Fractal Design Kelvin S24 – Test and Review

Kelvin is the name Fractal Design uses for their first attempt in the AIO liquid CPU cooling solutions. Before proceeding any further with the article let’s have a closer look at the respective models in the Kelvin range and their specifications:

  1. Kelvin T12 – the smallest of the bunch, featuring 120mm water cooling copper radiator with dimensions of 46 x 132 x 163 mm and cooled by two Fractal Design Silent Series HP 120 mm PWM fans with RPM range of 800 – 1700. The radiator has an innovative construction of copper and nylon, where the nylon is placed on the outer parts where heat transfer doesn’t take place. A ceramic pump is installed here and it has max RPM of 2400 with 72 l/h water flow.
  2. Kelvin S24 – this piece features a 240mm water cooling radiator, made entirely of copper and with physical dimensions of 30 x 124 x 275 mm.  Cooled by two Fractal Design Silent Series HP 120 mm PWM fans with RPM range of 800 – 1700. A ceramic pump is installed here and it has max RPM of 2400 with 72 l/h water flow.
  3. Kelvin S36 – the largest of the three models, S36 features a 360mm water cooling radiator with physical dimensions of 30 x 124 x 397mm, being cooled by three Fractal Design Silent Series HP 120 mm PWM fans with RPM range of 800 – 1700. Again the ceramic pump is present here and it has max RPM of 2400 with 72 l/h water flow.

I received the Kelvin S24 package and was pleased with it as S36 wouldn’t have been possible to test with my current case. S24 and overall the whole three AIO of Fractal Design look really shiny and bring the needed diversity in the CPU water cooling niche, so let’s examine the box, the content and afterwards the performance of Fractal Design Kelvin S24.

The front of the box The back of the box
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S24’s box looks quite simple, but comes with an attractive color scheme as black and blue always go well with each other. The Fractal Design logo stands on the left corner, right next to it is the model name and underneath that we have a nice, glossy printed picture of the AIO cooler itself. The background is all black and has a nice contrast with the white text at the back of the box, where further technical details and explanations are present. The pump and the radiator assembly are placed there for additional examination by the user.

I am quite pleased with the design of the box as it is informative and attractive at the same time, so Fractal Design did a very good job with the presentation of the Kelvin series, as the other versions of the cooler come with the exact same packaging, the only difference is the size.

I am very impatient to check out the contents of the box so let’s open it and see what’s under the carton pieces.

User guide
Kelvin S24 wrapped up
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So far so good, there was a soft styrofoam cover over the parts to protect from harm and on top of it I found the user guide, also wrapped up in nylon like the rest of the parts. Before proceeding further with unpacking I checked out the guide, as sometimes companies pay little to no attention in the included information on how to use the product inside without voiding the warranty or damaging other components. Fortunately, this is not the case with Kelvin S24 as the guide is extremely informative and inside you can see clear instructions on how to install the cooler easily. The information that I read will come in handy later onwards in the article, for now I will leave the guide aside.

The other parts have been laid out in separate chambers inside a large piece of recycled carton to provide support and protection. No harm was done to the AIO and I was pleased to see it in one piece.



Removing all of the nylon wrappings I ordered the pieces and took a photo so we can see what comes included in the box.


The standard Fractal Design Kelvin S24 package offers:

  • 1 x User guide
  • 1 x PWM Y-splitter with black sleeve
  • 2 x Fractal Design Silent Series HP 120 mm fan
  • 8 x mounting screws
  • 8 x mounting screws, long
  • 1 x Fractal Design thermal paste
  • 4 x retaining nuts
  • 4 x springs
  • 4 x washers
  • 4 x Intel 2011 mounting screws
  • 4 x AMD mounting screws
  • 1 x black, plastic backplate
  • 4 x Intel mounting screws
  • 2 x Intel bracket, 2 parts
  • 1 x AMD bracket
  • CPU cooler assembly (radiator, tubes and water block)

All of the screws, springs and nuts are painted in black to best suit a modern system build and were carefully placed in labelled transparent bags so you know immediately which package you need for your type of socket without searching for parts.

And here is the S24 radiator with tubes and the water block attached. At first glance it doesn’t look too different from any other AIO cooler, however it is needless to say that we can’t compare coolers only by their looks. There is something different and special about the cooler and I am going to describe its parts and check it out in depth to see what makes it the better option when choosing a new CPU cooler for your CPU.


So, let’s get started…


I will begin with the water block itself as it drew most of my attention when I first checked out the cooler. S24 has a square water block with a very stylish, but prone to fingerprints black piano finish covering the top part and a white Fractal Design logo in the lower right corner to complement the company. Sadly, the logo is not illuminated, but still it looks quite elegant. Actually Fractal Design worked co-op with Alphacool to develop and create the Kelvin series using premium grade, high quality materials which should result in very high performance and durability.

