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STANDARD SAVINGS ESTIMATION PROTOCOL
FOR PUMP VARIABLE FREQUENCY DRIVES
REGIONAL TECHNICAL FORUM
Release Date: June 10, 2013
Standard Savings Estimation Protocol - Pump VFD
TABLE OF CONTENTS
1. PURPOSE............................................................................................................ 1
2. SUNSET DATE ...................................................................................................... 1
3. DEFINITION
OF KEY TERMS ..................................................................................... 1
4. ELIGIBLE PROJECTS ............................................................................................... 2
5. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER ................................................... 3
6. DELIVERY VERIFICATION ......................................................................................... 3
7. DATA COLLECTION REQUIREMENTS ........................................................................... 3
7.1. Pump and Pump Motor Specifications .............................................................................. 3
7.2. Pump Operations ............................................................................................................... 4
7.3. Post-Period Electrical Measurements................................................................................ 4
7.4. Facility Control System Post-Period Trend Logs ................................................................ 5
7.5. Baseline Operation............................................................................................................. 5
8. PROVISIONAL DATA REQUIREMENTS ......................................................................... 7
9. SAVINGS ESTIMATION STEPS ................................................................................... 7
9.1. Derive Flow vs. Power Relationship for Post Period.......................................................... 8
9.2. Derive Flow vs. Power Relationship for Baseline Period ................................................... 8
9.3. Compute Savings for Trend Log Intervals .......................................................................... 8
9.4. Annualized Savings: Pump Speed Determined by OAT and Facility Operations
Schedule .................................................................................................................................... 9
9.4.1. Systems with On-Off Valve in the Baseline Period ............................................................. 9
9.4.2. Systems Without On/Off in Baseline Period..................................................................... 10
9.5. Annualized Savings: Pump Speed Determined by Facility Operations Schedule ............ 10
9.5.1. Systems with On-Off Valve in the Baseline Period ........................................................... 10
9.5.2. Systems Without On/Off in Baseline Period..................................................................... 11
10. SAMPLING PROCEDURE ...................................................................................... 11
11. RELATIONSHIP TO OTHER PROTOCOLS AND GUIDELINES ............................................. 11
12. TYPICAL COST OF APPLYING THIS PROTOCOL ........................................................... 12
13. USER’S GUIDE TO THE SAVINGS CALCULATOR .......................................................... 13
13.1. Information Tab ............................................................................................................. 13
13.2. Pump Operating Conditions Tab .................................................................................... 14
13.2.1. Motor Information.......................................................................................................... 14
13.2.2. Machine Curve ................................................................................................................ 15
13.2.3. Recirculation Inputs ........................................................................................................ 16
13.2.4. Baseline Period Control Strategy .................................................................................... 17
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13.2.5. System Curve Information .............................................................................................. 17
13.2.6. One Time Electrical Data ................................................................................................ 18
13.3. Pump Operating Schedule Tab ..................................................................................... 19
13.4. Trend Data (Pre) and Trend Data (Post) Tabs ................................................................ 20
13.5. Results Tab ..................................................................................................................... 20
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Standard Savings Estimation Protocol - Pump VFD
1. PURPOSE
This protocol establishes a method by which annual electrical energy savings (kWh) can be estimated for
a pump that has been upgraded by the addition of a Variable Frequency Drive (VFD). VFDs reduce
electric use by adjusting the pump motor’s speed to match the required load. Many pumps do not need
to run at full capacity all of the time, and VFDs are more efficient than other flow control methods, such
as throttling valves, at regulating pump flow rates.
This protocol specifies minimum acceptable data collection requirements and the method by which
these data are to be used in computing savings through two methods, (1) a best practices method
(BPM)1 and (2) the simplest reliable method2 (SRM). For some data elements, alternative sources of
data, considered to be of equal or superior quality, are also defined and are allowed. Savings are
computed using the Protocol Calculator that accompanies this document to ensure standardized
application of the savings estimation methods.
2. SUNSET DATE
This protocol is approved for use until June 30, 2015.
3. DEFINITION OF KEY TERMS
Project. A VFD installed to control one pump unit and baseline control mechanism (e.g. throttling valve)
is either removed or disabled and set to the maximum flow condition.
Baseline. This modifier; as in baseline control strategy has one of two meanings. (1) For pump units
upgraded in existing facilities, it refers to the period prior to the upgrade. (2) For pump units in new
construction, there is no such period. In these instances, the term baseline refers to the design
specification for the pump unit without the efficiency upgrade.
Post. This modifier; as in post current trend log, refers to the period after the pump unit VFD upgrade is
installed and fully commissioned.
1
The BPM is the ideal method to calculate energy savings for a measure. Data required to
compute savings using the best practices method are described in Section 8
2
The SRM is intended to yield similar results to the best practices method using minimum
possible data collection. The data required to compute savings using the simplest reliable
method are described in Section 7
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Standard Savings Estimation Protocol - Pump VFD
Qualified Electrical Worker. As defined in OSHA 29 CFR Part 1910.3993 or NFPA 70E4.
Machine Curve. The pump performance curve, obtained on site or from the manufacturer, showing the
flow vs. head relationship, along with efficiencies.
4. ELIGIBLE PROJECTS
Eligible pumps must follow the affinity laws. Centrifugal pumps and vertical and horizontal turbine
pumps are eligible. Positive displacement pumps are not eligible.
The methodology employed in calculating energy usage restricts what control strategies are eligible
under this protocol. The methodology requires a constant system curve in the post configuration.
Systems which incorporate operating valves in the post configuration are thus excluded. This excludes
many constant-pressure-controlled HVAC systems. Applications where this protocol might be suitable
include industrial transfer pumps, feedwater pumps, and water or wastewater pumps.
The following criteria define eligible projects.

