STANDARD PROTOCOL TEMPLATE – BASED ON FAN
VFD EXAMPLE
REGIONAL TECHNICAL FORUM
Release Date: April 16, 2013
Standard Savings Estimation Protocol
TABLE OF CONTENTS
1. PURPOSE............................................................................................................ 1
2. SUNSET CRITERIA ................................................................................................. 1
3. DEFINITION
OF KEY TERMS ..................................................................................... 1
4. ELIGIBLE PROJECTS ............................................................................................... 1
5. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER ................................................... 2
6. DELIVERY VERIFICATION ......................................................................................... 2
7. DATA COLLECTION REQUIREMENTS ........................................................................... 3
7.1. Fan and Fan Motor Specifications ..................................................................................... 3
7.2. Fan Operations ................................................................................................................... 3
7.3. Post-Period Electrical Measurements................................................................................ 4
7.4. Facility Control System Post-Period Trend Logs ................................................................ 4
7.5. Baseline Performance Curves ............................................................................................ 5
7.6. Typical Meterological Year (TMY) Weather Data .............................................................. 5
7.7. Inputs for Cost-Effectiveness Analysis ............................................................................... 5
8. PROVISIONAL DATA REQUIREMENTS ......................................................................... 6
9. SAVINGS ESTIMATION STEPS ................................................................................... 6
9.1. Compute Savings for Trend Log Intervals .......................................................................... 6
9.2. Annualized Savings: Fan Speed Determined by Production Level .................................... 7
9.3. Annualized Savings: Fan Speed Determined by OAT ......................................................... 7
9.4. Annualized Savings: Fan Speed Determined by Facility Schedule ..................................... 8
9.5. Life Cycle Costs and Benefits ............................................................................................. 8
10. SAMPLING PROCEDURE ........................................................................................ 8
11. RELATIONSHIP TO OTHER PROTOCOLS AND GUIDELINES ............................................... 8
12. TYPICAL COST OF APPLYING THIS PROTOCOL ............................................................. 9
13. USER’S GUIDE TO THE SAVINGS CALCULATOR ............................................................ 9
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Standard Savings Estimation Protocol
1. PURPOSE
This protocol establishes a method by which annual electrical energy savings (kWh) can be estimated for
a fan unit that has been upgraded by the addition of a Variable Frequency Drive (VFD). VFDs reduce
electric use by adjusting the fan motor’s speed to match the required load. Many fans do not need to
run at full capacity all of the time, and VFDs are more efficient than other throttling methods, such as
dampers, at regulating fan flow rates.
This protocol specifies minimum acceptable data collection requirements and the method by which
these data are to be used in computing savings. For some data elements, alternative sources of data,
considered to be of superior quality, are also defined and are allowed. Savings are computed using the
Excel workbook (To Be Developed) that accompanies this document to ensure standardized application
of the savings estimation methods.
2. SUNSET DATE
This protocol is approved for use until __________. This sunset date is based on the following factors:

_____
3. DEFINITION OF KEY TERMS
Project. A VFD installed to control one fan unit.
Baseline. This modifier; as in baseline control strategy has one of two meanings. For fan units upgraded
in existing facilities, it refers to the period prior to the upgrade. For fan units in new construction, there
is no such period. For them, the term baseline refers to the design specification for the fan unit without
the efficiency upgrade.
Post. This modifier; as in post current trend log, refers to the period after the fan unit VFD upgrade is
installed and fully commissioned.
4. ELIGIBLE PROJECTS
Following criteria define the eligible fan upgrade projects.

Fan speed must be available as a trend log point on the facility control system.

Fan type must be: Forward Curved, Backward Curved, Airfoil or Vane Axial. The baseline control
strategy must be: Outlet Damper, Inlet Vane, Variable Pitch or No Control. Fan types that are not
eligible include but are not limited to: Radial Blade (common in material handling systems). In
eligible control strategies include but are not limited to: bypass and cycling.

Fan motors must be single speed motors.
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
Fans must not be subject to a local energy code requirements for variable speed drive. This includes
many new construction HVAC fans.

Savings from the fan VFD upgrade must not have substantial effects on other energy end uses in the
facility. Excluded applications include but are not limited to: evaporator fans in refrigerated spaces
and cooling tower fans.

Fans must not be part of a constant volume to variable air volume conversion for an HVAC system.

The cost of implementing this protocol must not make the VFD project economically unattractive.
5. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER
The practitioner who has lead responsibility for applying this protocol to a fan unit must have at a full
understanding of the following:

Appropriate safety procedures for work involving fan units 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, by inspection, the fan type and control strategy.

Identify the primary determinant of fan operation: (1) outside air temperature, (2) production level,
or (3) facility operations schedule.

Supervise a licensed electrician in taking a series of spot measurements of true power and other
required parameters for the fan 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 fan units that pass the following delivery verification tests:

The baseline control mechanism is either removed or disable and set to the maximum flow
condition.

