CEMP-E
TI 811-12
18 August 1998
2
SA temperature
Set OA and relief dampers at
< OA temperature
100% open; RA dampers closed.
< Changeover temperature
3
SA temperature
Set OA and relief dampers at their
< Changeover temperature
minimum positions, and set RA
< OA temperature
damper at its corresponding open
position.
(7) Dual-Duct Terminal Box - All Modes. A space temperature sensor for each zone will signal
the UMCS to gradually operate the control dampers of the dual-duct box to heat and cool its respective
zone by mixing cold-deck air and hot-deck air to maintain the zone setpoint. On a rise in space
temperature, the hot-deck damper will gradually close, and the cold-deck damper will gradually open.
(8) Smoke Control. Smoke detectors in the supply-air and return-air ductwork will stop the
supply fan and the return fan and initiate a smoke alarm if smoke is detected at either location. Restarting
the supply fan and the return fan will require manual reset at the smoke detectors.
k. Bypass Multizone Air Handling System with Hot Water and Chilled Water Coils Sequence of
Operation (Figure 8-11 and Table 8-11).
(1)
Outside-Air, Return-Air, and Relief-Air Dampers.
(a) Occupied Mode. The minimum outside-air damper will open. The maximum outside-
air, return-air, and relief-air dampers will be modulated under mixed-air temperature and economizer
control.
(b)
Unoccupied Mode. The dampers will return to their normal positions as shown.
(2)
Supply-Fan and Return-Fan Control.
(a)
Occupied Mode. Supply and return fans will start in sequence and will operate
continuously.
(b) Unoccupied Mode. Supply fan and return fans will cycle on and off according to the
night setback control setpoint.
(3) Freeze Protection - All Modes. A low temperature device, located as shown, will stop the
supply and return fans, cause the outside-air, return-air, and relief-air dampers to return to their normal
position, and will initiate a low-temperature alarm if the temperature drops below the low temperature
device setpoint as shown. Return to the expected mode of operation will require manual reset at the low
temperature device. The UMCS will indicate an alarm condition when the low temperature device trips.
(4)
Cold-Deck Cooling Coil.
(a) Occupied Modes. The control valve will be modulated by the UMCS from the signal of
a temperature-sensor located in the coil discharge air to maintain the setpoint. The UMCS shall reset the
cold-deck temperature setpoint with respect to the hottest space zone temperature as directed by the hot
deck-cold deck temperature reset program.
(b)
Unoccupied Mode. The UMCS will close the cooling-coil control valve to the coil.
(5) Mixed-Air Temperature Control. When the UMCS places the system in the economizer
operation, it will modulate the dampers from the signal of a temperature sensor in the mixed-air stream to
maintain the setpoint based on the conditions shown in Table 8-19.
8-7
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