Synchronous and Cogged Fan 

Belt Performance Assessment

February 2014

Dylan Cutler

Jesse Dean

Jason Acosta

Prepared for the General Services Administration

By The National Renewable Energy Laboratory 
The Green Proving Ground program leverages GSA’s real estate portfolio 

to evaluate innovative sustainable building technologies and practices. 

Findings are used to support the development of GSA performance 

specifications and inform decision-making within GSA, other federal 

agencies, and the real estate industry. The program aims to drive 

innovation in environmental performance in federal buildings and help 

lead market transformation through deployment of new technologies.
Synchronous and Cogged Belt Evaluation Page i 

Disclaimer

This document was prepared as an account of work sponsored by the United States Government. While this 

document is believed to contain correct information, neither the United States Government nor any agency 

thereof, nor the National Renewable Energy Laboratory, nor any of their employees, makes any warranty, 

express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any 

information, apparatus, product, or process disclosed, or represents that its use would not infringe privately 

owned rights. Reference herein to any specific commercial product, process, or service by its trade name, 

trademark, manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or 

favoring by the United States Government or any agency thereof, or the U.S. Department of Energy’s National 

Renewable Energy Laboratory. The views and opinions of authors expressed herein do not necessarily state or 

reflect those of the United States Government or any agency thereof or the National Renewable Energy 

Laboratory.

 

The work described in this report was funded by the U.S. General Services Administration [and the Federal 

Energy Management Program of the U.S. Department of Energy] under Contract No. IAG-11-01815 and Task No. 

WFK91002. 

Acknowledgements

United States General Services Administration (GSA) Region 8: Silas Campbell, Douglas Rothgeb, Jessica 

Higgins, Andrew Bond, John Marino, and Joseph Baker

National Renewable Energy Laboratory: Peter McNutt

University of Michigan: Heath Hofmann

For more information contact:

Energy and Environment Team

Facilities Management and Services Programs 

Public Buildings Service - Rocky Mountain Region

U.S. General Services Administration

One Denver Federal Center 

P.O. Box 25546 (8P2PM)

Denver, CO 80225-0546

Phone: (303) 236 - 8000
Synchronous and Cogged Belt Evaluation Page ii

Table of Contents 

Page

I. Executive Summary............................................................................................................................ 1

A. Background ................................................................................................................................................ 1

B. Study Design and Objectives...................................................................................................................... 1

C. Project Results/Findings............................................................................................................................. 2

D. Conclusions ................................................................................................................................................ 5

II. Background ........................................................................................................................................ 6

A. Assessment................................................................................................................................................. 6

B. Opportunity................................................................................................................................................ 6

III. Measurement & Verification Project Plan......................................................................................... 8

A. Technical Objectives................................................................................................................................... 8

B. Technology Description............................................................................................................................10

C. Demonstration Project Location(s)..........................................................................................................11

IV. Measurement & Verification Evaluation Plan ................................................................................. 12

A. Facility Description...................................................................................................................................12

B. Technology Specification .........................................................................................................................14

C. Technology Deployment..........................................................................................................................14

D. Test Plan...................................................................................................................................................14

E. Instrumentation Plan ...............................................................................................................................15

V. Results.............................................................................................................................................. 16

A. VAV Fan Analysis......................................................................................................................................16

B. Economic Analysis....................................................................................................................................20

C. Power Factor Analysis..............................................................................................................................21

D. Noise Level Analysis................................................................................................................................. 22

E. CV Fan Analysis.........................................................................................................................................23

F. Economic Analysis....................................................................................................................................24

G. Power Factor Analysis..............................................................................................................................25

H. Maximum Power at Start-Up ...................................................................................................................26

VI. Conclusions...................................................................................................................................... 27

A. Overall Technology Assessment at Demonstration Facility.....................................................................27

B. Best Practice.............................................................................................................................................27

C. Barriers and Enablers to Adoption...........................................................................................................28

D. Market Potential within the GSA Portfolio ..............................................................................................28
Synchronous and Cogged Belt Evaluation Page iii

E. Recommendations for Installation, Commissioning, Training, and Change Management......................30

Appendices................................................................................................................................................ 32

A. Research Details.......................................................................................................................................32

B. References................................................................................................................................................33

C. Glossary....................................................................................................................................................33
Synchronous and Cogged Belt Evaluation Page 1 

I. Executive Summary

A. Background 

The U.S. General Services Administration (GSA) Region 8 office sponsored the technology evaluation of fan belt 

drives. The fan belt transfers the mechanical power from the motor to drive the fan. Traditionally, this is 

achieved with a standard V-belt. This study evaluated two different belt technologies that replace the V-belt: a 

cogged V- belt, and a synchronous drive belt. 

Standard V-Belt Cogged V- Belt Synchronous Drive Belt

Figure 1 – Fan belts analyzed during this technology demonstration. (Published with consent from Gates 

Corporation)

i

Ventilation fans consume a significant portion of the electricity used in buildings. According to the U.S. 

Department of Energy (DOE), ventilation accounted for approximately 12% of total electricity use in commercial 

buildings as of 2010ii. Total fan energy use is somewhat higher than this since belt driven fans are also present in 

some cooling towers and other applications. 

One of the significant inefficiencies in fan operation is associated with the losses that occur during the transfer 

of energy between the motor shaft and the fan. These losses are due to frictional losses between the belt and 

the pulleys, bending resistance, belt creep, and belt slippage. Both of the fan belt technologies tested in this 

study strive to minimize those inefficiencies, thus reducing energy consumption for ventilation. Cogged V-belts

are designed to reduce the bending resistance as the belt travels around the sheave (pulley) and have less 

frictional losses than standard V-belts. Synchronous drive belts are designed to reduce both belt slippage and

frictional losses. In addition to energy savings, synchronous drive belts may reduce operations and maintenance 

(O&M) costs. Synchronous drive belts have been reported to generate significant noise on occasion, though this 

was not observed in this demonstration.

iii

 

The belt manufacturers estimate energy savings of up to 5% for synchronous drive belts over standard V-beltsiv

, 

and cogged belts have been reported to show savings of 2% over standard V-beltsv

. While this is a small portion 

of overall building electricity use (0.3% to 0.5%), this technology has the potential to offer a relatively simple 

solution to reduce ventilation energy use in buildings. The GSA has jurisdiction, custody, or control over 354 

million square feet (ft2

) of federally owned and leased space in approximately 9,600 buildings.

vi Given the 

location, independent nature of this technology, and the size of the GSA portfolio, even the modest energy 

savings associated with this technology can result in a significant amount of total energy saved.

B. Study Design and Objectives

The U.S. Department of Energy’s National Renewable Energy Laboratory’s (NREL) study, conducted at the Byron 

G. Rodgers Federal Building and U.S. Courthouse in Denver, Colorado, consisted of measuring the real and 

apparent electricity consumption, fan speed, motor speed, and sound level of two fans. One of the fans serves 

as an exhaust fan for the building and is a constant volume (CV) fan. The other fan provides ventilation air for 
Synchronous and Cogged Belt Evaluation Page 2 

the parking garage and is a variable air volume (VAV) fan, equipped with a variable frequency drive (VFD). Both 

fans are served by 3-phase, 480-volt electricity.

The testing was performed three different times for each fan. For the CV fan, the testing was performed with 

the existing belts, with the existing belts appropriately tensioned, and with the synchronous drive belts. The VAV 

fan was tested with the existing V-belts (baseline), with cogged V-belts, and with the synchronous drive belts. 

The cogged V-belts were not tested on the CV fan due to logistical install issues at the site. All metering was 

performed with a Fluke Power Logger 1735.

The electrical performance was monitored for each belt placed on the CV fan for a period of 3 to 5 minutes, with 

data recorded at one second intervals. This captured both the start-up and the steady-state operation of the CV 

fan. The VFD on the VAV fan was placed into “hand mode” and the frequency was adjusted in increments of 5

hertz (Hz) from 15 to 60 Hz (the maximum) to capture the performance at different fan speeds. Approximately 2

to 3 minutes of metered data was recorded at each frequency, along with fan and motor shaft speed, and 

ambient noise in the room.

Results of the VAV system are adjusted for the outside weather due to the change in the density of air at 

different testing periods (variation in temperature, humidity, or barometric pressure). The CV fan exhausts 

conditioned air, so the results are not adjusted for weather. 

C. Project Results/Findings

Variable Air Volume Fan

The energy savings were calculated for the VAV unit for cogged v-belts and synchronous drive belts at various 

fan speeds. The power draw at each fan speed was normalized to account for the variation in fan speeds 

between tests and inlet air density. An increase (or decrease) in fan speed will lead to a significant change in 

power consumed that does not correspond to the belt changeover, but rather to the fact that the fan is moving

more (or less) air. The energy savings normalized for both fan speed and air density changes can be seen in

Table 1. 

