Honeywell AUTOMATIC CONTROL SI Edition, Engineering Manual

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ENGINEERING MANUAL OF AUTOMATIC CONTROL
AIR HANDLING SYSTEM CONTROL APPLICATIONS
246
HEATING SYSTEM CONTROL PROCESS
SPACE CONTROL OF HEATING, ECONOMIZER (FREE COOLING), AND HUMIDIFICATION
Functional Description
Item
No. Function
1,2 Control system energizes when fan is turned
on (See FAN SYSTEM START-STOP
CONTROL).
3-5 Space humidity PI loop controls humidifier
valve if space humidity falls to setpoint.
6,7 SA humidity high limit PI loop throttles
humidifier valve if duct humidity rises above
setpoint.
8 Control program coordinates space and
humidifier leaving air humidity control and
fan interlock.
9-11 Space temperature heating PI loop inputs to
SA temperature heating reset schedule.
12 SA temperature PI loop inputs to heating and
mixed air control programs.
13 Hot water valve modulates to maintain SA
temperature setpoint.
14 Control program coordinates space and SA
heating control and fan interlock.
15,16 Space temperature cooling PI loop inputs to SA
temperature cooling reset schedule.
17 Mixing dampers modulate to maintain SA
temperature setpoint.
18 Economizer decision program determines when
OA is suitable to assist with cooling demand.
19 Mixing dampers minimum ventilation value.
20 Control program coordinates space and supply
cooling control, ventilation control, and fan
interlock.
M15175
OA
RA
SA
7
6
5
28
NC
HEAT
N.O.
N.C.
ON
1
CONTROL
PROGRAM
4
3
45
88
52
52
16
2
13
13
27
SUPPLY AIR
TEMPERATURE
SETPOINT
SPACE
COOLING
DEMAND
100
0
17
83
00
NORMAL
ECONOMIZER DECISION.
REFER TO PREVIOUS
ECONOMIZER OPTIONS
OA MINIMUM SETPOINT
(NOTE: THE TEST AND BALANCE INITIAL
VALUE FOR PROPER VENTILATION IS 22)
18
12
8
20
CONTROL
PROGRAM
22
19
14
CONTROL
PROGRAM
41
13
SUPPLY AIR
TEMPERATURE
SETPOINT
SPACE
HEATING
DEMAND
100
0
13
9
15
10
11
25
22
23.5
SPACE
COOL