DIVISION 15 - MECHANICAL
Section 15175 – Variable Frequency Drives
1.00 PART 1 -GENERAL
1.01 DESCRIPTION OF WORK:
A. This section includes variable frequency drives (VFD), disconnects, fuses, communication
capabilities and bypass components required to produce a complete VFD unit, supplied as an
B. The VFD manufacturer shall furnish, field test, adjust and certify all installed VFD for
C. Any exceptions/deviations to this specification shall be indicated in writing and submitted with
1.02 SECTION INCLUDES:
A. Variable Frequency Drive
B. Construction - Disconnect, Fuses, and Enclosure
D. VFD Trim Components
E. Special VFD Controller Features
1.03 RELATED DOCUMENTS:
A. Drawings and general provisions of the Contract, including General and supplementary
Conditions and Division 1 Specification Sections, apply to this Sections.
； Section ***** - Basic Mechanical Materials and Methods
； Section ***** - Motors and Starters
； Section ***** – Mechanical Identification
； Section ***** – Vibration Isolation
； Section ***** – Hydronic Piping and Specialties
； Section ***** - HVAC Pumps
； Section ***** - Package Cooling Tower
； Section ***** – Heat Exchangers
； Section ***** – Packaged Air Handling Units
； Section ***** - Centrifugal Fans
； Section ***** - Fans
； Section ***** – Direct Digital Control Systems
； Section ***** – Testing, Adjusting, and Balancing
； Division 16 - Electrical
1.04 QUALITY ASSURANCE:
A. Manufacturer shall assume "Unit Responsibility" to ensure that all components effectively
interface to properly execute the sequence of operation specified herein. To ensure quality and
minimize infantile failures at the job site, the complete VFD shall be tested by the manufacturer.
The VFD shall operate a dynamometer at full load and speed and shall be cycled during the test. B. All optional features shall be functionally tested at the factory for proper operation. VFD shall
be functionally tested under motor load. During this load test the VFD shall be monitored for
correct phase current, Phase voltages, and motor speed. Correct current limit operation shall be
verified by simulating a motor overload.
C. All units shall be UL and cUL listed and labeled.
D. Scrolling through all parameters shall perform verification of proper factory presets by scrolling
through all parameters to ensure proper microprocessor settings. The computer port should also
verify that the proper factory settings are loaded correctly in the drive.
E. Every power converter shall be tested with an acutal VSD rated motor 100% loaded and
temperature cucled within an environment chamber at 104ºF (40ºC). Documentation shall be
provided to verify successful test.
F. All options shall be functionally tested including operation of a motor in the bypass mode if
supplied. Proper heater coil installation in motor overload, if supplied, shall be verified. G. All equipment or components of this specification section shall meet or exceed the requirements
and quality of the items herein specified, or as denoted on the drawings.
H. The manufacturer shall have a minimum of 10 years experience in the design and construction of
VFD equipment and shall be ISO 9001 certified facility.
I. Equipment provider shall be responsible for providing certified equipment start-up and, when
noted, an in the field certified training session. Start-up shall be for the purpose of determining
proper electrical connections, voltage, amperage readings, and drive logic controller
configuration. A copy of the start-up report shall be made and sent to both the contractor and to
1.05 PRODUCT HANDLING:
A. Protection: Use all means necessary to protect equipment before, during, and after installation. B. Store so condensation will not occur on or in VFDs. Provide temporary heaters as required to
C. Replacement and Repair: All scratched, dented, and otherwise damaged units shall be repaired or
replaced as directed by the Architect / Engineer.
