energy savings calculator for fan and pump drives-users manual.pdf

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SoftSave User’s Manual

Energy Savings Calculator

for Fan and Pump Drives

ABB Drives



© 1998 ABB Industrial Systems, Inc. All Rights Reserved

SoftSave

Energy Savings Calculatorfor Fan and Pump Drives

User’s Manual

SoftSave-US-04

3AUA 489002B4711 R0101 Rev. AEffective: 9/15/98

Supersedes: None



SoftSave User’s Manual v

Contents

1 — General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

2 — Starting and Running the Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Software Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Files Provided . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Opening the Spreadsheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Selecting Calculation Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Form Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Printing the Form Sheet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Viewing and Printing the Graphics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Returning to the Menu and Exiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 — Calculation Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4FanSave Calculation Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

PumpSave Calculation Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4 — Form Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Identification and Comments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Initial Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Results of Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

5 — Fan Drive Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Initial Data for Fan Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Fan Calculation Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6 — Pump Drive Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Initial Data for Pump Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Pump Calculation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7 — Explanation of Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Fan Drive Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Pump Drive Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8 — Conversion Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

9 — Blank Data Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Blank Data Form for Fan Drive Energy Savings Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Blank Data Form for Pump Drive Energy Savings Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21



SoftSave User’s Manual 1

1 — General

SoftSave is a collection of Microsoft Excel spreadsheets that are used to esti-

mate the energy savings available when using an adjustable frequency drive

compared to other Pump and pump flow control systems.

For fans, comparisons are made with damping control, pitch control, single-

speed vane control and two-speed vane control. For pumps, comparisons are

made with throttling control, ON/OFF control and adjustable speed control

using a hydraulic or other type of slipping drive.

Calculations are based on typical fan and pump operating characteristics. Con-

sequently the accuracy of the results is limited to ±10%. The accuracy of the

results is also affected by the accuracy of the input data.

Results should be used only for estimating purposes. The results of this pro-

gram must not be used as the basis for guaranteed energy savings.

Results of calculations can be printed out in numerical and in graphical form.



2 SoftSave User’s Manual

2 — Starting and Running the Program

Software Required Microsoft Excel® for Windows, version 4.0 or later is required to open the

energy calculation spreadsheets. Before using the SoftSave spreadsheets, the

user should have some familiarity with Microsoft Excel.

Files Provided The SoftSave files for fan drive calculations include a main menu file (FAN-

OPEN.XLS) and four macro controlled calculation spreadsheets (THROT-

FAN.XLS, PITCHFAN.XLS, VANEFAN1.XLS and VANEFAN2.XLS). There

are also four chart sheets for displaying and printing the results graphically

(THROTFAN.XLC, PITCHFAN.XLC, VANEFAN1.XLC and

VANEFAN2.XLC). The control macros are in FANOPEN.XLM.

The SoftSave files for pump drive calculations include a main menu file

(PUMPOPEN.XLS) and three macro controlled calculation spreadsheets

(THROTSAV.XLS, ONOFFSAV.XLS and HYDRSAV.XLS). There are also

two chart sheets for displaying and printing the results graphically(HYDR.XLC and THROT.XLC). The control macros are in

CONTROL2.XLM.

Installation The calculation files can be opened and run from the floppy disk or the files

can be copied to a hard disk. Hard disk installation is recommended if the pro-

gram will be used frequently. If the files are copied to a hard disk, all of the

files can be copied to one directory or the fan files and the pump files can be

copied to two separate directories. The files on the floppy are in directories

FanSave and PumpSave.

Opening the

Spreadsheets

Start EXCEL as usual. For fan calculations, open FANOPEN.XLS. For pump

calculations, open PUMPOPEN.XLS. To open the spreadsheets, select File from the menu bar at the top of the screen and then select Open from the drop-

down menu. In the dialog box, select the drive in which the SoftSave files are

located from the list of drives. Select the directory containing the FanSave or

PumpSave files from the list of directories. Select FANOPEN.XLS or PUM-

POPEN.XLS in the list of file names and click OK .

Selecting Calculation Options

When FANOPEN or PUMPOPEN is opened, a menu sheet is displayed. Figure

1 shows the menu sheet for FANOPEN. The menu sheet presents several alter-

native comparative calculation options represented by graphical icons. Click

on the button above the icon to select an option. Click on the Exit button to

close the menu sheet and exit from the program. Section 3 on page 4 providesadditional information about the calculation options.




