurred. Could this be a probe problem? Or is the entire device now useless?
nicholas p on Feb 13, 2018
BEST ANSWER: Sounds like a problem with the sensor. In the HVAC industry you often see high or null values when a sensor is busted.
Can I buy replacement grommets and o-rings? The unit came with a tiny little rubber grommet and o-ring that allowed the 12" probe to fit airtight inside of the thicker port on the standard carboy cap. I use the 12" probe in that port to monitor wort temp during primary and have a blow off tube hooked-up to the other port on the carboy cap. Only problem is I seem to have lost the rubber grommet/o-ring!
A shopper on Sep 10, 2017
ThermoStar® Dual-Mode Digital Temperature Controller
ThermoStar® Dual-Mode Digital Temperature Controller
Standard Carboy Cap - 3/5/6/6.5 gallon glass carboys
Standard Carboy Cap - 3/5/6/6.5 gallon glass carboys
BEST ANSWER: We do sell a replacement 12" probe, but none of the smaller components that make it up.
I get a flashing F1 error message when attaching the probe to my keg and I can't figure out how to fix it. Any ideas?
David C on Jul 26, 2017
BEST ANSWER: The only error code I am aware of is a flashing "L-F-" which means the probe is either not connected properly or malfunctioning. This sounds unique and I would attempt a test of the unit in different conditions and set ups to see when it does it and when it does not. Consider contacting Customer Service directly as it sounds like a unique situation - which often have simple solutions.
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.

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