NZXT Kraken X31 CPU Cooler Review
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NZXT Kraken X31 CPU Cooler Review

October 27th, 2015 James Leave a comment Go to comments



It’s strange a one point we seemed to be reviewing nothing but CPU Coolers here at pcG and then it all just stopped! Lately we seem to be reviewing nothing but peripherals, but that’s now about to change, why? Well, we’re back looking at CPU Coolers again, and this time it’s the NZXT Kraken X31 (RL-KRX31-01) that I’m going to take a look at. This is the second NZXT Kraken based Cooler we’ve seen here at pcG, but this will be my first time, you could say that I’m a Kraken virgin (although that does sound a little weird to me!). 😉

The NZXT Kraken X31 is a AIO liquid based CPU Cooler, sporting g a 120mm radiator and a single 120mm fan. What’s most important though is that this AIO liquid CPU Cooler features a variable speed pump, and that ladies and gentlemen has not been seen before, anywhere! In fact (according to the box) it is a world’s first! The cooler is designed for both Intel and AMD and supports the following socket types (Intel LGA 2011-3, 1366, 1156, 1155, 1150 / AMD FM2, FM1, AM3+, AM3, AM2+, AM2). Both the pump speed and the fan speed can be controlled via NZXT’s CAM software (not supplied).

NZXT ‘The Kraken X31 is one of the first consumer closed loop coolers with an integrated variable speed pump. The state-of-the-art variable speed pump keeps noise to a minimum during use without sacrificing top end pump power. he X31 utilizes a 120mm radiator platform to deliver the widest range of compatibility of any of our Kraken liquid coolers, making it compatible with any NZXT case available today and nearly all of our competitor’s.’


NZXT Kraken X31 - box top NZXT Kraken X31 - box front


The NZXT Kraken X31 arrived at pcG in a smart white ‘n black box with a large image of the Kraken X31 on the top showing of its radiator and pump. In addition to this when looking at the top of the box we can also see the following statement ‘THE WORLD’S FIRST VARIABLE SPEED LIQUID COOLER’, we can also see that the Cooler supports both Intel and AMD platforms and that it comes with a very impressive 6 year warranty.

Looking at what is effectively the front of the box we can see another image of the radiator and pump and a image of the NZXT CAM software. In addition to this NZXT highlights the following (via five icons): 120mm Radiator, FX120 Fan, Variable Speed Pump, CAM compatible & 16″ Tubing. There’s also an additional 6 points that NZXT has chosen to highlight (see image above right).


NZXT Kraken X31 - box left NZXT Kraken X31 - box right


Both the left and right sides of the box also feature additional information. On the left we have a list of compatible CPUs and associated sockets and also a small graph showing the difference between a 120mm cooler (single fan), a 120mm cooler (dual fans) and the NZXT Kraken X31. Of course the NZXT outperforms the latter two cooler, thanks in part (according to the side of the box) to the fact that the radiator is 16% thicker than normal. On the other side of the box we find a specifications section (see Specifications/Features below for more detail).


NZXT Kraken X31 - box open


On opening the NZXT Kraken X31 box we are greeted with the usual egg carton style (eco friendly) packaging that now seems to be the norm for water coolers!? It may not be the best presentation in the world but everything is well protected and it’s not cost the lives of too many trees!


NZXT Kraken X31 - box contents (fan & manual) NZXT Kraken X31 - mounting hardware


Within the box we find a single 120mm fan and a basic (very basic!) installation guide and a handful of mounting hardware for both Intel and AMD, with the latter clearly identified.


At the time of writing, the NZXT KRAKEN is retailing on Amazon for approximately £65 and comes with an impressive 6 year warranty.



courtesy of NZXT

Model Number RL-KRX31-01
Fan Air Flow 81.32 CFM (max.)
Fan Air Pressure 0.44 – 2.76 mmH20
Fan Bearing Hydro Dynamic Bearing
Motor Speed 2400-3600 ± 150 RPM
Fan Connector 4-Pin PWM
Motor Voltage 12V DC
Motor Connector 3-Pin
Compatibility Intel LGA 2011-3, 1366, 1156, 1155, 1150 CPUs
AMD FM2, FM1, AM3+, AM3, AM2+, AM2 CPUs
Fan Dimensions 120x120x25mm
Motor Current 325mA
Radiator Dimensions 155 x 120 x 30 mm
Fan Noise Level 18-34 dBA
Tube Length 400mm
Fan Speed 800-2000 RPM ± 10%
Fan Voltage 12V DC
Control Method Kraken+ Software Module
Warranty 6 Years

* Additional details available here


First Impressions


NZXT Kraken X31


First impressions of the NZXT Kraken X31 are that it looks pretty much the same as many other 120mm based AIO CPU Coolers that I’ve seen! That’s no bad thing though, there’s just very little that tends to separate a lot of the AIO coolers these days. The Kraken X31 appears to be well made though and NZXT also seem to be of that opinion judging by the impressive six year warranty. Let’s take a quick tour around the Kraken X31 and see what’s what, shall we!?