Figure 1 Menu Sheet for FANOPEN

Form Sheets When an option is selected, a form sheet will open for the selected option. Fig-ure 2 on page 6 shows a typical form sheet. The form sheets are calculation

spreadsheets where data is entered and results are presented in numerical form.

Section 4 on page 5 provides additional information about the form sheets.

Printing the Form Sheet

There are two or three buttons at the bottom of each form sheet. All of the

sheets have a Print button and a Select Type button and most sheets have a

Graphics button. To print the form sheet, click the Print button. The form sheet

can also be printed by selecting File and Print from the Excel menus or by

clicking the printer icon in the tool bar. If the menu or icon methods of printing

are used, set the page margins to zero, scale the page to fit 1 page wide by 1

page tall, select the appropriate print range and print in black and white.

Viewing and Printing the Graphics

Click the Graphics button at the bottom of the sheet to display a graph of

power usage vs. flow for adjustable speed flow control compared to the alter-

native method of flow control. Print and close the graph by selecting File from

the menu bar and using the appropriate commands from the drop down menu.

Select No in response to the question “Save changes in xx.XLC?” There is no

graph for the ON/OFF pumping calculation option.

Returning to the Menu and Exiting

Click the Select Type button at the bottom of the form sheet to return to the

menu to select a different calculation option or to exit from the program. To

select a different option, click on the button above the icon for the desired

option. Click on the Exit button to close the menu sheet and exit from the pro-gram. After you click the Select Type button, Excel will display the message

“Save changes in XLS?” If you wish to save the data, click Yes, otherwise click

No. You can also save the data by selecting File from the menu bar and Save

As from the drop down menu. Sheets saved under a different name must be

opened using the Excel File Open command rather than the menu sheet.




3 — Calculation Options

FanSave Calculation Options

There are four calculation options presented in the FanSave spreadsheets.

• Damping Control compares the energy required to control flow using an

adjustable frequency drive with the energy required to control flow by

restricting the flow with adjustable dampers.

• Single Speed Vane Control compares the energy required to control flow

using adjustable frequency fan speed control with the energy required to

control flow by adjusting the position of the fan inlet guide vanes. With this

option, the fan operates at a single speed.

• 2-Speed Vane Control compares the energy required to control flow using

adjustable frequency fan speed control with the energy required to control

flow by a combination of adjusting the fan inlet guide vanes and adjusting

the speed of the fan with a 2-speed motor.

• Pitch Control compares the energy required to control flow usingadjustable frequency fan speed control with the energy required to control

flow by adjusting the pitch of the fan blades in an in-flight vane-axial fan.

PumpSave Calculation Options

There are three calculations options presented in the PumpSave spreadsheets.

• Throttling compares the energy required to control flow using adjustable

frequency pump speed control with the energy required to control flow by

restricting the flow with a flow throttling control valve.

• ON / OFF compares the energy required to control flow using adjustable


cycling the pump on and off at full speed.

• Hydraulic compares the energy required to control flow using adjustable


controlling the speed of the pump with a hydraulic drive or some other type

of slipping drive such as an eddy current magnetic coupling drive.




4 — Form Sheets

Basics The form sheets are divided into several columns and cells where initial data

and other information must be entered. All white areas are spaces for entering

information and data. Labels, instructions and other fixed information isshown as white text on a blue background. Calculated results are displayed as

green or red text on a blue background. Figure 2 on page 6 shows a typical

form sheet.

Blank data forms are provided at the end of this manual for gathering initial

data to be entered in the energy calculation form sheets. Spaces are also pro-

vided on the blank forms for summarizing the results of the various energy

savings comparisons.

Identification and Comments

Several spaces are provided at the top of each form sheet for filling in informa-

tion to identify the application, the person filling in the data, the name of a

company and the date. At the bottom of each sheet, space is provided for com-ments.