Top of the waterblock
G 1/4″ thread brass fittings
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The physical dimensions of the water block are 69 x 69 x 40 mm and it is black, excluding the copper plate, which in fact is held by 4 screws to the base of the water block for improved durability. For the make of the water block plastic and metal are used in combination, which doesn’t disrupt the durability. Some other AIO use either glued copper plate or more screws for attachment, but that by itself doesn’t impact the cooling performance. The build quality of the block is very high and is quite solid overall.


The copper plate of S24 and all the other versions – T12 and S36 are special ones as they feature Jet stream plate which is designed in such a way that water flows through the pin array. Rubber rings seal the jet plate so that water does go only in one direction for a concentrated flow. That detail is supposed to provide additional cooling performance, which I will check later in the test section of the article.


The contact plate is with a perfect square shape and was protected by a nylon cover which of course should be removed prior to installing. As you can see from the photo the plate has loads of tiny holes and it is not mirror like polished. That’s where the thermal compound will be absorbed to create the necessary bond between CPU’s IHS and the copper plate.

One more feature of the Kelvin series is the dedicated fill port, located on the left side on the water block. This fill port is used mainly of you want to upgrade the loop in your system, refill the liquid or change it entirely and to perform regular maintenance.


Fractal Design has given general guidelines on how much the pump can take:

  • Kelvin T12 should cool up to 1 CPU and 1 GPU
  • Kelvin S24 should cool 1-2 CPU and 1-2GPU
  • Kelvin S36 should cool up to 1-4 CPU and 1-4 GPU

These figures are quite promising as there are little systems with more than 1 CPU and dual GPUs. Definitely a thing that will interest the modders out there and in the near future we may be able to see cool mods and high performance systems using the Kelvin.

It is time to attach the Intel bracket as later I will be installing the cooler to my system. The Intel bracket and the AMD one as well are painted completely in black and are both made of solid metal pieces.

AMD/Intel mounting kit
Intel kit, incl. s.2011
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What was really strange for me as I was trying to attach the Intel 2-piece bracket to the water block was the fact that although it aligns perfectly in “dry fit”, it is extremely difficult to actually install the bracket to the water block. The two pieces need slide on pre cut rails in the plastic mono block, however when they meet and should click to lock an enormous amount of force is required to fulfill this action. As could be seen from the picture below even when fully installed it doesn’t seem they align perfectly and the paint got scratched off. It is an interesting approach that Fractal Design went with but I believe this is not the optimal way of doing this.


Nothing severe though, once attached the paint damage could not be seen and the bracket is definitely firmly connected to the block. It will provide solid connection between the motherboard and itself that is for sure.

A powerful and durable ceramic pump is being used in this assembly which was optimized for best performance/noise ratio by FD. They do not recommend to alter in any way the voltage levels or pump speed as it may be an unpleasant sight. The pump also features “Dry Run Protection” so it can continue to operate even if there is no water in the system without getting damaged. All of Kelvin coolers feature the same ceramic pump, operating at 2400 RPM and producing noise level of about 25.0 dBA. It is powered by a not very long black sleeved cable with a 4-pin PWM connector at the end. Its operational voltage is 12V and the current is 0.27A. Because of its construction the pump has a water flow level of 72 l/h and the pressure is 1.0 m H2O. Combined with the Jet plate some serious performance is expected.

Okay, now that I’ve checked the pump/water block assembly I will proceed with the next essential part of Klevin S24 and that is the water cooling radiator.

S24 radiator
Radiator thickness
IMG_0336 IMG_0337


Kelvin S24 is equipped with a black painted slim radiator with physical dimensions of 30 x 124 x 275 mm and it almost looks like an aftermarket radiator as there are no fancy stickers different colors and such. Two small FD logos printed in white are placed on the sides of the radiator and will be visible regardless of the direction you mount the radiator. Clean, elegant and beautiful, these are the three words that come to my mind when I checked the radiator out.

Okay, visual coverage is done, but what about the materials used and the engineering? As I’ve said earlier, FD worked in cooperation with Aplhacool to give the users a premium product and in that relation the entire radiator is constructed from copper. Some of you might say that this is not the best possible material, FD were kind enough to announce it in the website. It may take the copper a bit more time to absorb the energy (heat) to a 100% but it will provide more consistent results overall in the end.

The radiator was in perfect condition and had no dents or damages so FD did a very nice job protecting it in the box, or the courier was a nice guy…


When speaking about radiators an important aspect needs to be examined and that is the FPI (fins per inch) figure, which in Kelvin S24’s case is 6-7 FPI. That is not a high density radiator, like for example – Silverstone Tundra TD02. That allows for lower operational speed of the fan, which results in lower noise output and not necessarily worse temperatures.

