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Cooler Master Nepton 280L CPU Cooler Review

April 16th, 2014 Mike Leave a comment Go to comments



Here we have a slight oddity, an AIO (All In One) CPU watercooler that is NOT a re-skinned and re-branded design?!? Ladies and Gentleman I give you the Cooler Master Nepton 280L (RL-N28L-20PK-R1)! This AIO has been totally designed by Cooler Master from the ground up, meaning despite a few similarities (radiator, block, tubes & fans), it is a completely new design. The Cooler Master Nepton series have followed a slightly different path to their competitors, this being the radiators aren’t in your typical 120mm/X format, but in 140mm/X. Which theoretically means they’ll dissipate more heat. Of course the radiator won’t shift all that heat alone, so Cooler Master have rather nicely included two JetFlo 140mm fans to aid the 280mm radiator in keeping your CPU cool.


Or by Cooler Master themselves.

cooler master logo ‘The Nepton 280L is Cooler Master’s latest watercooling kit that aims to bring water cooling to the next level. Nepton 280L is using a CM exclusive designed pump with a highly effective water block. It has thicker and longer tubing for upgraded performance. In addition, dual JetFlo 140 fans + an extra large 280mm radiator provide substantial cooling power with over 300W heat dissipation, which enables users to overclock their CPU and maximize performance.’


Cooler Master Nepton 280L - Box front Cooler Master Nepton 280L - Box back


Cooler Master have once again opted for the same premium finished boxes of last years AIO Coolers (Seidon & Eisberg), which is certainly no bad thing. The predominantly black and embossed silver box with the purple sides look really good and feel really solid and just like the previous offerings, the packaging is made using re-cycled materials (who says you can’t have style ‘and’ substance eh?)

The box front shows us an artistic impression of the Cooler Master Nepton 280L, Cooler Master logo, model name and a few descriptions rather nicely embossed in silver and also highlights the following features:

  • Liquid CPU Cooler
  • Extreme Cooling Performance
  • Extra Large 280mm Radiator
  • Dual JetFlo 140 Fans
  • Maintenance Free
  • UltraFine Micro Channel
  • Durable FEP Tubing

The reverse side again gives us the nicely silver embossed Cooler Master logo, model name, socket compatibility (Intel-Socket LGA 2011/1366/1150/1155/1156/775 or AMD-Socket FM2/FM1/AM3+/AM3/AM2), some technical drawings and highlights the following features in several different languages:

  • Pure Copper Waterblock
  • Micro Channel Technology
  • Factory-filled and sealed
  • Durable and powerful water pump – dissipates heat effectively and maintains temperature through stable water circulation

The reverse also shows a Perdormance (slight typo methinks ;)) test, showing the results of the Nepton 140 & 280 compared to the stock Intel heatsink (but then, who uses that!?).


Cooler Master Nepton 280L - Box left Cooler Master Nepton 280L - Box right


The left side of the box gives a full break down of the Nepton 280L Specifications (see Specifications/Features below), whilst the right shows very little although it does do it in style…


Cooler Master Nepton 280L - Box bottom Cooler Master Nepton 280L - Box top


The bottom of the box shows the Cooler Master support information and gives the Nepton 280L model number. The top shows nothing worthy of note (but it is purple and I like purple 🙂 (ED: Really, nobody likes purple do they!?)).



  • CM self-designed – Pump and water block guarantees the best water flow and system performance.
  • Robust & Extra Thick FEP Tubing – Strong and durable for 280mm radiator installation. Moreover, FEP tubing have great advantage for less liquid dissipation.
  • New UltraFine Microchannel – Is a new designed for best water flow and takes maximum heat from cold plate to coolant.
  • JetFlo 140 – Basic provides powerful air pressure. The rubber pad on the side of stiff reduce vibration and noise
    1. Advanced fan blade design – The 7 rigid fan blades cut through the air at speeds ranging between 800~2000 RPM and produce high airflow up to 122.5 CFM operating at full power.
    2. Shock-absorbing rubber pads – Rubber pads absorb vibrations and noise.
  • Advanced Fan Blade Design – Compared to other normal fans, the advanced fan blade design of JetFlo 140 can concentrate more air for excellent cooling performance with a low noise level.
  • Supports 120mm Fans/Case with 120mm Mounting Holes – The radiator of Nepton has additional mounting holes for 120mm fans, which provides better compatibility for cases without 140mm mounting holes.
  • Unique LED – Illumination on the water block lens.