NZXT Kraken X31 - radiator & tubing NZXT Kraken X31 - pump


The radiator itself measures in at 155mm (W) x 120mm (H) x 30mm (D) a little thicker (approx. 16%) than your standard 120mm radiator. The radiator has two end-tanks with one end tank (where the tubing connects) being thicker than the other. Attached (permanently) to the radiator we find the two rubber tubes that are around 400mm in length. This tubing is plenty long enough for most applications and is also nice and flexible and doesn’t kink easily.

Looking at the business end (the pump head) of the Kraken X31 we see a large circular housing adorned with the white NZXT logo and pattern. Unfortunately on the X31 version of the Kraken the NZXT logo doesn’t illuminate, which is a shame. Note the warning label (Connect Pump Power Before Turning On), although I would have thought that was a little obvious! 😉 By default the locking ring around the outside of the pump is for an Intel setup, this can be twisted off, removed and replaced with the supplied AMD ring should that be required.


NZXT Kraken X31 - cold plate NZXT Kraken X31 - connections


Looking at the base (or the cold-plate) of the pump head we see that it features an all-copper base plate held in place by eight screws. We can also see that the Kraken X31 has thermal paste pre-applied therefore this is how it will be tested.

Finally let’s take a quick look at the electrical connections required to make this AIO Liquid Cooler comes to life. When looking at the image above right we can see that the connections on the left are for the fan/s, while the connection on the right (USB 2.0) is for the pump and its associated CAM software. The 4 pin plug should be plugged into the motherboard’s CPU fan header while the supplied fan can be connected to either of the fan sockets on the other cable. As you can see an additional fan can be added and controlled should you wish to do so.

From what I’ve seen so far I rather like the look of the NZXT Kraken X31, it’s a clean and simple approach to a 120mm based AIO and one that I hope should work well. Let’s get it installed and see, shall we…


Hardware Installation


  • Test Rig Setup

  • Case Cooler Master HAF XB Power Supply Corsair Professional Series AX 760i
    Motherboard ASRock Fatal1ty Z170 GAMING K6 CPU Intel Core i5-6600K
    CPU Cooler NZXT Kraken X31 RAM G Skill Ripjaws 4 16GB
    Graphics Card XFX AMD Radeon R9 290X DD Black Edition SSD HyperX FURY 120GB


    NZXT Kraken X31 - mounting hardware for 115x NZXT Kraken X31 - fan etc


    The first task was to work out the mounting hardware required for our Intel Skylake socket 1151 CPU. This was made all the simpler by the bag of screws labelled AMD! One would therefore assume that all of the rest of the fittings would be Intel and therefore used, but no! And, reading the supplied instructions isn’t going to help much either as they are pretty rubbish to be honest (a better online version can be found here). The fittings that you need to remove (other than the AMD bag and mounting ring) are the stand-offs for LGA 2011, they can be identified by their coarser threads.

    All of the required fittings are shown in the images above (although there’s too many long screws (above right), only four are required). So that’s one back-plate, x4 stand-offs, x4 nuts and x1 fan, x4 small screws, x4 long screws and x4 washers (optional).


    NZXT Kraken X31 - backplate installed (front) NZXT Kraken X31 - backplate installed (back)


    The first task was to simply place the back-plate on the back of the motherboard and secure from the front with the four stand-offs. Note that the small posts attached to the back-plate slide and can be positioned specifically for the type of socket being used.