The primary determinants of pump speed are either facility operations schedule or outside air
temperature combined with operations schedule.

The baseline control strategy must rely on throttling valves, with or without recirculation. The
protocol is limited to a single pump.

The flow profile must be the same for baseline and post periods.

The system curve remains constant in the post period; all control valves have been removed or are
non-operational. This excludes many HVAC pump systems, in which operational valves continue to
be part of the system after VFD installation.

Pump motors must be single speed motors.

Pumps must not be subject to a local energy code requirement for variable speed drive. This
excludes many new construction HVAC pumps.

The cost of implementing this protocol must not make the project economically unattractive.
3
“One who has received training in and has demonstrated skills and knowledge in the
construction and operation of electric equipment and installations and the hazards
involved”
4
“One who has skills and knowledge related to the construction and operation of the
electrical equipment and installations and has received safety training to recognize and
avoid the hazards involved”
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5. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER
The practitioner who has lead responsibility for applying this protocol must have at a full understanding
of the following:

Appropriate safety procedures for work involving pumps and the measurement equipment
required by this protocol

This protocol and the accompanying savings calculator.
The practitioner must also be able to successfully perform the following tasks:

Identify the determinants of pump operation: (1) facility operations schedule or, (2) outside air
temperature combined with facility operations schedule.

Supervise a qualified electrical worker in taking a series of spot measurements of true power and
other required parameters for the pump unit circuit.

Install and operate a current logger and obtain necessary trend logs from facility control systems.
6. DELIVERY VERIFICATION
This protocol may only be used for pump units that pass the following delivery verification tests:

The baseline control mechanism is either removed or disabled and set to the maximum flow
condition in the post case.
7. DATA COLLECTION REQUIREMENTS
This section describes the data collection requirements for the SRM to estimate energy savings. The
details of the SRM energy savings methodology are presented in Section 9. The minimum acceptable
procedure for obtaining the data is specified. In some cases, alternative procedures are allowed which
would provide data of equal or better quality.
7.1. Pump and Pump Motor Specifications

Machine Curve. Obtained on site or from the pump manufacturer. Data points from the
manufacturer’s performance curve are required. Flow, pressure, and efficiency points must be read
from the appropriate machine curve and must match the conditions at the site in terms of impeller
size and speed (RPM). This is also sometimes referred to as the pump curve by practitioners.

Pump Motor HP. Obtained from the motor name plate.

Pump Motor RPM. Obtained from the motor name plate.

Pump Motor Enclosure type. Obtained from the motor name plate.
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7.2. Pump Operations

Determinants of Pump Speed. Obtained from facility operator. Possible determinants are: (1)
facility operations schedule, or (2) Outside air temperature combined with operations schedule.

Facility Operations Schedule. Obtained from facility operator. If the pump unit has
different operation modes determined by the facility’s operations schedule, e.g.,
setback of flow during night and weekend hours, determine the period for each mode,
defined as needed by hour of day, day of week, and season. This method requires that
all schedule modes are metered.

Typical Outside Air Temperature (OAT). Determine whether OAT is a significant
determinant by discussion with the facility operator and consideration of the types of
load being served by the pump.

Weather Station. If OAT is a significant determinant, identify the TMY (Typical Meteorological Year)
weather station which is closest to the project site.

Static Head. The head at zero flow – the net static head including elevation head – must be known.
Site personnel should be able to provide this value, or describe the means to acquire it.

