&EPA
United States
Environmental Protection
Agency
Air and Radiation
6202J
EPA 430-R-95-002
January 1 995
Variable Air Volume
Systems: Maximize
Energy Efficiency
and Profits
Findings and Recommendations
January 1995
\
US Environmental Protection Agency • Global Change Division • Washington, DC 20460
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CONTENTS
Page
Major Findings 1
Profitable Methods for Increasing the Efficiency of
Variable Air Systems 3
Section One: Opportunities to Upgrade Variable Air Volume Systems 5
Best Opportunities 5
Load Matching 6
Energy-Efficient Motors 6
Variable Speed Drives 7
Economic Benefits 9
How Variable Speed Drives Reduce Operating Costs 9
How Variable Speed Drives Save Energy 10
Potential Savings 10
Potential for Downsizing 10
Section Two: Variable Speed Drive Pilot Studies 11
Summary of Results 12
Study Methodology 15
American Express Company (Fifth Floor) 18
American Express Company (Fourth Floor) 20
Douglas County, Oregon 23
Eli Lilly & Company • 26
Hewlett-Packard Corporation (Colorado) 29
Hewlett-Packard Corporation (California) 32
IVAC, Incorporated 35
Mattel, Inc 37
Mobil Corporation 39
New York Telephone 42
Section Three: VSD Performance and Reliability Study 53
VSD Commercial HVAC Study 45
Findings 45
Methodology 48
Section Four: Fan Oversizing Study 51
Summary of Results 51
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FIGURES AND TABLES
Page
Figure 1 Five-Stage Energy Star Building Upgrade Strategy 3
Figure 2 Energy-Efficient Motors 6
Figure 3 Energy-Efficient Motor Efficiency Improvements 7
Figure 4 Percent Speed 8
Figure 5 Variable Air Volume System 8
Figure 6 Variable Air Volume System with Variable Speed Drive 9
Figure 7 American Express (Fifth Floor) Test Results 19
Figure 8 American Express (Fifth Floor) Test Results 19
Figure 9 American Express (Fourth Floor) Test Results 21
Figure 10 American Express (Fourth Floor) Test Results 21
Figure 11 Douglas County, Oregon, Test Results 24
Figure 12 Douglas County, Oregon, Test Results 24
Figure 13 Eli Lilly & Company Test Results 27
Figure 14 Eli Lilly & Company Test Results 27
Figure 15 Hewlett-Packard (Colorado) Test Results 30
Figure 16 Hewlett-Packard (Colorado) Test Results 30
Figure 17 Hewlett-Packard (California) Test Results 33
Figure 18 Hewlett-Packard (California) Test Results 33
Figure 19 Hewlett-Packard (California) Test Results 33
Figure 20 Hewlett-Packard (California) Test Results 33
Figure 21 IVAC, Incorporated Test Results 36
Figure 22 IVAC, Incorporated Test Results 36
Figure 23 Mattel Inc. Test Results 37
Figure 24 Mattel Inc. Test Results 37
Figure 25 Mobil Corporation Test Results 40
Figure 26 Mobil Corporation Test Results 40
Figure 27 New York Telephone Test Results 43
Figure 28 New York Telephone Test Results 43
Figure 29 Install VSDs Again 47
Figure 30 Level of Satisfaction with VSDs 47
11
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TABLES
Table 1 Summary of Observed Energy Savings 13
Table 2 Annual Energy Savings from VSDs Projected from Incremental Testing .... 14
Table 3 Assumed Load Profile Used in VSD Pilot Studies • 16
Table 4 Building Studied and Average Oversing 52
111
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MAJOR FINDINGS
The U.S. Environmental Protection Agency has researched variable air volume (VAV) systems
and identified several low-cost opportunities that can significantly reduce energy consumption
and increase fan efficiency. Upgrades to VAV systems can be profitable and, due to decreases
in energy consumption, will prevent pollution.
Variable Speed Drive (VSD) Pilot Studies
The EPA has conducted pilot studies of VSDs installed in 10 buildings around the country,
yielding the following lessons learned.
• A VSD is almost always profitable, but more so when the fan or motor is oversized.
• The benefits of VSDs diminish if the fan or motor is grossly undersized or always runs at
or near full capacity.
• Similarly, the benefits of VSDs diminish if the system on which the VSD is installed
suffers from control problems (for example, simultaneous heating and cooling of the same
area).
• In most cases, VSDs should be equipped with integral harmonic filters. Where this is not
possible, a three-phase AC line reactor should be installed to reduce total current harmonic
levels to within five percent.
• Backward-inclined and airfoil fans are the best candidates for VSDs. Forward-curved fans
become unstable and are more difficult to control at partial loads.
Commercial HVAC Survey
A total of 211 facility managers responded to the VSD Field Performance Questionnaire,
giving the following results.
• Most (95 percent) of the respondents indicate that they would install VSDs again.
• Reliability is a key factor in VSD application.
• VSDs experience less problems than previous control methods.
• VSDs have become more reliable over time.
• Installed VSDs meet or exceed predicted energy savings.
• VSD power quality/power factor problems are minimal.
• Pulse width modulation converter VSDs have become more popular over time.
• VSDs for water-side applications receive good performance ratings.
• Premature motor burnout is not reported.
• Proper VSD installation ensures against circuit board failure.
Fan Oversizing Study
A study has been conducted by EPA that investigates the prevalence of fan oversizing. Major
findings are as follows:
• Oversizing was found to be prevalent in the 26 buildings surveyed;
• More than half of the buildings had air handling units with oversizing greater than 10
percent; and
• Of those oversized greater than 10 percent, the average oversizing was 72 percent.
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INTRODUCTION
Improving fans and air distribution is one of the most profitable investments a buildings owner can
make when upgrading the performance of a building. EPA analysis estimates that fan and air
handling system upgrades can provide rates of return as high as 200%, with simple paybacks often
occurring in less than 1 year. Energy reductions due to upgrades have been estimated between 30
and 60%. These savings can be realized by participating in EPA's Energy Star Buildings Program,
a voluntary energy-efficiency program for U.S. commercial buildings. Building on the successful
Green Lights program, Energy Star Buildings focuses on profitable investment opportunities
available in most buildings, using proven technologies. A central component of the program is a
step-by-step implementation process that takes advantage of the system interactions, enabling
building owners to achieve additional energy savings while lowering capital expenditures.
The five-stage Energy Star Buildings upgrade strategy is shown below in Figure 1. One key
advantage of this approach is that it reduces equipment cost. By implementing Green Lights
(Stage 1), tuning up the building's systems (Stage 2), and investing in upgrades that reduce
heating and cooling loads (Stage 3), building owners can significantly reduce the size and cost of
mechanical equipment associated with Stages 4 and 5. Moreover, the program reduces
uncertainties about the proper sizing of upgraded cooling equipment (chillers and direct-expansion
units), leading to potential equipment downsizing, cost savings, and proper operation of
equipment.
Stage 4 of the Energy Star Buildings Program focuses on improved fans and air handling
systems. The purpose of this report is to present information to demonstrate the profitable energy
savings which are possible by upgrading fan systems, particularly with variable speed drives.
Improved Fans
and Air-Handling
Systems
Improved
Heating and
Cooling Plant
HVAC Load
Reductions
Green
Lights
Building
Tune-Up
Figure 1. Five-Stage Energy Star Building Upgrade Strategy
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Section One:
OPPORTUNITIES TO UPGRADE
VARIABLE AIR VOLUME SYSTEMS
BEST OPPORTUNITIES
The many different types of air handling systems installed in commercial buildings can
generally be classified as constant air volume (CV) or variable air volume (VAV) systems.
VAV systems are inherently more efficient than CV systems. This section describes
opportunities to further improve the efficiency of variable air volume systems while maintaining
indoor air quality. With these options, a fairly low initial investment can result in significant
reductions in energy consumption. The three options are as follows:
• Load Matching, in which the fans and motors in the air handling unit are sized to operate
efficiently at the reduced loads you have realized by implementing Green Lights upgrades;
tuning up your building's systems; purchasing Energy Star computers, printers, and
monitors; and implementing window and roofing upgrades.
