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Chapter 46: isolation and switchingIsolation, or switching off for maintenance?
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The last chapter of Part 4, and the end of this lesson's ground. Four kinds of isolation and switching, and the exam wants you to tell them apart.
| Section | Type | What it's for | On every circuit? |
|---|---|---|---|
| 462 | Isolation | Making dead for work — the big red-and-yellow rotary switch on a machine, or the main switch | Every circuit must be capable of isolation, but not by its own separate isolator (a circuit breaker suitable for isolation does it) |
| 463 | Functional switching | Turning the thing on and off in normal use | Yes |
| 464 | Switching off for mechanical maintenance | Stopping moving parts safely | Where needed |
| 465 | Emergency switching | Cutting the supply quickly to remove an unexpected danger | Where needed |
So the answer to "what is required for all single-phase equipment which requires separate control by the user?" is a functional switch. Work the options out by elimination:
- Double pole? No — ordinary circuit breakers are single pole and that's allowed.
- Isolator? No — you don't have a rotary isolator on every circuit in a house.
- Contactor? No — same reasoning.
- Functional switch? Yes. A light switch is one. A switched socket is one. A cooker switch is one. And that unswitched socket behind the washing machine is controlled by the switched fused connection unit above the worktop — which is its functional switch.
462 — the main switch in a dwelling
A typical Part 4 question: requirements for a main switch in a dwelling on a single-phase supply, operated by an ordinary person.
Remember the person definitions from Appendix 5 here: ordinary person is the householder, BA4 instructed is someone working under a skilled person's instruction, BA5 skilled is a qualified electrician. The question hinged on that single phrase.
Chapter 46 · isolation and switching (Chapter 45 withdrawn) 462 · isolation · main switch, both live conductors, on load 463.1.1 · functional switching for each part controlled independently
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