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Cooler Master Nepton 280L CPU Cooler Review


Well-known member
Oct 24, 2007
Bolstered by the success of their Seidon series of all in one water coolers, Cooler Master is stepping things up a notch by introducing the Nepton 280L. This represents an effort to offer up higher performance by utilizing the niche 280mm form factor and implementing several design additions to set the Nepton apart from its competition.

“Supersize me” is a fitting term for Cooler Master’s latest effort since everything built into the Nepton 280L has been upsized. It uses two 140mm fans, has a thicker radiator, boasts massive (for an AiO at least) tubing and even includes a completely custom water block design that’s supposed to drastically improve flow rates and CPU heat dissipation. Considering that most entrants in this market simply tow the same line by using rebadged Asetek and CoolIT derivatives, Cooler Master is hoping to breathe some new life into a somewhat stagnant market. However, is you might expect, there are risks associated with taking the path less travelled.


On paper the Nepton 280L's specifications and features do not appear to be all that unique. Many manufactures are now offering larger '280mm' / dual 140mm radiator based units. In fact the only item which will likely jump out at consumers is Cooler Master’s use of FEP tubing instead of more modern compounds which have rightly superseded FEP. In many ways this would make the Nepton 280L just another closed loop cooler with visions of grandeur from a company that has traditionally struggled to differentiate their wares. However, we’d dare say Cooler Master’s latest attempt will likely be enough to insure folks will rethink their purchasing decisions.

It’s impossible not to mention the Nepton 280L’s price because at $140 USD, this happens to be one of the most expensive units on the market. However, there is a real lack of competitors right now since Corsair’s H110 and NZXT's Kraken X60 are really the only other 280mm alternatives that are broadly available. With a situation like this taken into account, Cooler Master’s flagship will need to provide substantially better performance than dual bay 240mm AiO's in order to justify its cost and a lack of built-in fan speed control.


At just a cursory glance at the specifications the Nepton 280L appears to be nothing more than a slightly larger version of Cooler Master’s Seidon 240M. Like the Seidon, the Nepton uses a custom waterblock, older style FEP tubing and a unique 3 port radiator. However once you get beyond these superficial similarities and actually look at the Nepton the differences in designs become readily apparent.

The FEP tubing in particular is a key point of differentiation. It has been increased from the Seidon’s 9.5mm to 15.5mm, is a lot more flexible and Cooler Master has included a full 15” of tubing, making installation all that much easier.


The largest difference between the Seidon and Nepton series is the aforementioned water block. The Seidon’s was designed for pump noise reduction rather than raw, unadulterated performance and also came in a compact form factor. Cooler Master’s Nepton on the other hand uses a square and rather bulky waterblock that houses a more powerful (yet still quiet) pump yet still retains the same distinctive mounting design. It may look a bit utilitarian but the Nepton 280L’s focus is the lowest temperature possible rather than beautifying the inside of your case.


Internally the waterblock has also been upgraded and improved with better efficiency to take advantage of the large water pump’s increased flow rates. Like the Seidon before it Cooler Master includes a small tube of thermal compound rather than a single use pre-applied application, which will be great news to consumers who swap out their CPU on a semi-regular basis.

Cooler Master’s finishing process seems to have slipped a notch though. Not only does the copper surface lack fine-grain polishing, the base actually felt rough to the touch and had numerous machining marks visible to the naked eye.


The Nepton’s radiator uses Cooler Master’s signature 3 port design, though with a thickness of 30mm (versus most other units’ 27mm) for taking care of higher heat loads. It also uses 14 water channels instead of the usual 12 or 13.

What really sets this design apart addition of both 120mm and 140mm fan mounting holes, making it one of the most flexible All in Ones available today. Other 280mm-based coolers like Corsair’s Hydro H110 limit case compatibility and fan selection for those who want to upgrade the two included fans. However, Cooler Master has both bases covered, opening up a world of possibilities. Unfortunately, the Nepton only uses the newer 15mm spacing for its 140mm fans while the 120mm fan spacing is completely unique.


Cooling potential is left in the hands of two JetFlo 140 fans which rated for some very impressive performance numbers. They are 4-pin PWM capable, rated for 800-2000RPM and can move upwards of 122.5 cubic feet of air per minute with 3.5mm of static pressure. Cooler Master has once again opted for a Rifle Bearing design instead of Hydro / Fluid Dynamic bearings but we doubt many end users would notice a difference.

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Well-known member
Oct 24, 2007
Included Accessories / Installation (Intel / AMD)

Included Accessories


The accessories which accompany Cooler Master’s Nepton 280L are very similar to the Seidon but reflect the improved mounting procedure created for the Nepton series. There’s a well-documented installation pamphlet, a large bag containing mounting equipment for all current Intel and AMD systems and a small tube of thermal compound. Unfortunately, the anti-vibration gasket found in the Seidon series is conspicuous by its absence and has been replaced by simple strips installed directly onto the fans.

