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summary: The 24 V bed valves on the relay board: how they are switched, the 20-minute alert, manual override
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# Irrigation valve

24 V solenoid valves, one per bed, driven by a relay board that listens on `mqtt-broker.md`.

- A valve that stays open longer than 20 minutes raises an alert (`alerting.md`).
- Manual override: the switch on the relay box; see `runbook.md`.

## Why the schedule lives on the board (since 2026-02-28)
- The board keeps time for 72 hours without power, per `2026-02-28-rb-8-relay-board-manual.md` (not tested here yet). That is why the frost-night fix moved the schedule here.