Application

Sequence of Operation
Sash Area Alarms
21
Siemens Industry, Inc. Application Note, Apps 2941/2942 140-1319
Restricted 2015-11-04
Sash Area Alarms
NOTE:
Sash alarms are set to be OFF by default and are not required on most jobs. Enabling
sash alarms requires training for the operators.
Sash area alarms alert you when the sash area is above set limits. There are limits for
both attended and unattended modes of operation. The controller uses the following
points to perform this function:
DI2, ATTN.UNATTN, SASH TONE, UN ALRT AREA, AT ALRT AREA, OPEN TIME,
and SASH OP ALRT. ATTN.UNATTN is controlled by DI2, and when the DI is opened
the controller changes to ATTN mode.
When the DI is shorted, the controller changes to UNATTN mode.
 ATTN MODE – When in ATTN mode and the FACE AREA is larger than AT ALRT
AREA, the SASH OP ALRT point is turned on and the ODP horn beeps six times
every minute until the sash area is lowered below the AT ALRT AREA limit. The
horn beeping feature may be removed in ATTN mode by turning off the SASH
TONE point. When the FACE AREA is less than the AT ALRT AREA, the SASH
OP ALRT turns off and the ODP horn no longer beeps.
By pressing the horn silence button, you may stop the beeping for the time shown
in OPEN TIME.
 UNATTN MODE – When in UNATTN mode and the FACE AREA is larger than UN
ALRT AREA, the SASH OP ALRT point is turned on and the ODP horn beeps six
times every minute until the sash area is lowered below the UN ALRT AREA limit.
When the FACE AREA is less than the UN ALRT AREA, the SASH OP ALRT turns
off and the ODP horn no longer beeps.
Table Access Feature
The table access feature allows the controller to store values that are set once and left
alone, used infrequently or not accessed by the network.
These values are accessed using V TABLE PT. It will access the points TABLE FLOW
and TABLE VOLTS. For more information see the
Start-up Procedures for Application
6741 and Application 6742
.
Emergency Mode
The emergency mode operation overrides any other control mode in the Fume Hood
Controller. When the Emergency Purge button on the ODP is pressed, the following
sequence of events occurs.
1.
EMER ALM turns ON, the horn sounds, and the red LED on the ODP
illuminates. The ODP displays “EMERGENCY” mode and indicates to close
the hood.
2.
The Fume Hood Controller commands the damper/Venturi valve to fully open
for the time (in seconds) specified in EMER TIMER.