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Knowledge Centre

Here we have compiled a log of a large number of frequently ask question. If you can not find the answer to what you're looking for please don't hesitate to contact us direct.

Sequential or staggered start-up in a PDU means that individual sockets or clusters of sockets can be electronically switched on by use of relays. This is achieved by either pre-set or adjustable time controls on a PCB. The printed circuit boards we use are pre-set to one second intervals. The purpose of the sequencers is to avoid the harsh inrush currents that certain pieces of equipment can draw on initial start-up. In a situation where perhaps many PDUs are situated together such as a data centre, then the collective inrush currents perhaps following a loss of power can trip whole circuits causing substantial losses in finance and reputation. By using sequential start technology then such inrush currents can be evened out and smaller circuits and circuit protection can be employed. This obviously has financial benefits.

On a smaller scale many units are fitted within USB charging trolleys widely used in the educational sector or in the steel locker industry which is wide and hugely varied market. Such applications are either connected to a 13A plug top or often hard wired via a 13A fused connection unit. If multiple devices are connected and collectively the inrush loads far exceed the 13A then a sequencer unit can avoid unnecessary breaks in service and perhaps unhappy clients or pupils.

All circuits for socket outlets to comply with the latest wiring regulations must be protected by an RCD or RCBO. As most PDUs are plugged into existing circuits the circuit protection should be confirmed prior to fitting, otherwise an RCD or RCBO should be added to the PDU. This also applies to desk top units where BS6396 specifies the use of a 30mA RCD incorporated into the furniture power distribution system if the circuit is found not to be protected.

BS6396 relates to Electrical systems in office furniture and educational furniture. If a PDU is to be used in this way then it should comply with this standard. Employers have a duty of care as defined in the Electricity at work Regulation and the Health and Safety at Work act. A way of demonstrating compliance to these statutory requirements is to use products compliant to the relevant British Standard. The standard says that any electrical system being fed from one 13A UK plug must not consist of more than six individually fused sockets rated at no greater than 3.15A each or four individually fused sockets rated no greater than at 5A each. Equipment rated higher than 5A or products encompassing a greater number of socket outlets should not be used. Additionally, products should be provided with an earthing terminal and the whole construction should be made from durable materials. The standard also requires that any exposed supply leads should not be greater than two metres in length to minimise trip hazards.

Obviously the intention is to discourage the use of trailing (extension) sockets and multiple adaptors which have limited overload protection or offer any personal safety. The Health & Safety Executive and insurance companies, who wish to minimise accidents and claims, would expect to see British Standard compliant products used. Penalties can be applied from the HSE and claims not accepted from the insurers if non- compliant products are found to have been used in the event of any accidents or damage.

For full details of BS6396 go to

Standard PDUs are supplied ready to bolt and plug in and do not need any specialist knowledge in the fitting. However, care should be taken to note that the installation environment is suitable. That the electrical supply is adequate to cater for the load that the PDU is going to service. If in doubt then a suitably electrically qualified person should be consulted.

The fixing brackets of PDUs are designed to accept M5 (i.e. 5 mm diameter) machine screws. The most common form of fitting into data rack infrastructure is by using these screws with M5 cage nuts. Composite packs of these fasteners are available from many sources by simply searching for M5 Cage Nuts.

Yes, the rating of the PDU is determined by the capacity of the supply flex and supply plug irrespective of the individual capacity of the socket outlets deployed.

International Electrotechnical Commission which is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies. On PDU’s this applies to the use of C13 (sockets) and C14 (plugs); kettle connector type; 10A rated and the larger C19 (sockets) and C20 (plugs) 16A rated. These products can be used anywhere internationally on a 230v system.

19” relates to fixing centres across a standard data cabinet. A 19” PDU is therefore the horizontal unit that can be fitted into this space.

Only select a switch if there is an advantage in being able to switch off the power distribution unit. If this presents a risk from turning equipment off by mistake then choose a neon only. This indicates that power is being supplied to the PDU.

Not unless the PDU’s are being used in office furniture and equipment where BS6396 applies.

A surge module protects against voltage spikes that can occur from nearby lightning strikes or switching electrical motors. These temporary spikes can be harmful to sensitive equipment. Surge modules can absorb these spikes. They do not need to be re-set and only fail should that take an excessive surge or become satiated.

Certain pieces of equipment; fluorescent lights, mobile phones etc emit a certain amount of electromechanical energy which itself can disturb other sensitive equipment. EMC filters can screen out such interference.

This is determined by the total load you intend to plug into it. Provided you do not exceed the total loading (shown on the rating plate, usually 16 or 32A) you can specify any number. The largest we have made to date has been a 36 way unit.

12 months from date of purchase. Provided the unit has been installed correctly, not tampered with and there is proof of purchase.

Schuko is actually a trade mark that relates to a European style socket outlet that is made to the CEE7/3 standard. It accepts 2 round pins of 4.8 mm diameter (19 mm long, centers 19 mm apart) for live and neutral, + 2 spring contact areas on the top and bottom for protective earth.

Germany, Austria, the Netherlands, Sweden, Finland, Norway, Portugal, Spain and Eastern Europe

No. PDUs are intended for indoor use only and should not be fitted anywhere should there be a risk of being in contact with water.

The operating environment should be within +20°C to -45°C.

This is not recommended. The intended use of power distribution units is to be permanently fixed by means of the fixing brackets.

PDUs that have a supply plug and lead fitted (the majority) are classified as a portable appliance. Although within the Electricity at Work Regulations 1989 there is an obligation on UK businesses to provide a proper and safe working environment, there is no obligation to undertake PAT inspection. In reality neither act nor their corresponding regulations and associated statutory instruments detail PAT inspection as an obligation, but rather impose a requirement of maintenance of safety and evidence of routine maintenance for all hand-held, portable and plug-in equipment. PAT inspections is one way of demonstrating routine maintenance is being carried out.

This denotes that PDUs fall within the scope of the Waste Electrical and Electronic Equipment regulations (WEEE) and should be disposed of responsibly.

PDUs should be disposed of properly by taking to a licensed re-cycler and not sent to landfill.