Ch 00aCheckpoint
Checkpoint 00a¶
Checkpoint · Chapter 00a — Mains safety: read before Chapter 09
Do not open Ch 09 until every line is ticked.
- Decided and written down who lands the mains conductors in Ch 10 Section 1, and whether that is a certified person.
- The "who is in the room" rule is written and posted: adult-only for Ch 10 Steps 10.1–10.16 and 10.17–10.23, Ch 12 Step 12.11 through Checkpoint 12, Ch 11 Step 11.67 and Ch 13 Step 13.3; on the unplugged sweeps 10.74–10.78 she only records the readings while the adult holds the probes.
- Multimeter on the bench with a printed CAT rating (CAT III 600 V or better), matching leads, continuity, Ω, DC V and AC V all found.
- Meter proved live–dead–live once, probes shorted to a beep, both leads continuous, battery good.
- Printer's outlet is RCD/GFCI protected, trips on its TEST button, and its breaker is identified and labelled.
- Both of you have walked to the labelled breaker once and know which switch is the printer's.
- The five PE branches can be named from memory, and the M4×6 bed PE screw was confirmed present at Ch 03 Step 03.6.
- The SSR "earth the mounting rail" gap is understood and, if local rules require an earthed rail, it has been raised with whoever signs off the mains work.
- VE0508 ferrules located in the kit; the pull-and-look test at Ch 10 Step 10.8 is understood.
- Both power-on rituals read end to end; the two steps where the machine may be live with the bay open (10.23, 12.11) are known, and the hand-on-the-switch ritual is understood to apply at 12.11 as well as 13.3.
- The five failure responses are agreed out loud; extinguisher in reach; nobody re-energises a tripped circuit without a cause.
You built a posted room rule, a tested meter and a labelled breaker. 2 gummy worms.
Common mistakes¶
- Reading this chapter after Ch 09. By then the inlet, PSU and SSR are already mounted and the only decisions left are the ones you should have made first. Ch 09 is where the mains parts enter the machine; Ch 10 is only where they get connected.
- Buying a meter on price and range instead of on category. Display range tells you what it can show; the CAT rating tells you what it can survive. An unrated meter on a receptacle circuit is the wrong tool, not a cheap one.
- Trusting a "no voltage" reading from a meter you have not just proved. A flat battery, a broken lead or a blown internal fuse all read as dead. Live–dead–live costs fifteen seconds.
- Treating the frame PE bond as automatic. Anodising is an insulator. Ch 10 Step 10.16 says to scrape it under the washer for a reason, and the same logic is why the DIN rail's incidental bond is not a substitute for an earthed rail.
- Enlarging the inlet fuse because it blew. The fuse is reporting a short. Fitting a bigger one removes the report and leaves the short.
- Letting the "who is in the room" rule become implicit. An unwritten rule gets bent at 22:00 by whoever is holding the probes. Write it, post it, say it once.
Next¶
Ch 09 — Electronics bay: mount the DIN rails, ducts, PSU, SSR, Leviathan, Pi and mains inlet — everything placed, nothing wired. Then Ch 10, where the decisions above get spent.