Choosing a CPU cooler was the hardest part of the selection process. I probably spent couple of weeks trying to figure out what would fit, was compatible with the CPU, and how much noise the cooler would make. I started by looking at All In One (AIO) sealed water coolers because it would be easier to mount in the case and might be quieter than fans. The choice initially came down the Corsair H110i GT and the NZXT Kraken x61. Learning about noise levels was interesting. A quiet room has 30 to 40 dBa noise level and I looked for CPU coolers in this range.
Two factors lead me to drop water coolers from my list and consider air coolers only. First, the water coolers are controlled by a USB connection to the computer and the operating system. These coolers require a USB driver to function in order to control them. Many users in general complained about having trouble with getting USB drivers to load at boot and run properly. I felt that his was too complex for a critical cooling function. The second reason was that many users reported that their coolers leaked. This caused other components to short out (video card, motherboard). Reviews and users felt that the water cooler was quiet but the pump noise was annoying. The coolers have a water pump run at between 1000 and 3000 rpm, and apparently these run at a mostly constant rate that some people find objectionable. I have not heard them so I cannot say.
I then considered the twin tower heat pipe coolers form Phanteks PH-TC-14PE and Noctua NH-D14 SE2011. It was really hard to figure out if these would fit. The fans might interfere with the DDR4 DIMMs, or the graphics card or both. Motherboard, memory, graphics card, and cooler vendors don’t publish detailed measurements of their products. The compatibility lists from most vendors are seriously out of date. Sometimes it’s hard to know if the components are electrically compatible too. I selected and purchased the Phanteks cooler without knowing for sure if it would fit, but it seemed to be the most likely big air cooler to fit. It turned out to fit with just enough clearance between the memory and the heat pipes, and the tower fins and the graphics card. Four of the eight memory sockets are filled, and another set of four memory cards (DIMMS) will fit in the sockets right next to the processor. Low profile memory is required when using tower CPU air coolers. The cooler probably needs to come out first before the second batch of memory can be installed, however.
The PH-TC14PE is a twin tower CPU cooler that is supplied with two 140 mm fans but can support three fans if needed, and is designed for the LGA 2011-3 socketed processors. Figure 1 shows the front of the CPU cooler box.
Figure 1 Phanteks PH-TC14PE CPU Cooler Box Front
Figure 2 shows the side of the box with all the technical specs for the cooler.
Figure 2 Phanteks PH-TC14PE CPU Cooler Box Side
This heat sink is a work of art and it is surprising light for its size. Figure 3 shows the CPU cooler towers with the fans clipped into place. The fans fit nicely and are easy to clip on. There is room to place the fans so that they do not interfere with the memory DIMMS or anything else near the base of the cooler. Rubber strips are applied to the fan so that the fans clip in securely and don’t rattle, vibrate, or buzz even high rpm. The fans are quiet and typically run round 600 rpm after running the Fan Exper 3 tool as part ASUS AI Suite 3 utility.
Figure 3 Phanteks PH-TC14PE CPU Cooler with Fans
Figure 4 shows the Phanteks base and heat pipes. The base is covered with Thermal Interface Material (TIM) or thermal compound. The surface of the base had some adhesive from the protective plastic cover that took a while to remove with alcohol. Also, the cooler base was not as smooth as I would have expected. It had visible ridges in the surface. This should have been polished smooth. The TIM was rubbed in with a piece of plastic and then with a gloved fingertip.
Figure 4 Phanteks PH-TC14PE CPU Cooler Heat Pipes
In the past, I’ve been part of small team developing high power thermal management solutions for a power supply. This involved designing heat sink and selecting a TIM so that a FET could dissipate over 200 W. No thermal pad would permit operation in the safe thermal operation area of the FET. This was a very demanding design and we found that ceramic based TIMs worked the best. I also found coating the heat sink and the FET completely with TIM produced the lowest operating temperatures. The instructions with the PH-TC14PE direct you to clean the old heat sink compound off and place a 4-5 mm drop of the PH-NDC thermal paste on the center of the CPU before mounting the cooler. I’m concerned that the thermal may not spread uniformly when the cooler is mounted. I used a small piece of plastic to spread the TIM on the CPU and cooler base.
I don’t recommend using a plastic “spatula” because the PH-NDC thermal compound stuck to it better than the metal of the processor and the cooler base. The plastic was likely a polycarbonate and could generate an ElectroStatic Discharge (ESD) that could damage the process, motherboard, and memory. I also don’t recommend using a bare finger to spread the thermal compound either, because skin cells are about a micron in diameter and slough off creating large gaps with the 50-100 nm diameter ceramic nanoparticles in the thermal compound. The skin cells increase the thermal resistance between the processor and the heat sink and reduce the limits of overclocking rates. I would use an ESD gloved finger for the heat sink. Then I would use a metal “spatula” or a tool made of ESD safe material, or put the TIM down in array of small drops across the CPU and cooler base in the future (see Figure 5).
Figure 5 Thermal Interface Material Application Illustration
Figure 6 show the clearance between the Phanteks PH-TC14PE CPU Cooler and the ASUS STRIX GTX 980 graphics card. A 140 mm CPU cooler is the largest cooler that will fit and clear a graphics card with no components on the back of the card. The color match with the motherboard is also pretty good.
Figure 6 Phanteks PH-TC14PE CPU Cooler and ASUS STRIX GTX 980 graphics card Clearance
Figure 7 shows the unboxing video of the Phanteks PH-TC14PE CPU cooler.
Figure 7 Phanteks PH-TC14PE CPU cooler Unboxing Video
During my LINPACK tests, I recorded the ambient temperature, temperature rise, and processor power dissipation reported by the ASUS AI Suite 3 utility. With this information, the thermal resistance of the heat sink can be computed as Rth=(Tj-Tc)/P where Tj is the junction temperature of the processor, Tc is the ambient temperature, and P is the power dissipated by the processor. This yields an estimate of the thermal resistance at Rth=(87 ºC-37 ºC)/200W=0.25 ºC/W which is in the range of 0.25 ºC/W to 0.39 ºC/W for air CPU cooler according to some reviews. This would indicate that my thermal compound application was done well, and the roughness in the surface of the base of the cooler still provides relatively low thermal resistance.
Phanteks does not provide a maximum recommended Thermal Design Power (TDP) for the PH-TC14PE, but it seems to handle the 200 W load well. Intel indicated that their processors run fastest with junction temperatures below 80 ºC. The thermal resistance of all CPU air coolers limits the maximum processor power dissipation to keep the processor junction temperature at the optimum point. Thus to overclock the processor even further, it would seem that an AIO liquid CPU cooler would be needed. AIO liquid cooler have a thermal resistance that ranges from 0.08 ºC/W to 0.12 ºC/W according to measurements in some reviews. Some reviews also show the i7-5930k dissipating 352 W when overclocked at 4.55 GHz which would produce a processor temperature rise of 35 ºC using a water cooler and would keep the processor junction temperature at 72 ºC even on my hot 37 ºC summer day. Clearly, this would be a good upgrade path once the water coolers become more reliable (no leaking allowed), and provide simpler controllers (no USB drivers needed on boot). Still, the PH-TC14PE was easy to install, runs very quietly, allows for a reasonable level of reliable overclocking, and provides a good value.