Powering a Home Data Centre

 

Introduction.

This project is all about control. Controlling the mains supply to a bank of network servers and the necessary ancillary devices, while incidentally, monitoring said mains supply. I want to do this from my desktop computer in another room because servers are not good neighbours in a house (noisy things that they are).

Because this is something being run from my domestic supply, the whole project is based on a UK 230V single-phase supply. The same circuits (with tweaks for supply voltage) will work anywhere in the world. Three-phase supplies need more complex circuits for monitoring and control. Three-phase is outside the scope of this project.

The project is a thing of many parts which I intend to document pretty thoroughly.

The System Stack.

The stack, a mobile 12U high 19" rack, incorporates five assorted HP servers of various vintages, a gigabit network switch, a 100Mbps network switch and a KVM, with keyboard, mouse and monitor on top of the cabinet.

Worst case power demand: the whole lot, if running at maximum power would draw about 17 Amps off of the mains (UK domestic sockets are rated at 13A), with a potential power-on surge of in excess of 40A.

In order to mitigate this, the final system will require a separate power supply brought from the mains consumer unit - which has a two spare ways currently occupied by a 30A MCB and a 20A fuse. In the short term, while testing the installation, a 13A plug will be sufficient to supply one of the computers and the ancillary equipment.

Regardless of the supply used, the power will need to be sequenced onto the systems in order to reduce the power-surge at connection. In these lean times, I want to be able to monitor the mains power usage, and the presence or absence of mains to various parts of the server rack.

For safety's sake, the control and monitoring system will be integrated with smoke, heat and general environmental monitoring - with alarm levels that will shut down the systems with prejudice in case of fire (or smoke-rich failure).

The Project

Part 1. The mains monitoring sub-system comprising mains detection, mains voltage and circuit current sensors.

Part 2. The power control sub-system, including logic-level power relays and mains contactors.

Part 3. Ties the first two parts together using a microcontroller.

Part 4. Installation of the system.

Finally will be the environmental monitoring sub-system including the creation of a custom smoke detector and a custom rate-of-rise heat detector.

There will be microcontrollers used, which will even talk to the wired network - this is not an IoT project by any means. All data handled by this project will be internal to the network.

Electrical Safety

 

Mains voltages are dangerous. If you are not experienced with working with mains voltages, you should have any and all wiring checked and tested by a qualified electrician. In some countries, this is a legal requirement in any case.

Disconnect anything you are working on from the mains - either by unplugging it, or by using a lockable isolator. Do not reconnect until the wiring has been checked for safety.

Some circuit boards will have both logic level voltages and mains voltages on them. You should not consider doing anything around these boards unless the mains is isolated.

If in doubt - don't do it.

 

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