Initial Data The initial data that must be filled in by the user include the various physical

constants that apply to the applications. Since the accuracy of the results

depends on the accuracy of the initial data, this information should be deter-

mined or estimated as accurately as possible. The required data includes the

density of the fluid, the nominal maximum rate of flow, the operating pressures

and the efficiency of the motor and fan or pump. Operating time at reduced

flow rates must be estimated for flow rates between 30% and 100% of nominal

flow in 10% increments. The operating time at each flow rate is expressed as a

percentage of the total operating time per year.

The initial data is discussed in more detail in the detailed descriptions of the

individual form sheets.

Results of Calculations

The results of the calculations include the estimated energy required for each

method of flow control, the estimated annual energy cost for each method, and

the annual savings realized by using an adjustable frequency drive. Payback

time is also calculated for the additional cost of the drive as compared to the

alternative method of flow control.

The results of calculations is discussed in more detail in the detailed descrip-

tions of the individual form sheets.




5 — Fan Drive Calculations

Initial Data for Fan Applications

The initial data is entered in the areas marked 1 through 12 and 17 on the form

sheets for fan drive calculations as shown in Figure 2.

Figure 2 Form Sheet for Fan Drive Calculations (Variable Speed Control Compared to Damper Control)

The following initial data entries are required:

1. Gas Density, D (lb/cu ft)

Enter the density of the air or gas at the fan inlet in pounds per cubic foot

(lb/cu ft). The density of dry air is 0.0752 lb/cu ft at 68°F and a barometric

ABB ENERGY SAVINGS OF A FAN DRIVE

Variable Speed Control compared

with Damper Control Company:

Department:

Applic: Handled by:

Fan: Date:

INITIAL DATA:

1 Gas density at gas temperature D (lb/cu ft) 0.0752 OK Air = 0.0752 lb/cu f t at 68 °F

2 Fan nominal volume flow qvn (CFM) 55,000

3 Rated total pressure increase ptF (in H2O) 3 at flow 55000 CFM

4 Abs. static pressure at suction inlet pta (in H2O) 407 OK Atm. press.=407.43 in. H2O at 32 °F

5 Nominal efficiency of the fan nk (%) 85 OK

6 Transmission efficiency nt (%) 99 OK Type 100 if not used

7 Rated power of motor P1 (hp) 40 OK Pi = 31 HP (calc. power)

8 Nominal efficiency of the motor nm (%) 94 OK

9 Nominal efficiency of drive nd (%) 98 OK

10 Total operating time per year Tk (h) 8,760 OK Energy used per year [kWh]

11 Price of energy (per kWh) USD 0.050 Var. speed Damper

Flow (CFM) Time (%) Hours control control

30% 16500 0 = 0 h 0 0

12 Operating time in different 40% 22000 16 = 1401 h 7,772 22,144

flow rates as a percentage of 50% 27500 23 = 2014 h 14,156 36,956

the total operating time 60% 33000 23 = 2014 h 18,351 41,140

70% 38500 21 = 1839 h 21,841 40,576

80% 44000 12 = 1051 h 16,184 24,470

90% 49500 5 = 438 h 8,653 10,552

100% 55000 0 = 0 h 0 0

The sum must be = 100 % Sum 100 OK

Sum 86,957 175,840

Energy difference in favor of variable speed control [kWh] 88,882

RESULTS OF CALCULATIONS:

13 Shaft power of the fan at rated flow kW 23.1 (Incl. transmission losses)

14 Calculated input power of a drive at rated flow kW Max. 25.0 24.5

15 Energy cost per year USD 4,348 8,792

16 Cost difference in favor of variable speed control USD 4,444

17 Approx. add-on price of a drive installation USD 8,000

18 Direct payback time Years 1.80

COMMENTS:

Program made by : Date and Time

ABB Drives 4/2/98

Ref. Throtfan.xls V2.31-US 3/25/98 3:25 PM

Select TypePRINTGRAPHICS




pressure of 407 inches of water. For other temperatures and humidities, use

available references to find the correct density. Table 1 lists the

approximate density of dry air at normal air pressure (407 in. H2O) as a

function of temperature from 32°F to 1000°F. The correct density at

different temperatures and pressures can be calculated using the following

formula: where:

D1 = Density at new temperature and pressure

DX = Known density at known temperature and pressure

T1 = New temperature (°K)

TX = Temperature for known density (°K)

p1 = New pressure

pX = Pressure for known density

Table 1 Density of dry air as a function of temperature at normal air pressure (407 in. H 2O)

2. Fan Nominal Volume Flow, qvn (CFM)

Enter the nominal, maximum, or design-point flow for the fan in cubic feet

per minute (CFM). The value entered should be the maximum flow that

the fan is normally expected to deliver. All energy savings calculations

will be based on flow rates that are equal to or less than qvn.

