Coolermaster's Nepton 280L is the best performing all-in-one CPU watercooler Frostytech has tested... thus far. More surprisingly for us, the Nepton 280L managed to rise to the top of the 200W Intel LGA2011, 150W & 85W Intel LGA115x/775 and 125W AMD synthetic thermal heatsink test results charts. After testing +750 CPU thermal solutions, it's kind of nice to be surprised.

So what makes this particular all-in-one liquid CPU cooler tick?

For starters, Coolermaster's Nepton 280L uses a large, 280mm x 140mm (nominal) aluminum heat exchanger that is 30mm thick. On this radiator mount a pair of 140mm CM 'JetFlo' fans side-by-side. The fans operate at 2000RPM-800RPM and are rated to move anywhere from 122CFM to 54CFM according to manufacturer specs. Fans mounted side by side generally perform more optimally than fans mounted in a push-pull configuration where the rear fan is almost always starved for air.

Next, the large heat exchanger is connected to the Nepton 280L's waterblock by larger diameter tubing than is typical seen on All-In-One (AIO) liquid coolers. Here we have 15.5mm O.D. corrugated FEP tubing, prior to the Nepton series all FEP tubing we've encountered has been the smaller 9.5mm O.D. stock. Larger diameter tubing (and connectors) means more coolant is circulating through the waterblock and heat exchanger circuit.

At the business end of the Nepton 280L we find a new generation waterblock / pump head. Near as we can determine, the micro skived copper fins cover somewhat more surface area than previous generations we've tested, which means more copper is exposed to passing coolant and heat transfer is improved. Details on the integral pump are undisclosed, however pump life is pegged at 70,000hrs MTBF.

Coolermaster's Nepton 280L CPU liquid cooling system supports the full range of Intel socket LGA2011/1366/115x/775 processors and AMD socket AM3/AM2/FM1/FM2 CPUs. It retails for around $110 USD / CDN at NCIX.ca.

Coolermaster Nepton 280L Self-Contained Liquid Cooling System

heatsink specsheet manufacturer: coolermaster model no.: nepton 280l materials: aluminum radiator, copper-base water block. fan mfg: a14025-20rb-4cp-f1 fan spec: (x2) 2000-800rpm, 12v, 0.8a fan dim: (x2) 25x140x140mm waterblock dim: 48x70x75mm heat exchanger dim: 30x311x140mm pump spec: n/a flow rate: n/a head: n/a tubing: 15.5mm o.d., 35cm length coolant: distilled water/propylene glycol weight: est. 1100 grams includes: multi-socket mounting hardware, thermal compound, instructions. Compatible with Sockets: AMD - AM2/AM3/FM1/FM2 Intel - LGA2011/1366/115x/775 Est. Pricing: $110USD ($93CDN)

New Waterblock / Pump Head

The new generation pump head / water block measures 48x70x75mm in size and mounts directly onto the processor. The integral pump is very quiet under power and draws power from a 3-pin motherboard fan header. When the pump is on, the emblem around the Cooler Master logo glows white, care of a few LEDs. The lighting effect is useful indicator that the pump is actually powered up; a critical thing with AIO watercoolers.

Almost every self contained CPU water cooler we've tested has been OEM'd by either Asetek or CoolIT. We're not sure if CoolIT is the OEM behind the Nepton, or if it's a refined Cooler Master effort. Regardless, the waterblock / pump head behind the visible plastic shell is well designed and rigidly built.

In the photo above you can see the Nepton 280L waterblock (bottom) compared to the Seidon 280V waterblock (top). Note the difference in diameter of the two types of FEP tubing and the footprint of the water blocks.

Below, 15.5mm OD FEP tubing on the left from the Nepton 280L compared to smaller diameter 9.5mm O.D. FEP tubing from the Seidon 120M cooling system.

The FEP tubing connects to the Nepton 280L waterblock via swivelling 90-degree plastic pipe connections which are also about 14mm OD so flow is less restricted. The swivelling connections make routing hoses inside the PC case a bit easier to accomplish. During tested, we found that once the FEP tubing warmed up it tended to adopt the new position and stress relieve somewhat. The connecting tubing is 35cm long, better suiting large gaming chassis where the Nepton 280L radiator will need to be installed at the top of the chassis.

Cooler Master stock photo of the micro skived copper cold plate.

Coolant is most likely a Propylene Glycol distilled water solution. Water enters the skived copper fins along the center-line where it is forced by the rubber gasket to flow in between the micro-skived copper fins and pick up heat, before it exits at the sides and move on to the aluminum heat exchanger. The skived copper fin patch looks to be about 35x40mm or 40x40mm in size. If that's correct (we couldn't disassemble the waterblock owing to the anti-tamper screws used in assembly) it would make the Nepton's skived fin area larger than previous AIO water blocks Frostytech has disassembled.

Swivel, swivel!

Liquid-to-Air Heat Exchanger

The Nepton 280L's aluminum heat exchanger measures 30mm thick and 311x140mm in size. Two 140mm PWM fans are supplied with the Nepton 280L - Cooler Master call them 'JetFlo 140 fans'. The fans use rifle sleeve bearings and rotate at 2000-800RPM. Each fan is rated to 3.5mmH20 air pressure, 122CFM and have embedded rubber pads to cut down on vibrational noises.

The 280mm heat exchanger will make mounting the Nepton 280L a bit more difficult if you don't have a full tower gaming case. However, Coolermaster have built this radiator with mounting holes for 140mm and 120mm fans, so if need be it can accommodate cases designed for side-by-side 120mm fans... though that would also restrict air exhaust greatly.

The thumb screws used to mount the 140mm fans have threaded heads, which is incredibly handy! This means you can completely assemble the fans and heat exchanger together and mount everything to the chassis fan vents with a couple screws. No more fishing screws through the back of the case, the fan and into the radiator. Looking at you Corsair Hydro H80/H100!

As with all other self-contained CPU liquid coolers, you'll need to install the Nepton 280L into a PC case with accessible (rear or top) side-by-side 140mm fan vents. The heat exchanger mounts to the inside of the chassis with eight screws through the fan vents.

Installation Hardware

The Nepton 280L is compatible with Intel socket LGA2011/1366/115x/775 and AMD socket FM2/FM1/AM2/AM3 processors. The system ships with a universal motherboard bracket and a pair of metal mounting plates that attach to the pump head to facilitate each particular socket. A PWM fan splitter and small syringe of thermal compound are also included.

The Nepton 280L ships fully assembled and filled with coolant. A single 3-pin motherboard fan header supplies power to the pump and the two PWM fans can work off separate fan headers or via the PWM Y-splitter which is included.

This heatsink will be tested on FrostyTech's Intel and AMD version of the Mk.II synthetic thermal temperature test platform, and compared against hundreds of reference Intel and AMD heatsinks. The whole test methodology is outlined in detail here if you'd like to know what equipment is used, and the parameters under which the tests are conducted.