Hired-Hand Emergency Back-Up and Alarms: Secondary Sensing System Expansion - Manual (Page 18)

Manual No. 4801-3001 Rev 7-08 Secondary Sensing System Expansion 18 of 46
7. Fail-Safe Relay Operation
There are two types of Relay strips used in the S-3 Expansion. The Normally Open (NO) strip requires a signal
from the controller board in order to energize a stage of ventilation. Should power be removed from the S-3
Expansion, the Normally Open Relay strips would not be able to energize a ventilator. On the other hand, the Fail-
Safe relay strip would close each of the relays in the strip resulting in energizing the ventilators in case of a
controller power failure. Each of the relay strips contains four relays for controlling four stages. In the S-3
Expansion there are a total of four relay strips; Three will be N.O. and one will be a Fail-Safe. The operator must
insure that the Fail-Safe relay strip is connected only to stages that should be turned on in case of a controller
failure. See Sections 9.1.4, 9.1.5, & 13.3 for a physical description of the relay strips. It is not recommended to
place heating equipment on Fail-Safe stages.
WARNING: The Fail-Safe Relay Card Is Not Recommended For Use On Timer Stages.
8. General Operation
8.1 Alarm Inputs
The S
3
Expansion has seven inputs that can be used to sound an alarm; Three from temperature sensors,
three auxiliaries, and one for power out. The temperature sensors can be enabled or disabled. If a sensor is
enabled it will be used to generate an alarm. If a sensor is disabled, it will not generate an alarm, even if
the S
3
Expansion determines that its readings are out of limits. The Auxiliary and Power Out inputs are
always enabled. The seven alarm inputs are:
8.1.1 Temperature Sensors #1 ,#2 and #3
The S
3
Expansion comes from the factory with three temperature sensors. The S
3
Expansion will trigger
an alarm if the temperature goes above the high limit setpoint or below the low limit setpoint of the
sensors. The S
3 Expansion will wait 30 seconds after a sensor indicates it is out of range before triggering
an alarm.
8.1.2 Auxiliary Inputs #1, #2, and Control System
The S
3
Expansion is equipped with three auxiliary inputs. These inputs are connected in a closed loop
circuit. On the circuit board located on the door of the alarm enclosure there is a terminal block for
NOTE:
Older versions of the
Fail-Safe Relay Cards
will not have the
Yellow Warning
Label.
Look for the “FAIL-
SAFE RELAY
STRIP” text visible
on this end of the
Fail-Safe Relay Card
circuit board.
NOTE:
The Normally Open
Relay Card will have
the “N.O. RELAY
STRIP” text visible
on this end of the
Relay Card circuit
board.
Fail-Safe Relay Card Normally Open Relay Card