3. Rated Total Pressure Increase, ptF (in. H2O)

Enter the required pressure increase in inches of water column that must begenerated by the fan to produce the given nominal volume flow. The value

must be determined from the fan data and system characteristics.

4. Absolute Static Pressure at Suction Inlet, pta (in. H2O)

Enter the pressure at the inlet to the fan in inches of water column. Normal

atmospheric pressure is 407 inches of water column.

Temperature(°F)

Density(lb/cu ft)

Temperature(°F)

Density(lb/cu ft)

32 0.0807 250 0.0559

40 0.0794 300 0.0522

50 0.0778 350 0.0490

60 0.0763 400 0.0461

70 0.0749 450 0.0436

80 0.0735 500 0.0413

90 0.0722 550 0.0393

100 0.0709 600 0.0374

120 0.0684 650 0.0357

140 0.0661 700 0.0342160 0.0640 800 0.0315

180 0.0620 900 0.0292

200 0.0601 1000 0.0272

D1 D X T X × p1×( ) T 1 p X ×( ) ⁄ =




5. Nominal Efficiency of the Fan, nk (%)

Enter the efficiency of the fan at nominal flow.

6. Transmission Efficiency, nt (%)

Enter the efficiency of the mechanical power transmission device such as a

belt, between the motor and the fan. If the motor is connected directly to

the fan, enter 100%.

7. Rated (nameplate) Motor Horsepower, P1 (Hp)

Enter the nameplate horsepower rating of the motor. This entry is used

only to verify that the motor is large enough for the load. The program

uses calculated power requirements to determine energy savings.

The entered Hp value will be indicated as “Too small” if P1 is less than

90% of the calculated load power requirement, Pi shown at the right side

of the form.

8. Nominal Efficiency of the Motor nm (%)

Enter the motor efficiency from the motor nameplate or from other data

supplied by the motor manufacturer. Use the efficiency for full loadoperation on fixed frequency utility power. The program will adjust the

efficiency for operation at reduced speeds and loads. If the motor is

oversized for the application, enter the efficiency for operation at the

maximum applied load.

9. Nominal Efficiency of the Drive, nd (%)

Enter the drive efficiency from the data supplied by the drive

manufacturer. Use the efficiency for full speed, full load operation. The

program will adjust the efficiency for operation at reduced speeds and

loads.

10. Total Operating Time per Year, Tk (h)

Enter the estimated number of hours that the fan is expected to run during

a year. For 24 hour, 365 day operation, enter 8760 hours.

11. Price of Energy (per KWH)

Enter the currency unit such as US dollars (USD) and the price of energy

per kilowatt hour (kWh). Total annual energy cost will be calculated in the

same currency units. The SoftSave program does not have provisions for

calculating demand charges. To estimate energy cost including demand

charges, enter the average cost of energy per kWh including average

demand charges.

12. Operating Time in Different Flow Rates

Enter the estimated time as a percentage of the total operating time for

operation at each of the listed flow rates from 30% to 100% of nominal

flow. Enter zero for flow rates that are not used. The sum of the entered

percentages must be 100%. If the sum is not 100%, the word “Wrong” will

appear to the right of the sum.




17. Approximate Add-On Price of a Drive Installation

Enter the estimated additional cost of purchasing and installing an

adjustable frequency drive as compared to the alternative method of flow

control used in the comparison. Use the same currency units as entered for

energy cost. This entry will be used to calculate the direct payback time.

Fan Calculation Results

The results of the fan calculations are presented in the two right hand columns

of the area marked 12, the areas marked 13 to 16 and area 18 of the form sheet

as shown in Figure 2 on page 6.