• Replacing the existing motors on the air handling unit with new, smaller energy-efficient
motors.
• Installing variable speed drives that match the speed of the air handling unit's fans to the
required variable load.
These options can be profitable in most buildings. You can implement them individually or
combine them to provide maximum savings. As you develop your strategy:
• Consider installing properly sized equipment. This usually means you can downsize, which
consists of (1) replacing pulleys, (2) adjusting static pressure, and (3) installing smaller
energy-efficient motors.
• If you find that downsizing is not appropriate, you still may be able to replace existing
motors with energy-efficient motors of the same capacity or smaller.
• Always consider variable speed drives. These are the most energy-efficient and profitable
upgrades for variable air volume systems.
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
Load Matching
As you begin Stage 4 of the Energy Star Buildings program, you have reduced overall loads in
your building through some combination of Green Lights upgrades, building tune-ups, Energy
Star computer equipment, and window and roofing upgrades. As a result, fans and motors on
the air handling units in your building are probably oversized—that is, they are no longer
required to operate at previous capacities. Oversized fans and motors waste energy. They are
rarely required to run at full capacity, but still use the same amount of energy that full-capacity
operation requires. Therefore, you can save a significant amount of money by ensuring that
fans and motors operate efficiently at your newly reduced loads.
Energy-Efficient Motors
Energy-efficient motors use improved motor designs, more metal, and high-quality materials to
reduce motor losses and therefore improve efficiency. They are more reliable than standard-
efficiency motors and generally have longer manufacturer's warranties. These motors reduce
operating costs by:
• Lowering energy consumption, which saves money by reducing the monthly electric bill.
• Postponing or eliminating the need to expand the capacity of the electrical supply system in
the building in response to changes in building use or installation of additional equipment.
• Reducing downtime, replacement, and maintenance costs.
Energy-efficient motors can be implemented individually or as part of a retrofit that includes
downsizing, variable speed drives, or both.
Whenever a motor is operating, some loss in efficiency is incurred. For example, if a motor is
85 percent efficient, 15 percent of the energy input dissipates as heat, which increases motor
temperature. This in turn increases wear and wastes energy. Replacing a standard-efficiency
motor with an energy-efficient motor reduces those losses and therefore also reduces costs.
Fan motors operate best at 75 to 100 percent of their fully rated load because the efficiency
curve peaks between 75 percent and 100 percent. However, a smaller energy-efficient motor
can improve efficiency when operating under part-load conditions.
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Section One:
Opportunities to Upgrade
Variable Air Volume System
Most savings occur when the motor is properly matched to its load. Thus, motors operating at
less than 60 percent of their fully rated loads are excellent candidates for replacement with
smaller energy-efficient motors.
When energy-efficient motors are part of a downsizing program, savings increase significantly.
For example, downsizing a 75-horsepower standard-efficiency motor to a 40-horsepower
energy-efficient motor will result in average energy savings of 15 percent.
Variable Speed Drives
Variable speed drives—an efficient and economical retrofit option—should be seriously
considered for all variable air volume systems. These devices, which operate electronically
rather than mechanically, continually adjust the speed of the air handling unit's fan motor to
match the required load. Thus, the only power consumed is the power required to meet the
demand. Because motors used in air handling units can consume up to 20 percent of the
energy used in commercial buildings, significant energy savings can result. For example,
reducing a fan's speed by 20 percent can reduce its energy requirements by about 50 percent.
Variable speed drives require far less input power than existing methods used to control air-
flow in variable air volume systems (such as variable inlet vane control and outlet damper
control). In addition, variable speed drives reduce fan speed, resulting in more efficient control
of airflow because the motor's speed can then match the motor's load. Because they are
controlled electronically, the drives can respond quickly to changing load requirements. They
also reduce fan noise and vibration.
Variable speed drives reduce wear by controlling current surge when the motor starts up. This
surge of electric current, required to move the motor from its stationary position, is
approximately six times the normal operating current in motors with constant speed drives.
This produces great stress on the equipment, particularly the windings. Variable speed drives
reduce current surge by replacing instantaneous startup with "soft starting," where startup is
gradual, over several minutes.
All variable air volume systems should be good candidates for variable speed drives. The
drives can be implemented individually or as part of a retrofit that includes downsizing, energy-
efficient motors, or both. In retrofit applications, the existing control (an inlet vane or outlet
damper) is locked in the fully open position or removed and the variable speed drive controls
the amount of discharge air by altering the speed of the fan.
Section Two contains the results of several pilot installations of variable speed drives.
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
ECONOMIC BENEFITS
You can estimate the expected benefits of a variable air volume system upgrade for your own
building by running the EPA QuikFan program. This program provides estimates of the
potential for reducing equipment sizes for fan systems, thus saving money and energy.
QuikFan software is available to Green Lights and Energy Star Buildings Partners by writing to
the EPA Global Change Division, USEPA/OAR (6202-J), 401 M Street SW, Washington, DC,
20460. The software will also be available from the Green Lights bulletin board. Dial 202-
775-6671 and follow the instructions on the screen.
How Variable Speed Drives Reduce Operating Costs
• Soft start capabilities allow motor speed to be gradually increased, reducing starting
currents and thermal stresses.
• Controlled braking results in quick but safe reductions in motor speed.
• Soft start, controlled braking, and current reductions in response to reduced demand lead to
longer equipment life. Belts, pulleys, bearings, motors, and transformers will also last
longer.
• Routine maintenance is unnecessary. If service is required, the fan can operate
independently (at full speed or under the original controls), which eliminates downtime.
How Variable Speed Drives Save Energy
• The power required to run variable speed drives is proportional to rpm3. Therefore, a
reduction in speed of as little as 10 percent results in a 27 percent drop in power
consumption (100 - 0.93). With a variable speed drive, a fan in a typical variable air
volume system runs at 80 percent speed or less 90 to 95 percent of the time. Compare this
with a fan running at 100 percent speed 90 to 95 percent of the time.
• The initial power required to start a motor is about 600 percent of rated current when a
motor is started at full voltage and frequency. If a motor is started at low voltage and
frequency through use of a variable speed drive, it will never need more than 150 percent
of its rated current.
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Section One:
Opportunities to Upgrade
Variable Air Volume System
Potential Savings
Potential Air-Side Energy Savings From Downsizing,
Smaller Energy Efficient
Motors, and Variable Speed Drives
50-85%
Internal Rate of Return
25-55%
Potential for Downsizing
If You Reduce Loads By You Probably Can Downsize Airflow (cfm) By
Green Lights Upgrades
Energy Star Computers
Window and Roofing Upgrades
Total Potential for Downsizing
15-30%
10-20%
5-15%
30-65%
Section 2 contains a series of pilot studies conducted by EPA that demonstrate the effectiveness
of VSD installation. These studies illustrate the potential energy savings and profitability that
can be gained through the use of VSDs.
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Section Two:
VARIABLE SPEED DRIVE
PILOT STUDIES
One of the Energy Star Buildings Program's first efforts was to conduct pilot studies of variable
speed drives (VSDs) installed at 10 buildings around the country. The purpose of these studies
was twofold:
• Compare the airflow control provided by VSDs with that of variable inlet vanes (VIVs).
• Verify—through actual installations—the potential of VSD technology to provide profitable
energy savings for Energy Star Buildings Partners.
The studies showed that VSDs can greatly reduce the energy used by the same fan operating
under similar airflow volumes and static pressure conditions. Overall, VSDs provided average
energy savings of 52 percent, average demand savings of 27 percent, and an average simple
payback period of 2.5 years.
Major Lessons Learned Over the Course of the Pilot Studies
• A VSD is almost always profitable, but more so when the fan or motor is oversized.
• The benefits of VSDs diminish if the fan or motor is grossly undersized or always runs at or
near full capacity.
• Similarly, the benefits of VSDs diminish if the system on which the VSD is installed suffers
from control problems (for example, simultaneous heating and cooling of the same area).
