Emerson Hydrastep 2468 series - 3 B.3.2.7 Two out of Three Relay Alarm System

Delay Relay Output Board Option Hydrastep 2468CB and 2468CD Manual
3b-16 24685034
3b.3.2.7 ‘Two out of Three’ Relay Alarm System
In the following diagrams (7A & 7B)
 indicate the electrode channel selected for each
relay. A fully functioning system (NO FAULTS) will cause a low level trip at electrode level 2.
Using high-level electrode channels and SW5 set to ES, the circuit can perform a high level trip.
Note: Inputs from electrodes 1 & 2 are applied to two separate relays on their respective boards.
Case A - Relays normally energised, de-energise two to trip
(Relays shown in de-energised state)
1
4
3
2
5
8
7
6
(Switch SW5 is set to EW for low-level alarms and set to ES for high-level alarms)
1
4
3
2
5
8
7
6
To alarm
annunciator
or tripping
device
RL 1
RL 2
RL 2
RL 1
PL 2
PL 2
Odd electrodes
(RH input board)
Even electrodes
(LH input board)
3
2
2
Alarm off when contacts closed
RL 3
PL 3
1
1
1
4
3
2
Case B - Relays normally energised, de-energise two to trip
(Relays shown in de-energised state)
1
4
3
2
5
8
7
6
(Switch SW5 is set to EW for low-level alarms and set to ES for high-level alarms)
1
4
3
2
5
8
7
6
To alarm
annunciator
or tripping
device
RL 1
RL 2
RL 2
RL 1
PL 2
PL 2
Odd electrodes
(RH input board)
Even electrodes
(LH input board)
3
2
2
Alarm off when contacts open
RL 3
PL 3
1
1
1
4
3
2