    NZXT Kraken X31 - installed no fan NZXT Kraken X31 - installed with fan


    Once you have the back-plate in position the CPU Cooler itself can be installed. Note that I chose not to mount the fan to the radiator first, just to make it a little easier to move around. First I mounted the radiator to the back of the HAF XB case using the four small screws provided. Then the pump head was secured to the top of the CPU (using the pre-installed thermal paste) using the four nuts. Lastly the fan was secured to the radiator using the four long screws and washers provided. What’s a little odd is that there is another four screws should you wish to add another fan, but no washers!? 🙁


    NZXT Kraken X31 - installation complete NZXT Kraken X31 - closeup


    I have to confess that installing the NZXT Kraken X31 must be one of (if not the) easiest AIO CPU Cooler installs I’ve ever performed, and to be fair I’ve installed a few! 😉


  • Software
  • NZXT CAM software To ensure full functionality of the NZXT Kraken X31 the NZXT CAM software needs to be installed, this can be downloaded here. The software allows you to chose from a few predefined profiles Silent, Performance and Manual and you can also create your own profiles too! There’s a host of monitoring options also, although I did come across a strange anomaly during testing where the result would be lost during monitoring (see main image below).


    Testing Methodology/Setup


    NZXT Kraken X31 - ambient For CPU Cooler testing, we here at pcGameware run Prime95 for a 15 minute period. During this period the temperature is monitored via ASRock’s F-Stream utility and the CPU temperature recorded. Between each stress test we allow a 15 minute cool-down to allow for more accurate results. To adjust the fan speed we simply use the UEFI. But as the fan on the X31 is controlled via the CAM software, we just set the fan/pump to 100% via the Manual mode. A close eye is also kept on the ambient temperature, with the maximum being recorded for each run, this allows us to calculate the Delta temperature (Core – Ambient = Delta). Each run was performed with the Intel Core i5-6600K CPU at the following frequencies: 3.9GHz (Stock) and 4.4GHz (using the ASRock OC Tweaker, shown in the images below), all results have also been recorded with CPU-Z.

    * Please note: To ascertain the maximum and minimum noise levels produced by our test CPU Coolers, the dBA is recorded at a distance of 1 metre from the cooler, with all case fans unplugged to isolate the sound in question.


    ASRock UEFI - main ASRock UEFI - Load Optimized CPU OC Setting 151026155505

    Processor speed is set using the OC Tweaker tab within the UEFI, “Disabled” for stock speeds (3.9GHz) and “Turbo 4.4GHz” for the overclock tests. It should be noted that changing the OC settings resets the Fan Speeds, so these are checked on the next reboot and reset to “Full Speed” (see above right). All the fans installed in the system are set to 100% speed using the displayed settings, this is simple with the ASRock UEFI with the option of “Full Speed” being available for all system fans.


    Hardware Performance


    As stated above, to make our performance tests easier to follow and to get the most accurate recordings, all of the following tests have been carried out with case fans set at 100% and the NZXT Kraken X31 fan also set at 100%. This was done using the Manual mode in the CAM Software.


    • Intel Core i5-6600K – 3.9GHz (stock)


    NZXT X31 - FullSpeed STOCK

    ASRock F-Stream CPU @ 3.9GHz @ 1.120v (fans @ 100%)


    CPU Cooler Air/Liquid Fan Speed Ambient Temperature Max CPU Temperature (core average) Delta Temperature Noise Level
    NZXT Kraken X31 Liquid 100% 22.00 43.00 21.00 39dB
    Noctua NH-U12S Air 100% 22.00 44.00 22.00 38dB


    As you can see from the list above it’s pretty short! That’s because we just upgraded all of our Test Rigs to the new Skylake platform and this (unfortunately) means that all of the past results are no longer valid. But we have to upgrade at some point, so please bear with us as over time this list will surely grow…

    The only True comparison we have is against our own CPU Cooler of choice the Noctua NH-U12S and in comparison the NZXT X31 is surprisingly similar in performance. In our 3.9GHz test the Kraken X31 was able to keep our Intel Core i5-6600K skylake processor at a balmy 43 degrees Celsius, one degree cooler than the Noctua. Now that’s a pretty good result, but let’s see how it copes with a pretty hefty overclock…


    • Intel Core i5-6600K – 4.4GHz (OC Tweaker)


    NZXT X31 - FullSpeed 4-4GHz

    ASRock F-Stream CPU @ 4.4GHz @ 1.312v (fans @ 100%)


    CPU Cooler Air/Liquid Fan Speed Ambient Temperature Max CPU Temperature (core average) Delta Temperature Noise Level
    Noctua NH-U12S Air 100% 21.00 59.00 38.00 38dB
    NZXT Kraken X31 Liquid 100% 22.00 61.00 39.00 39dB