1.06 REGULATORY REQUIREMENTS:
A. ANSI/NFPA 70 National Electrical Code, Chicago Building Code
B. ANSI C84.1 - Voltages Tolerances for North America
C. IEC 255-8 Overload Relays
D. NEMA 250 Enclosures for Electrical Equipment
E. NEMA ICS 2-321 - Electrical Interlocks
F. NEMA ICS7 - Industrial Control and Systems Adjustable Speed Drives
G. NEMA ICS 7.1 - Safety Standards for Construction and Guide for SelectionInstallation and
Operation of Adjustable Speed Drives
H. UL 50 - UL Standard for Safety Enclosures for Electrical Equipment
I. UL 98 - UL Standard for Disconnect Switches
J. UL 507 - UL Standard for Safety Electric Fans
K. UL 508 - UL Standard for Safety Industrial Control Equipment
L. C-UL Conform to Canadian Underwriters Laboratory
M. UL 508C - UL Standard for Safety Power Conversion Equipment
N. UL 991 - UL Standard for Safety Tests for Safety Related Controls employingSolid State
O. OSHA 1910.95 - VSD Drive Controller Acoustical Noise
P. NEMA ICS 3.1 - Safety Standards for Construction and Guide for Selection,Installation and
Operation of Adjustable Speed Drive Systems
Q. NEMA MG-1-1993 - Motors and Generators
R. NEMA MG-1, Part 31 - Motors for Variable Speed Drives
S. IEEE 519-1992 - Recommended Practices for Harmonic Control in ElectricPower Systems
A. Submit each item in this article according to the Conditions of the Contract and Division 1
B. Submit manufacturer’s installation instructions under provisions of General Conditions and
C. Submit manufacturer’s performance data including dimensional drawings, power circuit
diagrams, installation and maintenance manuals, warranty description, VFD's FLA rating,
certification agency file numbers and catalog information.
D. Include shop drawings consisting of elementary power and control wiring diagrams and
enclosure outline drawings. The enclosure drawings shall include front and side views of the
enclosures with overall dimensions and weights shown, conduit entrance locations and
E. The specification lists the minimum VFD performance requirements for this project. Each
supplier shall list any exceptions to the specification. If no departures from the specification are
identified, the supplier shall be bound by the specification.
F. Harmonic filtering. The seller shall, with the aid of the buyer’s electrical power single line
diagram, providing the data required by IEEE-519, perform an analysis to initially demonstrate
the supplied equipment will met the IEEE standards after installation. If, as a result of the
analysis, it is determined that additional filter equipment is required to meet the IEEE
recommendations, then the cost of such equipment shall be included in the bid. A harmonic
analysis shall be submitted with the approval drawings to verify compliance with the latest
version of IEEE-519 voltage and current distortion limits as shown in table 10.2 and 10.3 at the
point of common coupling (PCC). The PCC shall be defined as the consumer–utility interface or
primary side of the main distribution transformer.
1.08 OPERATION AND MAINTENANCE DATA:
A. Submit Operation and Maintenance information under provisions of Division 15 “Mechanical
General Requirements” and the provisions of the General Conditions and Division 1.
B. Operation and Maintenance Data: Include installation instructions, assembly views, wiring
instructions, and replacement parts lists.
C. Under provisions of commissioning documentation; testing of VFD, as well as training of
owner’s operation and maintenance personnel may be required in cooperation with the
1.09 DELIVERY, STORAGE, AND HANDLING:
A. Deliver materials to the site in such a matter as to protect the materials from shipping and
handling damage. Provide materials on factory provided shipping skids and lifting lugs if
required for handling. Materials damaged by the elements should be packaged in such a matter
that they could withstand short-term exposure to the elements during transportation. B. Store materials in clean, dry place and protect from weather and construction traffic. Handle
carefully to avoid damage.
A. The VFD shall be warranted by the manufacturer for a period of 36 months from date of shipment. The warranty shall include parts, labor, travel costs and living expenses incurred by the manufacturer to provide factory authorized on-site service. The warranty shall be provided by the VFD manufacturer under provision of Section 15010.
