Before you start Chapter 00a¶
Before you start · Chapter 00a — Mains safety: read before Chapter 09
Everything you must decide, buy and agree before the electronics bay exists: who is allowed to do the mains work, who is allowed in the room, what meter you need, where the protective earth runs in this machine, and what to do when it goes wrong. Nothing is built here — this chapter exists so that Ch 09 and Ch 10 never stop to ask a question that should already have an answer.
What you're building in this chapter: no hardware — four decisions and one purchase, each of which has to exist before a part goes in. A named person for the mains connections, and a written rule about who is in the room while they are made. A multimeter with a category rating, proved on a live outlet, because Ch 10's Checkpoint #1 is seven measurements and a meter that has quietly died reads every one of them as safe. An RCD/GFCI outlet with a labelled breaker, so the circuit can be killed from outside the room. And a mental map of the parts you will meet in Ch 09–10: the combined AC inlet (socket, switch and fuse in one body), the WAGO lever blocks that fan mains out to three destinations, the Meanwell PSU that makes the machine's 24 V, the solid-state relay that switches mains to the bed heater, and the protective-earth chain that ties the frame, the plate and the PSU back to the wall socket's earth pin.
Time: 0.75–1.0 h hands-on, first build — reading, one shopping decision, one outlet check. No kit parts are touched.
Sessions: 2 × ~30 min
Prerequisites:
- Ch 00 — Before you start, at least through Step 00.8 (the tool table, where the multimeter is a "Buy if not owned" row) and Step 00.30 (the measurement log and your daughter's assigned jobs). This chapter turns both of those into rules.
- Print batches: none. Nothing here is printed, mounted or wired.
- Read this before Ch 09, not before Ch 10. Ch 09 already puts the inlet, the PSU and the SSR into the machine; by the time you open Ch 10 the decisions below are already spent.
Tools
- Digital multimeter — see Step 00a.3 for the minimum spec. This is the one tool in the build with a safety rating, not just a tolerance.
- The multimeter's own test leads, rated at or above the meter's category
- A known-live wall outlet you can reach (for the meter self-test)
Consumables: none.
Printed parts: none. No print batch gates this chapter.
Hardware
| Fastener / part | Qty | Note |
|---|---|---|
| — nothing is consumed in this chapter — | 0 | every mains part stays in its box until Ch 09 |
Read first
- Mains is the only irreversible hazard in this build. Every other safety fact in this manual is stated at the step that needs it. This one cannot be, because the decisions — who wires it, what meter, which outlet — are made weeks earlier. src
- There is no step in this manual where a 13-year-old touches mains wiring. Step 00a.2 names the exact stretches she is not present for, and what she does instead.
- The meter is not optional and it is not a formality. Ch 10's Checkpoint #1 is seven meter measurements on an unplugged machine, and it is the hard gate before the bay closes (survey §5.2 W8).
- If your local rules say a certified person must make the mains connections, that is the whole of Ch 10 Section 1. Decide it now, not with the printer on its back and the WAGOs half-populated.
- Nothing in this chapter overrides a step. Where this chapter and a step disagree, the step wins and the disagreement is a bug — log it in the corrections table in 00-index.md.
- Mirrored images in this chapter are LDO Motors' (LDOVoron2 wiring guide, docs.ldomotors.com), used with attribution; see
assets/remote/00a-mains-safety/SOURCES.txt. Each step keeps the original URL on itsSource:line.