The following results are presented:

12 Energy Used per Year (kWh)

The two columns to the right of the operating time columns in area 12 of

the form sheet list the energy used annually at the various flow rates. The

left column lists the energy used with variable speed flow control and the

right column lists the energy used with the alternative flow control

method. The sums at the foot of the columns are the total annual energy

requirements for the two flow control methods. Below the sums is theenergy difference in favor of variable speed control.

13. Shaft Power of the Fan at Rated Flow (kW)

The shaft power of the fan at rated flow is the mechanical power delivered

by the motor to the fan stated in kilowatts.

14. Calculated Input Power of a Drive at Rated Flow (kW Max.)

The calculated input power is the electrical power in kilowatts supplied to

the input terminals of the drive for variable speed flow control or supplied

to the motor for the alternative method of flow control.

15. Energy Cost per Year

The energy cost per year is the total annual energy requirement listed in

area 12 multiplied by the price of energy per kilowatt hour entered in area

11.

16. Cost Difference In Favor Of Variable Speed Control

The cost difference in favor of variable speed control is the annual energy

cost for variable speed control subtracted from the annual energy cost for

the alternative method of flow control.

18. Direct Payback Time

The direct payback time is the add-on price of a drive installation entered

in area 17 divided by the cost difference in favor of adjustable speed

control listed in area 16.




6 — Pump Drive Calculations

Initial Data for Pump Applications

The initial data is entered in the areas marked 1 through 13 and 22 on the form

sheets for pump drive calculations as shown in Figure 3.

Figure 3 Form Sheet for Pump Drive Calculations (Variable Speed Control Compared to Throttle Control)

ABB ENERGY SAVINGS OF A PUMP DRIVE

Variable Speed Control compared

with Throttle Control Company:

Department:

Applic: Handled by:

Pump: Date:

INITIAL DATA:

1 Liquid density (water = 62.2 @ 80 °F) D (lb/cu ft) 62.2 OK

2 Pump nominal flow Qn (GPM) 1870 = 250 CFM

3 Rated head (pipe & valve friction + stati Hn (ft) 664 Pump maximum head (at zero flow) Hmax (ft) 80 OK

5 Static head of the system Hst (ft) 15 OK

6 Nominal efficiency of the pump np (%) 82 OK

7 Valve friction head (zero if not removed) Hv (ft) 0 OK

8 Rated power of motor P1 (hp) 50 OK Pi = 38 hp

9 Nominal efficiency of the motor nm (%) 93 OK (calc. power)

10 Nominal efficiency of drive nVSD (%) 98 OK

11 Total operating time per year Tk (h) 8760 OK

12 Price of energy (per kWh) USD 0.050

Flow CFM Time (%) Hours

30% 561 0 %= 0

13 Operating time 40% 748 16 %= 1401.6

in different flow rates 50% 935 23 %= 2014.8

as a percentage of the 60% 1122 23 %= 2014.8

total operating time 70% 1309 21 %= 1839.6

80% 1496 12 %= 1051.290% 1683 5 %= 438

100% 1870 0 %= 0

14 The sum must be = 100 % Sum 100 OK

RESULTS OF CALCULATIONS:

18 Calculated energy / throttling 211,245 kWh

19 Calculated energy / variable speed 98,345 kWh

20 Total energy savings / year 112,901 kWh

21 Total energy cost savings / year 5,645 USD

22 Additional investment costs for drive 10,000 USD

23 Direct payback time 1.8 Years

24 COMMENTS:

Program made by : Date:

ABB Drives 4/2/98

Ref. throtsav.XLS V2.31-US 3/25/98 Time: 15:50

PRINT

SELECT

TYPE

GRAPHICS




The following initial data entries are required:

1. Liquid Density, D (lb/cu ft)

Enter the density of the liquid at the pump inlet in pounds per cubic foot

(lb/cu ft). The density of water is 62.2 lb/cu ft at 80F.

2. Pump Nominal Flow, Qn (GPM)

Enter the nominal, maximum, or design-point flow for the pump in gallons

per minute (GPM). The value entered should be the maximum flow that

the pump is normally expected to deliver. All energy savings calculations

will be based on flow rates that are equal to or less than Qn.

