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Basic protection: Section 416, IP2X and IP4XWhat does IP4X mean for an enclosure?

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Section 416 is provisions for basic protection — stopping you touching a live part in the first place. Two methods.

Insulation of live parts

Live parts shall be completely covered with insulation which can only be removed by destruction. That's the exam word: destruction.

Why "destruction"? Because once you strip a cable you cannot put that insulation back. If you could peel it off and refit it, it wouldn't be reliable protection — and a patched-up sleeve would fail an insulation resistance test anyway.

Barriers and enclosures

A consumer unit is an enclosure; its lid, and the little shield in front of the terminals, are barriers. The IP rating required depends on which surface:

RegulationSurfaceMinimum IPKeeps out
416.2.1Front and sides — live parts inside enclosures or behind barriersIP2XA finger (12.5 mm)
416.2.2Horizontal top surface that is readily accessibleIP4XA wire (1 mm)
↓Why the top is stricter. Things fall down. Screws, offcuts and swarf land on the top of a board far more readily than they arrive at its front or sides — so the top has to keep out something as small as 1 mm, not merely a finger.
IP first digit reminder. The first digit is solid bodies — fingers, wires, dust. IP2X = no finger. IP4X = nothing over 1 mm. The X means the liquid digit isn't specified.

IP ratings crop up all over the book, not just here. Section 701 (bathrooms) sets its own ratings for each zone — 701.512.2 — and the special locations in Part 7 each have their own.

✋The classic trap. "What prevents electric shock in a room containing a bath or shower?" Your instinct says Chapter 41, protection against electric shock. But the words "bath or shower" send you to Section 701. Read the whole question before you commit to a part.

416 · provisions for basic protection 416.2.1 · IP2X, front and sides 416.2.2 · IP4X, readily accessible horizontal top surface 701.512.2 · IP ratings in a location containing a bath or shower

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