5. To reverse the direction of rotation, first switch OFF the
power supply.
6. On three-phase motors, switch 2 of the 3 power leads
on the load side of the starter. On single-phase motors,
see the connection diagram on the motor nameplate.
Change the wiring as indicated.
Hazardous voltage.
Voltage can shock, burn
or cause death. Ground the pump motor correctly before
connecting to power supply per article 250-80 of National
Electrical Code (NEC) in the U.S., or the Canadian
Electrical Code (CEC), as applicable.
7. Switch on the power supply and recheck the direction of
motor rotation.
Starting
1. If a suction line isolation valve has been installed, check
to be sure that it is completely opened.
2. For initial starting, the isolation valve in the discharge
pipe should be almost closed.
3. Start the pump.
4. When the piping system has been filled with liquid,
slowly open the discharge isolation valve until it is
completely open. Opening the valve too fast may result
in water hammer in the discharge pipe. If the pump or
system start to rattle, the pump is cavitating; to avoid
damage to the pump, reduce the flow through the
discharge isolation valve until the rattling stops. If this
does not give adequate flow for your installation, call
your installer or system designer.
5. Record the voltage and amperage of the motor. Adjust
the motor overloads if required.
6. If pressure gauges have been installed, check and record
operating pressures.
7. Check all controls for proper operation.
Motor Bearings
For the greasing schedule and greasing procedure of the
motor bearings follow the motor manufacturers
recommendations.
Calculating Minimum Inlet Pressure:
Minimum inlet pressure is required to avoid cavitation in
the pump and is calculated as follows:
H = Pb - NPSHR - Hf - Hv - Hs
H = Minimum Inlet Pressure in Feet of Head
Pb = Barometric Pressure in Feet
1 Bar = 29.92 inches of Mercury (Hg)
1 PSI = 2.31 Ft of Head
1 Bar = 33.5 Ft. of Head
NPSHR = Net Positive suction head required. To be read
from the NPSHR curve, Figure 8, at the highest flow the
pump will be delivering.
Hf = Friction Loss in suction pipe in ft of head
Hv = Vapor pressure in feet of head (See Table VI).
Hs = A safety margin of 1.64 ft of head
Example for VM04:
If:
Flow = 60 GPM
Pb = 1 Bar = 29.92 Inches of Mercury*
(Convert from Bar to Feet of Head)
Inches of mercury = 1.33’ inches of mercury
T = 100° F
NPSHR = 10’ (See Figure 7)
Hf = 10’ of 2” Steel Pipe @ 11.9’ of loss per 100’
of Pipe (Hf = 11.9’/10’ = 1.19’)
Hv = 2.195’ (from Table VI)
Hs = 1.64’ (safety factor from above)
Then:
H = 33.5’* - NPSHR** - Hf - Hv - Hs
H = 33.5’ - 10’ - 1.19’ - 2.195’ - 1.64 = 18.475’
H = 18.475’ = Minimum Inlet Pressure
* 1 Bar = 14.5 PSI x 2.31 Ft of Head = 33.5’
7
5
10
15
20
30
25
0
10
20
30
40
50
60
70
80
90 100 110 120
NPSHR in Feet
Flow in GPM
VM06
VM04
VM02
VM01
FIGURE 8 - VM01 through VM06
Net Positive Suction Head Requirement (NPSHR)
Temperature
Vapor Pressure
Absolute Pressure
in °F (°C)
in PSIA (kPa)
in Feet (M) of Water
32 (0)
0.089 (.61)
0.205 (.062)
40 (4.4)
0.122 (.84)
0.281 (.086)
60 (15.6)
0.256 (1.77)
0.592 (.180)
80 (26.7)
0.507 (3.50)
1.172 (.358)
100 (37.8)
0.95 (6.55)
2.195 (.669)
120 (48.9)
1.695 (11.69)
3.914 (1.193)
140 (60.0)
2.892 (19.94)
6.681 (2.036)
160 (71.1)
4.745 (32.72)
10.961 (3.341)
180 (82.2)
7.515 (51.84)
17.36 (5.291)
200 (93.3)
11.529 (79.49)
26.632 (8.117)
210 (98.9)
14.125 (97.39)
32.629 (9.945)
212 (100)
14.698 (101.34)
33.952 (10.349)
220 (104.4)
17.188 (118.51)
39.704 (12.102)
230 (110.0)
20.78 (143.28)
48.002 (14.631)
240 (115.6)
24.97 (172.17)
57.681 (17.581)
248 (120.0)
28.79 (188.51)
66.505 (20.271)
TABLE VI – Vapor Pressure of Water
