Getting cables into a consumer unit safelyWhere must the cable sheath end?

• Knockouts: pre-made holes in the enclosure that you knock out with a screwdriver. On our board they're 20 mm, sized to suit a compression gland with a 20 mm thread.
• You can drill your own holes, in the top, sides or back, but always keep the IP integrity of the board (section 4).
• Metal boards have sharp edges. A compression gland smooths the hole. A bare drilled hole needs a grommet or grommet strip so conductors can't be damaged.
• Make sure your grommet strip suits the thickness of the metal. Use the right product for the equipment.
• Bring cables in with the outer sheath entering the enclosure. There's no set length, but the sheath must go inside. Conduit or trunking (plastic or metal) can also be connected straight to the board.
• Follow Chapter 52: cores without a sheath must be enclosed right up to where they enter the containment or enclosure.
• Fix it securely. Our board has four fixing points. Use all four. This is a regulation too.

BS 7671 · Chapter 52 · selection and erection of wiring systems Reg 526.9 (sheath removed: cores enclosed) and Reg 521.10.1 (non-sheathed cables in containment) · check your copy