2.00 PART 2- PRODUCTS
2.00 PART 2- PRODUCTS
A. The specifying engineer reserves the right to specify a primary supplier / lead spec manufacturer on all supplied schedule and specification documents. These primary suppliers have lead their respective industry in research and development and their products have had proven track records in the field. These primary suppliers, in the opinion of this engineering firm, produce a superior product to the alternately listed manufacturers. The contractor may choose to supply equivalent equipment as manufactured by the alternately specified manufacturer. This alternately specified equipment shall be supplied on a deduct alternate basis and based on the approval of the supplied alternate manufacturer’s submittals.
The use of a primary supplier and deduct alternates protects the specifying engineer’s design concept, but allows for a check-and-balance system to protect the post-commissioning owner.
2.01 Variable Frequency Drive
1. Contractor shall furnish and install a variable frequency drive units as indicated on the
drawings. Variable frequency drive units shall be model VLT6000 as manufactured by
Danfoss-Graham under base bid. Equivalent units as manufactured by ABB Industrial
Systems Inc., Toshiba International Corp., and Square D may be submitted as deduct
alternates. VFD shall meet design, types, sizes, and characteristics as scheduled/notes on the
Equipment Schedule drawings.
B Variable Frequency Drive - Construction:
1. Furnish complete variable frequency VFDs as specified herein for the fans and pumps
designated on the drawing schedules to be variable frequency operation. All standard and
optional features shall be included within the VFD enclosure, unless otherwise specified.
VFD shall be housed in a metal NEMA 1 enclosure, or other NEMA type according to the
installation and operating conditions at the job site. The VFD’s UL listing shall allow
mounting in plenum or other air handling compartments. If a NEMA 12 enclosure is
required for the plenum rating, the manufacturer must supply a NEMA 12 rated VFD. 2. The VFD shall convert incoming fixed frequency three-phase AC power into a variable
frequency and voltage for controlling the speed/frequency of three-phase AC motors. The
motor current shall closely approximate a sine wave. Motor voltage shall be varied with
frequency to maintain desired motor magnetization current suitable for centrifugal pump
and fan control and to eliminate the need for motor derating.
3. With the motor’s rated voltage applied to the VFD input, the VFD shall allow the motor to
produce full rated power at rated amps, RMS fundamental volts, and speed/frequency
without using the motor's service factor. VFDs utilizing sine weighted/coded modulation rd(with or without 3 harmonic injection) must provide data verifying that the motors will not
draw more than full load current during full load and full speed/frequency operation. 4. The VFD shall include an input full-wave bridge rectifier and maintain a fundamental power
factor near unity regardless of speed/frequency or load.
5. The VFD and options shall be tested to ANSI/UL Standard 508. The manufacturer shall
assemble the complete VFD, including all specified options, which shall be UL-508
certified for the building and assembly of option panels. Assembly of the option panels by a
third-party panel shop is not acceptable. The appropriate UL stickers shall be applied to both
the VFD and option panel, in the case where these are not contained in one panel. When
these VFDs are to be located in Canada, CSA or C-UL certifications shall apply. Both VFD
and option panel shall be manufactured in ISO 9001 certified facilities. 6. The VFD shall have DC link reactors on both the positive and negative rails of the DC bus
to minimize power line harmonics. VFDs without DC link reactors shall provide a minimum
3% impedance line reactor.
7. Insulated gate bi-polar transistors (IGBTs) shall be employed as the output switching device.
On drives less than 10 HP a slow switching IGBTs shall be employed as the output
switching device. VFDs without slow switching IGBTs shall provide another form of motor
insulation protection such as a motor line reactor.
8. The VFD’s full load amp rating shall meet or exceed NEC Table 430-150. The VFD shall
be able to provide full rated output current continuously, 110% of rated current for 60
seconds and 160% of rated current for up to 0.5 second while starting.
9. The VFD shall be able to provide full torque at any selected frequency from 28 Hz to base
speed to allow driving direct drive fans without derating.
