30 November 1998
temperature thermostat TSL-XX-01 and the control panel must be manually reset. The control panel is
reset by momentarily depressing manual switch HS-XX-02.
(5) When smoke detector SMK-XX-01 or smoke detector SMK-XX-02 detects the presence of
smoke, its normally closed contacts in the supply fan starter circuit open, de-energizing the supply fan.
The auxiliary contacts of the supply fan starter de-energize relay R-XX-05, and the contacts of relay
R-XX-05 in the return fan starter circuit de-energize the return fan. Its normally open contacts close,
energizing relay R-XX-09. The normally open contacts of R-XX-09 close, energizing relays R-XX-10 and
R-XX-11. One set of the contacts of relay R-XX-10 locks in relays R-XX-10 and R-XX-11; the other set
de-energizes the supply fan. The contacts of relay R-XX-11 de-energize the return fan. To restart the
fans after a smoke alarm shutdown, smoke detectors SMK-XX-01 and/or SMK-XX-02 and the control
panel must be manually reset. The control panel is reset by momentarily depressing manual switch
(6) A differential pressure gauge DPI-XX-01 across the filter gives local indication of filter
loading. On a rise in pressure drop across the filter to its setpoint, differential pressure switch
DPS-XX-01 turns on pilot light PL-XX-04.
(7) Temperature transmitter TT-XX-04 signals the cold deck discharge temperature to
temperature controller TC-XX-02. During the ventilation delay and occupied modes, relay R-XX-06 is
energized and its contacts close, allowing the TC-XX-02 signal to be received by current-to-pneumatic
transducer IP-XX-02. The pneumatic output of IP-XX-02 modulates cooling coil valve VLV-XX-01 to
maintain the setpoint of controller TC-XX-02. During the unoccupied mode, R-XX-06 is de-energized,
cooling coil valve control is interrupted, and the valve closes.
(8) On a rising space temperature, thermostat T-XX-XX first modulates reheat coil valve
VLV-XX-XX closed, through the auxiliary actuator driver (AAD) of damper actuator DA-XX-XX, and on a
further temperature rise modulates DA-XX-XX to close the zone damper to the bypass duct and open it to
the cold duct.
(9) When the occupied contacts of time clock CLK-XX-01 open to end the occupied mode and
index the system to the unoccupied mode, relays R-XX-01 and R-XX-02 are de-energized, and pilot light
PL-XX-01 is turned off. The contacts of relay R-XX-02 open, de-energizing the supply fan and placing
the system's night thermostat TSL-XX-02 in control of the supply fan and, through interlock, in control of
the return fan. On a fall in space temperature to 13 degrees C (55 degrees F), the contacts of
TSL-XX-02 close, energizing both fans; on a rise in temperature to 16 degrees C (60 degrees F), the
contacts open, de-energizing the fans.
d. Sequence of operation for DDC applications.
(1) Ventilation delay mode timing shall start prior to the occupied mode timing. During
ventilation delay mode the dampers shall remain in their normal positions as shown, except when under
economizer control. At the time shown, the DDC system shall place the system in the occupied mode.
At the expiration of the ventilation delay mode timing period, the DDC system shall place the outside air,
return air, and relief air dampers under mixed air temperature and economizer control. At the time
shown, the DDC system shall place the control system in the unoccupied mode of operation and the
dampers shall return to their normal positions as shown.