Mark asks this question about cables passing through zones in a bathroom. It has been answered by the ECA (Cables, Wiring and Wiring Accessories):
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Question: What does the term ‘passing through’ mean exactly? Is it a cable surface mounted in trunking, for example? Or could the cable be concealed in a wall?
Answer: According to section 701.411.3.3 from BS 7671:2008, Amendment 3, all the low voltages passing through Zone 1 and/or Zone 2 and not serving the location refers to all circuits that are pulled inside the bathroom, not in the wall.
But even if they are mounted inside the wall, they still need RCD protection if they don’t have at least 150 mm depth into the wall or additional mechanical protection.
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