Date: 11th March 2008
Consumer units to meet 17th Edition requirements
Four new consumer units from Eaton are designed to help specifiers and installers meet the requirements of the 17th Edition of the Wiring Regulations for increased RCD protection. They are the first offerings in a package to extend the Memera 2000 AD range of consumer units. They offer a dual-RCD, variable split-load configuration, providing residual current protection of all outgoing circuits, and a generous number of outgoing ways to meet modern installation needs.
The new Wiring Regulations (BS 7671), published on January 1 and coming into force at the end of June, call for much more extensive provision of residual current protection in domestic and non-domestic premises. The practicalities of meeting the requirements for protection of cables buried in the plaster surface of walls or enclosed within partition walls, will mean that most circuits will require 30mA RCD protection. It is also a requirement that all 13A and other socket-outlets up to 20A, for use by “ordinary persons”, should normally be protected by a 30mA RCD. In bathrooms for example, RCD protection is also required on all circuits, including lighting.
Whilst compliance with the new Regulations can be achieved with conventional isolator- controlled single or split-load consumer units in combination with individual circuit RCBO’s, a more cost effective solution may be found with a dual-RCD consumer unit.
The latest Memera 2000 AD consumer units include 8-way, 12-way and 15-way dual-RCD split-load units controlled by a 100A isolator feeding two separate variable split busbar sections each protected by a 30mA RCD. The fourth new unit is a 12-way dual-RCD variant which provides an additional, third, 3-way busbar section fed directly from the main isolator. The three unprotected ways can be used to supply non group RCD protected circuits and can be equipped with individual circuit MCB’s or, more likely, RCBO’s.
All four new consumer units use miniature circuit-breakers (MCBs) for final sub-circuit protection and feature Eaton’s variable split-load design, which allows on-site selection of the number of ways allocated to each main section. The new dual-RCD isolator-controlled units offer high-sensitivity protection of all circuits
Splitting the load over 2 or more sections of the consumer unit will reduce the instances of unwanted tripping and take account of other risks and inconvenience associated with such events. It would be prudent to separate the power circuits and lighting circuits in an area such as a bathroom in order to avoid danger to users in the event of an earth fault on a shower circuit also taking the bathroom lighting off at the same time.
Other consumer units are available which provide 100mA time-delayed RCD protection on the incoming device, which can be effectively co-ordinated with downstream RCD’s or RCBO’s.
Note: The number of ‘ways’ specified by Eaton for its consumer units is a true reflection of the number of outgoing MCB-protected or RCBO-protected circuits available; some manufacturers include the space occupied by isolators and RCDs in their calculation.
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