Single Pump, Pressure Bypass, Reverse Return - Honeywell AUTOMATIC CONTROL Engineering Manual

CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
TOP NUMBERS = FULL FLOW
BOTTOM NUMBERS = HALF FLOW, EACH COIL
PD = PRESSURE DROP
36
51
12
CHILLER
PUMP
48
54
ZERO
REFERENCE
RETURN
0
Fig. 74. Single Pump, Pressure Bypass, Direct Return at Full and Half Flow.
SUPPLY 3.2' DROP
CHILLER
9.6' DROP
*DP SETPOINT = 34'
PUMP
1080 GPM
50' HEAD
RETURN
3.2' DROP SYSTEM STRAINER
ENGINEERING MANUAL OF AUTOMATIC CONTROL
32
4
PD
50
1
PD
3
HEAT/ HEAT/
8 COOL COOL
PD
COIL COIL
2
1 2
24
48
V1
8
PD
44
16
4
B1
12
PD
3
4
4
PD
1
1
SYSTEM WITH 90% FLOW THROUGH EACH COIL
HEAT/
COOL
COIL
1
DP
B1
Fig. 75. Single Pump, Pressure Bypass System at 90 percent Flow.
NUMBERS IN CIRCLES = GAUGE PRESSURES
(PUMP INLET = ZERO FOR SIMPLICITY)
6' DROP TOTAL
6
PD
1.5
HEAT/ 200 GPM
COOL PER
COIL AHU COIL
3
V3
V2
B3
B2
6
PD
1.5
HEAT/ 180 GPM
HEAT/
COOL
COOL
COIL AHU COIL
COIL
3
2
V3
V1 V2
B3
B2
*DIFFERENTIAL PRESSURE CONTROLLER SETPOINT = 50' -9.6' -3.2' -3.2' = 34'
352
26
48.5
HEAT/
HEAT/ HEAT/
COOL
COOL COOL
COIL
COIL COIL
6
4 5
V4 V5
V6
B6
B4 B5
0
0
10
2.5
HEAT/ HEAT/
PER
COOL COOL
COIL COIL
4 5
V4 V5
B4 B5
8
PD
2
18
46.5
8
PD
44
10
2.5
PD
M15061
HEAT/
COOL
COIL
6
V6
B6
M15062