7
o
For the Periodic Load Shutdown monitoring type the minimum current for the output is 5mA.
Once per 30 seconds the unit will shut the load down for 125 ms when it will be inspecting integrity of
the line up to the termination element (the load connection module) of the monitored circuit.
o
For the Current Drop Monitoring type the unit, switching the output on, accumulates the
average value of the current in the monitored circuit. When the operating current drops more than a
quarter of the average value an open circuit failure in the monitored circuit is diagnosed. Smooth
changes of the operating current in the monitored circuit due to changes in the supply voltage are taken
into account in the accumulated average value.
The monitoring types other than Normal are recommended to be used when several load devices
are connected into the monitored circuit, for example for several light and sound alarms in a single
monitored circuit.
For example, for normally closed light alarm appliances the Periodic Load Shutdown monitoring
type is preferable. This type provides monitoring the circuit along the entire length to the termination
element (LCM) provided that the number of appliances is restricted only by the maximum current
value. If an open circuit failure has happened and a part of the monitored circuit with the LCM is
isolated then the unit, switching off the output once again, detects the open circuit and generates the
relevant message. The connection diagram is shown in Figure 4.
If a load doesn’t allow short-time shutting down, the Programmable Open-Circuit Threshold or
Current Drop Monitoring monitoring types is suitable. When a part of the monitored circuit with
several executive devices is isolated and as a consequence the operating current has dropped below a
programmed threshold the unit generates an Open Circuit message.
Current Drop Monitoring is recommended to be used when no more than four executive devices
with the same current consumption are connected to the output of the monitored circuit. Correct
operation of this monitoring type with a larger number of executive devices is not guaranteed.
When a short or open failure of a monitored circuit is detected the unit transmits a Loop Short
Circuit message or Loop Open Circuit message correspondently over the RS-485 interface. When the
monitored circuit has returned to the Norm state, the unit sends the relevant recovery message over the
RS-485 interface.
Note: If a short circuit failure has been detected while the output is activated then without regard
to the circuit monitoring type the executing program will be aborted and will continue running in 10 s.
States of the control outputs and the monitored circuits connected to them in Quiescent Mode are
indicated by “1” to 6” LEDs in accordance with Table 4.
Table 5. Indication of States of Outputs
Circuit’s
Condition
Output’s
Condition
Indicator Performance
Norm
On
Lit steady in green
Off
Off
Open Failure
On
While lighting in green, double flashes in yellow once per two seconds
Off
Double flashes in amber once per two seconds
Short Failure
On
Flashes in amber once per two seconds
Off