10. An Automatic Energy Optimization (AEO) selection feature shall be provided standard in
the VFD. This feature shall automatically and continually monitor the motor’s speed and
load and adjust the applied voltage to maximize energy savings and provide up to an
additional 3% to 10% energy savings.
11. Input and output power circuit switching shall be able to be accomplished without interlocks
or damage to the VFD. Switching rate may be up to 1 time per minute on the input and
unlimited on the output.
12. An Automatic Motor Adaptation (AMA) test algorithm shall measure motor stator
resistance and reactance to optimize performance and efficiency. It shall not be necessary to
run the motor or de-couple the motor from the load to run the test.
13. Galvanic and/or optical isolation shall be provided between the VFD’s power circuitry and
control circuitry to ensure operator safety and to protect connected electronic control
equipment from damage caused by voltage spikes, current surges, and ground loop currents.
VFDs not including either galvanic or optical isolation on both analog I/O and discrete I/O
shall include additional isolation modules.
14. VFD shall minimize the audible motor noise through the use of Automatic Switching
Frequency Modulation (ASFM). The carrier frequency shall be automatically adjusted to
optimize motor and VFD efficiencies while reducing motor noise.
15. VFD shall provide additional standard features of “Flying Start” which synchronizes the
drive with a motor rotating in either direction, Automatic High Ambient Derate which
reduces the drives carrier frequency and output current when ambient temperatures exceed
normal limits to protect the drive, Auto Ramping which ensures no-trip acceleration and
deceleration, Automatic Restart which allows the drive to self restart after a fault situation
has been cleared, and Sleep Mode which allows the drive to automatically stop the motor
when the demand is at a low level for a programmable period of time and restart when
16. The drive shall be rated for the following environmental operation conditions:
a. Ambient temperature, -10 to 40?C (14 to 104?F).
b. 0 to 95% relative humidity, non-condensing.
c. Elevation to 3,300 feet without derating.
d. AC line voltage variation, -10 to +10% of nominal with full output.
e. No side clearance shall be required for cooling of any units. All power and control
wiring shall be done from the bottom.
f. The VFD shall have temperature controlled cooling fans for quiet operation and
17. The drive shall be provided with the following minimum protective features: 2a. A minimum of Class 20 It electronic motor overload protection for single motor
applications and thermal-mechanical overloads for multiple motor applications shall
b. Protection against input transients, loss of AC line phase, output short circuit, output
ground fault, over-voltage, under-voltage, VFD over-temperature and motor over-
temperature. The VFD shall display all faults in plain English. Codes are not
c. Protect VFD from sustained power or phase loss. The VFD shall provide full rated
output with an input voltage as low as 90% of the nominal. The VFD will continue
to operate with reduced output with an input voltage as low as 164 V AC for 208-
230 volt units, and 313 V AC for 460 volt units.
d. The VFD shall incorporate a motor preheat circuit to keep the motor warm and
prevent condensation build up in the stator.
e. VFD package shall include semi-conductor rated input fuses to protect power
f. To prevent breakdown of the motor winding insulation, the VFD shall be designed to
comply with IEC Part 34-17. Otherwise the VFD manufacturer must ensure that
inverter rated motors are supplied.
g. VFD shall include a “signal loss detection” circuit to sense the loss of an analog
input signal such as 4 to 20 mA or 2 to 10 V DC, and shall be programmable to react
as desired in such an instance.
h. VFD shall catch a rotating motor operating forward or reverse up to full
i. VFD shall be rated for 100,000 amp interrupting capacity (AIC).
j. VFD shall include current sensors on all three output phases to detect and report
phase loss to the motor. The VFD will identify which of the output phases is low or
k. VFD shall continue to operate without faulting until input voltage reaches 300 V AC
on 208/230 volt VFDs, and 539 V AC on 460 volt VFDs.