• In most cases, VSDs should be equipped with integral harmonic filters. Where this is not
possible, a three-phase AC line reactor should be installed to reduce total current harmonic
levels to within five percent.
• In most cases, VSDs should be equipped with internal power factor correction capacitors.
Where this is not possible, a single capacitor should be installed, either on the main power
line serving all VSDs or on the main power line serving a section of the building or the
entire building.
• Backward-inclined and airfoil fans are the best candidates for VSDs. Forward-curved fans
become unstable and are more difficult to control at partial loads.
11
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
SUMMARY OF RESULTS
The two tests employed in the pilot studies, while relatively simple, provide a sound basis for
comparing the VSD and VIV of airflow control. The first provides a straightforward
comparison of actual energy consumption readings for the two types airflow controls under
similar normal operating conditions. The second compares power requirements over a range of
airflow rates.
The first test determined energy consumption savings on a day of normal operations. This
test involved recording the VSD's energy consumption (and, where possible, energy demand)
hourly during a day of normal operation (when the building was occupied) and comparing it
with VIV energy consumption during a similar day of normal operation (the following day).
Airflow and outside air temperature were monitored to ensure that both systems were operating
under similar conditions. Table 1 provides a summary of the results of this test.
The second test determined energy consumption savings for the fan over the range of its
operating load. For this test, airflow was manipulated so that VIV and VSD energy
consumption (and, where possible, demand) could be compared over a range of airflow rates
(in this case, increments of 10 percent) simulating the fan's operating load. The measurements
were taken during hours when the building was unoccupied. The results of this incremental
testing were used to estimate annual energy savings. Table 2 provides a summary of the results
of this test.
12
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Table 1. Summary of Observed Energy Savings
YIV Average
Airflow (cfm)
VSD Average
Airflow (cfm)
YIV One-Day
Energy
Consumption
(kilowatthours)
VSO One-Day
Energy
Consumption
(kilowatthours
Energy Savings
with VSD (percent)
VIV Maximum
Demand (kilowatts)
VSD Maximum
Demand (kilowatts)
Demand
Savings with
YSD (percent)
American Express
(Fifth Floor)
American Express
(Fourth Floor)
Douglas County,
Oregon
Eli Lilly & Company
Hewlett-Packard
(Colorado)
Hewlett-Packard
(California)
IVAC, Incorporated
Mattel, Inc.
Mobil Corporation
New York
Telephone
21,157
18,103
10,319
114,474
10,225
11,400
5,310
13,800
11,300
15,118
17,980
22,100
10,588
114,474
11,560
13,017
5,810
12,600
11,100
183.6
N/A
20,220
112.8
1,867.9
170.9
136.8
75.9
149.6
91.2
47.1
N/A
161.1
44.2
876.2
45.6
69.4
34.8
89.4
86.8
74.3
N/A
54.3
60.8
53.1
73.3
50.0
54.0
40.2
5.1
N/A
14.2
66.3
12.6
N/A
13.4
17.1
10.2
16.1
7.6
N/A
17.3
18.7
5.3
N/A
4.0
10.0
9.3
12.1
7.4
N/A
-21.0
8,554.5
54.0
N/A
70.1
41.5
8.2
24.8
2.6
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Table 2. Annual Energy Savings from VSDs Projected from Incremental Testing
Site Assumed Annual Projected Energy Annual Savings Simple Payback Internal Rate of
Hours of Operation (kilowatthours) (percent) Period (years)1 Return (percent)
American Express
(Fifth Floor)
American Express
(Fourth Floor)
Douglas County,
Oregon
Eli Lilly & Company
Hewlett-Packard
(Colorado)
Hewlett-Packard
(California)1
FVAC, Incorporated
Mattel, Inc.
Mobil Corporation
New York Telephone2
3,651
3,763
2,808
2,730
4,680
2,860
4,420
2,132
2,860
8,760
31,000
18,440
26,802
25,499
295,309
35,000
54,000
18,083
18,430
7,485
53
49
75
79
73
68
71
72
61
23
2.3
3.9
2.6
7.4
1.4
1.5
1.3
4.9
3.0
3.2
42
25
31
12
69
42
76
20
32
29
'Economic data are based on information provided by the building owners. Costs for Douglas County, Eli Lilly, and Mattel are installed costs; costs for American Express, Hewlett Packard, FVAC, and
Mobil were estimated.
2This system operates 24 hours a day. The projections are estimates of the savings that could be realized if the VSD is installed with appropriate HVAC controls and a properly sized fan.
'This system operates 24 hours a day. The projections are estimates of the savings that could be realized if the VSD installed with appropriate HVAC controls and a properly sized fan.
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Section Two:
Variable Speed Drive Pilot
Studies
STUDY METHODOLOGY
To conduct the pilot studies, the participants installed submetered VSDs on air handling units at
ftftch site. The participants were volunteers who were already Partners in the EPA's Green
Lights Program. The VSDs were installed at the following facilities:
• American Express Company, Shearson Plaza, New York City, New York (two VSDs).
* Douglas County Courthouse, Douglas County, Oregon.
• l-li Lilly & Company Corporate Center, Indianapolis, Indiana.
• I Icwlett-Packard Corporation, Palo Alto, California (Building 20).
• I Icwlett-Packard Corporation, Colorado Springs Division, Colorado Springs, Colorado
(Building C).
• IVAC, Incorporated, San Diego, California.
» Mattel, Inc., El Segundo, California.
* Mobil Corporation Research and Development Technical Center, Princeton, New Jersey
(Building 16).
• New York Telephone Company, Buffalo, New York (Building B).
The VSDs were used to control the airflow in air handling systems that previously had been
iuin£ VI Vs to control airflow. (VFVs control airflow by restricting air at the inlet vane, with the
fan nlwnys running at full speed. VSDs control air-flow by adjusting the speed of the fan.) The
performance of these two types of airflow control was compared across a range of operating
conditions
HI* A nnd the pilot study participants used the following procedure to estimate the annual energy
s of a VSD system:
I Measure the input power of the existing system under VFV control at various flow rates
(from 1 00 perc.ent to the lowest possible flow, usually around 40 percent, in increments of
10 percent).
* After the VSD is installed, measure the input power of the new system at the same airflow
rates used in the VIV testing.
15
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
3. Establish an assumed yearly load profile that defines hours of use at various airflow rates'.
The annual operating load profile used in these studies is shown in Table 5.
Table 3. Assumed Load Profile Used in VSD Pilot Studies
Airflow
(percent of
CFIV1)
Percentage of Annual
Operating Hours
40 or less
50
65
70
80
90
100
21.0
22.0
22.0
15.0
10.0
7.5
2.5
4.
Multiply the hours of use at each flow rate by the measured energy savings from VSD
installation at that flow rate. Sum these products over the fan's operating range to
determine total savings, in kilowatthours, over a given period.
This procedure incorporates many of the elements of approaches described by Stephen
Harding, P.E., writing for Bonneville Power Administration2, and Perigrine White, Jr., at the
Fifth National Demand Side Management Conference3. It provides a measurement of savings
that is unaffected by changes in weather, occupancy, equipment load, or indoor temperature;
that is, variables that cannot be reliably measured or controlled for a significant period of time.
The objective of these short-term studies is to simply verify savings resulting from VSD
installation.
'While an assumed profile was used for the purposes of the pilot studies, data can be gathered with a data
logger or the trending capabilities of an energy management control system to log the hours of use as a function
of flow rate.
'Harding, Steve, P.E., with Fred Gordon and Mike Kennedy, Site Specific Verification Guidelines, report
prepared for Bonneville Power Administration, May 199, pp. 27-29.
3 White, Peregrine, Jr., "DSM Savings Verification of Varying Loads," in Building on Experience:
Proceedings of the Fifth National Demand-Side Management Conference, Palo Alto, California: Electric
Power Research Institute, July 1991, pp. 103 -106.