Table 1 - VAV Weather-Adjusted and Fan-Speed-Normalized Savings in 

Real Power Consumption over Standard V-Belt

Predicted Power Percent Savings

VFD 

Frequency 

[Hz]

Fan Speed in 

Revolutions per 

Minute [RPM]

Baseline

in Watts

[W]

Cogged

[W]

Synchronous 

[W] Baseline Cogged Synchronous

15 130 770.7 698.8 615.9 NA 9.3% 20.1%

20 173 1,548.8 1,492.2 1,422.8 NA 3.7% 8.1%

25 216 2,712.6 2,636.4 2,588.7 NA 2.8% 4.6%

30 262 4,465.1 4,378.5 4,354.4 NA 1.9% 2.5%

35 303 6,821.0 6,494.0 6,483.9 NA 4.8% 4.9%

40 348 9,883.4 9,548.9 9,538.4 NA 3.4% 3.5%

45 391 13,748.7 13,302.1 13,267.9 NA 3.2% 3.5%

50 434 18,587.7 17,986.4 17,898.1 NA 3.2% 3.7%

55 478 24,058.4 23,863.2 23,679.9 NA 0.8% 1.6%

60 521 31,167.2 30,782.0 30,459.4 NA 1.2% 2.3%
Synchronous and Cogged Belt Evaluation Page 3 

The electricity savings ranged from 1.6% to 20.1% for the synchronous drive belt, and the electricity savings 

ranged from 0.8% to 9.3% for the cogged belts, with greatest savings at low fan speeds. For the synchronous 

drive belts retrofit the savings were on the order of 1.6% to 4.6% for the range of VFD frequencies at which most 

fan systems will operate. 

The economics for the VAV system were analyzed on a 25,000 cubic feet per minute (CFM) fan with a 40 

horsepower (HP) motor. The VAV fan operates continuously (24 hours-per-day), and ramps up due to high levels 

of carbon monoxide in the parking garage, which occurs approximately 4 hours per day. The life of the V-belt, 

the synchronous drive belt, and the cogged V-belt was assumed to be 3 years for the life-cycle analysis. The 

specific installation will dictate belt lifetime, and belts should be monitored multiple times each year to evaluate 

appropriate replacement schedules. The blended electric utility rate for the Byron Rogers Courthouse was

$0.084/kilowatt-hour (kWh). 

The life-cycle analysis is conducted over a 9-year period. Nine years was chosen for the period of analysis

because it includes three full life cycles for each belt. The life-cycle cost (LCC) analysis analyzes the total cost of 

ownership of each belt over the 9-year period, converting future costs to a present value based on the expected 

inflation rate and electricity escalation rate. Replacement costs are incurred at the beginning of years 4 and 7. 

The belt with the lowest LCC is economically the best decision for GSA over a 10-year period assuming the rates 

used in this analysis are consistent with future trends. 

The synchronous drive belt upgrade involves a one-time, upfront cost due to the required pulley changeovers. 

Once the pulleys on the fan and motor are replaced for the synchronous drive belt, they are expected to last 

throughout many belt replacements. This difference between initial cost and incremental cost was taken into 

account in all of the economic analyses. Table 2 shows the life-cycle analysis summary. Note that the belt type 

with lowest LCC, the synchronous drive belt, is economically the best option.

Table 2 - VAV Fan Economic Analysis

Cost V-Belt Cogged V-Belt Synchronous Drive

Belt

Initial Costs $379 $419 $1,280

Replacement Costs $379 $419 $372

O&M Costs $92 $92 $23

Energy Costs $4,772 $4,690 $4,608

Life-cycle Costs $37,694 $37,187 $36,809

Constant Volume Fan

The CV fan is rated at 12,000 CFM and is operated by a 10 HP motor. The fan operates 11 hours per day, 5 days 

per week. The installation of the synchronous drive belt in the CV system actually increased power consumption. 

This was due to the fact that the retrofit increased fan speed. This illustrates the importance of installing a belt 

and pulley system that accomplishes the desired objectives of the facility. The power consumption was 

normalized for fan speed and those results are shown in Table 3. 
Synchronous and Cogged Belt Evaluation Page 4 

Table 3 - CV Fan Average, Normalized Power Consumption

Belt Type Fan Speed 

(RPM)

Actual Average 

Power 

Consumption (W)

Percent Savings 

(Normalized, Average 

Power Consumption)

Loose V-Belt 1161.5 7,107.4 NA

Tensioned V-Belt 1164 7,153.3 0.001%

Synchronous drive 

belt 1183 7,368.9 1.871%

The two LCC analyses displayed in the tables below show the importance of proper installation. The increase in 

fan speed caused by the installation of the synchronous drive belt causes an increase in LCC versus the base

case. The synchronous drive belt is more efficient than the standard V-belt, yet this efficiency was outweighed 

by the RPM increase from the installation. If the efficiency gains are used to reduce power consumption, with no 

increase in fan speed, the synchronous drive belt offers the lowest LCC scenario.

Table 4 – CV Fan Life-cycle Cost Analysis

Cost Loose V-Belt

Tensioned 

V-Belt

Synchronous

Drive Belt

Synchronous Drive Belt 

(assuming no increase 

in fan speed)

Initial Costs $111 $111 $470 $470

Replacement Costs $111 $111 $165 $165 

O&M Costs $92 $92 $23 $23

Energy Costs $1,707 $1,719 $1,770 $1,676

Life-Cycle Costs $13,881 $13,964 $14,270 $13,556 

A return on investment was calculated for both the VAV and the CV fans. This was calculated as a simple 

payback period and these values are included in Table 5. For the synchronous drive belts, it was necessary to 

calculate both initial installation and repeat installation paybacks. This was due to the increased initial cost 

required for the pulley changeover. The “immediate” payback for the synchronous drive belt repeat installations 

on the VAV fan is due to the fact that replacing the single synchronous drive belt has a lower initial cost than 

replacing all four standard V-belts. This means that there is no initial cost to recoup. This is possible due to the 

robust materials used in the synchronous drive belt, which allows a single belt to perform the task that

previously required four standard V-belts.
Synchronous and Cogged Belt Evaluation Page 5 

Table 5 – Payback Period for VAV fan and CV Fan Belt Drives when Compared to Standard V-Belt

Payback Period (Years)

Fan Type Belt Type Initial Installation Repeat Installations

VAV Fan

Cogged V-Belt 0.49 0.49

Synchronous 

Drive Belt 3.87 immediate

CV Fan

Cogged V-Belt NA NA

Synchronous 

Drive Belt 3.56 0.54

D. Conclusions

It has been shown in this study that both cogged V-belts and synchronous drive belts can provide a reduction in 

energy consumption over the incumbent V-belt technology. This was demonstrated for the synchronous drive

belts on both a CV and VAV fan, and for the cogged V-belts on the VAV fan. The savings were greater for the 

synchronous belts on the VAV fan and were highest at lower fan speeds. For the cogged V-belts on the VAV fan, 

they realized percent-savings ranging from 0.8% (at 55Hz) to 9.3% (at 15 Hz). The synchronous drive belts on the 

VAV realized percent-savings from 2.3% (at 60 Hz) to 20.1% (at 15 Hz). For the CV fan, the synchronous drive 

belts showed potential savings of 1.9% (once the data was normalized for fan speed variation). The potential for 

increased fan speed (leading to increased power consumption) with incorrect synchronous belt sizing on CV fans 

is a risk associated with synchronous belts on CV fans. 

The synchronous drive belts showed lower LCC than both the cogged V-belts and the baseline (standard V-belts) 

on the VAV fan. They also showed the lowest LCC on the CV fan when using potential energy savings. The lower 

LCCs were due to a combination of reduced energy consumption and lower operation and maintenance costs. 

For this analysis, the belts were all assumed to have equivalent lifetimes. If the manufacturer estimates of longer 

belt lifespans are accurate, this would only improve the synchronous drive belt economics. The cogged V-belts 

showed savings over the standard V-belts in the VAV fan case.

It is recommended that GSA pursue implementation of synchronous drive and cogged belts in their buildings. 

The first fans that should be addressed are fans with high operating hours (leading to more energy savings). GSA 

should target VAV fan systems for synchronous drive belts. While the cogged V-belts were tested on the VAV fan 

only, the fact that they showed savings at all fixed speeds indicates that they would perform well on CV fans. 

Due to the potential install issues with synchronous belts on CV fans (increased fixed speed leading to increased 

power despite more efficient operation), GSA should target cogged V-belts for CV systems and should replace 

standard V-belts with cogged V-belts when the standard belts are due for replacement. 
Synchronous and Cogged Belt Evaluation Page 6 

II. Background

A. Assessment

According to the U.S Department of Energy (DOE), ventilation energy use accounted for approximately 12% of 

total electricity use in commercial buildings as of 2010. Ventilation systems in commercial buildings are typically

driven by centrifugal fans and asynchronous induction motors. The fan belt is the device that transfers the 

mechanical power from the motor to rotate the fan. Traditionally, this is achieved with a standard V-belt. 

Standard V-belts can have an efficiency as high as 95-98% at the time of installation. This efficiency can 

deteriorate as much as 5% during operationvii. This study evaluated two different belt technologies that replace 

the V-belt: a cogged V-belt, and a synchronous drive belt. These technologies aim to reduce frictional losses, 

bending resistance, and slippage losses, resulting in a potential increase to the operating efficiency of the 

fan/motor combination by 2-5%viii. The synchronous drive belt also can limit the degradation of performance 

over time due its integrated pulley/belt technology. 

While the efficiency improvement of fan operation only provides a small reduction in overall building electricity 

use, this technology has the potential to offer a relatively simple solution to reduce ventilation energy use in 

buildings. Given the location-independent nature of this technology and the size of the GSA portfolio, even the 

modest percent savings associated with this technology can result in a significant amount of total energy saved.

