User Manual

Alarm management

Alarm example

134 | 353 CM110664en_07

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.

6. The fault has been cleared. When DPMon.Dstb = 0, then Cmd.EnSfty → 0

and hence Cmd.PrVal → Cmd.ValPgm=1, that is, the fan motor is enabled.

Then, with Cmd.TraSta = 1 (transient state), the fan ramp-up time is