Upon flipping open the box lid, we find a recycled cardboard tray. This stores all of the separately bagged contents tightly to help prevent damage. This also contains the Cooler Master Nepton 280L warranty information, fitting instructions, an itemised contents list, fittings and the all important AIO Cooler itself.


Cooler Master Nepton 280l - unboxing Cooler Master Nepton 280L - full aio


Box Contents:

  • Cooler Master Nepton 280L
  • 2 X Cooler Master JetFlo 140mm PWM fans
  • PWM 2-1 Splitter cable
  • Universal Backplate
  • Mounting Brackets (Intel & AMD)
  • Fittings
  • Installation Guide
  • Warranty Information


At the time of writing the Cooler Master Nepton 280L has an SRRP of £114.99, but is available from Amazon for approximately £95 and comes with an incredible 5 year warranty!



courtesy of Cooler Master

Model RL-N28L-20PK-R1
CPU Socket Intel LGA 2011 / 1366 / 1150 /1155 / 1156 / 775
AMD Socket FM2 / FM1 / AM3+ / AM3 / AM2
Dimension 75 x 69.8 x 49.1 mm ( 3 x 2.7 x 1.9 inch )
Radiator Dimensions Aluminium
Fan Dimension 140 x 140 x 25 mm ( 5.9 x 5.9 x 1 inch ) *support 120mm fan x 2
Fan Speed 800~2000 RPM (PWM) ± 10%
Fan Airflow 54~122.5 CFM ± 10%
Pixel/Dot/Pitch 0.311(H) x 0.311(V)mm
Fan Air Pressure 0.7~3.5 mm H2O ± 10%
Fan Life Expectancy 40,000 hours
Fan Noise Level (dB-A) 21~39 dBA
Bearing Type Rifle bearing
Connector 4-Pin
Fan Rated Voltage 12 VDC
Fan Rated Current 0.3A
Power Consumption 3.6W
Pump Life Expectancy 70,000 hrs
Pump Noise <25 dBA
Pump Rated Voltage 12 VDC
Pump Power 2.9W

* Additional details available here


First Impressions


So after finally wrestling the Nepton 280L from it’s tight packaging (it’s pretty tightly wedged!) and checking through the other contents, the first impressions are pretty good. One surprise is the size of the radiator (anything bigger than a 240mm rad seems huge in the hand, in fact it’s not much smaller than my… Alphacool NexXxoS XT45 360mm). Unlike the well performing but somewhat ugly Cooler Master Seidon 240M or the expandable, but overpriced and huge Cooler Master Eisberg 120L Prestige, the Nepton 280L waterblock is surprisingly simple and almost elegant in it’s square design and not too big at (75W x 69.8L x 49.1D mm). The block case is entirely made out of black plastic (I’d hazard a guess this is actually a protective cap of sorts), atop of which is moulded the Cooler Master logo, which when powered on has an illuminated white surround. Just to the right of the block protrudes two heavy duty FEP (Fluorinated Ethylene Propylene) tubes (length 35cm), both of which are of a larger diameter to the usual AIO tubing (15.5mm OD (Outer Diameter) vs 9.5mm OD), this should mean more coolant will move through the AIO and improve cooling and efficiency. Just to the left of the block is a rather nice fully braided 3 pin power cable. Underneath the pump block is a full copper cold plate, which I’m a little surprised to see unpolished!


Cooler Master Nepton 280L - waterblock Cooler Master Nepton 280L - coldplate


The Cooler Master Nepton 280L as its name suggests, features a rather large 280mm aluminium radiator (139W x 311L x 30D mm). This may seem a little odd given the most popularly featured fan mount in most cases is 120mm, but in the last twelve months many case manufacturers seem to be headed in the direction of using the quieter and better performing 140mm. Of course if you actually look closely at the radiator fan mounts you’ll notice there are two sets, so not only can you use the included JetFlo 140mm fans, but also your current favourite 120mm fans, should you wish! I think this is a great idea and something I’ve not seen before. This potentially means if your case has space for a 240mm radiator, if space allows you still might be able to squeeze in the Nepton 280L!

Taking a closer look at the radiator shows that it is really well finished in black, even including the fins. So this should nicely fit in pretty much any colour schemed rig you have in mind. Looking at the radiator head you can see how heavy duty the FEP tubing is running to the inlet port and back from the outlet port. Given the amount of heat-shrink sleeving around the barb fittings, it’s hard to imagine the tubing springing a leak or coming loose. Just to the right of the tubes is the fill port, given the AIO and factory filled nature of the Nepton 280L, there are clear warning labels advising you not to tamper or remove the plug (why would you want to ruin a 5 year warranty anyway?).