This report will evaluate the installed performance of the different belt drives to verify the actual savings 

achieved through belt retrofits. 

B. Opportunity

This technology has the opportunity to provide savings in virtually every building under the jurisdiction, custody, 

or control of the GSA. Ventilation is required by code in almost every building type and ventilation air is often 

provided by belt-driven fans. Forced air heating and cooling also require fans to distribute the conditioned air. 

Belt-driven fans are also found in most cooling towers, presenting another opportunity for the technology. The 

technology is thus building type independent. 

The technology is also climate independent. Certain technologies are more applicable for heating- or coolingdominated climates or for climates with significant solar resources. Cogged V-belts and synchronous drive belts 

are an applicable technology independent of local climatic influences. The tested technologies have the 

potential to provide a relatively simple solution for increasing the operating efficiency for fan/motor 

combinations throughout the GSA portfolio.

The technology currently used in the majority of installations transfers mechanical power from the motor to the 

fan with a standard V-belt. V-belts depend on the friction between the belt and the pulley to transfer the 

mechanical power. This can lead to energy losses due to friction (given off as heat) and slippage losses if the belt 

is not appropriately tensioned.

Cogged V-belts reduce the amount of bending resistance as the belt travels around the sheave by reducing the 

amount of material on the inside (contact-point) edge of the belt. This allows cogged V-belts to run cooler and 

attain a higher efficiency. Cogged V-belts can also be used with the exact same pulleys as conventional V-belts.

The largest opportunity for cogged V-belts is with small-diameter motor or fan sheaves. Each V-belt has 

specifications on minimum recommended sheave diameters for operation. If the actual sheave diameters are at 

or below the minimum recommended diameters, then the cogged V-belt can reduce bending resistance and 

offer greater potential savings.

Synchronous drive belts are positive drive belts that actually mesh with the pulleys at the motor and fan. 

Therefore, this technology requires both new belts and new pulleys. The toothed belts synch with the grooves in 

the pulley (much like a motorcycle drive), which eliminates any slippage losses. They also run much cooler and 

do not require the frequent re-tensioning that V-belts require.
Synchronous and Cogged Belt Evaluation Page 7 

Belt manufacturers estimate energy savings of up to 5% over standard V-belts for synchronous drive belts and 

smaller savings for cogged V-beltsix. Both the cogged V-belts and the synchronous drive belts are available from 

a variety of vendors. 

Synchronous drive belts offer the largest potential efficiency gains. Yet they are also more application-specific; 

due to the lack of slippage, high torque startups can cause belt tooth jumping on the pulleys and lead to 

significant wear on the belts. It is important to size the belts and pulleys appropriately. If the fan is forced to run 

at a higher speed due to the new belts, it is possible that all efficiency gains will be overshadowed by higher 

power draw due to the increased revolutions per minute (RPM) dictated by the new belt/pulley system. 
Synchronous and Cogged Belt Evaluation Page 8 

III. Measurement & Verification Project Plan

A. Technical Objectives 

The testing of the fan belts aims to examine the effect of replacing the current V-belts with cogged V-belts or

synchronous drive belts on: real power consumption (watts), fan speed, and changes in the power factor of the 

motors. There are two elements to the power consumption that need to be analyzed separately: the peak 

startup consumption as the fan ramps up, and the power consumption once the fan has reached near steadystate operation.

The noise generated by the different belts was examined by recording ambient noise levels near the fan. Due to 

the location of the tested fans, noise in surrounding occupied space was not a concern. Both of the fans were 

located in a penthouse mechanical room above the elevator shafts. Ambient noise recordings were still taken 

near the fan to examine the effect of the different belts on noise production. This variation in noise production 

could be useful information for buildings with fans near occupied spaces. 

The three different fan belt drives (regular v-belt, cogged v-belt, and synchronous drive belt) are examined on 

two different fan types, a variable air volume (VAV) fan and a constant volume (CV) fan. A series of quantitative 

and qualitative performance objectives were created by NREL to evaluate the performance of the technology. 
Synchronous and Cogged Belt Evaluation Page 9 

Table 6 - Performance Objectives for Synchronous Belts

Performance 

Objective Metric Data Requirements Success Criteria

Results 

Constant 

Volume

Results 

Variable Air 

Volume

Quantitative Performance Objectives

Reduce Fan System 

Energy Use

Electrical 

power at 

pre-defined 

fan speeds

Electrical 

Power (true 

kW) > 2% fan power savings 

relative to new, 

tensioned standard vbelt

Fail (as 

installed) Pass Power quality 

(starting 

current, PF, 

THD)

Acceptable Increase 

in Ambient Noise 

Levels and 

Surrounding 

Occupied Space 

Noise Levels

Ambient 

noise level in 

surrounding 

occupied 

spaces

Ambient noise 

level pre and 

post retrofit 

(decibel)

Ambient noise level in 

surrounding occupied 

space within 

acceptable range, per 

ASHRAE requirements 

pre and post retrofit

No consistent noise 

increase with cogged or 

synchronous drive belts

over standard V-belts. No 

surrounding occupied 

space, which prevents 

analysis of ASHRAE noise 

standards.

Cost Effectiveness

Life-cycle 

cost 

effectiveness

Installation 

costs relative to 

standard V-Belt

Exceeds GSA's LCC 

criteria for energy 

efficiency projects for 

motors

Fail (as 

installed) Pass Electric rates 

for GSA 

facilities in 

each region

Motor run time

Qualitative Performance Objectives

Reduce Fan Belt 

Operation and 

Maintenance Time 

and Cost

HVAC 

technician 

labor time 

per motor 

per year

Current O&M 

protocol for 

belt driven 

systems 

Reduction in annual 

O&M costs Neutral Pass Labor hours for 

standard v-belt 

per year and 

cogged v-belt 

per year

Belt life
Synchronous and Cogged Belt Evaluation Page 10

Two variables that were important to account for in the analysis were

• Speed of the fan and motor shafts in revolutions per minute (RPM) 

• Density of the air during the different testing periods. 

The fan and motor speed were important to quantify so as to be able to calculate power consumption 

normalized for flow rate. This is especially important for VAV fans where the variable frequency drives (VFD) will 

ideally calibrate to a set point (usually pressure); therefore, an increase in RPM at the fixed test frequency would 

be adjusted for in normal operation and result in equal flow rate delivered to an equal load on the system. In the 

case of the CV fan it is still important to quantify the RPM-normalized power consumption, while also reiterating 

the fact that the installation must be carried out to achieve the same RPM post-retrofit (otherwise with a higher 

RPM in a CV fan, efficiency savings can be overshadowed by increased power consumption due to higher speed 

and the inability of the fan to ramp down). 

The density of the air has an impact on the power consumption of the fan as well. This was recorded for the 

different test periods and the power data was adjusted using the ratios of the air densities to ensure that the 

belt changeover was the only variable impacting any observed changes in power consumption.

B. Technology Description

Standard V-belts have several limitations that cogged V-belts and synchronous drive belts aim to overcome. Vbelts generate excessive friction when they travel around the motor and fan sheaves. This is due to the belt’s 

solid design, which inhibits bending and from the large amount of contact surface. The belt’s bending resistance 

generates extra friction. V-belts also rely on friction to transfer mechanical power, which can lead to slippage

(especially if improperly tensioned). This slippage leads to further friction losses and wasted power from the 

motor shaft.

Cogged V-belts overcome much of the bending resistance by removing some of the material from the belt. This 

allows for a reduction in the inner diameter of the belt as it travels around the pulleys, reducing the bending 

resistance. The cogged V-belts still rely on friction to transfer the mechanical energy from the motor and are, in 

general, very similar to the standard V-belt.

Synchronous drive belts have teeth on the inside of the belt. The shape of these teeth are usually curvilinear in 

shape (similar to a rounded-over trapezoid), yet the exact shape depends on the specific manufacturer. The 

belts integrate with specific pulleys that accept the teeth on the belt. This geared interaction between belt and 

pulley can, if installed properly, greatly reduce slippage and friction. Synchronous drive belts also do not need to 

be re-tensioned after installation, which can result in operation and maintenance (O&M) savings over cogged Vbelts and standard V-belts. The Gates® Poly Chain® GT® CarbonTM synchronous drive belts that were installed at 

the Byron Rogers Courthouse and monitored for this report are made of carbon fiber, which the manufacture 

claims provides longer lifetimes for the beltsx

. 
Synchronous and Cogged Belt Evaluation Page 11

Standard V-Belt Cogged V- Belt Synchronous Drive Belt

Figure 2 – Fan belts analyzed during this technology demonstration (Published with consent from Gates 

Corporation)xi

The tested belts would fall under a DOE technology readiness level (TRL) 8 or 9.

xii They are fully tested and 

deployed technologies that have seen successful operation. Limited independent testing has been conducted on 

fan belt drives. A study was conducted by the University of Virginia Facilities Managementxiii on a constant 

speed, 40 HP HVAC fan that contained 3 fan belts. They found that replacing worn, properly tensioned V-belts 

with a new V-belt reduced energy demand by 2.9%. Installation of cogged V-belts resulted in additional savings 

of 3.3% when compared to a new V-Belt and 6.3% when compared to the worn V-belt. The study findings 

resulted in a simple payback period of 0.5 years. Both the cogged V-belts and the synchronous drive belts are 

technologies that are available through various manufacturers. 

