Published: 3 March 2014
Category: Q&A
James asks this question, which is about any need for cable de-rating because of multiple circuits exiting a consumer unit. It has been answered by the NICEIC (Theme – Distribution Equipment including Cable Management):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: Appendix 4 of BS 7671:2008 provides details regarding rating factors for group circuits - effectively de-rating based on the number of circuits in a bundle.
Should this de-rating be applied based on the grouping of cables / circuits exiting the consumer unit?
An example is for an eight-way consumer unit, fully populated; methods A-F can be assumed within the consumer unit - therefore a rating factor of 0.52 should be applied to each circuits cable. Is this correct?
Answer: The recommendation for grouping factors in Appendix 4 does not apply to a standard circuit arrangement of a consumer unit if it has been adequately installed with consideration for the equal entry and correct spacing of conductors within the enclosure.
Should a series of cables be contained within a trunking or conduit system, or similar, then this would be a consideration, but within the space inside the consumer unit, it may not be appropriate to apply the recommendations to that issue.
To see many more Q & A in Voltimum UK's Experts Area, please click on the link. Experts from leading organisations provide online answers to your technical questions on a broad range of subjects. Our searchable database of existing Q & As now contains over 3,500 entries; you can browse through them here.