Cooler Master Nepton 280L - 280mm radiator Cooler Master Nepton 280L - fillport


Of course how much use is an AIO cooler without fans? The Cooler Master Nepton 280L comes fully packaged with two Cooler Master JetFlo 140mm fans(140W x 140L x 25D mm). These are both PWM fans which when fitted connect up to a 2-1 PWM Y splitter cable, then straight to any PWM (rule of thumb being if header has 4 pins it’s PWM) fan header on your motherboard. So far the full Nepton 280L package is pretty cool wouldn’t you agree? Well it doesn’t stop there!

For me the best feature of this cooler is the simple screw (no sniggering at the back there!). The Nepton 280L box contains two sets (eight in each) of limited thread thumb screws for the radiator (this is done to help prevent you from accidentally piercing the radiator during fitting). One set (the shorter) attach the fans directly to the radiator, the second set (slightly longer) are for attaching the fans on the outside of the case effectively making a sandwich. So you can set the two JetFlo 140 fans in either a push or pull configuration. The real beauty in these thumb screws is the threaded heads, this means you can quite happily fit your fans to the radiator, then attach to the case without having to fiddle around with trying to find the screw holes whilst your fans are slipping or sliding around! (Despite the references to screws, holes and slipping and sliding, anyone who’s had to fit a radiator will instantly see what I mean). On the downside by doing this you’ll find a big gap between the Nepton 280L radiator and the case, this shouldn’t be a problem with any SP (Static Pressure) styled fans that more or less blow air in a straight cylindrical line, but this could cause a drop in performance for AF (Air Flow) which blow air in a cone like fashion.


Cooler Master Nepton 280L - jetflo 140

Cooler Master Nepton 280L - components


Hardware Installation


The Cooler Master Nepton 280L installed into the trusty home of the pcG Test Rig, the Cooler Master HAF XB (this was done by having a quick glance over the included instruction sheet, then trusting my own judgement, which then resulted in further consultation of the instructions ;).

Actually the fitting went surprisingly well (after reading the instructions!). By starting off with the backplate (The plate is dual purpose and works for both AMD and Intel CPU’s), you push the silver standoff’s through the outside ‘X’ of the backplate, then fix them in place with the small plastic clips. This then fits through the CPU Socket (1150 in our case) mount holes in the back of the motherboard. Back at the top of the motherboard, you simply drop large black spacers over the top of the standoff’s. You now apply your Thermal Paste to the CPU using your method of choice (personally I use the squishy pea method) and the Nepton block then threads onto the standoff’s whilst giving the block a gentle wiggle to help evenly spread the Thermal paste. Then lightly tighten each of the standoff bolt heads (always in start in one corner and work in an ‘X’ shape, this helps to give you an even spread) until they’re all finger tight.


Cooler Master Nepton 280L - Backplate

Cooler Master Nepton 280L - Waterblock installed


For the fans and radiator I opted for the pull method, so in the Cooler Master HAF XB, the 280mm radiator is mounted on the inside, whilst the JetFlo 140mm fans are mounted on the outside. The main benefit of this of course is to allow more working space on the inside of the case. The two JetFlo 140mm then plug into the PWM Y Splitter, which in turn was plugged into CPU Fan Header 1, whilst the Nepton itself was plugged into CPU Fan Header 2.


Cooler Master Nepton 280L - Radiator installed

Cooler Master Nepton 280L - JetFlo 140 Installed


So a nice and simple install that can be fitted surprisingly quickly and with ease. Cooler Master have clearly put a lot of thought into the Nepton and given how stale the typical AIO design re-branding has become, is very refreshing to see.

But how cool is the Nepton 280L?


Testing Methodology/Setup


For CPU Cooler testing, we here at pcGameware run Prime95 for a 15 period. During this period the temperature is monitored with CoreTemp and the cooling performance recorded (the max recorded is the average for all core’s). Between each stress test we allow a 15 minute cool-down to allow for more accurate results. To help with fan speed accuracy we use SpeedFan whilst using MSI Command Center to adjust the fan speed. 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 i5-4670K CPU at the following frequencies: 3.4GHz (Stock), 4.0GHz (using MSI OC Genie, also shown in the picture below) and 4.5GHz (using Intel Extreme Tuning Utility, also shown in the pictures below), all results have been recorded with CPU-Z.

* Please note: To ascertain the maximum and minimum noise levels produced by our CPU test coolers. The db is recorded with all case fans unplugged to isolate the sound in question.