Pump Operating Point. This (flow, pressure) operating point must be with all valves removed or
wide open. The point may be taken from the equipment schedule on the facility’s mechanical plan.
Alternatively, this value may be determined by: (1) inspecting facility control system trend logs of
pump flow rate, if the system has a calibrated flow sensor and the log contains values at or near
100% speed; or (2) based on a pair of values – measured kW along with corresponding VFD speed.

On/Off Valve Presence. The implementer needs to ask the customer if the pump operated with an
on/off valve prior to VFD installation.
7.3. Post-Period Electrical Measurements

One-Time Electrical Measurements. Taken by a qualified electrical worker under the on-site
supervision of the practitioner. Power meter is attached as needed to record true RMS poly-phase
power and current on one leg of the circuit supplying power to the VFD. These measurements are
recorded while the VFD is set to a series of at least 3 levels of speed, including one at 100% speed.
Measurements should aim to capture VFD operation at low and medium speed as well.

Trend Log of VFD Current. A data logger is installed to measure 15-minute interval true RMS
current on the same leg of the circuit as was used in the one-time measurements. If the pump unit
speed is primarily determined by OAT, the measurement period must be at least two months and
must start between August 15th and October 15th or between March 15th and May 15th in order
to capture measurements for a sufficient range of OAT values. If the pump unit speed is primarily
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Standard Savings Estimation Protocol - Pump VFD
determined by facility operating schedule the period must be at least one month long, include all
modes of operation as dictated by the operating schedule, and can start at any time of the year.
 Alternative Measurements.

True Power. In lieu of the one-time electrical measurements and current trend log this
protocol allows for a trend log of true poly-phase RMS power for the circuit powering
the VFD. The same measurement interval, period and timing requirements apply as
described for the current measurement above.
7.4. Facility Control System Post-Period Trend Logs

Trend Log of VFD Facility OAT These data may be obtained from the facility’s control system if it
can be programmed to record OAT at 15-minute intervals. Data must be collected for the same
period as the VFD current trend log. These data are required only if pump speed is primarily a
function of OAT (such as for a heating or cooling units). If OAT is not available from the facility’s
control system or appears unreliable, an OAT data recorder should be installed to create this trend
log. Alternatively, OAT can be obtained from an applicable weather station.
7.5. Baseline Operation
If end-use demand in the baseline restricts flow, the flow may drop below the pump minimum
requirement. Recirculation of flow will likely be employed to counteract this. The recirculation would
not necessarily be required in the post period because lower speed operation is available. The flow
profile derived from the post period can be modified to include the baseline recirculation flow that is
over and above the post recirculation flow. Two types of recirculation can be defined:

Minimum flow. The baseline flow never drops below a given value. When applying the post flow to
the baseline period, all flows below this value are set to the minimum flow.

Constant recirculation flow. A constant amount is always recirculated. This flow is added to the
flow values derived in the post period when applied to the baseline. This value must be the flow
over and above any recirculation flow in the post period.
Data collection required to define recirculation can be achieved in one of three ways:
 1. Fixed orifice or similar device. Constant flow through the device is specified in one of four ways:
 Flow capacity (CV). Taken from device cut sheet,
AND

Pressure drop across valve. Observed during the baseline or found in records from the
baseline period,
OR
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 Orifice diameter,
AND
 Recirculation pipe diameter,
AND

Pressure drop across valve. Observed during the baseline or found in records from the
baseline period,
OR
 Engineering design documents. Design documents which specify the bypass flow rate.
OR

Measured flow. Observed or recorded flow through the bypass line during the baseline
period.
 2. Automatic recirculating valve (ARV). Minimum flow is specified in one of two ways:

Observed minimum flow rate. The minimum total pump discharge flow observed
during the baseline or found in records from the baseline period, if those observations
show a clear lower limit,
OR

Engineering design documents. Design documents, especially ARV manufacturer
documents, which specify the minimum flow rate of the installed device.
 3. Instrument controlled recirculating valve. Minimum flow is specified in one of three ways:

Observed minimum flow rate. The minimum total pump discharge flow observed
during the baseline or found in records from the baseline period, if those observations
show a clear lower limit,
OR

Engineering design documents. Design documents which specify the minimum flow rate
of the control valve.
OR

Controller setpoint. Controller minimum flow setpoint, observed during the baseline
period.
An alternative data collection method utilizes baseline electrical measurements:

Alternative Measurements. In lieu of the baseline performance curves, pump motor current or
power can be measured during the baseline period. The same measurement interval, period and
timing requirements apply as described under Trend Log of VFD Current in section7.3. This
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alternate method should be used only when operating conditions are reasonably similar between
baseline and post measurement conditions. The practitioner should use his best judgment to
discern whether the operating conditions are reasonably similar or not.
8. PROVISIONAL DATA REQUIREMENTS
This section outlines the data requirements for the BPM. During the period that the RTF classifies this
protocol as Provisional, the following data requirements will be in force:

Baseline Electrical Measurements. Trend log true poly-phase RMS power for the circuit powering
the pump unit. The same measurement interval, period and timing requirements apply as
described under Trend Log of VFD Current in section 7.3.