16
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Section Two:
Variable Speed Drive Pilot
Studies
This type of incremental power monitoring provides an exact comparison of the VSD and VIV
at the same points. The differences in power consumption can then be applied to any fan
operating load. However, unless the data upon which the load profile is based are collected
over several months or a complete year, it is difficult to account for seasonal variations in
airflow. This constraint is avoided by using the assumed annual load profile. To improve
confidence in the annualized results, operating trend data could be collected in the field.
17
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
AMERICAN EXPRESS COMPANY (FIFTH FLOOR)
This study highlighted the importance of weather conditions being similar on the two days of
testing.
Test Summary
The test on the fifth floor of American Express Company's facility at Shearson Plaza in New
York City was conducted on February 18, 19, and 22, 1993.
System Tested
Air Handling Unit (AHU 5-3)
Motor
VSD
Airflow Measurement
Energy Management System
Carrier 39EB3B
U.S. Electric Motor (Emerson) SK386AL223A-R (30 horsepower)
Asea Brown Boveri Model ACH 500 (40 horsepower)
Cambridge FMS-F
Landis & Gyr Power System 600
Test Conditions
Day One
(VSD Testing)
Day Two
(VIV Testing)
OA temperature range: 37.58-45.87° F
OA relative humidity range: 67.55-82.21 percent
OA temperature range: 33.45-39.57° F
OA relative humidity range: 98.09-106.6 percent
Note: Because relative humidity cannot exceed 100 percent, the measurements were assumed to be
inaccurate and 100 percent was used.
Results
Figures 2 and 3 show the results of the tests. These results are summarized below.
Energy consumption was 74.3 percent lower with the VSD. However, average airflow was
28.5 percent lower.
At minimum airflow, energy consumption was 87.5 percent lower with the VSD.
At maximum airflow, there was no difference in energy consumption between the VSD and
vrv.
18
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Section Two:
Variable Speed Drive Pilot
Studies
5 ,.
I I I I I I I I I \\
7AU 9AM 11AM 1PM 3PM 5PM
THE OF DAY
Figure 2. American Express Fifth Floor Test
Results
si M
35 45
15
n..,
r
/
wihw /y
x- - - i
JB'WIhVSD
.— ~— -*
45 55 66 75 K 100
PERCENTAGE OF AIRFLOW
Figure 3. American Express Fifth Floor Test
Results
The VSD would reduce annual energy consumption by about 31,000 kilowatthours and
demand by 8.4 kilowatts. Using an energy cost of $0.055 per kilowatthour and an equipment
cost of $4,000 for the 40-horsepower drive, the simple payback period was determined to be
approximately 2.3 years.
Unique Issues for This Study
The tests were performed during the winter, when airflow requirements in New York City are
typically less than during the summer. Average airflow during the test was approximately 59.1
percent of peak with the VSD and 82.6 percent with the VFV. In summer, airflow requirements
are closer to peak for a few hours on some days.
The large variance in outside air temperatures on the two testing days led to the difference in
average airflow. The average airflow would still lead to energy consumption savings between
23 percent (with the VSD normalized to the VFV's average airflow) and 70 percent (with the
VIV normalized to the VSD's average airflow).
19
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
AMERICAN EXPRESS (FOURTH FLOOR)
This study showed that energy savings can be realized only if the VSD is properly sized to
match motor horsepower requirements. The study also showed the importance of having the
inverter's line choke and capacitor properly sized for power factor correction.
Test Summary
The test on the fourth floor of American Express Company's facility at Shearson Plaza in New
York City was conducted on March 4-5, 1993.
System Tested
Air Handling Unit (AHU 4-3)
Motor
VSD
Airflow Measurement
Energy Management System
Carrier 39EB36
U.S. Electric Motor (Emerson) SK386AL223A-R
(40 horsepower)
Asea Brown Boveri Model ACH 500 (40 horsepower)
Cambridge FMS-F
Landis & Gyr Power System 600
Test Conditions
Day One
(VSD Testing)
Day Two
(VIV Testing)
OA temperature range: 14.88-24.76° F
OA relative humidity range: 45-72-70.93 percent
OA temperature range: 36-88-40.98° F
OA relative humidity range: 101.1-107.4 percent
Note: Because relative humidity cannot exceed 100 percent, the measurements -were assumed to be
inaccurate and 100 percent was used.
Results
Figure 4 and Figure 5 show the results of
the tests.
Due to the type of meter available, energy
consumption could not be measured.
Hourly readings for demand were used for
the analysis.
Demand was 21 percent higher with the
VSD while airflow was 0.4 percent higher
because an off-the-shelf 40-horsepower
6
vwiw
_
• • Hr-*-^
VflhVSD
\ I I I I I I I 1 I
7AU BAH 11AM 1PM 3PM 5PM
THE OF DAY
Figure 4. American Express Fourth Floor Test Results
20
-------
Section Two:
Variable Speed Drive Pilot
Studies
VSD was installed on a 30-
horsepower motor; thus, the
VSD was over-sized.
At minimum airflow, demand
was 78 percent lower with the
VSD, which required
73 percent less current.
At maximum airflow, demand
was 3.4 percent higher with the
VSD, which required
7.9 percent more current.
Sk W HI
UJ t
s*
£ a
V»W ^^
•^"^"^ /^
^•^^ WBlVSO
m^
\ II 1 1 1 1 1 1
30WSD GO 70 80 10 100
PERCENTAGE OF ARROW
Figure S. American Express Fourth Floor Test Results
Based on 3,763 hours of operation per year, the VSD would reduce annual energy consumption
by approximately 18,440 kilowatthours and demand by 4.5 kilowatts. Using an average energy
cost of $0.055 per kilowatthour and an equipment cost of $4,000 for the 40-horsepower drive,
the simple payback period was determined to be approximately 3.9 years. The payback period
for a 30-horsepower drive, after taking into account the lower initial cost and the higher
efficiency, would be approximately
2.7 years.
Unique Issues for This Study
To facilitate test scheduling, the 40-horsepower VSD was bought off-the-shelf. The motor was
30 horsepower. This difference is seen in the relatively higher energy usage of the VSD. A
properly sized VSD would be more energy efficient. In addition, the system operated at 91
percent of maximum airflow during normal operation with the VSD. The system should not be
operating at such a high airflow during the winter; normal operation would be between 40 and
60 percent of maximum. If the VSD had been operating in this range, demand would have
been 69 percent lower with the VSD. With a properly sized VSD, energy savings would be
even greater.
AHU 4-3 with the VFV showed a power factor between -0.9 and -0.94. With the VSD, the
power factor was between -0.86 and -0.97. The VSD power factor range should normally be
between 0.96 and 0.99. Here it is low because the VSD was oversized. In addition, the VSD
procured for this test was an off-the-shelf unit and the inverter's line choke and capacitor were
not sized properly for the motor's power factor. The negative numbers indicate a capacitive
load rather than an inductive load.
21
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
DOUGLAS COUNTY, OREGON
This study provided the expected results.
Test Summary
The VSD pilot study at the Douglas County Courthouse was conducted on February 25-26,
1993.
System Tested
Air Handling Unit (AHU-8)
Motor
VSD
Airflow Monitoring Station
Energy Meter
Backward-inclined fan by PACE
Lincoln (30 horsepower)
Asea Brown Boveri Model ACH 500
Paragon/Honeywell
Dranetz 808
Test Conditions
Day One
(VSD Testing)
Day Two
(VIV Testing)
OA temperature range: 3 1 -54 ° F
OA relative humidity range: 73.8-80.4 percent
OA temperature range: 29-50° F
OA relative humidity range: 73.2-86.9 percent
Results
Figure 6 and Figure 7 show the results of the tests. These results are summarized below.
105'
B-
Is*-
5S
3 5 «-
s-
MtlW
z
v»vso
1IIIIII!TT
8AM 10AM 12 AH 2PM 4PM
TIME Of DAY
Figure 6. Douglas County, Oregon, Test Results
I I I I I 1^1 |
25 38 « SS 65 76 8S 93 110
PERCENTAGE Of AIRFIOW
Figure 7. Douglas County, Oregon, Test Results
22
-------
Section Two:
Variable Speed Drive Pilot
Studies
Energy consumption was an average of 66.3 lower with the VSD.