3. Rated Head (friction + static), Hn (ft)

Enter the head in feet that must be generated by the pump to produce the

given nominal flow. The value must be determined from the pump data

and system characteristics. The rated head includes the static head (item 5

below) plus the friction head due to all piping and valves at nominal flow.

Include the head loss at nominal flow due to any throttling or control valve

(item 7 below).

4. Pump Maximum Head at Zero Flow, Hmax (ft)

Enter the discharge head pressure that will be developed by the pump at

full speed and zero flow. The value must be determined from the pump

data.

5. Static Head of the System, Hst, (ft)

The static head is the difference in static pressure at the pump discharge

minus the static pressure at the pump inlet. It is the net distance that the

pumped fluid is lifted. Static head does not depend on flow.

6. Nominal Efficiency of the pump, np (%)

Enter the efficiency of the Pump at nominal flow.

7. Valve Friction Head, Hv (ft) (Entered only for throttling calculation)

If item 3 includes the friction head of a throttling valve that will be

removed or not installed if an adjustable speed drive is used, enter the

friction head of the valve here. If the valve will be left in place or if the

valve friction head in not known, enter zero (0).

8. Rated (nameplate) Motor Horsepower, P1 (Hp)

Enter the nameplate horsepower rating of the motor. This entry is used

only to verify that the motor is large enough for the load. The program

uses calculated power requirements to determine energy savings.

The entered Hp value will be indicated as “Too small” if P1 is less than90% of the calculated load power requirement, Pi shown at the right side

of the form.

9. Nominal Efficiency of the Motor nm (%)

Enter the motor efficiency from the motor nameplate or from other data

supplied by the motor manufacturer. Use the efficiency for full load

operation on fixed frequency utility power. The program will adjust the

efficiency for operation at reduced speeds and loads. If the motor is




oversized for the application, enter the efficiency for operation at the

maximum applied load.

10. Nominal Efficiency of the Drive, nd (%)

Enter the drive efficiency from the data supplied by the drive

manufacturer. Use the efficiency for full speed, full load operation. The

program will adjust the efficiency for operation at reduced speeds andloads.

11. Total Operating Time per Year, Tk (h)

Enter the estimated number of hours that the Pump is expected to run

during a year. For 24 hour, 365 day operation, enter 8760 hours.

12. Price of Energy (per KWH)

Enter the currency unit such as US dollars (USD) and the price of energy

per kilowatt hour (kWh). Total annual energy cost will be calculated in the

same currency units. The SoftSave program does not have provisions for

calculating demand charges. To estimate energy cost including demand

charges, enter the average cost of energy per kWh including average

demand charges.

13. Operating Time in Different Flow Rates

Enter the estimated time as a percentage of the total operating time for

operation at each of the listed flow rates from 30% to 100% of nominal

flow. Enter zero for flow rates that are not used. The sum of the entered

percentages must be 100%. If the sum is not 100%, the word “Wrong” will

appear to the right of the sum.

22. Investment Costs

Enter the estimated additional cost of purchasing and installing an

adjustable frequency drive as compared to the alternative method of flow

control used in the comparison. Use the same currency units as entered forenergy cost. This entry will be used to calculate the direct payback time.

Pump Calculation Results

The results of the Pump calculations are presented in the areas marked 18 to 21

and area 23 of the form sheet as shown in Figure 3 on page 10.

The following results are presented:

15. Calculated Power Demand of a Pump (kW)

(Given for ON/OFF calculation only)

The calculated power demand of the pump is the mechanical power

delivered by the motor to the pump stated in kilowatts.

16. Calculated Input Power of a Motor (kW)(Given for ON/OFF calculation only)

The calculated input power of a the motor is the electrical power delivered

to the motor.




17. ON/OFF Control Run Time Hours/Year (hours)

(Given for ON/OFF calculation only)

The total number of hours that the pump actually operates to deliver the

average flow as entered in area 13.

18 Calculated Energy / [Alternative Control] (kWh)

The calculated energy used annually with the alternative flow controlmethod.

18. Calculated Energy / Variable Speed (kWh)

The calculated energy used annually using an adjustable frequency drive

for flow control.

20. Total Energy Savings / Year (kWh)

The total energy savings is the calculated energy used annually using an

adjustable frequency drive for flow control (item 19) subtracted from the

calculated energy used annually with the alternative flow control method

(item 18).