The connection between the water block and radiator is done by two black, non-transparent tubes with 320mm of length and Ø11mm diameter. Inner diameter is 8mm to provide nice and steady water flow. The tubes provide UV protection so if your system is exposed to sunlight often, sadly, there will be no frogs jumping around randomly. Anti-kink coils are added to prevent bottlenecks of water flow and they also look quite attractive.

For the fittings used in this assembly Fractal Design went with G 1/4″ ones, used for the fill port, water block and radiator as well. Compatibility with other water cooling products is supported out of the box, so less hassle is expected when dealing with expansion or modding. The fittings are black and made of brass and also made with German quality. It is not recommended to replace them with lower grade fittings, but I believe none of the enthusiasts will accept lower grade components in his system.

Now that I’ve covered the water block and radiator with the tubing as well, I should say a couple of words about the oh-so-important fans, cooling this premium grade metal. Kelvin S24 is able to accommodate 2 x 120 mm fans, so let’s check them out, as they are included in the package.


The standard included fans are Fractal Design Silent Series HP 120 mm, featuring an all black plastic frame design, with 7-blade propeller. When looking at the wide blades HP should mean High Pressure, however I was not able to find any additional information in the FD website, except the one provided in the Kelvin S24 specifications, so I will go with it. Power is coming through a not very long black sleeved cable with a 4-pin PWM connector at the end.

Black, nylon sleeve
IMG_0333 IMG_0332


Both fans have 62.4 CFM of maximum airflow each, generating around 26.9 dBA of noise when rotating at maximum RPM. Speaking of RPM the official specifications state the range is 800 – 1700 RPM, so this indeed should provide quieter operation as we’ve seen fans of AIO rotating at 2000 RPM or more. That is not a bad thing of course, but it is not silent either. What this means is that the cooler is properly optimized to give best performance/noise level ratio. Each of the fans has a maximum of 2.33 mm H2O static pressure level and I believe this might be just sufficient for doing a brilliant cooling job. No bearing type is confirmed yet on the website, but I think it might be Fluid Dynamic Bearing. I may be wrong so if you know it, feel free to post it in the comments below.

Installing the two fans on the radiator is a pretty straight-forward job and all you’ll need is a screwdriver. All the necessary screws are included and additional installation methods are covered as well, there are enough screws to mount the radiator to the case with fans under, or fans to the case and radiator attached to the fans, that way the internals will be better looking.

And here are the attached fans to the radiator. I will be using the standard setup of mounting the radiator to the case with fans underneath, blowing air through the fins, rather than sucking it.

Installed fans
Thickness with fans mounted
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Now that the whole assembly is finished I have to say that the design is quite attractive and elegant. The white propeller and white text on the radiator and water block create a nice contrast and is very appealing even without any LED lights.

To use the AIO I will have to install it using the mounting kit provided in the package and according to the official details announced on the company web page, the AIO is made to be compatible with:

  • Intel – 775,1150,1155,1156,1366 and 2011
  • AMD – AM2,AM2+,AM3,AM3+,FM1,FM2,FM2+

For doing my tests I will need the Intel brackets, if you remember I’ve already installed one of them to the actual water block, so the second mounting stage is about to commence.

Mounting bolts
Mounted on water block
IMG_0369 IMG_0371


With one part of the kit already (painfully) mounted the next step was to assemble the bolts, which consists of the bolts themselves, a spring, washer and a retaining nut. When done, you need to install all 4 of them in the pre cut holes as shown on the photo above.

Backplate installed
IMG_0372 IMG_0373


Installing the backplate is as easy as it gets – it has 4 nuts on it that you can move so they align with the socket on your motherboard. In this case socket 1150 and just align the nuts, pop them into place and you’re ready with it. Although it is plastic the plate has a solid construction and I wouldn’t worry if it is easy to break, because it is durable.

Ready for mounting
Water block installed on s.1150
IMG_0375 IMG_0377


With the back plate ready, all that was left was applying the thermal paste. Included in the package there is a 1 g syringe with Fractal Design Zero™ thermal paste that should be enough for multiple applications.

It is always recommended to cross tighten the bolts so the pressure applied to the CPU is equalized and the paste is somewhat evenly distributed. That is shown as well in the manual on how to properly fit the water block – great thinking Fractal Design.

And this is what the final picture looks like with the AIO ready to be tested.

Interior shot
Kelvin S24 ready to roll
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As you can see from the picture above, when the water block is attached to the processor it will not block any of the DIMM slots and will provide full low profile and high profile RAM compatibility, as well a beautiful view.



