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External influences and Appendix 5Where do you look up a code like BA4?
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Chapter 32 covers external influences, but it's mostly a signpost: it directs you to Chapter 52 and to Appendix 5, which holds the full classification.
Appendix 5 codes each influence with a letter pair. Category A is environment, category B is utilisation — and the B codes describe the people using the installation:
| Code | Who | Example |
|---|---|---|
| BA4 | Instructed person | Someone working under a skilled person's instruction |
| BA5 | Skilled person | Trained, qualified and experienced — a practising electrician |
The related term to keep with these is ordinary person — neither instructed nor skilled. That's the householder, and it becomes the deciding word in a main-switch question later on.
Chapter 32 · external influences (signposts onward) Appendix 5 · classification of external influences · BA4, BA5 Chapter 52 · wiring systems, external influences (522)
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