    In our high overclock test (4.4GHz @ 1.312v) the NZXT Kraken X31 still performed well keeping our now toasty Core i5-6600K processor at no more than 61 degrees Celsius. Although that allowed the Noctua NH-U12s to nudge ahead by one degree! Considering the large overclock and the high voltage the Kraken X31 does very well as 61 degrees is well within my comfort zone and well within Intel’s guidelines. In Gaming the temperatures will be even lower, and let’s be fair who sits down for an evening of Prime 95 anyway!? 😉


  • Acoustics

    I must admit I was pretty impressed with the acoustics of the NZXT Kraken X31; normally these AIO CPU Cooler have a fan speed of around 2,000 plus RPM with the noise that goes with it. But the Kraken X31’s 120mm fan at 100% speed only produced 39dBA of noise and that’s pretty impressive. What we have here then is a cooler that’s both cool and quiet even when at full speed.

    For testing purposes I also used the in-built profiles that are present within the NZXT CAM software, these are Silent and Performance. Remember not only does the fan speed change for each profile but the pump speed changes too! Using the Silent profile in our 4.4GHz overclocked test saw the fan speed at 25% and saw the maximum temperature rise to 71 degrees. Using the Performance profile (with the fan now at 50%) the temperature dropped back to 65 degrees. The cool thing here (ha ha get it!) is that via the CAM software you can pretty much set you own temperature and fan speed, either by using one of the built-in profiles or creating your own! Now NZXT cant surely do much more than that… 🙂


    Final Thoughts


    There’s no doubt in my mind that the NZXT Kraken X31 (RL-KRX31-01) is a truly great little AIO CPU Cooler, that’s extremely easy to fit and offers good cooling at a low noise levels, but it’s still not exactly cheap!

    The NZXT Kraken X31 arrived at pcG in a regular white ‘n black box with all of it contents safety packaged within that eco friendly egg carton style packaging. Once out of the box the Kraken X31 looks like any other 120mm AIO liquid CPU Coolers. There’s a radiator (a little thicker at 30mm) some nice flexible rubber tubing and a pump head found at the other end, pretty standard stuff to be honest! But it all looks well made and designed and let’s not forget the pumps party trick of being variable in its speed!

    Installation is best described as ‘one of the easiest I’ve ever installed’, honestly it really is that simple. Just a back-plate, 4 stand-offs and four nuts and the pump is installed. Other than attaching the fan to the radiator and the radiator to the case (8 screws), it just leaves the cabling. Three connections need to be made (assuming your using the one fan), that’s the pump to motherboard (CPU fan header), one fan to fan socket from the pump and one to a motherboard USB socket. The latter allows the Kraken X31 to be controlled via the NZXT CAM software.

    Once installed the NZXT Kraken X31 looks good and the tubing is nice and long and very flexible, without kinking easily. Unfortunately (as this is a budget model) the smart NZXT logo in the centre of the pump head doesn’t illuminate, which is disappointing IMHO.

    In testing with our new Intel Core i5-6600K Skylake Test Rig the Kraken X31 performed well, although I have to confess we don’t have much data on this new Test Rig as of yet! At stock speeds and with both pump and fan at full speed the Kraken X31 kept our 6600K at 43 degrees Celsius which is pretty impressive, but it’s the overclocked test that really shows a CPU Coolers true potential. At 4.4GHz with a voltage of 1.312 volts the NZXT Kraken kept temperatures down at 61 degrees (Delta 39) just one degree off of the Noctua NH-U12S. All in all a pretty good result, especially when you consider that the noise produced at full speed (with no detectable pump noise) was around 39dBA.

    Of course using the CAM software allows you to select a couple of in-built profiles such as Silent and Performance. In the overclocked test using the Silent profile temperature increased significantly to 71 degrees but at this setting the acoustics dropped to near silent at around 31dBA. Swapping to the Performance profile saw temperatures drop back down to 65 degrees with a minor increase in noise. But if you’re not happy with these profiles the NZXT CAM software will allow you to create your own, and to be fair NZXT cant do much more than that… 😉

    Overall I have been pretty impressed with the NZXT Kraken X31, it really is a nice little cooler and a good alternative to some of the bigger air based CPU Coolers. It’s extremely easy to install and offers good cooling at low noise levels. The CAM software also gives it that extra dimension allowing you to modify/monitor your pump/fan/temp to your hearts content.



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    Where possible we always use Amazon’s price for Value…
    Design/Quality pcGameware awards the NZXT Kraken X31 a Silver


    Many thanks to NZXT for providing this sample for review


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