With the AIO installed, the time to check my testing rig has arrived and I continue the article with the tests…

  • CPU: Intel i5-4670K
  1. At standard frequency 3.400 MHz (Voltage set to Auto when not OC-ing)
  2. At low overclock frequency of 3.900 MHz  (at 1.24V)
  3. At medium overclock frequency of 4.300 MHz (at 1.25V)
  • Motherboard: ASUS Maximus VII HERO Z97
  • Video card: MSI AMD R9 280X GAMING 3G
  • Memory: A-Data XPG 8 GB Dual channel, 1600 MHz
  • Solid State Drive: Intel 530 Series, 120 GB
  • Hard drive: Western Digital 640 GB Black Series
  • Case: Antec Nineteen Hundred
  • Power supply:  Corsair RM750 W
  • Cooler: Fractal Design Kelvin S24
  • Thermal paste: Noctua NT-H1

For the test I will be using the supplied 2 x 120mm fans and will test the cooler at maximum RPM.

The tests were conducted in a closed system with:

  • Three Antec 120mm fans, installed as intake, rotating at ~1200 RPM
  • Two Antec 120mm fans, installed on the HDD cage inside the case, rotating at ~1200 RPM
  • One Antec 120mm fan, installed as exhaust at the rear of the case, rotating at ~1200 RPM

Room temperature of about 23-24 degrees.

And here I want to describe my testing method.

I will install Fractal Design Kelvin S24 and do stress tests using Prime95 AVX software with constant load on the cooler for 14:30 minutes with custom settings of minimum FFT size (in K of 128), max FFT size (in K of 128) and Run FFTs in place at standard frequency of 3.4 GHz (Voltage set to Auto when not OC-ing), at low overclock frequency of 3.9 GHz (at 1.24V) and at medium overclock frequency of 4.3 GHz (at 1.25V) using the supplied fans installed on the radiator.

Now let’s check out the test results:

Kelvin S24 @3.4 GHz, Idle Kelvin S24 @3.4 GHz, Load
S24 Idle S24 @3.4 load


Kelvin S24 @3.9 GHz, Load
Kelvin S24 @4.3 GHz, Load
S24 @3.9 load S24 @4.3 load


All of the test results have been summed up in the following charts:


And the fans/pump speed during the tests:


I believe the time for conclusions has arrived.


Fractal Design Kelvin S24 CONCLUSIONS

1. Fractal Design Kelvin S24 performance:

Brilliant job from Fractal Design! This is their first attempt in this cooling segment and they definitely did their homework. Kelvin S24 is one of the best AIO liquid cooling 240mm radiators I have tested so far. Build quality is superb and we have to give it to them that all the proper research was done before releasing this on the market. In the coming years I expect FD to surprise us with an even better version of the Kelvin series.

Kelvin S24 is easy to install, easy to use and quite an amazing piece of cooling equipment. I have to admit I had my doubts about these three new coolers, but I should have thought twice – outstanding work.

Even though the S24 doesn’t outperform some other coolers we’ve tested here, it does stand its ground perfectly fine as it achieves excellent temperatures with bearable noise level. The pump spinning at 2500 RPM is perceptible, at least for me, but it is more on the silent side. The fans when spinning at low RPM are almost silent, one thing that made me a bad impression was that I could hear the motors more than the actual airflow. Due to the orientation of the fans or due to the bearing type I do not know, however I would like to see Fractal Design change or make another revision of the fans, why not include one of their premium fans.

2. Fractal Design Kelvin S24 appearance:

Beautiful design as far as I am concerned. I prefer the black/white color scheme as it fits with everything in almost any system and looks quite elegant. One thing I want to see in the next versions is LED lights included on the water block with the logo of Fractal Design as it deserves some attention for the good job done here.

This cooler will be a nice addition to a wide spectrum of system out there, because it has a very unobtrusive design and looks great when installed.

According to my review, I think that Fractal Design Kelvin S24 deserves the following reward:


Official price (MSRP) for Fractal Design Kelvin S24:  $119.95

Official warranty: 24 months

I thank Fractal Design for the test sample.


Fractal Design Kelvin S24 – Test and Review
9.9 Total Score
Amazing cooling performance, simle, yet elegant looks and very high build quality

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Nikola Milanov is reviewer and newsman at DVTests and has more than 6 years of experience in telecommunications. I'm really enthusiastic about the website and its development by sharing a user's point of view and experience with the products we test. We are honest and objective in all of the articles, the products get tested and reviewed thoroughly with no exception! Feel free to ask any questions in the comment section or use the emails in About us page!
  1. Reply Alex1 16.03.2015 at 20:03

    Good review, I really liked the detailed info, pictures and graphs.
    Good work!

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