You are here

SMSR: power

Power is distributed by the 'power bars' attached to the rear of each rack, which present as IEC C13 and C19 outlets. Most machines will be connected to C13 outlets on the power bars and, when your machine is installed, the support team will supply the appropriate IEC C14-C13 power cables.

We try to balance the total electrical load within and between the power bars. When your machine is installed, it will be assigned a power-bar outlet (or outlets, in the case of a machine with multiple power supplies). If you ever need to work on your machine in a way which means that you need to disconnect its power cables, you must subsequently reconnect each cable to its assigned outlet. Please, never rearrange any power connections.

As machines are added and removed, the support team might need to rearrange power connections within any particular rack in order to rebalance the total loads. If such work is necessary, we will always try to schedule it with advance notice.

All of the rack power bars are networked, which allows us to remotely monitor their total loads, and also to remotely control each individual power outlet on any particular power bar. In particular, this allows us to remotely power cycle any machine which is housed in any of the racks. If your machine has become unresponsive, and you would like us to power cycle it, please submit a support request via the support form.

In a few cases, equipment will expect C19 or even 13A power. If yours is one of these, please contact support in advance, so that the technicians have time to source or make up something suitable. Note that in no case should the 13A wall sockets be used to power equipment in the racks or shelves, as this would cause a trip hazard.

If you don't know the terms C13, C14 and C19 mean, see the wikipedia article below.


All power in the Informatics Forum self-managed server rooms IF-B.Z14 and IF-B.01 is supplied by the same 200kVA Uninterruptible Power Supply (UPS) system as supplies the main Forum server server room IF-B.02. The purpose of the UPS is to:

  1. Provide a clean and conditioned power supply, in order to deal with power spikes, surges, lags and brownouts which occur on the direct mains supply from from time to time.
  2. Provide a continued power supply in the event of a mains power cut. This is achieved by a large bank of batteries which is an integral part of the UPS system.

At full load, the expected run time on batteries (or 'autonomy') of the UPS which supplies our server rooms is about 30 minutes.

No special action is required by owners of self-managed machines to take advantage of any of this, but the facility exists for any self-managed machine to monitor the UPS, and to automatically shut itself down in the case that mains power has been lost for an extended period, and the UPS is signalling a 'low battery' condition. For details on how to arrange this, please refer to our Monitoring the server room UPS page.

Three phase power

WARNING: Three phase power is in use in the self-managed server rooms.
A machine must only be connected to the power bars fitted to the rack in which the machine itself is housed.

Each individual power bar or 13A socket provides the usual single-phase nominal 240V between live and neutral. However there is a nominal 440V between phases.

Both power bars on any rack use the same phase; however, power bars on different racks might use different phases. The 13A wall sockets use a different phase to the power bars.

Power bars and 13A sockets are all labelled with their circuit numbers, which includes the phase they are on (either L1, L2 or L3.)

A machine must only be connected to the power bars fitted to the rack in which the machine itself is housed.

More info

Find out more about the self-managed server rooms:

Last reviewed: 

System Status

Home dirs (AFS)
Other services
University services
Scheduled downtime

Choose a topic