The risks associated with installation of the technology apply mainly to the synchronous belt drives. The belt and 

pulley for the synchronous drive belt must be properly selected to ensure the desired fan speed is achieved. An 

unintended increase in the fan speed will increase the power consumption of the motor. An unintended

decrease in fan speed will reduce the volumetric flow of the fan and could lead to building performance issues. 

Having access to the technical expertise to specify and commission the belts is the biggest barrier to entry. 

Without the proper specification, installation, and commissioning of belts, an undesired change in performance 

may occur. Cogged V-belts are similar to standard V-belts and the challenges and risks with installation are 

comparable. Proper belt tension and preventative maintenance will ensure a longer life and good performance 

of the fan and motor system.

C. Demonstration Project Location(s)

The Byron Rodgers Courthouse in Denver was selected as an installation site for this study. A CV fan and a VAV 

fan were both necessary for the technology demonstration and the selected facility had both of these in close 

proximity. The fans are located in a penthouse mechanical room above the elevator shafts. 
Synchronous and Cogged Belt Evaluation Page 12

IV. Measurement & Verification Evaluation Plan

A. Facility Description

The facility that was selected for this technology demonstration (the Byron Rogers Courthouse) had both a CV 

and a VAV fan that were studied. The CV fan is a centrifugal building exhaust fan rated at 10 HP and 12,000 CFM. 

The fan is fitted with two traditional V-belts and operates from 6:00am to 5:00pm, Monday through Friday, 

throughout the entire year. A picture of the motor/fan assembly with the original V-belts is provided in Figure 3. 

A close-up of the installed synchronous drive belt and pulley combination on the CV fan is presented in Figure 4. 

Figure 3 – CV exhaust fan with two standard V-belts. Image Credit: Jesse Dean (NREL)

Figure 4 – CV Exhaust Fan with single Synchronous drive belt. Image Credit: Jesse Dean (NREL)
Synchronous and Cogged Belt Evaluation Page 13

The VAV fan provides ventilation air for the garage. The VAV system is a 100% outside air unit, and the outside 

air is brought in through a filter on the penthouse wall. The VAV fan is a Trane centrifugal air foil fan with a 

nominal airflow of 25,000 CFM. The original pulley system used four separate V-belts to drive the fan. The 

motor associated with the VAV fan with the cogged V-belts installed is shown in Figure 5. The VAV fan operates 

24/7 for the entire year. It is controlled by a carbon monoxide sensor in the garage and is ramped up whenever 

the CO sensor reads 35 ppm or more. It was stated that this increased flow requirement occurs approximately

four hours per day. Otherwise, the fan operates at a reduced state (approximately 20 Hz at the VFD).

Figure 5 – VAV Fan Motor with Cogged Belts Installed. Image Credit: Jesse Dean (NREL)

Both of these fans were driven by Baldor Super E motors. The motor characteristics are listed in Table 7. 

Table 7 – Motor Characteristics for the CV and VAV Fans

Motor Characteristics Units Constant Volume 

Fan Motor

Variable Air Volume 

Fan Motor

Location - EF-P3 MAU P-1

Manufacturer - Baldor Super E Baldor Super E

Horse Power (HP) HP 10 40

Voltage Volts 480 460

Full Load Current Amperes 12 50

Speed RPM 1760 1185

Efficiency % 91.7 94.1

Enclosure Type - ODP ODP

Operational Hours hrs/yr 2860 8760

Original Fan Belt Info. Traditional V Belt Traditional V Belt
Synchronous and Cogged Belt Evaluation Page 14

The average phase-to-phase root mean squared (RMS) voltage for the CV unit with standard V-belts was 485.27 

volts and the average RMS current across all three phases was 11.96 amps. The motor load for the CV unit was 

calculated to be 100.79%, and the motor is sized correctly to meet the given load.

The average phase-to-phase RMS voltage for the VAV unit with the standard V-belts was 486.37 volts and the 

average RMS current across all three phases was 39.89 amps. The motor load for the VAV unit at 60 Hz was 

calculated to be 84.35%, and the motor is slightly oversized for the particular application. 

B. Technology Specification

The technology specification is included in Section III. B (Technology Description) and Section IV. A (Facility

Description). 

C. Technology Deployment

There were two stages of deployment in the technology demonstration. The first stage was the removal of the 

standard V-belts and replacement with the cogged V-belts. This stage required: 

1. Removal of the belt and pulley guards

2. Loosening of the motor mount

3. Removing the old V-belts

4. Installing the new cogged V-belts

5. Tensioning the new belts 

6. Securing the motor mount and guards. 

This stage was only applied to the VAV fan. The CV fan received tensioning of the existing V-belts during this 

stage and was then retested with appropriately tensioned belts. 

During the re-tensioning phase, the motor shafts were aligned to be parallel and in-line with each other to avoid 

uneven wearing and excess friction. This was achieved with a magnetic laser alignment tool that would attach to 

the motor pulley and project a line onto the other pulley to demonstrate whether the two drive shafts were out

of line or in parallel. This was followed by appropriate tensioning of the belts using a sonic tension meter. The 

motor mount was adjusted closer or further away from the fan pulley to achieve the appropriate harmonics in 

the V-belt (read with a sonic meter, similar to an electronic tuning fork for musical instruments).

The second stage of the technology deployment was the changeover to synchronous drive belts. This process 

was more involved due to the fact that the pulleys had to be removed from both the fan and the motor drive 

shafts and replaced with the synchronous drive pulleys. This step occurred between steps 3 and 4 in the process 

described above and required a mechanic to uninstall and reinstall the pulleys.

D. Test Plan

The test plan for this technology demonstration consisted of monitoring the fan/motor power characteristics 

(including real and apparent power, power factor, and harmonics), fan and motor shaft speed, and ambient 

noise levels for each of the tested belts. 

The monitoring was performed as “spot checks” that recorded the fan/motor performance for periods of 1 to 5 

minutes. For the VAV fan the monitoring was performed at 5 Hz intervals from 15 to 60 Hz. For the CV fan, there 

was only the single speed to test. These time periods were sufficient to see the fan operating in a steady-state 

condition. The fan/motor performance should not vary until significant wear or elongation of belts occurs (a 

time period much longer than possible to capture in time-series monitoring). The time-invariant nature of the 
Synchronous and Cogged Belt Evaluation Page 15

fan/motor operation makes it possible to draw conclusions on future performance from the spot testing taken 

during site visits. 

A baseline test was conducted on both the CV and the VAV fans to establish the performance of the standard Vbelts that were in place before the study commenced. This established the baseline power consumption and 

characteristics as well as the shaft speeds that needed to be matched for the synchronous drive belt installs.

For the VAV fan, the baseline test was followed by a replacement of the V-belts with cogged V-belts. Once the 

cogged V-belts were installed and properly tensioned, they followed an identical test procedure of spot tests at 

each 5 Hz interval from 15 to 60 HZ. The cogged V-belts were then removed and replaced by the synchronous 

drive belts. The synchronous drive belts received the identical test procedure as previously described.

For the CV fan, the baseline test was followed by accurate tensioning of the existing V-belts. The performance of 

the tensioned belts was recorded. The V-belts were then removed and replaced by the synchronous drive belts. 

The synchronous drive belts were tested in an identical manner to the baseline and tensioned belts.

E. Instrumentation Plan

The power monitoring was done at the electrical boxes for the CV and VAV fans. All of the power metering was 

done by a Fluke Power Logger 1735. The Fluke Power Logger records: 

• Minimum, maximum, and average RMS voltage, RMS current, real power, reactive power, apparent 

power, power factor, and total harmonic distortion for each of the three phases; 

• Minimum, maximum, and average total real, total reactive, total apparent power, and total power 

factor; 

• Frequency. 

All of the variables listed above are collected on a one-second time interval and recorded in a text file that can 

either be viewed in Fluke software or imported into Excel. For this study, the raw data was imported into Excel 

files.

The power meter was installed at the electrical box as shown in Figure 6. Both panels had a Y configuration 

requiring metering of the three phases and the neutral line. The Fluke Power Logger 1735 measures RMS 

voltage accurately within ± 0.5%, RMS current within ± 1%, and energy within ± 1.5%. It should be noted that 

these are absolute error values, not indicative of the error between measurements. The amount of absolute 

error should be the same on two different measurements leading to almost no error in the difference between 

the measurements (also referred to as negligible error in repeatability). Technical support at Fluke confirmed 

the negligible error in repeatability through phone correspondence.

xiv
Synchronous and Cogged Belt Evaluation Page 16

Figure 6 – Fluke power meter installed on the CV fan electrical box. Image Credit: Jesse Dean (NREL)

The fan and motor shaft speed were measured using a digital photo sensor tachometer (a Monarch PT99 

meter). A small piece of reflective material is placed on the rotating shaft and then RPM is read with the 

tachometer. The RPM readings from the photo sensor tachometer were verified by a stroboscope tachometer. 

The two devices differed by less than 0.5% between their readings. The fan and motor shaft speed were 

recorded at each spot test.

The ambient noise was recorded using an Extech 407730 Sound Level Meter. The noise level also was recorded 

at each spot test. The Extech 407330 is accurate to within ± 2dB.

