Topower TOP-420NF

The text on the cardboard box the TOP-420NF power supply comes in reads “Fanless Enhanced Cooling Power Supply”. The words “enhanced cooling” actually mean an ordinary 80mm fan installed on the front panel of the PSU (this panel will be inside the system case after the installation). Why “fanless” then? The manufacturer claims the fan starts to work only at a 250W and higher load, but remains absolutely silent at other times. You can also turn the fan on with a button on the PSU case, but the fan will then be working at its full speed only.

Topower is not only known under its own brand, but also as the actual manufacturer of power supplies from OCZ and BeQuiet!. The TOP-420NF has the familiar features like a black glossy case, a graphics card power cable with an LC-filter on the connector and screening, and black heatsinks with small and dense ribbing:

Unlike with the FSP Zen, this model has one heatsink on the outside – its L-shaped internal part is put on the heatsink with the diode packs. Otherwise, the design of the PSU is somewhat closer to the classic samples than the Zen. The TOP-420NF seems to be an adaptation of an existing power supply rather than a product developed from scratch. The adaptation wasn’t too serious, though. For example, the employed heatsinks with numerous small ribs and slits are obviously supposed to be cooled with a fan. Even the external heatsink is shaped like that, while a heatsink with larger and less densely placed ribs would suit better for natural passive cooling.

Moreover, the ribs of the heatsinks are directed towards the inside of the power supply rather than to the outside which worsens the efficiency of passive cooling even more. The external heatsink also almost entirely covers the opening in the PSU rear panel, so the air from the fan (when it is turned on) goes out through the opening in the top of the case mostly. As a result, the power supply is driving hot air in a circle rather than exhausts it to the outside.