FSP Epsilon 700W, 800W, and 900W
We have regularly reviewed products from FSP Group, including the high-wattage Epsilon series in which we tested the 600W and 700W models. The company has recently extended its model range towards higher wattage, up to 1010W. So, I am going to test new Epsilons and take the Epsilon 700 for the comparison’s sake.
All Epsilon series products have attractive violet-blue cases. The coating is high quality and durable. It is difficult to scratch it as opposed to the dark glossy metallization of most other PSUs.
The On/Off switch is highlighted with blue at work but the fan lacks any highlighting.
The internal design of FSP Group’s power supplies has long been a shocking view for reviewers and buyers due to the size of the heatsinks. Two out of the three heatsinks are simple aluminum bars without any ribbing. The third heatsink has but very superficial ribbing. Why? Because the developer preferred to reduce the heat generation of the transistors and diode packs rather than to increase the size of the heatsinks. There are much more elements in this PSU than usual. Most of them are connected in parallel. In an ordinary PSU, the 30A power rail has one diode pack rated for a current of 30A, but there are two such packs here, each working at half the rated load. Why? The correlation between heat generation and current is non-linear with diodes. When a 30A current is flowing through one 30A pack, the latter is generating more heat than two 30A packs, each with a current of 15A, would.
Of course, semiconductor components cost money and two packs are more expensive than one, but the manufacturer saves on the heatsinks and on the overall weight of the PSU. The latter thing makes the transportation cheaper and also helps save on the European electronics recycling tax that depends on the weight of the device.
I can’t catch any difference in the circuit design of the two senior models (800W and 900W) except for the different color of the PCB and the ribbing on the heatsinks. The marking on the PCB reads “FSP850-80GLN REV.: 1” and there is a list of possible PSU wattages on the left, from 500W to 900W.
It was to be expected that the heatsinks would grow larger. Whatever tricks the manufacturer may resort to, there is ever more heat generated inside the PSU as its wattage increases. So, the heatsinks in the Epsilon 800 and 900 are larger than in the Epsilon 700, yet still much smaller than in other PSUs of their wattage.