Honeywell AUTOMATIC CONTROL User Manual

ENGINEERING MANUAL OF AUTOMATIC CONTROL
CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
395
Control Strategies
1. Secondary Supply Flow Temperature Control: The SSF
temperature is reset from outdoor air temperature. TIC
32 provides the SSF temperature to the DDC controller.
Valve Y 13 regulates flow through HEX3 primary .
2. Secondary Flow Loop Differential Pressure Control:
Circulating pumps Y 37 and Y 36 are switched off or on
and the speed varied to maintain the differential pressure
setpoint. The pump speed is controlled by a frequency
converter (fc).
3. Secondary Supply Flow Temperature Control: The SSF
temperature is reset from outdoor air temperature (Fig.
141). The actual SSF temperature is measured by sensor
TIC 32. The regulation of the heat flow through the HEX
is provided by the actuator control valves Y 13 in the
primary supply flow line of HEX3.
4. Secondary Loop Make-up Water: Pumps Y 38 and Y39
through Valve Y 310 provide make-up water from the PRF.
5. DHW Pressure Control: Booster Pumps Y29, Y210,
Y211, and Y212 boost the cold water pressure to the
pressure at PI 213.
356
320
284
248
212
176
140
-13 -6 1 9
16
23
30
37
45
52
59 66
SSF SETPOINT TEMPERATURE (F)
OUTSIDE AIR TEMPERATURE (F) M11441
Y
12
TI
11
M
Y
33
DDC
TI
01
OUTSIDE AIR
QIR
02
COLD WATER
Y
34
TIC
32
TIC
31
Y
24
CENTRAL
SYSTEM
DISTRIBUTION SUBSTATION
CONSUMER
Y
49
TZA+
21
TIC
22
TI
14
QIR
15
TIC
13
HW
STORAGE
TANK
COLD WATER
DHW SUPPLY
DHW
RECIRCULATED
SRF
SSF
C-BUS/S-BUS
HEX2
SSF
SRF
HEX1
PSF
PRF
M11432
6. DHW Circulating Pumps Control: Circulating Pumps Y
25, Y26, and Y27 circulate DHW through the pipes to
maintain hot water temperature at the end of the DHW
system.
7. DHW Supply Temperature: Valve Y 14 modulates the
PSF water to HEX 1 and HEX 2 to maintain the DHW
supply temperature at Y 27.
Functional Diagram
Fig. 141. Secondary Supply Flow
Temperature Reset schedule.
DDC Control of Combination Heat Exchanger and Domestic Hot Water Storage Tank
Fig. 142. DDC Control of Dual Heat Exchangers for SSF and DHW Storage.

Honeywell AUTOMATIC CONTROL Specifications

General

Brand	Honeywell
Model	AUTOMATIC CONTROL
Category	Controller
Language	English