Post-Period Electrical Measurements. Trend log true poly-phase RMS power for the circuit
powering the pump unit. Trend log amperage of at least one leg with the same time stamp
signatures as the true poly-phase RMS power trend logs for verification. The same measurement
interval, period and timing requirements apply as described under Trend Log of VFD Current in
section 7.3.
9. SAVINGS ESTIMATION STEPS
This protocol defines a method to derive energy savings based on power (or current) measurements
taken post-VFD-installation, together with pump performance specifications and site operating
characteristics. The basis for the calculation is that the post power trend, combined with site system
specification, allows the derivation of the post flow trend. This flow trend is assumed to apply in the
baseline case (with exceptions in the case of recirculation), where it is used to derive the baseline power
trend from the pump performance curve.
The post operating curve (system curve) is assumed to not vary. All valves have either been removed or
are fixed. The system curve is specified with two points – the static head and an operating point.
Baseline power is derived from the flow profile. Flow, head, and efficiency points from the performance
curve are used to develop a flow-to-power relationship. To account for cases where a recirculation flow
exists in the baseline that does not exist in the post period, the user can specify a minimum flow or a
constant circulation flow that will be used to modify the flow profile.
Savings from the period of measurement are annualized based on annual facility operations schedules
or a correlation with outside air temperature.
Savings are estimated using the savings calculator that accompanies this protocol.
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9.1. Derive Flow vs. Power Relationship for Post Period

System Curve. The full-flow operating point is used to derive an equation for the system curve
(flow vs. pressure) as the parabola (or lower order equation) from the static head value through the
point on the machine curve matching the operating point collected as described in Section 7.1.

Flow vs. Power Curve. The pump will operate along the system curve as the VFD changes pump
speed. Pump efficiency may vary along this curve, and is included in the flow vs. power
calculations. The calculator derives an equation for flow as a function of power (kW) along this
curve. Motor efficiency and VFD efficiency are based on default relationships (DOE tables5)
according to motor percent load.
9.2. Derive Flow vs. Power Relationship for Baseline Period

Flow vs. Power Curve. Assuming constant speed, the pump will operate along the machine curve.
Using the machine curve data points entered, the calculator derives an equation for power as a
function of flow along the machine curve.

Recirculation Flow. Recirculation flow, if present in the system, is accounted for in the calculator as
either a constant or minimum recirculation flow. Constant recirculation is taken into account at
each calculated flow value (calculated via the Flow vs. Power curve) to determine flow with
recirculation. Minimum recirculation flow is taken into account only when calculated flow falls
below the minimum specified amount; in this case, the calculated flow is set to minimum
circulation flow.
9.3. Compute Savings for Trend Log Intervals

Data Synchronization. Start times for all trend log intervals are synchronized by moving each to
the closest standard sub-hourly interval start times, e.g. 0, 15, 30 and 45 minutes after the start of
each hour.

Power and Current Curve Fit. Spot measurements of true power and current (taken at least for 3
levels of speed, including 100%) are fit to a second order equation.

Post kW. Calculate kW from fitted equation for each current (amps) value.

Post flow. Calculate flow as a function of kW using the equation derived from the system curve.
5
Motor efficiencies are taken from MotorMaster+ International version 1.1.5, August,
2011. https://www1.eere.energy.gov/manufacturing/tech_assistance/software_motormaster.html. VFD
efficiencies were obtained from DOE Motor Tip Sheet 11, June
2008. https://www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/motor_tip_sheet11.pdf.
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
Baseline flow. The assumption is that the baseline flow profile is identical to the post flow profile,
with the exception of recirculation adjustments to the baseline flow.

Baseline kW. Calculate kW as a function of flow using the equation derived from the machine
curve.

Savings for Trend Log Period. Calculate the kW savings profile as the difference between baseline
kW and post kW.
9.4. Annualized Savings: Pump Speed Determined by OAT and
Facility Operations Schedule
This method for annualizing savings assumes the load can be characterized by outside air temperature
changes combined with a facility operations schedule. In BPA terminology, this is also a VLVS (Variable
Load Variable Schedule) case. The methods used are essentially the same as those described in the BPA
guidelines, except that baseline kW is modeled rather than metered.
9.4.1. Systems with On-Off Valve in the Baseline Period
This method makes the assumption that in the baseline period, there is no control valve installed, only
an on/off valve. Implying that in the baseline period, the pump either operates at the operating point
and at 100% speed or is off. In this case, the annual energy savings will be calculated in the following
manner:

Calculate Total Consumption for Post Period. Using post period trended data, first calculate
consumption at each logged interval during the trending period.

