Honeywell AUTOMATIC CONTROL User Manual

ENGINEERING MANUAL OF AUTOMATIC CONTROL
CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
341
Figure 55 illustrates a pump fitted with a 6-1/2 inch impeller,
operating at 45 ft of head, and delivering 65 gpm of water.
Water hp = 65 gpm x 45 ft x 1.0/3960
=0.74 hp
The curves show that the motor output is 1.17 horsepower.
Efficiency = (water horsepower)/(motor horsepower) x 100 =
(0.74/1.17) x 100 = 63 percent. This agrees with the efficiency
curves shown in Figure 55.
Pump Affinity Laws
Pump affinity laws (Table 3) show how pump flow, head,
and brake horsepower vary as impeller diameter or speed
change. These laws help when adjusting an installed pump to
changes in the system served. For example, if a pump with an
8-inch impeller delivers 80 ft of head, with a 7.21-inch impeller
it would deliver 65 ft of head. It is calculated as follows:
Table 3. Pump Affinity Laws.
Fig. 55. Pump Curve for 1750 RPM Operation.
C1051
CAPACITY IN GALLONS PER MINUTE
45%
55%
60%
68%
68%
65%
60%
55%
45%
3HP
2HP
1 1/2HP
1HP
3/4HP
1/2HP
7"
6 1/2"
6"
5 1/2"
5"
0
20
30
40
50
60
0 10 20 30 40
50
60 70 80 90 100 110 120 130 140 150 160 170 180 190
TOTAL HEAD IN FEET
SYSTEM CURVE OPERATING POINT
65%
New head = Old head x




New Diameter
Old Diameter
2
= 80




7.21
8
2
= 64.98 ft
Impeller
Diameter Speed
Specific
Gravity
(SG)
To
Correct
for
Multiply
by
Flow
()
New Speed
Old Speed
Constant Variable Constant Head
()
New Speed
Old Speed
2
Bhp
or kW
()
New Speed
Old Speed
3
Flow
()
New Diameter
Old Diameter
Variable Constant Constant Head
()
New Diameter
Old Diameter
2
Bhp
or kW
()
New Diameter
Old Diameter
3
Constant Constant Variable Bhp
or kW
New SG
Old SG
Source: ASHRAE Handbook--1996 System and Equipment

Honeywell AUTOMATIC CONTROL Specifications

General

Brand	Honeywell
Model	AUTOMATIC CONTROL
Category	Controller
Language	English