User Manual

Alarm management
Alarm example
9
138 | 351 CM110664en_07
Ⓐ State machine
Ⓑ CFC program
Ⓒ Desigo CC plant graphic page
Ⓓ Desigo CC popup
Ⓔ PXM… Values (in a PXM10 alarm handling is only possible for connected PXCs or PXRs)
Ⓕ PXM… Popup (in a PXM10 alarm handling is only possible for connected PXCs or PXRs)
Time sequence in the example:
1. Ventilation system on (e.g., in automatic mode, Cmd.ValPgm = 1), single-speed extract air fan running,
fan blades rotating
2. The V-belt breaks, the pressure drops, the differential pressure monitor responds (delta p < X) and
DPMon.PrVal goes to zero. This activates the alarm monitoring function in the DP monitoring block, and
the [TiMonDvn] timer starts counting down.
3. After expiry of the time [TiMonDvn], the DPMon block (BI) establishes that DPMon.PrVal (0) is still
equal to DPMon.RefVal (0). This is equivalent to the OFFNORMAL state. DPMon.Dstb then goes to 1,
and a TO_OFFNORMAL event is transmitted.
An alarm pop-up window is then displayed, in which the alarm message reads Alarm, Unacked.
4. The motor of the single-speed extract air fan is disabled (that is, Cmd.PrVal → 0) because [EnSfty → 1
and Cmd.ValSfty=0, Prio1 Cmd Input]. As a result, DPMon.RefVal goes to 1, thereby activating the
alarm monitoring function. After expiry of the time [TiMonDvn], the alarm monitoring function
determines that [DPMon.PrVal (0) <> DPMon.RefVal (0)]. The state therefore changes to NORMAL
and a TO_NORMAL event is transmitted.
The alarm display now changes to Alarm = Normal, UnAcked.
5. The operator now acknowledges the alarm with Ack in the alarm pop-up dialog box. The alarm display
now changes to Alarm = Normal, Acked. The operator sets the maintenance switch [MntnSwi] to
Maintenance ON, replaces the fan belt, returns the maintenance switch to Maintenance OFF and resets
the alarm with Reset.
The alarm in the display changes to Alarm = Normal, Unlocked and DPMon.Dstb → 0.