Nepton 280L Installation (Intel)


Cooler Master has done away with plastic Intel or AMD-specific backplates and instead designed an all-metal one size fits all solution. It’s quite actually brilliant, with sensible position indicators and double sided Intel / AMD labels for its various positions. As an added bonus the Nepton 280L supports 115x, 1366 and 2011 systems along with older 775 socketed motherboards. Spacers are also included to insure backplate mounting pressure remains consistent across every CPU type.


With the backplate and its associated posts installed, plastic spacers have to then be attached to each of the posts. These will hold the posts and backplate in position without the need for double sided tape. This is another area of improvement over the Seidon's metal standoffs.


There are two universal Intel top brackets and mounting them to the waterblock is done via small screws. These screws are the single weak link in this design as they are easy to lose and finicky to get into place.


Installing the water block into position is quite easy with each of the four posts sliding up through the water block’s retention bracket and then a quartet of nuts being used to provide even mounting pressure. The nuts are a touch small and can be difficult to manipulate but they aren’t spring loaded, making them much easier to work with.


This is where the installation does go off the rails somewhat Even though Cooler Master has included both 120 and 140mm fan mounting holes, the Nepton 280L is not compatible with their own HAF-X case nor any enclosure which has only 120mm fan mounting options. Much like the NZXT X60 and Corsair H110, we had to resort to brackets to mount this to our case. How is this possible? Even though the Nepton 280L can use 120mm fans their spacing is proprietary and will not line up with dual 120mm fan mounting holes in any case.


AMD System Installation


The AMD installation uses most of the same hardware as its Intel counterpart though this time the “AMD” side of the backplate is used. Once again, everything is clearly labeled.


Prepping the water block is straightforward as well, with AMD brackets being used this time.


With the brackets in place the installation continues to follow along the same lines as we saw above, with the exact same radiator installation hiccups. Luckily, the Nepton 280L is one of the more AMD friendly AIOs available today.
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HardwareCanuck Review Editor
Staff member
Feb 26, 2007
Test Setup & Methodology

Testing Methodology

To ensure that the results from one review to another are not only reproducible but actually pertinent to this review, the Testing Methodology will be the same throughout all water cooling review. If something does change we will be sure to make a special note of it and explain why this change was done and more importantly why things had to be changed or altered.

Thermal Paste and Application Methods:

Arctic Cooling MX-2 thermal paste was used for all water based CPU cooling solutions during these tests unless otherwise noted. Application of thermal paste was in accordance with the TIM manufacturer’s instructions; and while not necessary, the TIM was allowed to cure for 24 hours under moderate to high loads (with periods of low loads) prior to testing.

Fans Used:


For all water based CPU Cooling Solutions which do not come standard with a fan, a pair of Noctua NF-P12-1300s and a Scythe S-Flex “G” 1900RPM fan will be used if it accepts 120mm fans. With these two fans we are able to simulate different fan speed conditions as indicated below.

High Speed:

1900RPM Scythe S-Flex “G”. To be more precise our specific fan runs at 1860RPMs. Any stock fan which comes with the ability of being controlled by means other than the motherboard (e.g. remote fan speed controller, potentiometer, rheostat, etc) will be set to this speed during the High speed test and BOTH sets of performance results will be included.

Dual Fans:

Dual NF-P12-1300s

*Dual fans only used if the cooler comes with the necessary mounting hardware.

92mm Fan:

If the cooler being tested only accepts 92mm fans, a Noctua NF-B9-1600 will be used.

If the given CPU cooling solution comes with a stock fan we will also include its numbers in the closest of the main tests BUT we will also include our standard fan results in that particular tests.

Fan Notes:

- If a water cooling solution cannot mount an aftermarket fan, we will be only including the stock fan results. However, if the stock fan speed can be precisely controlled by means other than the motherboard BIOS (an included remote fan speed controller, potentiometer, rheostat, etc), the cooler will be tested at different fan speeds.

- For dual fan results ALL water coolers capable of mounting two fans (and come with the necessary hardware) will be tested with two NF-P12s and the Dual Fan graph will contain data for other such dual capable fan coolers.

We feel that the combination of multiple speeds and multiple fans will allow us to give you our readers clear and precise idea of the capabilities of a given unit, in an accurate comparison. It will also help eliminate the occasional “zinger” such as when a manufacturer includes an extremely high-speed fan in order to possibly offset poor thermal performance.


Except where noted all comparison testing was done inside a closed case with a room ambient temperature of 24c. If at any time the room temperature increased or decreased by more than 1°C, testing was halted until the temperature constant was re-established.


