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CALIFORNIA WASTEWATER TREATMENT OPERATOR
GRADE V COMPLETE VERIFIED QUESTIONS AND
DETAILED SOLUTIONS LATEST UPDATE THIS YEAR
JUST RELEASED
When calculating electrical cost - Answer-Motor power
(Pm) is ALMOST always converted to kW then multiplied
by the number of hours connected over a billing period.
(kW x h = kWh)
What does 'Break Power (Pb)' refer to? - Answer-Output
power of the motor
Pb = Pm x .Em
What is the other name for Break Power (Pb)? - Answer-
Input power to the pump
What does the nameplate reading 'HP' indicate? - Answer-
Break Power (Pb)
Water Power (Pw) - Answer-Output power of the pump.
Power the pump delivers to the water.
Pw = Pb x .Ep
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Water Power (Pw): Calculation - Answer-Q rate of the
pump (no matter what the units are) x TDH (always in ft.)
(H suction + H discharge (H static)) + H friction. When H
friction is not given assume TDH is equal to H static)
Pw = Q x TDH x min.HP/33,000 ft.lb (0.746 kW/HP when
kW is needed instead of HP).
Total Dynamic Head (TDH) - Answer-Head Static (H.static)
& Head Friction (H.friction) = TDH
If Head Friction (H.friction) is not given, assume TDH is
equal to the Head Static (H.static).
H.static - Answer-= H.suction + H.discharge
H. static in regards of H.suction (water level above the
pump) - Answer-Can be either below the pump or above
the pump.
If above the pump:
H.static = H.discharge - H.suction
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H.friction - Answer-Always added to H.static to get TDH
(Note: x amount of feet is needed to push the water higher
due to frictional loses at bend, elbows, etc.)
When does frictional loss occurs? - Answer-Suction pipe,
bends, elbows, valves and outlet from the discharge pipe,
even in the pipe itself, the smaller the pipe the more
friction loss occurs.
H.discharge - Answer-Is the difference in elevation
between the centerline of the pump and the point of
discharge (or water surface level, which ever one is
greater)
The efficiency of all mechanical equipment is calculated...
- Answer-Output power / Input power x 100
(Often expressed in %)
Motor efficiency (.Em) - Answer-Brake Power (PB) / Motor
Power (PM) x 100
Pump efficiency (.Ep) - Answer-Water Power (Pw) / Brake
Power (PB) x 100
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"Wire to Water" Efficiency Calculated - Answer-Water
Power (Pw) / Motor Power (Pm) x 100
Electrical cost - Answer-Pm is converted to kW then
multiplied by hours connected.
kW x h = kWh
Energy (kWh) - Answer-Power x Duration that Power is
consumed.
kW (or HP) x hours connected.
The meter is only concerned about energy not power.
kW are units of... - Answer-Power, just like horsepower
(HP)
Electrical companies looks at...... - Answer-...the power
being drawn by the equipment, not what the equipment is
delivering (Pm).
CALIFORNIA WASTEWATER TREATMENT OPERATOR
GRADE V COMPLETE VERIFIED QUESTIONS AND
DETAILED SOLUTIONS LATEST UPDATE THIS YEAR
JUST RELEASED
When calculating electrical cost - Answer-Motor power
(Pm) is ALMOST always converted to kW then multiplied
by the number of hours connected over a billing period.
(kW x h = kWh)
What does 'Break Power (Pb)' refer to? - Answer-Output
power of the motor
Pb = Pm x .Em
What is the other name for Break Power (Pb)? - Answer-
Input power to the pump
What does the nameplate reading 'HP' indicate? - Answer-
Break Power (Pb)
Water Power (Pw) - Answer-Output power of the pump.
Power the pump delivers to the water.
Pw = Pb x .Ep
,2|Page
Water Power (Pw): Calculation - Answer-Q rate of the
pump (no matter what the units are) x TDH (always in ft.)
(H suction + H discharge (H static)) + H friction. When H
friction is not given assume TDH is equal to H static)
Pw = Q x TDH x min.HP/33,000 ft.lb (0.746 kW/HP when
kW is needed instead of HP).
Total Dynamic Head (TDH) - Answer-Head Static (H.static)
& Head Friction (H.friction) = TDH
If Head Friction (H.friction) is not given, assume TDH is
equal to the Head Static (H.static).
H.static - Answer-= H.suction + H.discharge
H. static in regards of H.suction (water level above the
pump) - Answer-Can be either below the pump or above
the pump.
If above the pump:
H.static = H.discharge - H.suction
,3|Page
H.friction - Answer-Always added to H.static to get TDH
(Note: x amount of feet is needed to push the water higher
due to frictional loses at bend, elbows, etc.)
When does frictional loss occurs? - Answer-Suction pipe,
bends, elbows, valves and outlet from the discharge pipe,
even in the pipe itself, the smaller the pipe the more
friction loss occurs.
H.discharge - Answer-Is the difference in elevation
between the centerline of the pump and the point of
discharge (or water surface level, which ever one is
greater)
The efficiency of all mechanical equipment is calculated...
- Answer-Output power / Input power x 100
(Often expressed in %)
Motor efficiency (.Em) - Answer-Brake Power (PB) / Motor
Power (PM) x 100
Pump efficiency (.Ep) - Answer-Water Power (Pw) / Brake
Power (PB) x 100
, 4|Page
"Wire to Water" Efficiency Calculated - Answer-Water
Power (Pw) / Motor Power (Pm) x 100
Electrical cost - Answer-Pm is converted to kW then
multiplied by hours connected.
kW x h = kWh
Energy (kWh) - Answer-Power x Duration that Power is
consumed.
kW (or HP) x hours connected.
The meter is only concerned about energy not power.
kW are units of... - Answer-Power, just like horsepower
(HP)
Electrical companies looks at...... - Answer-...the power
being drawn by the equipment, not what the equipment is
delivering (Pm).