V. Results

A. VAV Fan Analysis

Energy Savings 

The results for the VAV fan show significant power savings at every VFD frequency that was tested for both the 

cogged V-belts and the synchronous drive belts. The synchronous drive belts provided larger savings at all 

frequencies tested. For the synchronous drive belts, the savings ranged from 1.6% (at 55Hz) to 20.1% (at 15 Hz). 

For the cogged V-belts, the savings ranged from 0.8% (at 55Hz) to 9.3% (at 15 Hz). Table 8 shows the power at 

each VFD frequency that was tested, along with the percent savings for both the cogged V-belts and the 

synchronous drive belts. 
Synchronous and Cogged Belt Evaluation Page 17

Table 8 - VAV Weather-Adjusted and Fan-Speed-Normalized 

Savings in Real Power Consumption over Standard V-Belt

Predicted Power Percent Savings

VFD 

Frequency 

[Hz] 

Fan Speed 

[RPM]

Baseline 

[W]

Cogged

[W]

Synchronous 

[W] Baseline Cogged Synchronous

15 130 770.7 698.8 615.9 NA 9.3% 20.1%

20 173 1,548.8 1,492.2 1,422.8 NA 3.7% 8.1%

25 216 2,712.6 2,636.4 2,588.7 NA 2.8% 4.6%

30 262 4,465.1 4,378.5 4,354.4 NA 1.9% 2.5%

35 303 6,821.0 6,494.0 6,483.9 NA 4.8% 4.9%

40 348 9,883.4 9,548.9 9,538.4 NA 3.4% 3.5%

45 391 13,748.7 13,302.1 13,267.9 NA 3.2% 3.5%

50 434 18,587.7 17,986.4 17,898.1 NA 3.2% 3.7%

55 478 24,058.4 23,863.2 23,679.9 NA 0.8% 1.6%

60 521 31,167.2 30,782.0 30,459.4 NA 1.2% 2.3%

The power consumption must be normalized for fan speed. Regression based curve fits were developed to 

calculate power consumption as a function of fan speed. The regression based curve fit for the synchronous 

drive belts is provided in Figure 7 (regression plot for the standard V-belts and the cogged V-belts are provided

in the appendix). The regression curve fits for the cogged V-belts and the synchronous drive belts were then 

used to predict the power consumption at the exact fan speeds at which the baseline data was recorded. These 

values are shown in Table 8 and were used to calculate the percent savings in the table.

This normalization is especially important because power varies with the cube of the fan speed according to the 

fan affinity laws: kW1

KW2

= (RPM1

RPM2

)3. A doubling of fan RPM leads to eight times larger power consumption (23 = 8). 

Therefore, it is critical to evaluate the savings of the replacement belts at the same fan speed as the baseline 

test. It can be noted that the cubic nature of the fan law is clearly represented in the measured data shown in 

Figure 7, and the relationship results in the very high R2 value associated with the 3rd order polynomial 

regression line. 

It also can be noted that the regression curve fit shown in Figure 7 is a third order polynomial, not a straight 

cubic function. This fit was used for two reasons: the third order term dominates the polynomial (showing the 

agreement with the fan laws), and the main objective of the curve fit was to be able to predict accurate power 

consumption at points not measured during the spot testing. Due to the fact that the third order polynomial had 

a higher R2 value than the cubic fit (0.99994 vs. 0.9997), this curve was utilized in the normalization process. 
Synchronous and Cogged Belt Evaluation Page 18

Figure 7 - Average power and regression curve fit for the synchronous drive belts

It also was necessary to account for the differences in air density from one test to another. Variations in air 

density were accounted for in the VAV unit by calculating the air density at the time of each test. There is a 

direct relationship between air density and fan power consumption. Therefore, the power could be multiplied 

by the ratio of the air densities from the two different test dates to normalize for a constant air density. This 

correction was done before the regression curve fits shown here. The following fan law shows the relationship 

between power and air density: 

kW1

KW2

= ρ1

ρ2

Figure 8 shows the power consumption as a function of fan speed for all three different belt types. It can be 

noted that the cogged and synchronous drive belts show reduced power consumption across the entire range of 

fan speeds.
Synchronous and Cogged Belt Evaluation Page 19

Figure 8 – VAV fan Average Power Consumption vs. Fan Speed (shown for each belt type)

To calculate the average power consumed at each VFD speed, the power spikes and variation at the beginning of 

each change in fan speed were discarded. The remaining period of steady state operation at each VFD frequency 

was then averaged to get a single power value for each VFD frequency.

An example of the recorded power consumption of the fan equipped with a synchronous drive belt is shown 

below. Note the spike in power consumption at the beginning of each increase in fan speed. 

Figure 9 – Testing data for the VAV fan with Synchronous Belt (Power Consumption vs. Time)
Synchronous and Cogged Belt Evaluation Page 20

B. Economic Analysis

The expected life of each belt, as well as the method of economic analysis, are important to understanding the 

reported economic findings. The life of the V-belt, the synchronous drive belt, and the cogged V-belt are all 3 

years for the life-cycle analysis. Conversations with a senior engineer at one of the principal belt manufacturers 

did not identify any established trends in either absolute lifetimes or relative lifetimes (between different belt 

types). In general, belts can be expected to last between 1 and 3 years, but this was established only as a very 

rough estimate. The specific installation will dictate belt lifetime, and belts should be monitored multiple times 

each year to evaluate appropriate replacement schedules. Manufacturers also estimate a longer lifespan for 

synchronous drive belts. The 3-year lifespan was selected to represent the longer belt-life. The economic

analysis was conducted with identical lifespans for each belt and should, therefore, conservatively estimate lifecycle cost savings for the synchronous drive belts (no extra belt replacements were assumed for the standard Vbelts). In reality, belt life is dependent on the rated belt load carrying capacity, the duty cycle of the fan that the 

belt is driving, and maintenance. A generalized estimation of belt lifespan is not feasible.

The life-cycle analysis is conducted over a 9-year period. Nine years was chosen for the period of analysis, 

because it includes three full life-cycles for each belt. The life-cycle cost analysis analyzes the total cost of 

ownership of each belt over the 9-year period, converting future costs to a present value based on the expected 

inflation rate and electricity escalation rate. Replacement costs are incurred at the beginning of years 4 and 7. 

The belt with the lowest life-cycle cost is economically the best decision for GSA over a 10-year period, assuming 

the rates used in this analysis are consistent with future trends.

To calculate annual electricity savings, an average daily profile was documented for the VAV fan. The linear 

regressions were then used to predict the power consumed at each frequency that the fan encountered

throughout the 24-hour period. It was noted by the facility manager that the garage ventilation fan operates 24

hours a day, 365 days per year. The fan was stated to operate at 20 Hz for the majority of the day and cycle up 

to maximum speed (60 Hz) for approximately four hours a day when the carbon monoxide sensor delivers a 

reading that exceeds 35 ppm. Thus, the daily schedule was modeled as 20 hours per day at 20 Hz and 4 hours 

per day at 60 Hz. The calculated energy and cost savings are shown in Table 9. 

Table 9 – Electricity and Costs Savings for the Tested VAV Fan

Belt Type Savings Per Day

[kWh]

Savings Per Year

[kWh]

Annual Utility Savings

[$]

Cogged V-Belts 2.67 976 $82

Synchronous Drive 

Belt 5.35 1953 $164

All life-cycle analyses conducted in this report were calculated according to NIST Handbook 135xv and are 

presented in Table 10. The life-cycle analysis covers a period of 9 years. A discount rate of 3% for commercial 

buildings located in Colorado was used to conduct the analysis. The blended electric utility rate for the Byron 

Rogers Courthouse of $0.084/kWh was used in the calculations. The life-cycle analysis shows that electricity 

costs play an important role in determining the cost effectiveness of belt replacements. Synchronous drive belts

also have lower O&M costs, due to the fact that they do not require re-tensioning over time, which improves the 

total life-cycle cost. In this study, one synchronous drive belt replaced four V-belts, making the replacement 

costs very competitive. The one synchronous drive belt replacement is far less expensive than installing four 

cogged V-belts at the end of the product life.
Synchronous and Cogged Belt Evaluation Page 21

Table 10 - VAV Fan Life Cycle Cost Analysis

Cost V-Belt Cogged V-Belt Synchronous Drive 

Belt

Initial Costs $379 $419 $1,280

Replacement Costs $379 $419 $372

O&M Costs $92 $92 $23

Energy Costs $4,772 $4,690 $4,608

Life Cycle Costs $37,694 $37,187 $36,809

A return on investment also was calculated in terms of simple payback period (SPP). SPP is defined as the initial 

cost divided by the annual savings and portrays the number of years to recover the initial investment (without 

taking into account the time value of money). The SPPs are presented in Table 11. Two SPPs are presented, an 

“initial installation” and a “repeat installation” value. This is to account for the fact that synchronous drive belts 

contain the one-time purchase cost for the new pulleys (as explained above). For the VAV fan the repeat 

installation for the synchronous drive belt has an immediate payback. This is due to the fact that the single 

synchronous drive belt is actually cheaper than replacing the four standard V-belts. A single synchronous drive 

belt is used because of the more robust materials used in synchronous drive belt fabrication, allowing a single 

belt to perform the task that previously required four standard V-belts.

