CEMP-E
TI 810-11
30 November 1998
(4) On a fall in temperature to its setpoint, low temperature protection thermostat TSL-XX-01
opens a set of closed contacts in the supply fan circuit, 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. A set of open contacts in low temperature protection
thermostat TSL-XX-01 close, energizing relay R-XX-08 and lighting pilot light PL-XX-05. The contacts of
relay R-XX-08 energize 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, and another set de-energizes the supply fan. The contacts of relay
R-XX-11 de-energize the return fan. To restart the fans after a low temperature shutdown, both the low
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 contacts of relay R-XX-10 locks in relays R-XX-10 and R-XX-11. The other set of
the contacts of relay R-XX-10 de-energizes the supply fan, and 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 HS-XX-02.
(6) 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
filter pilot light PL-XX-04.
(7) Temperature transmitter TT-XX-04 signals the cold duct 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, the contacts of relay
R-XX-06 are open, cooling coil valve control is interrupted, and the valve closes.
(8) Hot duct temperature controller TC-XX-03, with its temperature transmitter TT-XX-05 in the
heating coil discharge, modulates hot duct heating coil valve VLV-XX-02 to maintain its temperature
setpoint. Controller TC-XX-04, with its temperature transmitter TT-XX-02 in the outside air, raises the
setpoint of controller TC-XX-03 on a fall in outside air temperature, and lowers it on a rise in outside air
temperature.
(9) On a rising space temperature, thermostat T-XX-XX modulates dual-duct box actuator
DA-XX-XX to gradually close the box to the hot duct and gradually open it to the cold duct.
(10) 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 as previously
described, 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.
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