We used an infrared thermometer to record CPU, motherboard, graphics card, and hard drive temperatures (in Celsius) after booting the system and letting it idle for 15 minutes. We checked temperatures again after running Prime 95 for 15 minutes, thus achieving both idle and load readings. The ambient temperature was maintained as consistently as possible. Where applicable, such as with motherboard temperatures, we took readings from multiple spots and averaged the results.
Because the Phantom 820 has an integrated fan controller, we ran tests with the fans running both at full bore and at their minimum speed as allowed by the controller.
First off, we can see that there’s a substantial difference between the NZXT Phantom 820’s cooling performance with the fans running full blast versus set on low, both when idling and under load, particularly for the CPU and motherboard.
At idle with the fans cranked all the way up, the Phantom 820 was right about on par with the rest of the field in terms of the CPU and motherboard temperatures, although the graphics card and hard drive were a little warmer than we’d like to see. The hard drive score in particular was somewhat disappointing. Do note, however, that the reason for the very low HDD temp in the Switch 810 is due to a fan inside that chassis that sits right next to the drives and keeps them nice and chilly. With the fans on low, the Phantom 820's cooling performance isn't very strong.
The story is much the same when the systems were under load: The NZXT Phantom 820 was a bit on the warm side compared to the field, though not by much. Again, the Phantom 820’s hard drive cooling left something to be desired. Keep in mind, however, repositioning or adding a fan to better cool the hard drive bays is possible.
It should also be said that even with the fans running full bore under a nasty Prime95 load, the system remained impressively quiet; with the fan speed turned down low and the system idling, the case fans are only about as intrusive as the hum of the lights overhead.