ENGINEERING MANUAL OF AUTOMATIC CONTROL
INDIVIDUAL ROOM CONTROL APPLICATIONS
416
Fig. 28. Cycle II with Enhanced Digital Control.
On mor ning occupanc y star tup, the fan oper ates with the hot
water v alve open, the face damper open, and the O A damper
closed; and as the r oom war ms to a v ent/r ecirculate setpoint,
the OA damper opens to a minim um ventila tion position. As
the hea ting load dr ops, the face and b ypass damper s modula te
to maintain the r oom hea ting temper atur e setpoint. As the r oom
temper atur e rises to a value midpoint betw een the hea ting and
cooling setpoints, the hea ting valve closes. If the r oom
temper atur e rises to the cooling setpoint, the OA damper
modulates to maintain the cooling setpoint.
Although the disc har ge air sensor could be used as a lo w
limit onl y, Figur e 28 shows it as the pr imar y contr oller r eset
from the demands of the r oom sensor.
In the unoccupied mode , the valve is contr olled in a tw o-
position manner to maintain an unoccupied con vection hea ting
room temperature setpoint. If the room temperature cannot be
maintained b y convection hea ting, the fan is cycled to maintain
the unoccupied hea ting fan-on setpoint. The face damper is
open and the O A damper is c losed.
Figur e 29 adds a chilled water coil to F igur e 28.
RA
FAN
M15315
OA
CONTROL
PROGRAM
24
22.5
8
77
WALL MODULE
22.5
TEMPERATURE
HEATING
SETPOINT
COOLING
SETPOINT
00
24
00
PERCENT OPEN
TO OUTSIDE AIR
PERCENT OPEN
TO BYPASS
OPEN
CLOSED
MINIMUM
RECIRCULATE
SETPOINT
HEATING
SETPOINT
COOLING
SETPOINT
HEATING LOAD
PERCENT
COOLING LOAD
PERCENT
100 10000
HOT WATER VALVE
HOT WATER VALVE
OUTSIDE AIR
DAMPER
FACE
DAMPER
FAN ON
OCCUPIED MODE
OPEN/ON
CLOSED/OFF
FAN ON
SETPOINT
CONVECTION
SETPOINT
FACE DAMPER
FAN
UNOCCUPIED MODE
OA DAMPER
CLOSED
13
41
0
100
0
100
DISCHARGE
TEMPERATURE
SETPOINT
HEATING
LOAD
PERCENT
COOLING
LOAD
PERCENT
DISCHARGE
TEMPERATURE
SETPOINT
24
13
MINIMUM
VENTILATION
DAMPER
SETPOINT
13
ON
PERCENT
OPEN
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