Table 11 - VAV Fan Payback Period Analysis

Payback Period (Years)

Belt Type

Initial 

Installation Repeat Installations

Cogged V-Belt 0.49 0.49

Synchronous Drive

Belt 3.87 Immediate

C. Power Factor Analysis

It is important to evaluate the effect of the tested belts on the motor’s power factor. Power factor is defined as 

the ratio of real to apparent (or total) power. The customer is usually only charged for the real power consumed, 

even though the utility still has to provide the apparent power required. Resistive devices have power factors of 

one, while inductive loads, such as a fluorescent light fixture or an inductive motor, will have power factors less 

than one.

xvi Utilities will often place a lower limit on the power factor that a building can have. When the total 

building power factor falls below that limit, the customer will receive an incremental charge relative to how low 

their power factor has fallen. Therefore, it is still important to consider the potential effect of multiple devices 

with low power factors. 

Part of the savings in real power consumption is due to a reduction in power factor for the synchronous drive 

belt. Real power is defined as PR = IRMS × VRMS × PF (where IRMS is the root mean squared current, VRMS is 

the root mean squared voltage and PFis the power factor). Thus, a reduction in power factor can lead to a 

reduction in real power. The cogged V-belt showed a very small change in power factor when compared to the 

standard V-belt (higher at some VFD frequencies and lower at others). The synchronous drive belts showed a 

reduction in power factor at all frequencies. Average power factors for each fan speed in the VAV air handler are 

presented in Table 12. 
Synchronous and Cogged Belt Evaluation Page 22

The apparent power was analyzed and the results showed savings in apparent power for both the cogged Vbelts and the synchronous drive belts. This demonstrates that not all of the savings in real power consumption 

was due to a reduction in power factor, but rather a reduction in RMS current, RMS voltage delivered, or both. 

It is important to note that a reduction in power factor should be expected when a synchronous drive belt is 

installed. This is due to the fact that motors have lower power factors at lower loads (which the synchronous

drive belts provide). The Gates Corporation, in a discussion on energy savings from synchronous drive belts,

xvii

notes that often the entire reduction in real power consumption from switching to a synchronous drive belt is 

due to a reduction in power factor. This was not observed in this study (savings were observed in apparent 

power), but demonstrates the importance of monitoring power factor in synchronous drive belt retrofits. Actual 

monetary savings can vary depending on how a change in power factor can affect the bill. Power factor 

reductions easily can be mitigated by the installation of capacitors in parallel to the load. Power factor reduction 

or the installation of capacitors was not considered in the analysis of cost savings.

Table 12 - VAV Motor Power Factor for 3 Different Belts

VFD 

frequency 

(Hz)

Synchronous

Drive Belt

Baseline VBeltCogged VBelt

15 0.490 0.527 0.520

20 0.577 0.608 0.597

25 0.644 0.658 0.661

30 0.690 0.713 0.704

35 0.731 0.753 0.746

40 0.776 0.799 0.796

45 0.823 0.850 0.848

50 0.876 0.889 0.891

55 0.906 0.909 0.915

60 0.925 0.930 0.935

D. Noise Level Analysis

The ambient noise levels were recorded at all VFD speeds for each belt type. The noise levels for the different 

belts are listed in Table 13. 
Synchronous and Cogged Belt Evaluation Page 23

Table 13 – Noise Levels Recorded for the Different Belt Tests

VFD 

Speed V-Belts Cogged V-Belts

Synchronous

Drive Belts

[Hz] [dB] [dB] [dB]

15 65-68 62 62-65

20 65-72 66-68 74-76

25 69-71 70-73 67-69

30 70-72 74-76 72-74

35 73-76 75-78 74-75

40 76-78 76-78 83-85

45 78 76-79 75-80

50 78-82 78-83 78-80

55 80-84 80-83 80-84

60 85-87 83-86 82-85

The sound level readings did not show any consistent increase in noise level due to the cogged or synchronous 

drive belts. Certain VFD speeds had increased noise and others recorded a slight decrease in noise. In most 

cases, the 2 dB error associated with the meter was greater than the actual variation in noise level. This does not 

imply that an increase of noise will never be associated with new drive installs; it is simply the case that the 

recorded noise levels for this installation did not demonstrate any significant increase in noise level.

E. CV Fan Analysis

Energy Savings

The CV fan is an exhaust fan for the building rated at 10 HP and 12,000 CFM. The fan operates from 6:00am to 

5:00pm, Monday through Friday. The fan was tested with the original belts. The original belts were then retensioned and tested again. A synchronous drive belt also was tested, but no cogged V-belt was analyzed due to 

logistical install issues at the site. A CV fan requires a different analysis, because there is only one fan speed. If 

the installation of a synchronous drive belt results in an increase in fan speed, there will be diminished energy 

savings and potentially an increase in power consumption, unless a control strategy is put in place to reduce the 

run time of the fan (acceptable because the fan would be delivering more air at the higher constant speed). The 

correct synchronous drive belt and pulley system must be selected to achieve the desired speed. 

The CV fan’s energy consumption can first be analyzed by comparing the energy use of the motor with the 

different belts, while adjusting for the fan speed. The installation of the synchronous drive belt at the Byron 

Rogers Courthouse resulted in an increase in fan speed (and a proportional increase in volumetric flow). 
Synchronous and Cogged Belt Evaluation Page 24

Table 14 – CV Fan and Motor Speeds for Tested Belts

Belt Type Motor Speed (RPM) Fan Speed (RPM)

Loose V-Belt 1778 1161.5

Tensioned V-Belt 1777 1164

Synchronous drive 

belt 1778 1183

The equivalent power in the table below is the power consumed if no changes are made to the efficiency of the 

belt drive system. This value accounts for only changes in the fan speed, and no changes in the belt drive 

efficiency. It is calculated using the cube of the fan speed ratio in accordance with the fan affinity laws. While 

the synchronous drive belt case actually consumes more power (due to the higher RPM with the new belts), its 

power consumption (at the higher fan speed) is less than the original belts would have consumed at that higher

fan speed. This results in the percent increase in efficiency noted in Table 15. 

During the testing of the synchronous drive belt, some abnormal fluctuations in power consumption were 

observed, which were discarded. This analysis also ignores the initial spike in electricity consumption as the 

motors are turned on. 

Table 15 – CV Fan Average, Normalized Power Consumption

Belt Type

Fan 

Speed

(RPM)

(RPM1/RPM2)

3 Equivalent Power 

Consumption (W)

Actual Average 

Power 

Consumption (W)

Percent Increase

in Efficiency 

Original V-Belt 1161.5 1 7,107.4 7,107.4 NA

Tensioned V-Belt 1164 0.9935 7153.3 7,153.3 0.001%

Synchronous 

drive belt 1183 0.9464 7509.4 7,368.9 1.871%

Table 15 shows that the installation of the synchronous drive belt led to an increase in fan speed, and an 

increase in power consumption (shown in the actual average power consumption). Without adjustments to the 

fan control, the retrofit will result in increased power consumption and increased volumetric air flow through 

the fan. 

F. Economic Analysis

Two life-cycle cost analyses are presented below. The synchronous drive belt, as installed, actually increases the 

cost of operating the exhaust fan, despite more efficiently transferring power from the motor to the fan. 
Synchronous and Cogged Belt Evaluation Page 25 

Table 16 – CV Fan As Installed Fan Life Cycle Cost Analysis

Cost Loose V-Belt Tensioned VBelt

Synchronous Drive

Belt

Initial Costs $111 $111 $470 

Replacement Costs $111 $111 $165 

O&M Costs $92 $92 $23

Energy Costs $1,707 $1,719 $1,770 

Life Cycle Costs $13,881 $13,964 $14,270

If the fan speed is not increased and all of the efficiency gains created by using the synchronous drive belt are 

used to reduce the energy consumption of the motor, the synchronous drive belt becomes the most cost 

effective option. It is especially important to achieve the desired fan speed for CV fan belt replacements, as 

options for adjusting the fan controls are limited.

Table 17 – CV Fan Equivalent RPM Fan Life Cycle Cost Analysis

Cost Loose V-Belt Tensioned VBelt

Synchronous Drive

Belt

Initial Costs $111 $111 $470

Replacement Cost $111 $111 $165

O&M Costs $92 $92 $23

Energy Costs $1,707 $1,707 $1,676

Life Cycle Costs $13,881 $13,880 $13,556

Similar to the VAV fan, the SPPs are presented below for the synchronous drive belt on the CV fan. In the CV 

case, the repeat installations are not immediate, yet they are still significantly lower than the initial install.

Table 18 - CV Fan Payback Period Analysis

Payback Period (Years)

Belt Type Initial Installation Repeat Installations

Synchronous 

Drive Belt 3.56 0.54

G. Power Factor Analysis

Unlike the VAV fan, the power factor actually increased with the synchronous drive belt installed for the CV fan. 

