Energy consumption of pumps
The percentage distribution of service life costs of a pump is:
5 % initial purchase price
85 % operating costs or the energy consumption
10 % maintenance costs
Highest savings is achieved within energy consumption
The annual energy consumption, E, of a pump can be calculated as follows:
c = specific energy price (USD/kWh)
h = operating hours/year (hours)
P1 = horsepower of pump (hp) x 800 watts.
.15/Kwh x 730 hours (2 hours per day) x 1 Hp swimming pool motor (800 watts) = 584000 watthours (584 Kwh) x .15 = $87.60
Example:
Calculation of the annual energy consumption of 8000 gpm, 60 hp,
3-phase 460 V, 60 Hz with flow rate 335 ft head pressure, 528 GPM water
flow, Operating hours/year: h = 3200.
First step of 3: Calculate power consumed in Kilowatts
Duty
point: the intersection of Flow (Q in GPM or gallons per mimute) and
generated Head pressure of pump (H measured in ft) Resource pdf
Choosing correct pump maximizes economy, so the pump is not oversized or undersized for the job
Example: For calculating P1 (power) in kW (kilowatts = volts x amps x1000)
Flow rate: Q = 528 GPM gallon per minute water flow
Total head pressure: H = 335 ft
Specific energy price:c = USD 0.15/kWh (day and night rate)
Operating hours/year: h = 3200
Density p = lb/ft³ (assumed 1)
367 = standard conversion factor
n-motor = (example 84.5 %, in equation 0.845)
n-pump = (not to be confused with the stage efficiency curve).
By showing the P2/Q curve makes it easier to calculate energy consumption.
P2 = 35 hp (power requirement of pump at 88 GPM, from curve P2 / Q.
Second step: Calculatie motor efficiency at duty point
As standard the SP 625S-3 is equipped with a 60 hp (45 kW for P1) MS6 motor.
At
duty point (Q = 528 GPM) the pump requires 59 hp (44 kW for P1), thus:
a motor load of 87 % (44 kw / 45 kw) and a power reserve of 2 %.
From the table on page 72 the motor efficiency can be read as:
84.6 % at a load of 75 %. ( 75 %)
85.6 % at a load of 100 %. ( 100 %)
The interpolated value in this example is
motor = 85.1 %, motor = 0.851.
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