Establish Relationship between Calculated Flow, OAT, and Facility Operating Schedule: Using the
calculated consumption at each logged interval, the OAT at each interval and data on facility
operating schedule (during trending period), a relationship between the three variables is
established.

Annualize Post Period Consumption: Using the relationship derived above, post period
consumption should then be annualized applying the derived relationship to the annual facility
schedule, and annual OAT data.

Calculate Total Annual Flow Volume through Pump. Using the power-flow relationship derived
from the post period and annuialized post period consumption data, calculate total annual flow
through pump in the post period.

Calculate Total Annual Energy Consumption in Baseline Period. As the total annual volume moved
through the pump is now known, use the power – flow relationship at the operating point to
calculate the total annual baseline energy consumption.
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
Calculate Total Annual Energy Savings. This is the difference between the annualized energy
consumption in the baseline and the post period.
9.4.2. Systems Without On/Off in Baseline Period

Average Savings by Trend Log Bin. Average kW savings by two degree temperature bins for all
trend log intervals during operating hours, as defined by facility operations schedules (Section 7.2).
If the facility has more than one operation mode (that determines pump speed), temperature bin
averages are separately computed for each operation mode.

Operating Hours by TMY Bin. Divide the 8,760 TMY OAT data into two degree bins and compute
frequency of annual operating hours for each bin, as defined by facility operations schedules
(Section 7.2).

Average Savings by TMY Bin. TMY bin average bin savings equal trend log average bin savings for
each matching bin. Extrapolate average savings for TMY bins that do not have trend log data.
Higher temperature bins are extrapolated by a linear equation fit to the trend log bins above 57
degrees and lower temperature bins by a linear equation fit to the bins below 57 degrees. No bin
value is allowed to exceed the rated pump motor kW.

Saving by Bin. For each TMY bin, multiply the average bin savings by the number of operating hours
in each bin, to get kWh savings in each bin.

Annual Savings. Sum the kWh values across TMY bins.
9.5. Annualized Savings: Pump Speed Determined by Facility
Operations Schedule
This method makes two assumptions: 1) There is a strong correlation between schedule periods and
savings; and 2) Power trends for the post period are available for all schedule periods. In BPA
terminology, this is a Variable Load Timed Schedule (VLTS) case. The methods used are essentially as
described in the BPA guidelines, except that baseline kW is modeled rather than measured.
9.5.1. Systems with On-Off Valve in the Baseline Period
This method makes the same assumption stated in Section 9.4.1, The annual energy savings will be
calculated in the following manner:

Calculate Total Consumption for Post Period. Using post period trended data, first calculate
consumption at each logged interval during the trending period.

Establish Relationship between Calculated Flow, and Facility Operating Schedule: Using the
calculated consumption at each logged interval, and data on facility operating schedule (during
trending period), a relationship between the two variables is established.
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
Annualize Post Period Consumption: Using the relationship derived above, post period
consumption should then be annualized by applying the derived relationship to the annual facility
schedule.

Calculate Total Annual Flow Volume through Pump. Using the power-flow relationship derived
from the post period and annuialized post period consumption data, calculate total annual flow
through pump in the post period.

Calculate Total Annual Energy Consumption in Baseline Period. As the total annual volume moved
through the pump is now known, use the power – flow relationship at the operating point to
calculate the total annual baseline energy consumption.

Calculate Total Annual Energy Savings. This is the difference between the annualized energy
consumption in the baseline and the post period.
9.5.2. Systems Without On/Off in Baseline Period

Average Savings for Trend Period. For the trend log period, average the savings for each operation
mode, as determined by facility operations schedule (Section 7.2).

Annual Operating Hours. Determine the number of operating hours for each operating mode in a
year.

Savings by Operating Mode. Multiply the number of annual operating hours times the average
saving for each operating mode.

Annual Savings. Sum savings across operating modes.
10. SAMPLING PROCEDURE
No sampling is permitted by this protocol. Data collection and savings estimation is required for each
upgraded pump unit regard less of the number of such units that may be upgraded at a facility.
11. RELATIONSHIP TO OTHER PROTOCOLS AND GUIDELINES
The relationship between this protocol and other relevant protocols and guidelines is as follows:

International Performance Measurement and Verification Protocol – 2007 (IPMVP), Efficiency
Valuation Organization. This protocol is consistent with Option A - Retrofit Isolation: Key Parameter
Measurement described in the IPMVP, as a number of key parameters are measured (VFD current,
VFD %speed and OAT). The use of default pump performance curves is consistent with this option.

