Pumping Calculations - Basic Mathematics for Water and Wastewater Operators - page 210

■ Example 14.34
Problem: The motor nameplate indicates that the output of a certain motor is 33 hp.
How much horsepower must be supplied to the motor if the motor is 90% efficient?

Solution:

bhp
Motorefficiency

33 hp
0.90

mhp = = = 36.67 hp

■ Example 14.35
Problem: The motor nameplate indicates that the output of a certain motor is 25 hp.
How much horsepower must be supplied to the motor if the motor is 90% efficient?

Solution:

bhp
Motorefficiency

25 hp
0.90

mhp = = = 27.78 hp

■ Example 14.36
Problem: A certain pumping job will require 11 whp. If the pump is 80% efficient
and the motor is 74% efficient, what motor horsepower will be required?

Solution:

whp
Pump efficiency

11 whp
0.80

bhp = = = 13.75 hp

bhp
Motorefficiency

13.75 hp
0.74

m hp = = = 18.58 hp

■ Example 14.37
Problem: A certain pumping job will required 7 whp. If the pump is 80% efficient
and the motor is 90% efficient, what motor horsepower will be required?

Solution:

whp
Pump efficiency

7whp
0.80

bhp = = = 8.75 hp

bhp
Motorefficiency

8.75 hp
0.90

mhp = = = 9.7 hp

■ Example 14.38
Problem: Based on the gallons per minute to be pumped and the total head the pump
must pump against, the water horsepower requirement was calculated to be 18 whp.
If the motor supplies the pump with 20 hp, what must be the efficiency of the pump?