This is because the load on the motor increased due to the increase in fan speed. 
Synchronous and Cogged Belt Evaluation Page 26

Table 19 – CV Motor Power Factor for the Tested Belts

Belt Type Power Factor

Original V-Belt 0.706

Tensioned V-Belt 0.705

Synchronous Drive Belt 0.716

H. Maximum Power at Start-Up

Like the VAV fan, no definitive conclusions can be drawn from the data on the maximum startup power 

consumption. The graph below shows the power consumption of the fans over the measured period. Note that, 

initially, the synchronous drive belt has very high startup power consumption. The motor was turned off and 

restarted. The second time, the startup power consumption is below that of the V-belt. The brief, 1-second dips 

in power consumption recorded during the synchronous drive belt case were discarded in the analysis, as 

mentioned previously. 

Figure 10 – CV tested belt power consumption vs. time

5,000

7,500

10,000

12,500

15,000

17,500

20,000

22,500

25,000

27,500

30,000

32,500

35,000

1 2 3 4 5 6 7 8 9 10

Real Power (Watts)

Time (seconds)

CV Fan Instantaneous Start Up Power

Loose Belt

Tensioned Belt

Synchronous Belt #1

Synchronous Belt #2
Synchronous and Cogged Belt Evaluation Page 27

VI. Conclusions

A. Overall Technology Assessment at Demonstration Facility

It has been shown in this study that both cogged V-belts and synchronous drive belts can provide a reduction in 

energy consumption over the incumbent V-belt technology. This was demonstrated for the synchronous drive 

belts on both a CV and VAV fan, and for the cogged V-belts on the VAV fan. The savings were greater on the VAV 

fan and were highest at lower fan speeds. For the cogged V-belts on the VAV fan, they realized percent savings 

ranging from 1.2% (at 60 Hz) to 9.3% (at 15 Hz). The synchronous drive belts on the VAV realized percent savings 

from 2.3% (at 60 Hz) to 20.1% (at 15 Hz). For the CV fan, the synchronous drive belts showed potential savings of 

1.9% (once the data was normalized for fan speed variation). 

It should be noted that the synchronous drive belts as installed on the CV fan actually consumed more energy 

than the existing belts due to the fan running at a higher RPM. This is an issue that will need to be addressed 

with all new synchronous drive belt installs. A qualified installer will be required to size the pulley/belt 

combinations so that the current fan speed is maintained. With the VAV system, the sizing issue is somewhat 

less crucial due to the fact that the system is self-correcting if the control logic is working properly; a higher fan 

speed will deliver more air to the space, yet the control sensor should command the fan to turn down more 

quickly due to the higher fan speed, resulting in savings. It should be noted that the fan still needs to provide a 

similar amount of air at full capacity due to the fact that the fan was originally sized for a certain maximum air 

flow rate.

The synchronous drive belts showed lower LCC than both the cogged V-belts and the baseline (standard V-belts) 

on the VAV fan. They also showed the lowest LCC on the CV fan when using potential energy savings. The lower 

LCCs were due to a combination of reduced energy consumption and lower operation and maintenance costs. 

For this analysis, the belts were all assumed to have equivalent lifetimes. It the manufacturer claims for longer 

lifespans are accurate, this would only improve the synchronous drive belt economics. 

It is recommended that GSA pursue implementation of synchronous drive belts on VAV systems. While the 

cogged V-belts were tested on the VAV fan only, the fact that they showed savings at all fixed speeds indicates 

that they would perform well on CV fans. GSA should target cogged V-belts for CV systems where GSA should 

replace standard V-belts with cogged V-belts when the standard belts are due for replacement. 

The first fans that should be addressed are fans with high operating hours (leading to more energy savings). VAV 

fans show greater opportunity for savings (at a variety of loads) and they also have less risk associated with the 

replacement due to the self-correcting nature of the VFD system (avoiding the potential increased speed issue).

The VAV fans also generally undergo fewer high-torque starts, which can damage the synchronous drive belts. 

B. Best Practice 

It has been shown that the switch-over to synchronous drive belts is a cost-effective way to address fan energy 

use in the GSA building portfolio. The synchronous drive belts demonstrated energy savings in all cases that 

were tested, and should be considered as a technology that can reduce electricity usage across GSA’s portfolio.

The three most significant variables that need to be considered and addressed when evaluating a new belt 

installation are:

• Fan runtime (operating hours and speed)

• Type of fan (VAV versus CV)

• Fan/Motor dimensions, and measured operating speeds for accurate sizing. 

The fan runtime will directly impact the amount of energy and money saved. Fans that serve a more constant 

load will result in quicker paybacks and more electricity saved. The fan speed also should be considered. This 
Synchronous and Cogged Belt Evaluation Page 28

report showed greater percent savings at lower fan speeds, yet this may not result in greater absolute savings 

due to smaller total power consumption at the lower speeds. Due to larger total savings with fans that operate 

at higher fan speed, fans that operate at higher fan speeds should be pursued first.

The type of fan also should be considered. The VAV fan demonstrated a greater opportunity for savings in this 

study and should be selected before a CV fan, given the opportunity. It also is important to consider the controls 

that are dictating the operation of a VAV fan. Fully continuous controls that maintain the fan at a certain set 

point (such as a static pressure sensor in ductwork) are ideal for this technology and will ensure that all potential 

savings are obtained. Control systems such as the one monitored in this study (a single setting under a certain 

threshold and another setting until that threshold has been re-achieved) are not as ideal due to the fact that any 

changes in fan RPM will not be automatically adjusted for. This is a secondary effect (and only an issue if sizing 

leads to higher fan speeds), but one worth considering.

The cogged V-belt replacement should target CV fans where the standard V-belt was installed on sheave 

diameters that are at or below the minimum recommended sheave diameter for that specific belt. This will lead 

to more efficiency gains, as reductions in the bending resistance will be greater on small diameter sheaves.

The final variable affects both installation and operation of the technology. It is critical to ensure that an 

experienced installer takes the appropriate measurements (both diameters/lengths and RPM of the fan and 

motor) and accurately sizes the pulley/belt combination. If the pulleys and drives are not sized such that the 

motor mount can be adjusted to receive the new belt, significant labor hours may be required and parts may 

need to be reordered. Assuming the install is successful, it is still critical to have selected the pulley/belt 

combination that matches the measured RPM of the previous system. This will ensure that the new belt does 

not drive the fan at higher RPM, consuming more rather than less energy. This applies most directly to the CV 

fan, yet can impact VAV fan performance as well.

Finally, motor bases should be rigid and non-compliant. They should not be spring or flex mounted, as belt 

operating tensions will overcome the springs and allow belt slippage. They also should utilize twin adjustment 

screws for versatility in aligning the motor and applying belt installation tension.

C. Barriers and Enablers to Adoption

There should be no significant barriers preventing the adoption of synchronous drive belt switchover. It is a 

proven technology that is offered by multiple manufacturers. It will be important to source a qualified and 

knowledgeable installer for installations at GSA buildings. This will help ensure correct belt/pulley sizing and 

ensure that the potential savings are captured.

Further observation of the cogged and synchronous drive belts should be undertaken to evaluate their installed 

lifespans. This will have to take place over a number of years to determine if their lifespans are longer than the 

typical V-belt. If the manufacturer’s estimates of longer lifespans for synchronous drive belts are substantiated, 

this would improve the economics outlined in this report and further substantiate widespread deployment of 

the technology. 

It also should be noted that the synchronous drive belts will require larger investment on the initial changeover 

from standard V-belts. This is due to the required pulley changeover. After this initial investment, only belt 

replacement will be necessary. This difference between initial cost and incremental cost was taken into account 

in all of the economic analysis presented in this report.

D. Market Potential within the GSA Portfolio

Synchronous belt driven fans have the potential to be cost effectively deployed across the country. The O&M 

savings and potentially longer lifetime of synchronous drive belts are as important as energy savings when 
Synchronous and Cogged Belt Evaluation Page 29

considering the economics. Due to these considerations, a simple payback does not accurately assess the 

economic benefits of the retrofit. 

To provide an example of the impact of fan operation and varying utility rates on the economic benefits of 

synchronous and cogged V-belts, the performance characteristics of the tested VAV fan were applied to 

different operating scenarios. With less operation, the monetary savings become smaller, and more reliant on 

O&M savings and competitive installation costs. With higher electricity prices, the savings become more and 

more positive and the synchronous drive belt further differentiates itself from the cogged V-belt.

Figure 11 and Figure 12 present the net present value of the belt replacements for the VAV fan. A positive net 

present value indicates positive, inflation-adjusted savings over the baseline V-belt over the 9-year period of 

analysis. The cogged V-belt becomes more cost-effective than the baseline V-Belt at $0.015/kWh, and the 

synchronous drive belt is more cost-effective than the baseline V-belt at $0.024/kWh. At electric rates higher 

than $0.032/kWh, the synchronous drive belt is more cost-effective than the cogged V-belt. For fan runtime, the 

cogged V-belt is more cost-effective than the baseline V-belt if the fan runs at least 4.3 hours/day, and the 

synchronous drive belt is more cost-effective if the fan runs 6.8 hours per day.

Figure 11 - Net present value of belt replacement as a function of electricity rate
Synchronous and Cogged Belt Evaluation Page 30

Figure 12 – Net present value of belt replacement as a function of operating hours

These graphics should help GSA determine which sites and which fans are most appropriate for belt drive 

retrofits. As previously noted, synchronous drive belts have been shown to provide greater savings for VAV fans, 

and CV fans should receive appropriately installed cogged V-belts as the standard V-belts need replacement.