M&V Guidelines: Measurement and Verification for Federal Energy Projects Version 3.0, U.S.
Department of Energy Federal Energy Management Program. The relevant part of this guideline is
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Standard Savings Estimation Protocol - Pump VFD
Section 11.4 Variable Speed Motors. This guideline requires both baseline and post measurements,
which is not consistent with this protocol.

Verification by Equipment or End-Use Metering Protocol, 2011, Bonneville Power Administration.
This BPA guideline, based on ASHRAE Guideline 14-2002, in general requires both baseline and post
metering. The protocol described herein is based on post-only metering, although its provisional
form calls for pre- and post- metering. The BPA guideline End-Use Metering Absent Baseline
Measurement is aimed at new construction projects, and does not provide additional guidance for
VFD retrofit projects where baseline measurements are not taken. The BPA guidelines emphasize
measurements of the load, which in this case would be the fluid flow, together with spot
measurements of power, rather than requiring a trend of just power. In BPA terminology, the
eligible VFD pump projects described herein are either Variable Load Timed Schedule (VLTS) or
Variable Load Variable Schedule (VLVS), in which neither the load nor the schedule changes
between baseline and post.

Sampling Reference Guide, BPA. It is unlikely that more than 20 pump units would be upgraded as
part of any one project. It is difficult to obtain reliable sample estimates from populations this
small, especially given the likely variation in savings between units. Therefore no sampling is
allowed. This is consistent with the BPA guide.

Regression Reference Guide, BPA. This protocol uses regression techniques to fit a linear equation
to the measurements of true power and current for the VFD and to extrapolate savings to
temperatures beyond those observed in the trend logging period (for pump units whose speed is
primarily determined by OAT). The application of these regression techniques is consistent with
the BPA guide.
12. TYPICAL COST OF APPLYING THIS PROTOCOL
Shown below is an estimate of typical cost of applying this protocol for a single pump unit. Projects that
involve more than one pump unit at the same facility are likely to see lower cost per unit. Expenses for
alternative measurements, allowed by this protocol, are not included in this estimate of typical cost.
Item
Quantity $ / Hour Rental Total Cost ($)
Equipment
Power Meter
1
100
100
Current Logger
1
200
200
Labor
Practitioner
Travel
3
110
330
Scheduling
1
110
110
Facility Operator Interview
2
110
220
0.5
110
55
VFD Inspection
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Item
Quantity $ / Hour Rental Total Cost ($)
Electrical Measurements
0.5
110
55
Install/Remove Current Logger
2
110
220
Savings Estimate
5
110
550
Travel
2
90
180
Electrical Measurements
1
90
90
2
150
300
Electrician
Controls Specialist
Setup and Export Trend Logs
Total
$2,410
13. USER’S GUIDE TO THE SAVINGS CALCULATOR
This section is a step by step guide for using the Pump VFD Excel Savings Calculator (Savings Calculator).
The Savings Calculator is an Excel-based, tool that implements the savings calculation methodology
outlined in this protocol document.
The Savings Calculator is organized by tabs, with each tab containing a related set of inputs required by
the protocol to calculate energy savings. The Savings Calculator contains the following tabs:

Information

PumpOperatingConditions

PumpOperatingSchedule

Trend Data (Pre)

Trend Data (Post)