At minimum airflow, AHU-8 required 86.5 percent less demand with the VSD than with the
vrv.
At maximum airflow, AHU-8 required 25.5 per-cent less demand with the VSD than with the
vrv.
Using an energy cost of $.0328 per kilowatthour and demand and distribution charges of $2.48
per kilowatt, the $2,850 AHU-8 drive (30 horsepower) would reduce yearly energy
consumption by about 26,802 kilowatthours and demand by 7.5 kilowatts. The simple payback
period was determined to be approximately 2.6 years.
Unique Issues for This Study
The tests were performed in winter, when airflow requirements in Oregon are typically less
than during the summer. Average airflow during the test was approximately 80 percent of peak
with the VSD and 87 percent with the VIV. In summer, airflow requirements are closer to
peak for a few hours on some days.
Without the VSD, AHU-8 showed a power factor between 0.71 and 0.79. With the VSD, the
power factor improved to 0.99 at varying speeds. The VSD installed for this test was provided
with an internal power factor correction capacitor that provides automatic power factor
correction.
23
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
ELI LILLY & COMPANY
This study found that a significant reduction in fan energy consumption does not always mean
that a VSD retrofit will be profitable. Although the test confirmed that a VSD brings significant
energy savings when applied to variable air volume air handling systems (in this case 81 percent
better than the VIV airflow control), the relatively low cost of energy for the facility examined
caused a longer payback period.
Test Summary
The VSD pilot study at Eli Lilly & Company's Corporate Center in Indianapolis, Indiana, was
conducted on February 11-12, 1993.
System Tested
Air Handling Unit (AHU 5-3)
Motor
VSD
Airflow Measurement
Energy Meters
Energy Management System
Vibration Meter
Canier 39ED, size 32, double-width double-inlet (DWDI)
airfoil fan
Marathon MN 284TTDR7026FN-F2 (25 horsepower)
Allen Bradley Model 1336VTB0235EA-FL1
Tele-Air Vortek airflow monitoring station located in each
branch duct
Esterline PMT3B and Dranetz 658
Johnson Control System 686
Computational Systems Model 21 10-4D
Test Conditions
Day One
(VSD Testing)
Day Two
(VIV Testing)
OA temperature range: 37.2-40.6° F
OA relative humidity range: 82.5-98.9 percent
OA temperature range: 34.5-36.5° F
OA relative humidity range: 100 percent
Results
Figure 8 and Figure 9 show the results of the tests. These results are summarized below.
Energy consumption was 60.8 percent lower with the VSD, while airflow was 2.5 percent
higher.
24
-------
Section Two:
Variable Speed Drive Pilot
Studies
12-
10-
WBiVSO
I I I I I I I T 1
9 AW 11AM 1AM 3PM 5PM
TNE OF DAY
Figure S. Eli Lilly & Company Test Results
120-
'100-
40-
20-
0 -
WlhW
Will VSD
I I I I I I
43 60 70 80 90 100
PERCENTAGE Of AKR.OW
Figure 9. Eli Lilly & Company Test Results
Demand was 54 percent lower with the VSD, while airflow was 3.4 percent higher. At
minimum airflow, demand was 91.7 percent lower with the VSD, which required 93.3 percent
less current. At maximum airflow, demand was 1.6 percent higher with the VSD, which
required 18.2 percent less current.
The VSD would reduce annual energy consumption by about 25,499 kilowatthours and
demand by 9 kilowatts. Using an energy cost of $.0368 per kilowatthour and an equipment
cost of $6,900 for the 25-horsepower drive, the simple payback period was determined to be
approximately 7.4 years.
Unique Issues for This Study
During the incremental testing, the fan became unstable at 43 percent of maximum airflow. No
further measurements were possible.
The static pressure setpoint was not maintained during the incremental testing. If static
pressure had been maintained during the incremental testing, demand for both the VIV and the
VSD would have increased at all intervals. However, the difference in demand between the
two would have been close to the results shown.
The tests were performed during the winter, when airflow requirements in Indianapolis are
typically less than during the summer. Average airflow during" the test was approximately 62
percent of peak. In summer, airflow requirements are closer to peak for a few hours on some
days.
AHU-FQ3 with the VIV showed a power factor between 0.658 and 0.755. With the VSD, the
power factor improved to 0.99 at varying speeds. The VSD installed for this test is provided
with a line choke and a capacitor that provides automatic power factor correction.
25
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Pro/its
HEWLETT-PACKARD CORPORATION (COLORADO)
This study demonstrated the need to have an airflow monitoring station to obtain accurate
readings to use in calculating energy savings. Lack of airflow monitoring data necessitated use
of manufacturer's data Because use of this theoretical data conflicted with the methodology,
the margin of error for the predicted savings is understandably larger.
Test Summary
The VSD pilot study at Building C of Hewlett-Packard's Colorado Springs complex was
conducted on January 25-26,1993.
System Tested
Air Handling Unit (AHU 5-2)
Motor
System
VSD
Airflow Measurement
Energy Meter
Field-erected, size 66, double-width single-inlet (DWSI) airfoil fan by
Trane.
1 50 horsepower
Dual-duct VAV system controlled by outside air temperature Note: This
system does not maintain or monitor static pressure.
Graham
Pilot tube located in the cold deck
BMI
Test Conditions
Day One
(VSD Testing)
OA temperature range: 22.5-49. 1 ° F
Note: No VIV testing was conducted.
Results
Figure 10 and Figure 11 show the results of
the tests. These results are summarized
below.
I I 1 I I I I I r
7AM 11AM 3PM 7PM 11PM
THE OF DAY
Figure 10. Hewlett-Packard (Colorado) Test Results
26
-------
Section Two:
Variable Speed Drive Pilot
Studies
Energy consumption was 53.1 percent lower i».
with the VSD at equivalent airflow levels. ,„.
a
At minimum airflow, demand was 92 || ™
percent lower with the VSD. || 60~
At maximum airflow, demand was 6 percent *
lower with the VSD.
7
2
w».vso
II I I I I ITilI
The VSD would reduce annual energy ns
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
HEWLETT-PACKARD CORPORATION (CALIFORNIA)
This study showed that return fans are excellent candidates for VSDs. A system that is
oversized when a VSD is installed will have even greater savings because the VSD will operate
the system only at the required load.
Test Summary
The test at Building 20 of Hewlett-Packard's Palo Alto facility was conducted on January
11-12, 1993. It evaluated energy consumption for both the air handling unit and the return fan.
System Tested
Air Handling Unit (AHU-3)
Return Fan (RF-3)
Motors
VSD
Airflow Monitoring Station
Energy Meter
Field-erected, size 490, single-width single-inlet (SWSI) airfoil fan (Twin
City)
SWSI airfoil (Twin City)
Lincoln (30-horsepower for AHU-3; 1 5-horsepower for RF-3)
Asea Brown Boveri
Paragon
Dranetz 8000
Test Conditions
Day One
(VSD Testing)
Day Two
(VIV Testing)
OA temperature range: 39-54° F
OA relative humidity range: 55-95 percent
OA temperature range: 4 1 -5 1 ° F
OA relative humidity range: 87-100 percent
Results
Figure 12 through Figure IS show the results of the tests. The results are summarized below.
«*V3>
I I I I I I I I I I 1 7
r*H IJU 1IAU tPU JW »M
HE Of MY
:z
11 41 s a n a » m
pEdcomoE of um.au
28
-------
Section Two:
Variable Speed Drive Pilot
Studies
_^
•-•''^
• • • -1
1 1
7AM 6AM
-»-» —»-•-»
~ W1HW THi
VAhVSD
1 1 1 1
11AM 1PM JPU iPM
is "
r..
PERCENTAGE OF ARHW
AHU-3 energy consumption was 73.3 percent lower with the VSD, while average airflow was
13.1 percent higher. RF-3 energy consumption was 85.9 percent lower with the VSD, while
average airflow was 10.4 percent higher. AHU-3 maximum demand was 70.1 percent lower
with the VSD, while maximum airflow was 17.6 percent higher. RF-3 maximum demand was
84.4 percent lower with the VSD, while maximum airflow was 19.3 percent higher.
