WMD Part II by G-gnome

Power Supplies - Selection

When deciding on the power supplies to use in the project I had a few requirements. They needed to be small form-factor and powerful (these are often mutually exclusive), and water-cooled. A big ask really. I was fortunate that Engelking in Germany make a fantastic, high-quality SFF PSU, which happens to be fanless, and thus silent - the U1-6250C. These PSUs are also easy to convert to water-cooling which I will show you later. Engelking was a terrific supporter of the project from day one. To buy, these are expensive PSUs, however, in this case you certainly get what you pay for. (or would if you'd paid for them! - Ed.)



With all the pumps, displays and a reasonably power-hungry system, the 250W rating of the PSUs prompted me to install two of them into the case. This will give me 500W, which will be plenty of juice. One review I read tested them and reckoned they were more like a 350W PSU than 250W, so I'd probably be justified in saying 500+ watts.



The PSUs are a very compact size and completely fanless. They are designed with internal heatsinks and thermal-transfer compound which transmits generated heat to the aluminium shell of the case - designed for an external heatsink to then be attached (or in my case, a waterblock).



When running two power supplies simultaneously, they need to be linked in a master-slave relationship. When the computer is powered on, the master PSU, which is usually the one powering the motherboard, triggers the second PSU to switch on. There are various hacks and guides on how to do this, but Engelking has a great ready-made solution called a PC Link cable. This is an optional extra when ordering and consists of a special cable and plug permanently wired from each PSU.

Plug them together and hey-presto, when one switches on, so does the other. You'll notice the wires are black and green, the same wires you short in an ATX cable to be able to switch on a PSU without plugging it into a motherboard. The special shape of the plugs means that, while identical, they can only be joined in one orientation and are very secure.



The PC Link cable is only an on-switch: both PSUs still need to be plugged into mains power. I will be using a Y-splitter IEC cable, re-wired to an external, well insulated, IEC socket. When re-wiring mains power you have to be incredibly careful and I'd discourage anyone from doing it themselves unless they absolutely know what they are doing. Unlike 12 volt, mains power will happily fry you to a crisp if you wire it incorrectly or have poorly insulated joins. I use a multimeter to check for shorts to the case, and don't just use double-layered heatshrink to seal and insulate the joins to the socket pins, but also a special rubber 'boot' that fits over the back of an IEC socket to seal it.