Results
The following subsections explain the intent of each tab, the data inputs required by each tab, and
instructions on how to interpret results.
13.1. Information Tab
The user enters descriptive information regarding the project being analyzed in this tab. This descriptive
information consists of the customer information, project location and the properties of the fluid that is
being pumped. Figure 1 presents a screenshot of the data input required in this tab.
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Figure 1 Customer and Project Information Section in the Savings Calculator
Customer Information
Facility Site Contact Name:
Phone:
Email:
Fax:
Address:
Facility Type:
Please choose a specific gravity fluid
Pump Fluid Type:
Water @ 70 F
Calculated Specific Gravity:
0.999
Custom Specific Gravity (optional):
Please choose nearest TMY city
State:
City:
ID
Idaho Falls Fanning Field
The customer and project information are descriptive fields that the user can enter in any format. The
primary purpose of these inputs is documentation; these descriptive inputs are not required for energy
savings calculations. The user can choose fluid properties by using a prepopulated dropdown list, or by
entering custom values for fluid properties. To enter custom values, the user must choose the option
“Other” from the dropdown list. Care should be taken while selecting fluid properties; unlike the project
detail fields on this tab, fluid properties are used to calculate energy savings.
13.2. Pump Operating Conditions Tab
Inputs that define the pump, motor and system characteristics are entered in this tab. These inputs are
used to calculate energy savings through the SRM; therefore, the energy savings results are sensitive to
the inputs in this tab. The inputs required by this tab are subdivided into six categories, presented
below.
13.2.1. Motor Information
The user shall enter motor nameplate data including motor size, type, and efficiency. These inputs and
their format required by the calculator are presented in Figure 2.
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Standard Savings Estimation Protocol - Pump VFD
Figure 2 Motor Name Plate and Manufacturer's Information
The user needs to enter the motor size in horsepower (HP) based on motor nameplate information; this
is entered using a prepopulated dropdown list. The mechanical converter efficiency can be set to any
valid number the user chooses; however, the calculator indicates typical values of 97% for belt-driven
applications and 100% for direct-drive. The minimum allowable flow speed for the system must also be
specified. While this input does not directly impact savings, care must be taken when specifying this
parameter in relation to the other pump inputs, particularly static head. For example, if the minimum
allowable flow speed is set too low, such that the system cannot meet the static head requirement, the
calculator will not be able to generate a flow versus power relationship.
The user has the option to either enter the motor full load efficiency manually, or let the calculator look
up the efficiency value based on motor nameplate information. The calculator requires the user to enter
motor speed (rpm), and motor enclosure type in addition to the motor size (entered previously) for the
calculator to estimate motor full load efficiency. Motor speed and enclosure type are standardized
inputs; the user can select a value for these fields via a prepopulated dropdown list.
13.2.2. Machine Curve
The Machine Curve (also often referred to as the pump curve) is a set of flow rates (gpm), and
corresponding pressure (ft) at which the pump operates. For each flow rate and pressure combination,
the pump operates at a different efficiency level and power (Brake Horse Power, expressed as BHP). The
Savings Calculator requires the user to enter ten points to describe the machine curve. These points on
the machine curve are entered by specifying a flow (gpm), pressure (ft) and corresponding efficiency (%)
or BHP. The user can use a dropdown menu to enter either the efficiency or BHP for each point (as
shown in Figure 3). Machine curve input format as required by the calculator is presented in Figure 3.
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Standard Savings Estimation Protocol - Pump VFD
Figure 3 Machine (Pump) Curve Inputs Required by the Calculator
If the user does not have all ten points required to define a machine curve, the user can repeat the last
point a few times; however, it is strongly advised to enter at least six distinct points to accurately define
a machine curve.
13.2.3. Recirculation Inputs
The user can specify in the Savings Calculator if the system in consideration has recirculation. If the user
selects the “with recirculation” option, a “Enter Recirculation Inputs” button will appear, as shown in
Figure 4.
Figure 4 Recirculation Input Options & Recirculation Input Screen
3. Recirculation
If the system includes recirculation please indicate so
and enter information regarding recirc
Enter Recirculation
Inputs
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Also presented in Figure 4 is a detailed recirculation input screen, which appears once the user clicks on
the “Enter Recirculation Inputs” button. In this screen, the user can choose the type of recirculation flow
present in the system and state the amount of recirculation flow. The input options presented in this
screen are aligned with Section 7 of this standard protocol.
13.2.4. Baseline Period Control Strategy
The user can specify if the baseline system relies on a throttling valve or an on/off valve. This can be
entered using a simple button as shown in Figure 5.
Figure 5 Baseline Period Control Strategy
4. Baseline Period Control Strategy
Did the baseline system rely on a throttling valve or an
on/off valve in the baseline period?
13.2.5. System Curve Information
The Savings Calculator plots a quadratic system curve using the static head value (ft.) and the operating
point of the system. The operating point can be specified in two ways, (1) through the system flow
