Year-Round System Control Processes; Heating, Cooling, And Economizer - Honeywell AUTOMATIC CONTROL Engineering Manual

AIR HANDLING SYSTEM CONTROL APPLICATIONS

YEAR-ROUND SYSTEM CONTROL PROCESSES

HEATING, COOLING, AND ECONOMIZER

Functional Description
EA
NC
100
5
NO
OA
NC
PERCENT
20
21 OPEN
100
64
4
ECONOMIZER DECISION.
REFER TO PREVIOUS
ECONOMIZER OPTIONS
7
Item
No. Function
1-3 Control system energizes when fan is turned
on (See FAN SYSTEM START-STOP
CONTROL).
4-6 Mixing dampers modulate to maintain
minimum ventilation value and free cooling
SA temperature setpoint.
7 Economizer enables free cooling when OA is
appropriate.
ENGINEERING CMANUAL OF AUTOMATION CONTROL
RA
ON
3
2
NORMAL
64
19
36 0
22
CONTROL
PROGRAM
6
22
OA MINIMUM SETPOINT
(NOTE: THE TEST AND BALANCE
INITIAL VALUE FOR PROPER
VENTILATION IS 22)
SPACE TEMPERATURE
CHILLED WATER COOLING
SETPOINT = FREE COOLING
SETPOINT PLUS
2.0
10
(1.5 MINIMUM)
FREE COOLING
SETPOINT
HEATING SETPOINT = FREE
COOLING SETPOINT MINUS
2.0
12
(1.5 MINIMUM)
15
SA
59
1
14
ON
SUPPLY
FAN
16
17
18
8 Space temperature dictates heat and cool
demands.
9-13 Free cooling setpoint and heat/cool deadband
values determine the SA temperature setpoint
for hot and chilled water control setpoints.
Software has a minimum 1.5 Fahrenheit
degree heating and cooling deadband.
14 Heat demand varies SA temperature setpoint.
15,16 Hot water valve modulates to maintain SA
248
8
76
SETPOINT
76
11
9
74
SETPOINT
72
13
SUPPLY AIR SPACE
TEMPERATURE HEATING
SETPOINT DEMAND
100
105
0
55
SUPPLY AIR FREE
TEMPERATURE COOLING
SETPOINT DEMAND
75
0
100
57
SUPPLY AIR CHW
TEMPERATURE COOLING
SETPOINT DEMAND
75 0
55 100
0
100
96
M10478