Honeywell AUTOMATIC CONTROL User Manual

ENGINEERING MANUAL OF AUTOMATIC CONTROL
CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
343
Fig. 57. Matching Pump to System.
Fig. 58. Pump and System Curves and Control Valves
To better understand system curves, pump curves, and flow
control, Figure 58 shows the control valve(s) (the only variable
element of a typical system curve) separately from the rest of
the system elements. Lines are shown for each of three valve
positions; full, 80 percent, and 50 percent flow. These lines,
when added to the curve for all other elements of the system
intersect the pump curve at the corresponding operating point(s).
Figure 58 shows a system with 500 gpm and 70 foot head at
design, 10 ft of which is a full open control valve at the end of
the piping run. Line “A” represents the control valve and
connects the pump curve to the static-element system curve. If
all control valves positioned to 80 percent flow, the pump head
rises, the static-element system resistance drops, and the control
valve, represented by line “B”, makes the difference; about 36
ft. Similarly, at 50 percent flow, the valve drop, represented by
line “C”, accounts for about 63 ft.
C1055-1
SYSTEM CURVE
9 1/2"
8 3/4"
8"
7 1/4"
5 HP
7 1/2 HP
10 HP
12 HP
15 HP
OPERATION WITH 8 3/4" IMPELLER
DESIGN OPERATING POINT
BALANCED OPERATING POINT
WITH 9 1/2" IMPELLER
100
90
80
70
60
50
40
30
20
10
0
0 100 200 300 400 500 600 700 800
CAPACITY IN GALLONS PER MINUTE
TOTAL HEAD IN FEET
LINE “A” CONTROL VALVE*
FULL OPEN @ DESIGN 10'
DROP AT 500 GPM
LINE “B” @ 80% FLOW,
CONTROL VALVE TAKES
36' DROP
LINE “C” @ 50% FLOW,
CONTROL VALVE TAKES
63' DROP
* THE LINE “A” VALVE IS
AT THE END OF THE
PIPING RUN, AND THE
SYSTEM CURVE IS FOR
THE REST OF THE
SYSTEM.
IN A BALANCED SYSTEM,
THE SYSTEM CURVE IS
THE SAME AT ANY AIR
HANDLING UNIT, WITH
THE AIR HANDLING UNIT
BALANCING VALVES
MAKING UP FOR ANY
REDUCED PIPING
LOSSES.
SYSTEM CURVE FOR STATIC
ELEMENTS OF SYSTEM (CHILLER,
PIPING, FITTINGS, BALANCING COCK,
COILS, STRAINERS, ETC.)
DESIGN
OPERATING
POINT
OPERATING POINT
@ 50% FLOW
PUMP
CURVE
LINE A
LINE BLINE C
PUMP REQUIRED:
500 GPM @ 70' HEAD
0
100 200 300 400 500
M15056
HEAD IN FEET
SYSTEM FLOW IN GPM
80
70
60
50
40
30
20
10
0

Honeywell AUTOMATIC CONTROL Specifications

General

Brand	Honeywell
Model	AUTOMATIC CONTROL
Category	Controller
Language	English