E. Recommendations for Installation, Commissioning, Training, and Change Management

Cogged V-belts are a straightforward technology that essentially replaces the standard V-belt with almost no 

difference in operation, commissioning, or maintenance. These belts should be installed in place of standard Vbelts in situations where the sheave diameters are below the listed minimum for the standard V-belt. This will 

ensure the largest efficiency savings. Maintenance and commissioning are identical to the standard V-belt.

The synchronous drive belts present a slightly more complicated installation. This is due to the fact that the 

motor and fan sheaves need to be replaced by the synchronous pulleys. To facilitate a successful installation, it 

is critical that an experienced installer measure the pre-existing diameters, belt length, and fan/motor shaft 

speeds. This will allow the installer to select the appropriate pulley/belt combination and ensure a successful 

install. The range of mobility in the motor mount also should be considered; due to different belt/pulley sizes, 

the motor may be required to move more or less to accommodate the synchronous belt drive. If synchronous 

drive belts are to be installed on CV fans, a soft start should be investigated for concurrent installation. The soft 

start will reduce the initial torque on the system and reduce the chance for tooth jump and increased wear on 

the synchronous drive belt. 

The synchronous belt drive should actually require less maintenance than the standard V-belt. The synchronous 

drive belt does not stretch due to extended operation; therefore, yearly re-tensioning of belts is not required 

with this technology. Periodic inspection of belt performance and wear is still required. 

The useful lifetime of both the cogged and synchronous drive belts is a difficult metric to define. This is due to 

the individual characteristics of each different motor/fan scenario, the different runtimes associated with 

different fan uses, and multiple other variables. Conversations with a senior engineer at one of the principal belt 

manufacturers did not identify any established trends in either absolute lifetimes or relative lifetimes (between 

different belt types). In general, belts can be expected to last between 1 and 3 years, but this was established 
Synchronous and Cogged Belt Evaluation Page 31

only as a very rough estimate. The specific installation will dictate belt lifetime, and belts should be monitored 

multiple times each year to evaluate appropriate replacement schedules. 

This technology should not present any issues with on-going operation, change management for 

tenants/occupants, or public perception.
Synchronous and Cogged Belt Evaluation Page 32

Appendices

A. Research Details

The regression curve fits for the cogged V-belt and standard V-belt on the VAV fan are presented below.

Figure 13 – Curve Fit for the cogged V-belt for power consumption as a function of fan speed

y = 15.802x3 + 118.37x2 + 313.76x + 313.31

R2 = 0.9999

0

5000

10000

15000

20000

25000

30000

35000

130 173 216 262 303 348 391 434 478 521

Average Power Consumption (Watts)

Fan Speed (RPM)

Baseline V Belt Average Power

Baseline V Belt Average Power

Poly. (Baseline V Belt Average

Power)
Synchronous and Cogged Belt Evaluation Page 33

B. References 

[1] Buildings Energy Data Book. http://buildingsdatabook.eren.doe.gov/TableView.aspx?table=3.1.4 Accessed 7/20/12.

[2] Synchronous Belt Noise Problems. The Gates Corporation. http://www.gates.com/facts/documents/Gf000185.pdf. 

Accessed 26 June 2012. 

[3] Energy Savings from Synchronous drive belts. The Gates 

Corporation. http://www.gates.com/ptPartners/file_display_common.cfm?thispath=Gates%2Fdocuments_module&file=En

ergy%20Savings%20from%20Synchronous%20Belt%20Drives.pdf&location_id=3427. Accessed 26 June 2012.

[4] Energy Tip Sheet #5. Motor Systems. Industrial Technologies Program. Office of Energy Efficiency and Renewable 

Energy. Department of Energy. September 

2005. http://www1.eere.energy.gov/manufacturing/tech_deployment/pdfs/replace_vbelts_motor_systemts5.pdf. 

Accessed 26 June 2012

[5] GSA Portal. http://www.gsa.gov/portal/content/104501 Accessed 7/10/12.

[6] http://www.gatesprograms.com/ptsavings/rollerchain?sid=gnothingtougher. It should be noted that that 

Gates®, Poly Chain®, GT® are registered trademarks of Gates Corporation.

[7] Technology Readiness Levels Presentation http://www1.eere.energy.gov/femp/pdfs/ns/ntwg_032012_livingood.pdf. 

Accessed 6/12/12.

[8] Cost and Energy Savings with Cogged V-belts. http://utilities.fm.virginia.edu/UtilityDocuments/energy/pdf/Vbelt%20case%20study.pdf. Accessed 27 June 2012. 

[9] Phone correspondence with Fluke technical support (1(800) 443-5853). 8/25/12.

[10] Energy Price Indices and Discount Factors for Life-Cycle Cost Analysis – 2011. Annual Supplement to Handbook 135 and 

NBS Publication 709. U.S Department of Commerce. http://www1.eere.energy.gov/femp/pdfs/ashb11.pdf

[11] Krarti, M. Energy Audit of Building Systems. CRC Press LLC, 2000

[12] Product Application Notes: Energy Savings and the Relationship of Power. The Gates Corporation. November, 

2006. http://www.gates.com/ptpartners/file_display_common.cfm?thispath=Gates%2Fdocuments_module&file=Vol%2053

%20No%209%20Energy%20Savings%20and%20power.pdf. Accessed 27 June 2012. 

C. Glossary 

CV – Constant Volume

HVAC – Heating, Ventilation, and Air Conditioning

LCC – Life-cycle Cost, taking into account discount rates and inflation

O&M – Operations and Maintenance

PF – Power Factor, the ratio between real and apparent power

RPM – Revolutions per minute

Sheave – Fan/motor pulley used with standard and cogged V-belts

SPP – Simple payback period defined as initial cost divided by annual savings

VAV – Variable Air Volume

VFD – Variable Frequency Drive
Synchronous and Cogged Belt Evaluation Page 34

 

i

All images in Figure 1 are from Gates® Corporation

ii Buildings Energy Data Book. http://buildingsdatabook.eren.doe.gov/TableView.aspx?table=3.1.4 Accessed 7/20/12.

iii Synchronous Belt Noise Problems. The Gates Corporation. http://www.gates.com/facts/documents/Gf000185.pdf. 

Accessed 26 June 2012. 

iv Energy Savings from Synchronous drive belts. The Gates Corporation. 

http://www.gates.com/ptPartners/file_display_common.cfm?thispath=Gates%2Fdocuments_module&file=Energy%20Savi

ngs%20from%20Synchronous%20Belt%20Drives.pdf&location_id=3427. Accessed 26 June 2012.

v Energy Tip Sheet #5. Motor Systems. Industrial Technologies Program. Office of Energy Efficiency and Renewable Energy. 

Department of Energy. September 2005. 

http://www1.eere.energy.gov/manufacturing/tech_deployment/pdfs/replace_vbelts_motor_systemts5.pdf. Accessed 26 

June 2012

vi GSA Portal. http://www.gsa.gov/portal/content/104501 Accessed 7/10/12.

vii Energy Savings from Synchronous Belts. The Gates Corporation. 

http://www.gates.com/ptPartners/file_display_common.cfm?thispath=Gates%2Fdocuments_module&file=Energy%20Savi

ngs%20from%20Synchronous%20Belt%20Drives.pdf&location_id=3427. Accessed 26 June 2012. 

viii Energy Tip Sheet #5. Motor Systems. Industrial Technologies Program. Office of Energy Efficiency and Renewable Energy. 

Department of Energy. September 2005. 

http://www1.eere.energy.gov/manufacturing/tech_deployment/pdfs/replace_vbelts_motor_systemts5.pdf. Accessed 26 

June 2012.

ix Energy Savings from Synchronous Belts. The Gates Corporation. 

http://www.gates.com/ptPartners/file_display_common.cfm?thispath=Gates%2Fdocuments_module&file=Energy%20Savi

ngs%20from%20Synchronous%20Belt%20Drives.pdf&location_id=3427

x http://www.gatesprograms.com/ptsavings/rollerchain?sid=gnothingtougher. It should be noted that that Gates®, 

Poly Chain®, GT® are registered trademarks of Gates Corporation.

xi All images in Figure 2 are from Gates® Corporation

xii Technology Readiness Levels Presentation http://www1.eere.energy.gov/femp/pdfs/ns/ntwg_032012_livingood.pdf. 

Accessed 6/12/12.

xiii Cost and Energy Savings with Cogged V-belts. http://utilities.fm.virginia.edu/UtilityDocuments/energy/pdf/Vbelt%20case%20study.pdf. Accessed 27 June 2012. 

xiv Phone correspondence with Fluke technical support (1(800) 443-5853). 8/25/12.

xv Energy Price Indices and Discount Factors for Life-Cycle Cost Analysis – 2011. Annual Supplement to Handbook 135 and 

NBS Publication 709. U.S Department of Commerce. http://www1.eere.energy.gov/femp/pdfs/ashb11.pdf

xvi Krarti, M. Energy Audit of Building Systems. CRC Press LLC, 2000

xvii Product Application Notes: Energy Savings and the Relationship of Power. The Gates Corporation. November, 2006. 

http://www.gates.com/ptpartners/file_display_common.cfm?thispath=Gates%2Fdocuments_module&file=Vol%2053%20N

o%209%20Energy%20Savings%20and%20power.pdf. Accessed 27 June 2012.