Pump; Miscellaneous; Relay Behaviour Under Fail-Safe Conditions; Alarm Relays - Siemens SITRANS LUT400 Operating Instructions Manual

7.2.2.2

Pump

Setpoint - ON / OFF
If the ON setpoint is higher than the OFF setpoint, the relay operates as:
● pump down control
If the ON setpoint is lower than the OFF setpoint, the relay operates as:
● pump up control
7.2.2.3

Miscellaneous

Totalizer and samplers
Refer to Other Pump Controls (Page 113). Relays are normally de-energized, contact
closure is approximately 200 ms duration.
7.2.3

Relay behaviour under fail-safe conditions

A fail-safe condition generally indicates that the level reading is not reliable or is unknown. In
such a situation, pumps will not run and alarms (that are based on level or a derivative
reading) will not activate. The following describes this behaviour in detail, by relay function.
7.2.3.1

Alarm relays

Any alarm that is based on level, or a reading derived from level such as flow rate, will not
activate if there is a fail-safe condition. If the fail-safe condition occurs and the alarm is
already active, the alarm will de-activate.
The following alarm types will de-activate during a fail-safe condition:
● High Level
● Low Level
● In-bounds Level
● Out-of-bounds Level
● High Flow Rate
● Low Flow Rate.
Note
A dedicated alarm exists for fail-safe condition as described above. See Fail-safe Fault
Alarm (Page 102).
SITRANS LUT400
Operating Instructions, 07/2019, A5E33329501-AC
General Operation
7.2 Relays
87