At minimum airflow: AHU-3 demand was 95.5 percent lower, AHU-3 required 99.5 percent
less current, and RF-3 required 99.5 percent less current. At maximum airflow: AHU-3
demand was 16.5 percent lower, AHU-3 required 12.0 percent less current, and RF-3 required
31.2 percent less current.
For the air handling unit, the VSD would reduce annual energy consumption by approximately
35,000 kilowarthours and demand by 9.6 kilowatts. Using an energy cost of $0.06 per
kilowatthour, demand and distribution charges of $10 per kilowatt, and equipment costs of
$5,000 for the 30-horsepower drive, the simple payback period was determined to be
approximately 1.5 years.
For the return fan, the VSD would reduce annual energy consumption by approximately 17,500
kilowatthours and demand by 5.0 kilowatts. Using an energy cost of $0.06 per kilowatthour,
demand and distribution charges of $10 per kilowatt, and equipment costs of $3,500 for the 15-
horsepower drive, the simple payback period would be approximately 2.1 years.
Unique Issues for This Study
The tests at Hewlett-Packard were conducted in the winter, when cooling load requirements in
the San Francisco area typically are lower than in the summer. Thus, average airflow during
the test was around 40 percent of peak. In summer, airflow requirements are closer to peak for
a few hours on some days.
The large difference in peak demand at maximum airflow found in these tests (16.5 percent)
was a result of oversizing. This oversizing also allowed the VSD to consume much less energy.
29
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
IVAC, INCORPORATED
This study showed that VSDs provide significant energy savings even if the system operates
with higher average airflow.
Test Summary
The test at IVAC, Incorporated, a subsidiary of Eli Lilly & Company in San Diego, California,
was conducted on March 10-12, 1993.
System Tested
Air Handling Unit (AHU-4)
Motor
VSD
Airflow Monitoring Station
Energy Meter
Energy Management System
Backward-inclined fan by Trane (CLCH-35)
Gould Century (30 horsepower)
Magnetek GPD 503
Air Monitor
BMI 3030
Trane Tracer
Test Conditions
Day One
(VSD Testing)
Day Two
(VIV Testing)
OA temperature range: 53-65.0° F
OA relative humidity range: 76.1-89.5 percent
OA temperature range: 64. 1 -8 1 .4 ° F
OA relative humidity range: 72.7-90.4 percent
30
-------
Section Two:
Variable Speed Drive Pilot
Studies
Results
Figure 16 and Figure 17 show the results of the tests. These results are summarized below.
IB
*o? 16
IP
^ 0 19
££. "
UJ
B
WlhVIV
WithVSO
_ • _ • B-^"
• — ^— •- ™ •
i i i i I I i r
BAM 10AM 12AM 2PM
TNE OF DAY
Figure 16. IVACIncorporated Test Results
\\ I I I I I I
34 39 « 56 62 68 79 90 100
PERCENTAGE OF ARH.OW
Figure 17. IVAC Incorporated Test Results
Energy consumption was 50 percent lower with the VSD, while airflow was 10 percent higher.
At minimum airflow, demand was 92.9 percent lower with the VSD.
At maximum airflow, demand was 14 percent lower with the VSD.
The VSD would reduce annual energy consumption by about 54,000 kilowatthours, summer
demand by 2.7 kilowatts, and winter demand by 10.7 kilowatts. Using an energy cost of
$.03332 to $.07201 per kilowatthour and demand and distribution charges of $7.02 to $20.47
per kilowatt, and an equipment cost of $5,000 for the 30-horsepower drive, the simple payback
period was determined to be approximately 1.3 years.
Unique Issues for This Study
Average airflow during the test was around 72.7 percent of peak with the VSD and 65.8
percent of peak with the VFV. The VSD still consumed less energy than the VIV, even though
it was operating at airflow that on average was 10 percent higher and an average outside air
temperature 14.6° F. higher. The large difference indicated here could be due to motor
oversizing.
Without the VSD, AHU-4 showed a low power factor of 0.75, which indicates that the motor
is inefficient. With the VSD, the power factor gradually improved from a low reading of 0.6 at
low speed to 0.89 at the full 60 Hz speed. Without replacing the motor, the VSD provided a
remarkable power factor improvement.
31
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
MATTEL, INC.
This study provided the expected results.
Test Summary
The test at Mattel, Inc., in El Segundo, California, was conducted on March 24-26,1993.
System Tested
Air Handling Unit (AHU-5)
Motor
VSD
Airflow Monitoring Station
Energy Meter
Energy Management System
Forward-curved fan
20 horsepower
Graham 1700
Tek-Air
Dranetz 8000
Teletrol Control System
Test Conditions
Not available.
Results
Figure 18 and Figure 19 show the results of the tests. These results are summarized below.
T I I I I I I I I I
8AM 10AM 12AM 2PM 4PM
TIME OF DAY
Figure 18. Mattel Inc. Test Results
I I 1 I I I I i T
17 30 40 SI 53 69 79 93 tDO
PERCENTAGE OF ARROW
Figure 19. Mattel Inc. Test Results
Energy consumption was 54 percent lower with the VSD, while airflow was 4.3 percent higher.
At minimum airflow, demand was 83.3 percent lower with the VSD.
32
-------
Section Two:
Variable Speed Drive Pilot
Studies
At maximum airflow, demand was 8.5 percent higher with the VSD.
The VSD would reduce annual energy consumption by approximately 18,083 kilowatthours
and demand by 1.5 kilowatts. Using an energy cost of $0.13784 per kilowatthour during the
summer on-peak hours and $0.05675 per kilowatthour during all other hours, $19.45 per
maximum demand and $3.65 for demand ratchet, and an equipment cost of $8,742, the simple
payback period was determined to be approximately 4.9 years.
Unique Issues for This Study
Average airflow during the test was approximately 33.8 percent of peak with the VSD and 30.8
percent with the VFV. In summer, airflow requirements are closer to peak for a few hours on
some days. VSDs may require slightly more energy at peak airflow than VIVs.
When VSD testing began, the drive was operating the fan at 68 percent of maximum airflow,
causing the higher initial energy consumption for the VSD shown in Figure 26. More typical
percentages of maximum airflow were recorded during the remainder of the test.
The VSD used for this study was more expensive than comparable drives of its size, even when
installation is included. This caused the longer payback period, with a IRR of 20 percent.
With the VIV, AHU-5 showed a power factor between 0.675 and 0.869. This indicates that
the motor is inefficient. With the VSD, the power factor ranged between -0.21 and -0.77. The
VSD installed for this test was not equipped with power factor correction capability (indicated
by the low power factor reading). The negative number indicates the measured load is
capacitive.
33
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
MOBIL CORPORATION
This study provided an example of what can happen when cooling and heating systems are not
properly coordinated. This coordination could be achieved by connecting perimeter heating
valves to the thermostats that control the VAV boxes. If this were done, the VAV boxes would
modulate the airflow down to the minimum position before allowing the heating valves to open
when there is demand for heating. On the other hand, the heating valves would close
completely before allowing the VAV boxes to open when there is demand for cooling.
Test Summary
The test at Building 16 of Mobil's Princeton, New Jersey, complex was conducted on April 13
and 15, 1993.
System Tested
Air Handling Unit (FNS-4)
Motor
VSD
Airflow Monitoring Station
Energy Meter
Trane Climate Changer (CLCH) with a single-width single-inlet (SWSI)
backward-inclined fan
Magnetek 25 horsepower
Asea Brown Boveri model 501 ACH
Multi-tube, multi-hole station built on site by Mobile's Facilities staff, a
pilot tube, and a pressure differential gauge
Dranetz 8000
Test Conditions
Day One
(VIV) Testing
Day Two
^VSD Testing)
OA temperature range: 40-61 °F
OA temperature range: 5 1 -65 °F
34
-------
Section Two:
Variable Speed Drive Pilot
Studies
Results
Figure 20 and Figure 21 show the results of the tests. These results are summarized below.