Cooler Master Nepton 280L - Command Center

Cooler Master Nepton 280L - Intel XTU 4.5GHz


Hardware Performance


Because the Cooler Master Nepton 280L is shipped with 2x140mm JetFlo fans that also happen to be PWM, I decided to let the MSI Z87-G45 GAMING Motherboard and MSI Command Center do all the fan work for me. So using this great bit of software I’ve recorded the performance of the Nepton with the fans at 100% full speed (2000RPM±10%) and at the lowest 25%, according to the Command Center software (but the lowest the fans will run at is actually 800RPM±10%). The SpeedFan images below show the true RPM at the time of testing (on the left we have the Cooler Master Nepton 280L fan’s set at 25% and 100%, on the right we have the Raijintek Themis, also at 25% and 100% fan speed).


Cooler Master Nepton 280L -SpeedFan  - 25

Cooler Master Nepton 280L – SpeedFan – (fans @ 25%)

Cooler Master Nepton 280L -SpeedFan - 100

Cooler Master Nepton 280L – SpeedFan – (fans @ 100%)

Raijintek Themis - SpeedFan - 25

Raijintek Themis – SpeedFan – (fans @ 25%)

Raijintek Themis - SpeedFan - 100

Raijintek Themis – SpeedFan – (fans @ 100%)


So on goes the Test Rig and immediately there is a problem… Due to the JetFlo 140mm size, the fan blades clip the fan mounts or grill causing a horrible noise (having tested the Nepton 280L in the roof of the Cooler Master Cosmos SE for a future review, the fans cause a similar problem 🙁 ), this was easily remedied by using a couple of washers as spacers between the case and fans (sadly not included in box). Of course you could always mount your fans the opposite way and have them pulling air in from outside the case, I just prefer the heat from the radiator to be exhausted out.

So on it goes again. The Cooler Master Nepton pump is very quiet and looks pretty cool when on, thanks to the illuminated white border which makes up part of the Cooler Master emblem. Of course looks aren’t everything so let’s see exactly how well this new AIO performs.


Cooler Master Nepton 280L - Installed


  • Intel Core i5-4670K – 3.4GHz (stock)


Cooler Master Nepton 280L - 3.4 - Prime95 - 25

Cooler Master Nepton 280L – Prime95 – 3.4GHz (fans @ 25%)

Cooler Master Nepton 280L - 3.4 - Prime95 - 100

Cooler Master Nepton 280L – Prime95 – 3.4GHz (fans @ 100%)

Raijintek Themis - 3.4 - Prime95 - 25

Raijintek Themis – Prime95 – 3.4GHz (fans @ 25%)

Raijintek Themis - 3.4 - Prime95 - 100

Raijintek Themis – Prime95 – 3.4GHz (fans @ 100%)


CPU Cooler Fan Speed Ambient Temperature Max CPU Temperature (core average) Delta Temperature Noise Level
Cooler Master Nepton 280L 25% 20.00 58.25 38.25 41db
Cooler Master Nepton 280L 100% 20.50 54.75 34.25 67db
Raijintek Themis 25% 19.50 63.25 43.75 38db
Raijintek Themis 100% 19.00 60.75 41.75 47db


As you can see from the Prime95 results above, at stock speeds (3.4GHz) the Cooler Master easily outperforms the Raijintek Themis in our Test Rig. Of course you’d expect that when comparing a £100.00 AIO Cooler to a £20.00 Air Cooler. Surprisingly though, if you compare the Themis running with the fan at 100% to the Nepton at 25%, there is isn’t as big a gap in performance as you may expect. So what happens when we throw a few more volts through the CPU and Overclock it further?


  • Intel Core i5-4670K – 4.0GHz (OC Genie)


Cooler Master Nepton 280L - Prime95  - 4.0 - 25

Cooler Master Nepton 280L – Prime95 – 4.0GHz (fans @ 25%)

Cooler Master Nepton 280L - Prime95 - 4.0 - 100

Cooler Master Nepton 280L – Prime95 – 4.0GHz (fans @ 100%)

Raijintek Themis - 4.0 - Prime95 - 25

Raijintek Themis – Prime95 – 4.0GHz (fans @ 25%)

Raijintek Themis - 4.0 - Prime95 - 100

Raijintek Themis – Prime95 – 4.0GHz (fans @ 100%)


CPU Cooler Fan Speed Ambient Temperature Max CPU Temperature (core average) Delta Temperature Noise Level
Cooler Master Nepton 280L 25% 19.00 67.50 48.50 41db
Cooler Master Nepton 280L 100% 18.00 59.00 41.00 67db
Raijintek Themis 25% 20.00 70.75 50.75 38db
Raijintek Themis 100% 19.50 68.00 48.50 47db


