PureAire Monitoring Systems, Inc.
10/25/07
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3.3.3 Alarm Relays
The alarm option provides 5-amp resistive form C relays for Alarm 1, Alarm 2,
and Alarm 3 conditions. They may be wired for either normally open or normally
closed operation.
IMPORTANT: The relay contacts are rated for 5 amp resistive loads.
Appropriate surge suppressors should be installed across loads to prevent arcing
on the contacts. Arcing generates high levels of RFI that may interfere with
measurement signals.
The alarm relay PCB also incorporates a remote reset switch (TB4) for use if the
alarm relays are configured for latching operation (see Appendix).
These alarms are factory-set as follows:
Alarm 1
— 20% LEL, non-latching.
Alarm 2
— 40% LEL, latching.
Alarm 3 —
This is a fail-safe Fault relay and is activated when a sensor fault,
such as a missing sensor, is detected. It also indicates loss of power conditions.
NOTE: Alarm 1 and 2 setpoints and operation (latching/non-latching/fail-safe)
are user-adjustable. See the Appendix for more information.
Alarm Relay
Terminals
TB4
— Remote Alarm
Reset Connection