21. Total Energy Cost Savings / Year

The energy cost per year is the total energy savings per year (item 20)

multiplied the energy cost per kilowatt hour as entered in area 12.

23. Direct Payback Time

The direct payback time is the add-on price of a drive installation entered

in area 22 divided by the total energy savings per year (item 20).




7 — Explanation of Calculations

Fan Drive Calculations The power required to operate a fan is given by the formula:

where:

P = Power supplied to the motor (kW)

D = Gas density

qvn = Fan nominal volume flow

ptF = Rated total pressure increase

kp = Compression factor

ku = A constant that is determined by the units of measurement

Pr = Relative power required at reduced rates of flow

nk = Nominal efficiency of fan

nt = Transmission efficiency

nm = Nominal efficiency of motor

nd = Nominal efficiency of drive (used only for drive calculations)

Most of these parameters are the initial data entries that are explained in Sec-

tion 5. The compression factor, kp compensates for the fact that the air or gas is

compressed as it passes through the fan; kp = 1 - 0.0035 × ptF × nk/pta. The

relative power parameter, Pr is used to determine the power required at

reduced flow rates as compared to nominal volume flow. Values of Pr for the

various flow control methods are shown graphically in Figure 4. The relative

power curves are normalized graphs of power usage vs. flow that are typical of the various flow control methods shown. They are used to predict the reduction

in power usage as flow is reduced. They compensate for the changes in motor,

fan and drive efficiency that take place as flow is reduced.

P D qvn ptF kp ku Pr ⋅ ⋅ ⋅ ⋅ ⋅

n k n t n m n d ⋅ ⋅ ⋅---------------------------------------------------------------=




Figure 4 Relative Power Required, Pr for Various Flow Control Methods

Pump Drive Calculations

The power required to operate a pump is given by the formula:

where:

P = Power supplied to the motor (kW)

D = Liquid density

Q = Flow

H = Head

ku = A constant that is determined by the units of measurement

npc = Pump efficiency, corrected for operating conditions

nmc = Motor efficiency, corrected for operating conditions

nVSDc = Drive efficiency, corrected for operating conditions

(used only for drive calculations)

These parameters are based on the initial data entries that are explained in Sec-

tion 6. D is the density of the liquid as entered in the form sheet. Q is the actual

flow for which power consumption is to be calculated. In the calculation

sheets, calculations are made for Q = 30% to 100% of nominal pump flow Qn.

H is the total dynamic head at flow Q. The efficiency figures are the valuesentered in the from sheet corrected for operating conditions.

For adjustable frequency flow control, the total dynamic head, H is given by:

, where Qu is a decimal fraction of nominal pump

flow, Qu = Q/Qn, and the total friction head, Hf = Hn - Hst - Hv. Pump effi-

ciency for adjustable frequency flow control remains constant at np. The motor

and drive efficiency are corrected for operating conditions by multiplying the

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0% 20% 40% 60% 80% 100%

Flow

R e l a t i v e P o w e r ,

P r

Adjustable Frequency Speed ControlDamping ControlSingle Speed Vane ControlTwo Speed Vane ControlPitch Control

PD Q H ku⋅ ⋅ ⋅

npc nmc nVSDc⋅ ⋅-----------------------------------------------=

H Hst Qu2

Hf ×+=




initial data entry values of nm and nVSD by the correction factors shown Fig-

ure 5. The correction factors for motor efficiency that are shown in the figure

are for a system with static head, Hst = 0. For systems with higher static head,

the correction factor is closer to 1.0 at all flow rates.

Figure 5 Motor and Drive Efficiency

For flow control by throttling, the total dynamic head is given by:

, where Qu is a decimal fraction of

nominal pump flow, Qu = Q/Qn. Pump efficiency is given by:

. Total dynamic head and pump efficiency

are illustrated graphically in Figure 6. Motor efficiency with throttling remains

constant at nm.

