Heating, Cooling, Humidification, And Dehumidification Control; Without Deadbands - Honeywell AUTOMATIC CONTROL Engineering Manual

AIR HANDLING SYSTEM CONTROL APPLICATIONS

HEATING, COOLING, HUMIDIFICATION, AND DEHUMIDIFICATION CONTROL

WITHOUT DEADBANDS

Functional Description
EA
N.C.
83
5
NORMAL
N.O.
OA
N.C.
9
7
PERCENT
83
49
OPEN
60
4
28
ECONOMIZER DECISION.
REFER TO PREVIOUS
ECONOMIZER OPTIONS
8
6
22
OA MINIMUM SETPOINT
(NOTE: THE TEST AND
BALANCE INITIAL
VALUE FOR PROPER
VENTILATION IS 22)
Item
No. Function
1-3 Control system energizes when fan is turned
on (See FAN SYSTEM START-STOP
CONTROL).
4-6 Manual positioning value determines
minimum ventilation mixing damper position.
7 Operator information, outdoor air
temperature.
8 Economizer enables free cooling when OA is
suitable.
9 Operator information, MA temperature.
10,27 Heating coil valve modulates to keep reheat
coil entering air from getting too low.
11-16 Space temperature PI loop resets setpoint of
reheat coil SA PI loop to maintain constant
space temperature.
ENGINEERING CMANUAL OF AUTOMATION CONTROL
RA
ON
3
2
10
18
55
27
0
100
CONTROL
PROGRAM
24
52
SA
88
25
56
16
1
ON
15 SUPPLY
FAN
26
11 0
17,18 Chilled water valve modulates in sequence
with mixing dampers as required to maintain
SA PI setpoint.
19 Chilled water coil leaving air temperature
lowered if required for dehumidification.
20-26 Space humidity PI control loop modulates
humidifier valve to maintain space relative
humidity, subject to an SA high limit
humidity PI loop.
27 Control program coordinates ventilation,
heating, cooling, humidification,
dehumidification, and fan interlocks.
252
52
20
21 50
SPACE
74
11
12 74
SUPPLY AIR
TEMPERATURE COOLING
SETPOINT DEMAND
105
REHEAT
14
55 40
45
75
OA
CW
55
100
17
COOL COIL
LEAVING AIR HUMIDI-
TEMPERATURE FICATION
SETPOINT DEMAND
0
55
19
70 45
HUMIDIFIER
VALVE POSITION
55
0
23
100
100
35
13
0
50
22
M10480