Again the Cooler Master Nepton 280L, jumps ahead of the Raijintek Themis. Surprisingly still, there’s very little difference between the Nepton fans running at 25% and the Themis at 100%. Looking at the noise levels, is another important factor when looking at any CPU Cooler, the Nepton at 25% fan speed throws out a meagre 41db of noise, which is nearly silent when compared to the rest of your rig. The Themis does however performs similarly when the fans are set at 100% and although the 47db of noise is a little more noticeable, it’s something you will not notice when Gaming. By setting the Nepton 280L’s JetFlo fans to 100% things really change! The CPU temp drops down to 59.00 Vs the 68.00 for the Themis, this DOES come at a cost….. 67db of noise, which if your happy to game with a closed-cup headset at a reasonable volume level will not be an issue for you. For me this is far too loud :(.

Now we have an easily attainable and automatic OC using the MSI OC Genie tool, can we push a little further with a Manual Overclock?


  • Intel Core i5-4670K – 4.5GHz (manual overclock via Intel XTU)


Cooler Master Nepton 280L - Prime95 - 4.5 - 25

Cooler Master Nepton 280L – Prime95 – 4.5GHz (fans @ 25%)

Cooler Master Nepton 280L - Prime95 - 4.5 -100

Cooler Master Nepton 280L – Prime95 – 4.5GHz (fans @ 100%)

Raijintek Themis - 4.5 - Prime95 - 25

Raijintek Themis – Prime95 – 4.5GHz (fans @ 25%)

Raijintek Themis - 4.5 - Prime95 - 100

Raijintek Themis – Prime95 – 4.5GHz (fans @ 100%)


CPU Cooler Fan Speed Ambient Temperature Max CPU Temperature (core average) Delta Temperature Noise Level
Cooler Master Nepton 280L 25% 19.00 72.50 53.50 41db
Cooler Master Nepton 280L 100% 18.00 69.25 51.25 67db
Raijintek Themis 25% 19.00 76.75 57.75 38db
Raijintek Themis 100% 20.00 75.00 55.00 47db


There are a few Air Coolers that’ll perform to such a high degree that you can run an Intel Core i5-4670K stably at 4.5GHz through a stress test and I was rather shocked to find the Raijintek Themis is one of them, although there is a pretty big heat spike (as shown above).

The Cooler Master Nepton 280L however flew through the test rather coolly. With the JetFlo fans set at a highly audible 100%, the CPU temperature sat at an average of 69.25, surprisingly at the near silent 25% the temperature was only 3.25 higher at 72.50! Which for a Haswell Core i5 is not bad at all.

It is also worth bearing in mind that while Prime95 is an excellent tool for testing the stability of any CPU overclock, it does this by running your CPU at 100%, in your average Gaming session you’ll most likely not even use half that.

I can’t help but wonder how much extra cooling the Nepton 280L would gain with two sets of fans set in a push/pull configuration!?

Performance-wise you can’t argue with the results above, the Cooler Master Nepton 280L is pretty damn good and dare I say probably one of the best AIO CPU Coolers currently available.


Final Thoughts


Overall I’m very impressed with Cooler Master’s new and refreshingly cool AIO, the Cooler Master Nepton 280L. The whole package from unboxing, installing through to the testing of the cooler has been a great experience from start to finish.

The Cooler Master Nepton 280L is surprisingly easy to fit (with the aid of the instructions! :)). The new pump design, not only looks good, but when combined with the 280mm radiator and the JetFlo 140mm fans offer extremely good performance even at low (and quieter!) fan speeds. Of course for the maximum performance your going to have to be happy to put up with a fair bit of noise, personally I found 67db far too high, but many of you out there wouldn’t bat an eyelid when when considering the performance gain. Or perhaps you could replace the JetFlo fans with something a little quieter? The Nepton 280L does have fan mounts for 120mm and 140mm fans giving you a wealth of choice too, but personally I’d be more than happy to run it on the quieter setting in my own rig 24/7.

It would seem Cooler Master have been listening keenly to feedback and learned a lot from both their competitors and indeed their own AIO line up. The Nepton 280L as far as I’m concerned, covers all the areas you’d want covered by an AIO. It has the looks, performance, at approximately £95.00 a fantastic price, easy fitting, low noise level (with the right setting) and possibly more importantly the versatility that I don’t believe any other AIO has, certainly not one with a 280mm radiator.



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  Design/Quality pcGameware awards the Cooler Master Nepton 280L a Gold


Many thanks to Cooler Master for providing this sample for review


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