9UI II All IfV m 51V
TIME OF DAY
i i I i i i r
40 50 K 74 80 SO 100
PERCENTAGE OF ABFLOW
Figure 20. Mobil Corporation Test Results
Figure 21. Mobil Corporation Test Results
Energy consumption was 40.2 percent lower with the VSD. However, average airflow was 9.2
percent lower.
At minimum airflow, demand was 92.3 percent lower with the VSD, which required 89.6
percent less current.
At maximum airflow, demand was 15.5 percent lower with the VSD, which required 15.3
percent less current.
The VSD would reduce annual energy consumption by about 18,430 kilowatthours. Using an
average energy cost of $0.07 per kilowatthour and a VSD cost of $4,000, the simple payback
period was determined to be approximately 3 years. This figure is based on a load ratio that
varies during the year according to the heating and cooling load.
Unique Issues for This Study
The tests were performed in early spring, when airflow requirements in Princeton are typically
40 percent to 70 percent of peak. Average airflow during the tests was approximately 86 to 87
per-cent of peak, a figure more comparable with summer airflow. This high airflow was a
result of cooling demand caused by excessive heat from perimeter heating, which is controlled
by outside air temperature (airflow is controlled by space thermostats). This setting causes the
airflow to run high to remove the heat from the space.
With the VIV, AHU FNS-4 showed a power factor of 0.9, which indicates that the motor is
efficient. With the VSD, the power factor remained in the 90 percent and above range. The
VSD installed for this test was provided with power factor correction capability.
35
-------
Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
NEW YORK TELEPHONE
This study provided another example of what can happen when cooling and heating systems are
not properly coordinated. This coordination could be achieved by connecting perimeter heating
valves to the thermostats that control the VAV boxes. If this were done, the VAV boxes would
modulate the airflow down to the minimum position before allowing the heating valves to open
when there is demand for heating. On the other hand, the heating valves would close
completely before allowing the VAV boxes to open when there is demand for cooling.
Test Summary
The test at New York Telephone was conducted at Building B of the company's Buffalo
complex on March 17-19,1993.
System Tested
Air Handling Unit (AHU-7B)
Motors
VSD
Airflow Monitoring Station
Energy Meter
Energy Management System
Packaged, size 3 1 , single-width single-inlet (SWSI) airfoil fan (Climate
Changer by Trane)
(1 5 horsepower for AHU-7B; 5 horsepower for RF-7)
ASEA Brown Boveri model ACS 501
Tek-Air Vortek
Dranetz 808
Johnson Control Systems DSC 8540 and DSC 8500
Test Conditions
Day One
(VSD Testing)
Day Two
(VIV Testing)
OA temperature range: 16-24T
OA relative humidity range: 42-45
0 A temperature range: 12-26T
OA relative humidity range: 41-48
percent
percent
Results
Figure 22 and Figure 23 show the results of the tests. These results are summarized below.
Energy consumption was 5.1 percent lower with the VSD. However, average airflow was 1-.8
percent lower. Demand was 2.6 percent lower with the VSD, while average airflow was 1.8
percent lower. At 20 percent of maximum airflow, demand was 62 percent lower with the
VSD, which required 55 percent less current. At maximum airflow, demand was 0.6 percent
higher with the VSD, which required 7.2 percent more current.
36
-------
Section Two:
Variable Speed Drive Pilot
Studies
12-
10-
WBiW
WthVSD
85.
H-
;25-
15-
I I \IIIIITl 1
8AM 10AM 12AM 2PM 4PM 6PM
TWEOFDAY
Figure 22. New York Telephone Test Results
WthW
i i i i i i rnrr
16 21 31 38 50 63 72 60 91 100
PERCENTAGE OF AIRFLOW
Figure 23. New York Telephone Test Results
because the system was operating at peak airflow at all times with the VSD as well as with the
VTV, energy savings from using the VSD could only be estimated. If the control problem is
corrected and the fan is sized properly, the VSD would reduce annual energy consumption by
about 7,485 kilowatthours. Using an energy cost of $0.095 per kilowatthour and an equipment
cost of $2,300 for the 15-horsepower drive, the simple payback period was determined to be
approximately 3.2 years.
Unique Issues for This Study
Due to the lack of a second energy meter and an additional airflow monitoring station in the
return air ductwork, airflow, demand, energy consumption, power factor, and harmonics data
were not obtained during the incremental testing.
AHU-7B was adjusted during the incremental testing, while RF-7B tracked AHU-7B. The
lowest frequency setpoint on AHU-7B and RF-7B with the VSD was 10 Hz. That setpoint
coincided with an AHU-7B airflow of 1,820 cfm (16 percent of the maximum airflow). Using
the VFV with dampers set at the maximum closed position, AHU-7B airflow was 1,360 cfm
(10 percent of the maximum airflow).
The design of the existing HVAC system had a major effect on this test. The building is heated
by individually controlled radiators that operate independently of cooling system controls.
Therefore, as long as the room is being heated, the room thermostat will call for cooling. This
results in VAV boxes being constantly in a full open position. Since the VAV system was run
at maximum airflow, the test showed only minor differences between VSD and VFV operation.
Nevertheless, when airflow was adjusted manually, a significant reduction in energy
consumption was observed.
37
-------
Section Three:
VSD PERFORMANCE
AND RELIABILITY STUDY
VSD COMMERCIAL HVAC STUDY
Motors account for up to 50 percent of total electric energy use. They convert electricity to
mechanical energy for operation of equipment such as fans, blowers, pumps, and compressors.
The output of the equipment is typically adjusted by various means (clutches, brakes, valves,
and dampers) to satisfy dynamic system requirements; however, these adjustments waste
energy to varying degrees. A variable speed drive (VSD) saves significant energy by
modulating the output of the motor to satisfy changing system requirements.
VSDs offer much more than energy savings, however. Less maintenance is one benefit since
electronic speed control replaces a mechanical transmission system. The mechanical stresses
on machine bearings and shafts are lower which prolongs the service life of equipment.
Because of the low starting current, the thermal stress on the machine itself and the electrical
stress on the power supply are substantially reduced. All these factors contribute to higher
reliability and reduced downtime of the equipment.
In order to obtain a better understanding of VSD performance and reliability in commercial
heating, ventilating and air-conditioning system applications, The Alliance to Save Energy
(ASE) performed a survey of facility managers' experience with installed VSDs. Data obtained
from the survey was shared with the Global Change Division of the U.S. Environmental
Protection Agency (EPA). A technical assessment of the survey data was performed by
Enviro-Management and Research, Inc. (EMR).
Findings
A total of 211 facility managers responded to the VSD Field Performance Questionnaire,
.representing a 8.8 percent rate of response. The survey response included information on more
than 200 separate facilities and 3,000 VSDs representing 36 manufacturer product lines. The
major findings of this survey are briefly detailed below.
Energy and Operating Cost Savings Are Very Important
More than three quarters (80 percent) of the respondents indicate that potential energy savings,
improved efficiency, or reduced operating expenses are very important factors that led them to
consider installing VSDs.
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
Reliability Is A Key Factor In VSD Application
Although not the most important factor in VSD application, reliability is one of the key factors
in decision-making with regards to the installation of VSDs. The majority of facility managers
also consider independent documentation of reliability as being very critical in decision-
making with regards to the application of VSDs in facilities.
VSDs Experience Less Problems Than Previous Control Methods
The majority of facility managers (59 percent) indicate that the frequency of problems with
VSDs is less or far less than problems experienced with previous control methods (e.g., outlet
dampers and inlet vanes).
VSDs Have Become More Reliable Over Time
The facility managers who report encountering more frequent problems than with previous
control systems had typically installed VSDs with older technology (average installation date:
1986) than facility managers reporting less frequent problems (average installation date: 1988).
This data suggests that the reliability of VSDs has improved over time.
