The controller’s hardware clock was not detected at start-up. Time may be lost after a power failure.
| At a glance | |
|---|---|
| Code | 520 |
| Shown as | RTC Missing |
| Severity | Severe |
| Category | 5xx — System / lifecycle |
| Clears | Only after a restart with a working clock |
Without the hardware clock the controller cannot keep time across a power cut. Features that need a trusted time — Calendar programs, timed manual On — may be unavailable after a restart until time is set again.
Keeps running, and uses network time when it has it.
Restart once — if the alarm returns, the clock hardware needs service.