Figure 6 Total Dynamic Head and Pump Efficiency with Throttling

For ON/OFF flow control, the power required while the pump is operating is

the power calculated using Qn, Hn, np and nm. The annual energy consump-

0.75

0.80

0.85

0.90

0.95

1.00

0 20 40 60 80 100

Percent Flow

E f f i c i e n c y C o r r e c t i o n F a c t o r

Drive

Motor

H Hmax Qu2

Hm ax Hn–( )×–=

nmc np 2.44Qu 1.44Qu2

–( )=

0%

25%

50%

75%

100%

125%

150%

0 25 50 75 100

Percent Flow

Head

Efficiency




tion in kilowatt hours is: , where TON is the summa-

tion of the ON times required to produce the various flow rates:

E ON/OFF PON T ON⋅=

T ON Tk T %

100%--------------

Q%

100%--------------⋅

30%=

Q 100%=

∑×=




8 — Conversion Factors

The SoftSave calculation sheets require initial data to be entered in the units of

measurment customarily used in the USA. The following table provides con-

version factors for converting metric units into the units used by SoftSave.

Table 2 Conversion Factors

To Convert Into Multiply By

kg/m3lb./cu. ft. 0.0624

kg/liter, kg/dm3 or g/cc lb./cu. ft. 62.42

m3 /s CFM 2119

liters/s CFM 2.119

m3 /h GPM 4.4029

liters/s GPM 15.85

Pascals or Newtons/m2 in. H2O (68°F) 0.004022

Head in meters Head in feet 3.281

kW Hp 1.34




9 — Blank Data Forms

The blank data forms on the following pages are provided for gathering initial

data to be entered in the energy calculation form sheets. Spaces are also pro-

vided on the blank forms for summarizing the results of the various energysavings comparisons.




Blank Data Form for Fan Drive Energy Savings Calculations

Company:

Department:

Handled by: Date:

Application:

Fan:

1. Gas density, D (lb/cu ft)

2. Nominal flow, qvn (CFM)

3. Pressure increase, ptF (in. H2O)

4. Static pressure, pta (in. H2O)

5. Fan efficiency, nk (%)

6. Transmission efficiency, nt (%)

7. Motor horsepower, P1 (Hp)

8. Motor efficiency, nm (%)

9. Drive efficiency, nd (%)

10. Total annual operating time, Tk (h)

11. Price of energy (per KWH)

12. Operating time (%) at 30% flow

Operating time at (%) 40% flow







16. Add-on price for drive installation

Calculation Results (check items needed)

15. Annual energy cost, drive

Annual energy cost, damping

Annual energy cost, 1-speed vanes

Annual energy cost, 2-speed vanes

Annual energy cost, pitch control

16. Payback time, drive vs. damping

vs. 1-speed vanes

vs. 2-speed vanes

vs. pitch control




Blank Data Form for Pump Drive Energy Savings Calculations

Company:

Department:

Handled by: Date:

Application:Fan:

1. Liquid density, D (lb/cu ft)

2. Nominal flow, Qn (GPM)

3. Rated head, Hn (ft.)

4. Maximum head (at zero flow), Hmax (ft.)

5. Static head of system, Hst (ft.)

6. Pump efficiency, np (%)

7. Valve friction head, Hv (ft.)

8. Motor horsepower, P1 (Hp)9. Motor efficiency, nm (%)

10. Drive efficiency, nVSD (%)

11. Total annual operating time, Tk (h)

12. Price of energy (per KWH)

13. Operating time (%) at 30% flow








22. Add-on price for drive installation

Calculation Results (check items needed)

18. Annual energy use, throttling

Annual energy use, ON/OFF control

Annual energy use, hydraulic drive

19. Annual energy use, drive

21. Energy cost savings vs. throttling

vs. ON/OFF control

vs. hydraulic drive

23. Payback time vs. throttling

vs. ON/OFF control

vs. hydraulic drive



S

o f t S a v e - U S - 0 4

3 A U A

4 8 9 0 0 2 B 4 7 1 1 R 0 1 0 1 R e v .

A

E

f f e c t i v e : 9 / 1 5 / 9 8

S

u p e r s e d e s : N o n e

ABB Industrial Systems Inc.

16250 W. Glendale DriveNew Berlin, WI 53151

USATelephone:(414) 785-3200

(800) 243-4384Fax: (414) 785-8525

energy savings calculator for fan and pump drives-users manual.pdf

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