Fan unit is responding to the control sensor signal and is monitored from the facility control system
at the beginning of the trend log period (see section 7.4).

Practitioner confirms by examining a plot of %speed vs. current that the fan unit was responding to
the control signal at least 90% of the trend log period (see 6.4).
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7. DATA COLLECTION REQUIREMENTS
The following data must be collected and entered into the savings calculator. The minimum acceptable
procedure for obtaining the data is specified. In some cases, alternative procedures are allowed which
would provide data of higher quality.
7.1. Fan and Fan Motor Specifications

Fan type. Determined by inspection. A fan unit may be one of the following types: Forward Curved,
Backward Curved, Airfoil or Vane Axial. For some types of fans it will be necessary to stop the unit in
order to complete the inspection.

Baseline Control Strategy. Determined by inspection. A fan unit may utilize one of the following
baseline control strategies: Outlet Damper, Inlet Vane, Variable Pitch or No Control. In some cases
the baseline control mechanism may no longer be present. In this case, the control strategy should
be determined by interviewing the most knowledgeable member of the facility operation staff.

Full Load Air Flow. 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
fan flow rate, if the system has a calibrated flow sensor and the log contains values at or near 100%
speed or (2) taken from an air balance report.

Fan Motor HP. Obtained from the motor name plate. Full load fan kW (computed by the savings
calculator) should not exceed 115% of fan motor nameplate HP times 0.746.
7.2. Fan Operations

Primary Determinant of Fan Speed. Obtained from facility operator. There are three possible
determinants: (1) Outside air temperature, (2) facility operations schedule or (3) production level.

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
fan.

Facility Operations Schedule. Obtained from facility operator. This is not required if the fan
speed is determined by a production variable. If the fan speed is a function of outside air
temperature, obtain the fan hours of operation by hour of day, day of week and season. If fan
unit has different operation modes determined by the facility’s operations schedule, e.g.,
setback of airflow during night and weekend hours. Determine range of fan speeds for each
period during the year defined as needed by hour of day, day of week and season.

Production Level by Month. Obtained from facility operator. This is required if the fan speed is
determined by a production variable, e.g., steam production, moisture level, CO concentration.
Determine for each month of the year the typical % of full production level.
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
Weather Station. If OAT is a significant determinant, identify the TMY (Typical Meterological Year)
weather station which is closest to the project site.
7.3. Post-Period Electrical Measurements

One-Time Electrical Measurements. Taken by a licensed electrician 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.

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 fan unit speed is
primarily determined by OAT, the measurement period must be at least two month 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 fan unit speed is primarily determined by
facility operating schedule the period must be at least one month long, and can start at any time of
the year. If the fan unit speed is primarily determined by production level the period must include
at least one calendar month.

Alternative Measurements. 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 % Speed. The facility’s control system is programmed to record VFD % speed at
15-minute intervals. This data must be collected for the same period as the motor current trend log.

Trend Log of VFD Facility OAT This data may be obtained from the facility’s control system if it can
be programmed to record OAT at 15-minute intervals. This data must be collected for the same
period as the VFD current trend log. This data is required only if fan 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.
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7.5. Baseline Performance Curves

Baseline Performance Curves. Equations describing the % full power vs. % full flow performance
curve for each of the fan and control types are contained in the savings calculator and are used to
model baseline power consumption1.

Alternative Measurements. In lieu of the baseline performance curves, fan motor current and flow
proxy (% of full outlet damper position, inlet vane position, or blade pitch position) can be measured
during the baseline period and entered in the savings calculator. The same measurement interval,
period and timing requirements apply as described under Trend Log of Motor Current in section 7.3.
7.6. Typical Meterological Year (TMY) Weather Data

TMY OAT. Typical Hourly OAT data for Pacific Northwest weather stations are contained in the
savings calculator to be used in estimating annual saving. Data from the station selected in 6.2 will
be used.
7.7. Inputs for Cost-Effectiveness Analysis
The following data need to be gathered to support the cost/benefit analysis feature of the calculator.
Entries will be limited by the calculator to a restricted set of options. Certain entries are completely predetermined.
The following data must be gathered.

Project completion date.

Measure cost. The initial cost of installing the new equipment, including all materials and labor
costs. This is the full cost of the VFD installation. This value must be supported by invoices or other
documentation.

Sector. Possible values are Agricultural, Industrial, and Commercial.
The following values are used in the cost-effectiveness calculation, but are pre-set in the calculator.

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Electric shape. The calculator assigns an appropriate electric shape based on fan operation data
describe in section 7.2 and the profile of savings computed from the trend log data.
Non-Residential Alternative Calculation Method (AC M) Approval Method for the 2008 Building Energy Efficiency Standards,
California Energy Commission, Section 2.5.3.4 “Fan Volume Control” and Section 3.3.10 “Air Foil Centrifugal Fan with
Discharge Dampers”
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
Periodic costs or savings. Any non-annual periodic costs associated with the measure, and the
associated time period. These are incremental costs of the efficient option over the costs of the
baseline. For a fan VFD, the calculator restricts this value to be zero.