The case chosen for this test bed is a Cooler Master HAF-X. We chose the HAF-X as it a highly adaptable case with not only multiple fan ports but is capable of handling even the largest of AIO coolers. To populate these fan ports we chose Scythe E 120mm units with Sony Fluid Dynamic Bearings. Unless otherwise noted, only one of the top two exhaust fan ports, the rear exhaust port and front fan intake port will be populated. The front fan port will use the stock CM 230mm fan. The rear exhaust port will be populated by the review item's fan and radiator where possible, for the air based cooling alternative used in the review as a counter example another Scythe E will be used.

Warm Up:

Before testing commenced 15 minutes of running Prime95 “small fft” followed by 45 minutes of idling was done. This warm up period was done at stock CPU core frequencies. This additional pretest was done to ensure that the fluid in the liquid CPU cooling solutions were at ambient room temperature and thus the test results would be more indicative of real world scenarios. For all air based cooling solutions the same 15 minutes of heavy load followed by 45 minutes of idle was also done.

Temperature Recording:

Recorded temps were as reported via the Real Temp plug-in for the RivaTuner monitor program.

Max and Average load temps are based on 15 minutes of running Prime95 “small fft” and are taken directly from RivaTuner’s built in capabilities.

The maximum temperatures will be the highest recorded temp displayed for any of the cores during the 15 minute test. While RivaTuner will display each core's average temperature it does not easily show the average of ALL the cores. To this end we will be simply taking the average of all the cores adding them together and then dividing by the number of cores.

If during any test temperatures of 95°C or more are displayed in RivaTuner (for any core) for more than 10 consecutive seconds the testing will be halted and that test run will be considered a "fail".

Idle temperatures are the lowest recorded temperature during idle period as recorded by the RealTemp Rivatuner monitoring program.

All CPU throttling technology was disabled in the BIOS; as was all CPU fan speed control. In addition, Turbo Mode was disabled and Hyperthreading was enabled. All power connectors for the review item are connected directly to Molex connectors to ensure they were running at full speed.

All tests are run a minimum of three times and only the best results are represented.

Charts & Graphs:

Each chart will include the Maximum or “peak” temperature we recorded, the average temperature and the idle temperature.

No passive results will be shown UNLESS manufacturer claims the ability to passively cool a processor. If a manufacturer claims passive capabilities we will include the performance numbers in the charts. The only exception to this is if the review is a “review roundup” and to keep the charts from becoming confusing we may not do so.

All water cooling reviews will also include a air based CPU cooling which best approximates the price range of the water cooling solution being reviewed. This way you will not only know how it compares to other water cooling units but also an Air based CPU cooling solution which is in the same approximate price range.

Sound Pressure Testing:

To give a more accurate and less of a personal opinion on the noise level of the stock fan which accompanies the heatsink, we have included a new section for sound pressure testing. These tests are done in our open case setup outlined above with the meter positioned 30 inches away from the cooler and mounted on a tripod. To ensure the background noise does not skew the results all tests will start by recording the ambient noise of the room. Only when it meets our standards will the testing commence.

To ensure that no external noise unduly skews the results, the GPU used will be a passively cooled unit and the only active fan will be the one on the cooler while the PSU and HDD are isolated away from the immediate area.

These tests are run late at night when no other people or animals are awake and thus unable to influence the results.

All fans are run at their maximum speed with no voltage or PWM control being used during the sound pressure tests.

The sound pressure meter used is a DT-805 which has been professionally calibrated and NIST certified. We will record the highest levels obtained with said meter and record it as our result. The test will be 15 minutes long and will be run while the fan is running full speed via a Molex connector and the CPU cores are under a full load via Prime 95 Small FFT.

Please note: The Scythe S-Flex G and Noctua NF-P12-1300 (at 1300 and 900rpms) numbers are taken when mounted to a Cooler Master Hyper 212+. We feel that it would be extremely unfair and unrealistic to include noise rating for these after market fans if they were NOT mounted onto a cooler. They are included to help give some sense of proportion to the charts and allow you to more easily compare a stock fan against a known quantity.

Complete Test System:

Case: Cooler Master HAF-X
Processor: Intel i7 920(Intel)
Motherboard: Gigabyte X58-UD3R
Memory: 6GB Mushkin Silverline Stiletto DDR3-1600
Graphics card: EVGA GeForce GT 240
Hard Drive: 1x 240GB Intel 520 SSD
Power Supply: Topower Powerbird 900W

Special thanks to Gigabyte for their support and supplying the i7 motherboard.
Special thanks to NZXT for their support and supplying the NZXT 140mm fans.