(gpm) and the system pressure (ft.), or (2) by specifying the VFD speed (in percentage) and measured
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Standard Savings Estimation Protocol - Pump VFD
power (kW). Figure 6 presents the Standard Calculator input cells used to enter the system curve
information.
Figure 6 Inputs Required to Plot System Curve
5. System Curve Information
Please enter information for system curve.
Value
10
Static head
Units
ft.
Operating point
Please enter system operating point either by specifying system
flow and pressure (Option 1) OR measured power and VFD speed
(Option 2).
Please select:
Option 1
Option 1
System Flow (Q)
System Pressure (H)
Option 2
VFD Speed
Measured Power
3250
135
gpm
ft.
kW
Update Pump Operating Conditions
The user should note that either Option 1 (system flow and pressure) or Option 2 (VFD speed and
measured power) can be entered, not both. The user can select the option being used to input the
system operating point using a dropdown menu. Once the operating point has been entered, the user
should click on the “Update Pump Operating Conditions” button (bottom of Figure 6).
13.2.6. One Time Electrical Data
The user has the option of either logging the power or the current of the system being studied. If the
user is logging current, the user is required to take three measurements of power (kW) and current
(amps) at different VFD speeds. It is required to have one measurement at 100 % speed. The input
section for one time electrical data is presented in Figure 7.
Figure 7 One-Time Electrical Data Input
6. One-Time Electrical Data
(Optional) Enter electrical data measurements in lieu of trended data
VFD Speed
kW
Amp
100%
132.2
200
70%
109.1
150
60%
76.6
100
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13.3. Pump Operating Schedule Tab
A detailed annual operating schedule of the pump is entered in this tab. As per the Standard Protocol,
the user can specify pump operating schedule using one of two options, (1) “Operations Schedule Only”
or (2) “Outside Air Temperature and Operations Schedule”. Once the user selects one of these two
options, the user should click on the “Enter Operations Schedule” button to enter operating schedule
details, as presented in Figure 8.
Figure 8 Pump Operating Schedule Input Screen
INPUT - Pump Operating Schedule
Pump speed and hours of operation are determined by the following two options. Please choose
one. If Outside Air Temperature is chosen please enter operations schedule by pressing the button
"Enter Operations Schedule"
Enter Operations
Schedule
As shown in Figure 8, once the user presses the “Enter Operations Schedule” button, a detailed
operations schedule input screen will appear. This screen allows users to specify the hour, day, and
month the pump is operational for up to three different schedules. The screen contains instructions on
how to assign hours, days and months to each schedule.
The user will then indicate shutdown periods for the pump using the boxes shown in Figure 9.
Shutdown periods are defined as atypical times during which the pump is shut completely down, such as
holidays and maintenance periods. Here the user shall record the total number of shutdown days per
year which are not already captured in the trend data/ logging period.
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Standard Savings Estimation Protocol - Pump VFD
Figure 9 Pump Shutdown Period Input Screen
Annual Days of Shutdown (excluding those already captured in trend data):
Days per Year
Schedule 1:
Notes (indicate reason for shutdown)
Schedule 2:
Schedule 3:
Total:
Estimated Annual Operating Hours (calculated result):
0 days
8,760 (based on typical operating schedule and shutdown
periods entered above)
13.4. Trend Data (Pre) and Trend Data (Post) Tabs
Both the Trend Data (Pre) and Trend Data (Post) tabs have the same layout. In these tabs, the user can
paste data logged at the site. The data logged can be in either kW or amps; the user can specify this
before pasting in the trend data. Power (kW) or current (amp) data MUST be all non-negative, numeric
values (i.e. not text). The time stamp for the trend data must be in the form "mm/dd/yyyy hh:mm:ss" in
order for the calculator to function properly. Time stamp and power data which does not follow these
specifications may result in calculator errors. If pump operation depends on Outside Air Temperature
(OAT), OAT trend data must also be provided. The trend data input screen is presented in Figure 10.
Figure 10 Trend Data Input Screen
Trend Data
Please select whether power (kW) or current (amp) was logged in the pre-period:
OAT
Time Stamp
kW
6/2/2006 17:53
127.49
52.0
6/2/2006 17:58
127.54
73.0
6/2/2006 18:03
127.49
24.0
6/2/2006 18:08
127.39
68.0
kW
Once all the data has been entered, the user should press the "Update Logged Data" button.
13.5. Results Tab
Once all the inputs have been entered, the user can go to the Results tab and view the energy savings
estimates for both the BP and the SRM. The calculator presents the results for both BP and SRM in
tabular and graphical form. This is presented in Figure 11.
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Standard Savings Estimation Protocol - Pump VFD
Figure 11 Savings Calculations Results Screen
Results: Simplest Reliable Method
130.3
80.3
Savings
347,977
49.9
Baseline vs. Proposed kW/kWh Using Simplest
Reliable Method
kWh/yr
1,200,000
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
1,000,000
kW
800,000
kWh
Avg Power
Proposed
703,580
600,000
400,000
200,000
Results: Best Practice Method
Annual Energy
Baseline
1,088,210
Proposed
703,580
Savings
384,630
0
Baseline
kWh/yr
Proposed
kWh
Avg Power
124.2
80.3
43.9
kW
Annual Energy
Baseline
1,051,558
kW
kW
kW Savings % Difference, Simplest Reliable
Savings vs. Best Practice:
-9.5%
13.7%
kWh
kWh Savings % Difference, Simplest Reliable
Savings vs. Best Practice:
500,000
60.0
400,000
50.0
40.0
300,000
30.0
200,000
20.0
100,000
10.0
0
0.0
Simplest Reliable
kWh
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kW
Simplest Reliable vs. Best Practice Method:
kW/kWh Savings
Best Practice
kW
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