O&M costs or savings. Annual O&M costs or savings associated with the measure. These are costs
or savings which occur with the efficient option that would not occur with the baseline option, i.e.
the costs associated with VFD maintenance. The calculator restricts this value to be zero.

Non-energy benefits. Annual non-energy related costs or savings associated with the measure. The
calculator restricts this value to be zero.

Measure life. Number of years the measure is expected to be in effect. For a fan VFD, the calculator
restricts this value to be 10 years.
8. PROVISIONAL DATA REQUIREMENTS
During the period that the RTF classifies this protocol as Provisional, the following data requirements
will be in force:

Post-Period Electrical Measurements. Trend log true poly-phase RMS power for the circuit
powering the fan unit. The same measurement interval, period and timing requirements apply as
described under Trend Log of VFD Current in section 7.3.

Baseline Performance Curves. Trend log fan motor current and % speed during the baseline period.
The measurement interval, period and timing requirements apply as described under Trend Log of
Motor Current in section 7.3.
9. SAVINGS ESTIMATION STEPS
Savings are estimated using the savings calculator that accompanies this protocol (To be developed).
Savings are estimated as follows.
9.1. Compute Savings for Trend Log Intervals

Data Synchronization. Start times for all trend log intervals are synchronized by moving each to the
closest standard interval starts times of 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 linear equation.

Post kW. Calculate kW from fitted equation for each current value.

Fraction of Full Flow. Equals the trend log fan Speed values. If the fan speed trend log values are
shown as a percent (0-100), they are converted to a decimal fraction.
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
Fan Motor Full Load kW. Average the kW values corresponding to %speed values greater than 99%.
If there are any such values, use this average to define fan full load kW. If not, use the one-time
measurement of kW at 100% speed (Section 7.3).

Baseline Fraction Full Load kW. For each fraction of full flow, calculate, using the baseline
performance curve equation (selected by the appropriate fan type and control strategy, Section 7.5),
the corresponding baseline fraction of full load kW.

Baseline kW. Calculate baseline kW as the product of the baseline fraction of full load kW and the
fan motor full load kW.

Savings for Trend Log Period. Calculate the savings as the difference between baseline and post kW.
9.2. Annualized Savings: Fan Speed Determined by Production
Level

Savings Trend Log Month. Sum the savings for the full calendar month found in the current trend
log period.

Monthly Production Multiplier. Calculate monthly production multipliers by the ratio of each
month’s % of full production (see Section 7.2) to the trend log month’s % of full production.

Savings by Non-Trended Months. Calculate the savings for the non-trended months by multiplying
the trended month’s savings by each non-trended month’s production multiplier.

Annual Savings. Sum savings across all months.
9.3. Annualized Savings: Fan Speed Determined by OAT

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 fan 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 60 degrees
and lower temperature bins by a linear equation fit to the bins below 55 degrees.

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.
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
Annual Savings. Sum the kWh values across TMY bins.
9.4. Annualized Savings: Fan Speed Determined by Facility
Schedule

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.

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.
9.5. Life Cycle Costs and Benefits
The calculator contains model called ProCost which computes life cycle costs and benefits. Inputs to the
model include the estimates of first year savings described in sections 9.2, 9.3 and 9.4 and the costeffectiveness input data described in section 7.7 ProCost computes life cycle costs and benefits from
the economic perspectives of the end user, utility, and region. The calculator can be used to review
these results.
10. SAMPLING PROCEDURE
No sampling is permitted by this protocol. Data collection and savings estimation is required for each
upgraded fan 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 fan 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 Section 11.4 Variable Speed Motors. This guideline requires both baseline and post
measurements, which is not consistent with this protocol.

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Sampling Reference Guide, BPA. It is unlikely that more than 20 fan units would be upgraded as part
of any one project. It is difficult to obtain reliable sample estimates from populations this small,
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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 fan 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 fan unit. Projects that
involve more than one fan unit at the same facility are likely to see lower cost per unit. Expense for
alternative measurements, allowed by this protocol, are not included in this estimate of typical cost.
Item
Hours $ / Hour Rental Total Cost
Equipment
Power Meter
100
100
Current Logger
200
200
Labor
Practitioner
Travel
3
110
330
Scheduling
1
110
110
Facility Operator Interview
1
110
110
VFD Inspection
0.5
110
55
Electrical Measurements
0.5
110
55
Install/Remove Current Logger
2
110
220
Savings Estimate
4
110
440
Travel
2
90
180
Electrical Measurements
1
90
90
2
150
300
Electrician
Controls Specialist
Setup and Export Trend Logs
Total
$2,190
13. USER’S GUIDE TO THE SAVINGS CALCULATOR
[To be developed once this protocol is finalized and savings calculator is developed. This Guide and the
Calculator are outside the scope of SBW’s current contract.]
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