Most Facility Managers Would Install VSDs Again
Nearly all facility managers (95 percent) who returned a survey questionnaire indicate that they
would install VSDs again (Figure 24). About two-thirds of these managers are very satisfied
with the performance of currently installed VSDs since initial start-up (Figure 25). Some of
the major factors leading to their high satisfaction are:
• Energy savings—due to significant kWh reductions
• Flexibility—superior control in operating equipment
« Product quality—basically trouble-free, reliable, no environmental complaints
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Section Three:
VSD Performance and Reliability
Study
No 5%
Very Satisfied 66%
Yes 95%
4% Very Dissatisfied
7% Dissatisfied
Satisfied 23%
•60% of Respondents
Figure 24. Install VSDs Again
' 64% of Respondents
Figure 25. Level of Satisfaction with VSDs
Of the facility managers who expressed dissatisfaction with VSDs, 69 percent reported they
•would install VSDs again. In addition, many facility managers who used VSDs for certain
applications are considering installing VSDs for other applications in the near future.
Installed VSDs Meet or Exceed Predicted Energy Savings
The majority of facility managers indicate that annual energy savings after installation of VSDs
are equal to or greater than predicted energy savings. In fact, one in three respondents
indicate that their VSDs have produced greater energy savings than they had predicted before
installation.
VSD Power Quality/Power Factor Problems Are Minimal
Of the facility managers providing information on both power quality and power factor
problems, more than 80 percent indicated that they did not experience any power quality
problems and 95 percent indicated that they did not experience any low power factor problems.
Of the minority that did experience these problems, many resolved them by installing harmonic
filters, isolation transformers, and power factor correction capacitors or by adjusting the set-
points.
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
PWM VSDs Have Become More Popular Over Time
Three types of variable speed drives are currently available in the marketplace. These are:
variable voltage inverter (WI), current source inverter (CSI), and pulse width modulation
converter (PWM). According to survey results, facility managers are opting for PWM VSDs
over WI VSDs at a rate of 2 to 1, while opting for PWM VSDs over CSI VSDs at a rate of 11 to
1. Furthermore, facility managers report having to service their PWM VSDs less frequently
than other VSD types.
VSDs for Water-Side Applications Receive Good Performance Ratings
Although the majority of VSDs have been installed in air-side applications, facility managers
indicate very favorable results for VSDs installed in water-side applications. For example, few
managers report that they have experienced more or far more problems in using VSDs as
compared to previous control systems when utilized in chilled water/hot water pumps, chillers,
and cooling tower fans.
Premature Motor Burnout Is Not Reported
Results of the survey contain no evidence that VSDs cause pre-mature motor burn-out. In fact,
of the 59 facility managers that report experiencing performance problems with VSDs, not one
reported motor bum-out. In addition, only four managers report having experienced motor
overheating.
Proper VSD Installation Ensures Against Circuit Board Failure
Thirty of the 59 facility managers (50 percent) that report experiencing performance problems
with VSDs cite circuit board failure as a common performance problem. This problem can be
avoided by ensuring the VSD is installed correctly by the manufacturer's distributor or electrical
contractor. Contacting the manufacturer is recommended if there are any questions that arise
before, during or after the installation.
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Section Three:
VSD Performance and Reliability
Study
Methodology
The specific objectives of this project were to:
1. Obtain data/information on facility managers' experience with installed VSDs.
2. Assess the performance and reliability of VSD technology on the basis of the
data/information obtained from a survey.
The Alliance to Save Energy initiated the project by developing the VSD Field Performance
Questionnaire. The questionnaire requested data/information on:
1. Manager's decision-making process when considering installation of VSDs in their facility.
2. Existing VSDs, including name of manufacturer, HP range, type of VSD, date installed, and
application.
3. Level of user satisfaction with the performance of VSDs.
4. Importance of various factors (cost, flexibility, efficiency, utility rebate, energy savings,
reliability, etc.) relating to the installation of VSDs.
5. Types of start-up problems experienced and the amount of time it takes to correct them.
6. Frequency of problems.
7. Type of service contract, the annual cost of the contract, contract scope, service frequency,
and response time.
8. Measures that have been implemented to correct power quality problems and low power
factor problems.
9. Amount of energy savings due to the installation of VSDs.
10. Likelihood of additional VSD installations in the facility.
Once the questionnaire was finalized, ASE mailed copies of the questionnaire to approximately
2,400 facility managers using 11 different mailing lists. The data collected by ASE was then
analyzed by EMR using the following methodology:
1. Reviewed questionnaires for completeness of response.
2. Compiled data/information in Paradox 4.0 Relational Data Base.
3. Analyzed data/information for specific trends.
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Section Four:
FAN OVERSIZING STUDY
The EPA has investigated the prevalence of supply fan oversizing. The purpose of the study was to
quantify the percentage of buildings with oversized fans and to encourage downsizing as a viable option
of reducing upgrade costs while further increasing energy efficiency.
The study consisted of a cross section of 47 air handling units (AHUs) located in 26 commercial
buildings throughout the continental U.S. Data were collected in Indianapolis, IN; New York, NY;
Pennington, NJ; Los Angeles, CA; Seattle, WA; Weston, MA; Washington, DC, and Fairfax, VA. The
study was conducted in July, August, and September 1993.
Air flow rates were measured with air flow monitoring stations at outside air temperatures near or
above the 2.5 percent design temperature for each location. These measurements were compared to
the design air flow from the building specifications. .
Due to the nature of the study (traveling from city to city as heat waves moved from region to region)
and the lack of time to carefully calibrate all equipment, errors of plus or minus 15 percent were
expected for each AHU. Although no single measurement can be taken as exact, the average of all 47
AHUs clearly leads to one conclusion.
Over half of the 26 buildings had AHUs with oversizing greater than 10 percent. Of those buildings,
the average percent oversizing was 72 percent! Fan energy reductions of 50 percent would be expected
simply by reducing the oversizing from 72 percent to 10 percent.
Summary Of Results
*includes all 26 buildings
** only includes those that are oversized greater than 10 percent
Oversizing was found to be prevalent in the 26 buildings surveyed. This conclusion agrees with the
opinion of those involved in the building industry. Any attempt to conserve fan energy must therefore
begin by investigating oversizing that may exist.
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Variable Air
Volume Systems: Maximize Energy
Efficiency and Profits
Oversizing not only wastes energy but also leads to greater wear on equipment. Thus, reducing
oversizing will reduce maintenance costs. Care should be taken to measure and reduce oversizing
when upgrading fan motors or adding variable speed drives. Smaller motors and VSDs will also costs
less to purchase.
The following table lists buildings included in the study and the average oversizing.
Table 4. Buildings Studied and Average Oversizing
Statenet Building, Indianapolis, IN
American United Life, Indianapolis, IN
54 Monument Circle, Indianapolis, IN
Eli Lilly Corporation Center #73, Indianapolis, IN
Eli Lilly Corporation Center #76, Indianapolis IN
Eli Lilly Corporation Center #75, Indianapolis IN
Methodist Hospital, Indianapolis, IN
Mobil Research and Development Corp. #16, Pennington, NJ
Mobil Research and Development Corp. #19, Pennington, NJ
Mobil Research and Development Corp. #17, Pennington, NJ
American Express Tower, New York, NY
Liberty Mutual Building, Weston, MA
UCLA Medical Plaza 200, Los Angeles CA
UCLA Medical Plaza 300, Los Angeles, CA
Kaiser Imperial Medical Office, Los Angeles, CA
Children's Hospital of LA., Los Angeles, CA
Boeing Building #40-03, Seattle, WA
Boeing Building #40-04, Seattle, WA
Boeing Building #40-23, Seattle, WA
Boeing Building #40-22, Seattle, WA
Boeing Building, #87, Seattle, WA
Boeing Building, #40-83, Seattle, WA '
Boeing Building, #88, Seattle, WA
International Square, 1825 I St., Washington, D.C.
International Square, 1850 K St., Washington, D.C.
International Square, 1875 I St., Washington, D.C.
;igS?i^^^||^'t^g
IQversizihgi
38%
88%
8%
28%
-12%
-11%
-11%
-33%
62%
-2%
13%
-14%
15%
34%
15%
0%
88%
422%
113%
11%
27%
86%
33%
1%
6%
-21%
46
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