CEMP-E
TI 811-12
18 August 1998
cooling setpoint.
2
Changeover temperature
Set OA and relief dampers at their
< OA temperature
minimum positions, and set RA
damper at its corresponding open
position.
(5) Smoke Control. Smoke detectors in the supply-air and return-air ductwork will stop the
supply fan and initiate a smoke alarm if smoke is detected at either location. Restarting the supply fan
will require manual reset at the smoke detectors.
(6)
Humidity Control.
(a) Occupied Mode. The UMCS will gradually operate the humidifier valve from the signal
of the return duct relative-humidity sensor /transmitter to maintain relative-humidity space low limit
setpoint. If the return duct relative humidity rises above its space high limit setpoint the UMCS will
temporarily transfer control of the cooling coil control valve from temperature control to relative humidity
control. When the return duct relative humidity drops to its setpoint, control of the cooling coil control
valve will be transferred to the temperature control loop. The UMCS will monitor a duct high limit relative-
humidity sensor in the supply duct downstream of the humidifier and will modulate the humidifier valve to
a fully closed position when the duct high limit setpoint is exceeded.
(b)
Unoccupied Mode. The humidifier valve will be closed.
(7) Smoke Control. Smoke detectors in the supply-air and return-air ductwork will stop the
supply fan and initiate a smoke alarm if smoke is detected at either location. Restarting the supply fan
will require manual reset at the smoke detector.
o. Single Zone Air Handling System with Hot Water and DX Refrigeration Coils Sequence of
Operation (Figure 8-15 and Table 8-15).
(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 modified under mixed-air temperature and economizer
control.
(b)
Unoccupied Mode. The dampers will return to their normal positions as shown.
(2)
Supply-Fan Control.
(a)
Occupied Mode. The supply fan will start and will operate continuously.
(b) Unoccupied Mode. The supply fan will cycle on and off according to the night setback
schedule 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's setpoint as shown. Return to the normal 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)
Direct Expansion Cooling Coil and Heating Coil Control.
(a) Occupied Modes. On a rise in space temperature, the UMCS will first gradually close
the heating-coil valve. After passing through a deadband. The UMCS will then gradually operate the
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