Well-known member
Oct 24, 2007
Stock Fan Performance Results

Stock Fan Performance Results




There really isn't much to dislike about these results, but by the same token we are not overly surprised by them either. Everything about the Nepton 280L simply screams 'extreme performance' and anything less than best in class results would have been disappointing.
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Well-known member
Oct 24, 2007
Dual & Quad Fan Performance Results

Dual & Quad Fan Performance Results

<div align="center">
<img src="http://images.hardwarecanucks.com/image/akg/water_cooling/Nepton_280L/dual.jpg" border="0" alt="" />
<img src="http://images.hardwarecanucks.com/image/akg/water_cooling/Nepton_280L/quad.jpg" border="0" alt="" /></div>

Stock fan vs stock fan results are very important, but they only tell half the story. It is only when you test all devices with the same fans that the true abilities of a cooler become apparent. When we did swap out the JetFlos for NZXT fans the results simply blew us away. The Nepton 280L is the best AIO cooling device we have tested to date. Even the previous best in class NZXT X60 runs hotter.

Thanks to its rather unique abilities we can even see how it stacks up against 120mm-based designs in this test. While doing this does handicap the Nepton 280L, the reduction in performance is not all that severe and we were actually expecting a larger loss of performance. The unique spacing may mess with mounting the radiator but it does minimize cooling loss.
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Well-known member
Oct 24, 2007
Sound Level Testing

Sound Level Testing

<i>While everyone "hears" noise differently there is one easy way to remove all subjectivness and easily compare different fans: use a sound level meter. This way you can easily compare the various fans noise envelopes without us colouring the results and see what fans fit within your personal comfort level. Of course, we will endeavour to try and explain the various results (which are taken at a 30 inch distance) to help you our readers get an even better understanding of how loud a cooler's stock fan is, but even if you discount our personal opinions, the fact remains numbers don't lie. All fans are tested with both voltage regulation / PWM turned off.</i>

<div align="center">
<img src="http://images.hardwarecanucks.com/image/akg/water_cooling/Nepton_280L/noise.jpg" border="0" alt="" /></div>

These JetFlo fans may indeed be -slightly- quieter than those which accompanied the smaller Seidon 240M but that is not saying much. Their noise profile is much, <i>much</i> more noticeable than most 140mm fans we have tested. The combination of Rifle bearings and high rotational speed is makes them among the loudest but among other components and the noise of gaming, they'll likely be lost in the background.
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Well-known member
Oct 24, 2007


It’s always nice to go into a review without any expectations and come out pleasantly surprised. With its oversized dimensions, old school tubing and massive water block, Cooler Master’s Nepton 280L looks like an all-in-one cooler from a bygone era. However, based on results alone, it obviously packs enough current technology to be one of the best cooling options if your case is compatible and cost isn’t a deciding factor.

The dual bay 280mm market doesn’t have all that much competition but the few coolers that occupy this segment like Corsair’s H110 and NZXT’s X60 are class-leaders in their own right. Going up against the incumbents wasn’t easy but in every test, the Nepton 280L was the frontrunner, sometimes by a significant margin. Granted, Cooler Master’s flagship is quite a bit more expensive but for those who want the best water cooling performance around without going to a custom loop, this is in pole position.

Above and beyond raw cooling performance the Nepton provides extremely long and flexible tubing which simplifies mounting and a well designed multi-disciplinary backplate for quick water block installation. It was also great to see a nod to AMD users and a full tube of thermal compound rather than the pre-applied TIM route most competitors take.

In order to achieve such low temperatures, Cooler Master did have to use fans that operate at a relatively high acoustical level which runs contrary to the entire “raison d’être” of 140mm fans. It also places the Nepton at a distinct disadvantage in this respect against the H110 and X60. This cooler certainly aren’t the loudest we’ve heard but without built-in speed controls, users will have to go through the sometimes-clunky process of modifying RPMs in the BIOS.

While the inclusion of 120mm mounting locations on a 280mm cooler is nothing short of inspired, we can’t help but feel Cooler Master rendered this potential breakthrough all but pointless. In what can only be classified as an oddball design decision, they built in dual 120mm fan mounts (brilliant!) but then provided non-standard spacing, making Nepton 280L incompatible with every case that supports 240mm radiators. Even with those handy 120mm mounts beckoning, it is only compatible with enclosures that have an available 280mm bay.

With everything tallied, Cooler Master has created a surprisingly flexible cooler. As long as your case can accommodate its form factor, and your budget can accommodate its equally large asking price, the Nepton 280L is one of the best CPU cooling options available. It may have taken Cooler Master a few tries, but they now have a flagship model which can once again compete with the best the industry has to offer.

<div align="center">
<img src="http://images.hardwarecanucks.com/image/akg/water_cooling/Nepton_280L/dam_good.jpg " border="0" alt="" /> <img src="http://images.hardwarecanucks.com/image/akg/water_cooling/Nepton_280L/di.png" border="0" alt="" /></div>
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