Temperature Tests

The last test is to see how hot the ZEN400 gets when under load, we used the PSU in our low noise test setup dedicated to CPU heatsink reviews:

Intel S775 Setup
CPU	Pentium 4 524 @ 3628Mhz - 1.36v vcore
Mainboard	Asrock 775Dual-VSTA
Memory	1 * 512Mb Mushkin PC3200 LVLII V2
Other	Antec Sonata II with AcoustiFan DustPROOF 120mm @ 5v in the rear as outtake (mounted with soft-mounts) ATI R9000 Passive Cooling FSP ZEN400 Passive Cooled PSU Seagate 7200.8 200Gb HDD in Scythe Quiet Drive

The heatsink used is a brand new ZEROtherm BTF90 which was set to run at low fan speed, noise was ~2dBA over ambient measured at very close distance. A temp probe was stuck between the fins of the ZEN400’s large heatsink and system run under full load for several hours, the end result in a ~21°C room was impressive, no hotter than 40~45°C and this in a case case with only one single 120mm exhaust (at 5v!).

Conclusive Thoughts

We were impressed by the product quality and performance, FSP has a winner on their hands with the ZEN400, ideal for a silent setup or HTPC where noise is not welcome. Its 400W rating is enough to power most recent systems, even higher end is possible, we tested and stressed the ZEN400 with an overclocked C2D / 8800 GTS SLI setup and couldn’t get it to fail.

The FSP ZEN 400 can be found online at €152/$149 , not the cheapest, but certainly still within reasonable limits. If you’re building a new PC or plan to silence your current one, swapping CPU and VGA coolers will only get you so far, an actively cooled PSU will become the main source of fan-noise, with a unit like the ZEN 400 you can get closer to total silence.

We thank Heidi from FSP for the opportunity and her patience. Stay tuned as we’ll be reporting back on more FSP products, including a 900W power house which will be pushed to its limit (maybe?) by two HD 2900 XT cards.