Configuration
Entek IRD 6687 Protection Monitor
23
Failsafe operation
Failsafe operation means that when in alarm, the relay contacts are in their “normal,” de-
energized, or “shelf-state” positions. In other words, normally closed relays are closed in
alarm, and normally open relays are open in alarm. With failsafe operation, a power failure
equals an alarm. The following are true of a relay in failsafe condition:
z
The relay is energized when power is applied to the unit.
z
The relay in a nonalarmed condition has power applied to the coil.
z
In alarmed condition, power is removed from the relay coil, causing the relay to change
state.
For failsafe operation, the following are true:
z
Under normal (nonalarm with power applied to the unit) conditions, the relay closes the
circuit between the common and the N/O (normally open) terminals.
z
Under alarm or loss-of-power conditions, the relay changes state to close the circuit
between the common and N/C (normally closed) terminals.
The following are true of a relay in nonfailsafe condition:
z
The relay is not energized when power is applied to the unit.
z
The relay in a nonalarmed condition does not have power applied to the coil.
z
In alarmed condition, power is applied to the relay coil, causing the relay to change
state.
For nonfailsafe operation, the following are true:
z
Under normal (nonalarm) conditions, the relay closes the circuit between the common
and the N/C (normally closed) terminals.
z
Under alarm conditions, the relay changes state to close the circuit between the
common and the N/O (normally open) terminals.
N/C
N/O
COM
N/C
N/O
COM
N/C
N/O
COM
N/C
N/O
COM