C. Variable Frequency Drive - Interface:
1. The operator interface terminal will offer the modification of VSD adjustments via a touch keypad. The display shall have four lines, with 20 characters on three lines and eight large characters on one line. All electrical values, configuration parameters, 1/0 assignments, application and activity function access, faults, local control, adjustment storage, self-test and diagnostics will be in plain English. The display will be a high resolution, back lighted screen capable of displaying graphics such as bar graphs as well as alphanumeric characters.
2. Hand/Start, Off/Stop and Auto/Start selector switches shall be provided to start and stop the VFD and determine the speed reference. The VFD shall provide digital manual speed control. Potentiometers are not acceptable.
3. The keypad shall be of a removable design. The keypads for all sizes of VFDs shall be identical and interchangeable. VFD shall function normally when the keypad is removed while the VFD is running and continue to follow remote commands. No warnings or alarms shall be issued as a result of removing the keypad.
4. To set up multiple VFDs, it shall be possible to upload all setup parameters to the VFD’s
keypad, place that keypad on all other VFDs in turn and download the setup parameters to each VFD. To facilitate setting up VFDs of various sizes, it shall be possible to download from the keypad only size independent parameters.
5. The removable and lockable, alphanumeric backlit display keypad shall be able to be
remotely mounted up to 3 meters (9.8 ft.) from the VSD.
6. The VSD model number, torque type, software revision number, horsepower, output current,
motor frequency and motor voltage shall all be listed on the drive identification display as
viewed on the LCD display.
7. The display shall be configured to display numeric data that are selectable and scalable by
the operator. As a minimum the selectable outputs shall consist of speed reference output
frequency, output current, motor torque, output voltage, DC voltage, motor thermal state
and motor speed.
8. Display shall allow viewing and adjustment of four simultaneous variables. 9. The terminal keypad will consist of programmable function keys. The functions will allow
both operating commands and programming options to be preset by the operator. A
hardware selector switch will allow the terminal keypad to be locked out from unauthorized
10. The operator terminal will offer a general menu consisting of parameter setting,1/0 map,
fault history, and drive configuration. A software lock will limit access to the main menu.
The main menu will consist of keypad configuration, drive configuration, general
configuration, diagnostic mode, and drive initialization screens.
11. There will be arrow keys that will provide the ability to scroll through menus and screens,
select or activate functions or edit the value of a selected parameter.
12. A data entry key will allow the user to confirm a selected menu, numeric value or allow
selection between multiple choices.
13. An escape key will allow a parameter to return the existing value if adjustment is not
required and the value is displayed. The escape function will also return to a previous menu
14. A RUN key and a STOP key will command a normal starting and stopping as programmed
when the VSD is in keypad control mode. The STOP key must be active in all control
15. A red FAULT light, a yellow WARNING light and a green POWER-ON light shall be
provided. These indications shall be visible both on the keypad and on the VFD when the
keypad is removed.
16. A quick setup menu with factory preset typical HVAC parameters shall be provided on the
VFD eliminating the need for macros.
D. Variable Frequency Drive - Programming:
1. VFD shall have an adjustable carrier frequency in steps of not less than 0.1 kHz to allow
tuning the VFD to the motor.
2. Programmability for up to sixteen preset speeds shall be provided.
3. Programmability for four acceleration and four deceleration ramps shall be provided. Accel
and Decel time shall be adjustable over the range from 0 to 3,600 seconds to base speed.
The shape of these curves shall be automatically contoured to ensure no-trip acceleration
4. Programmability for four current limit settings shall be provided.
5. Programmability for VFD trips on one of the following conditions, the VFD shall be
programmable for automatic or manual reset: under-voltage, over-voltage, current limit and
6. Programmability for the number of restart attempts shall be selectable from 0 through 20 or
infinitely and the time between attempts shall be adjustable from 0 through 600 seconds. 7. Programmability for an automatic “on delay” may be selected from 0 to 120 seconds.
8. Programmability for the VFD shall be able to be programmed to provide a 24 V DC output
signal to indicate that the VFD is in Auto/Remote mode.
E. Variable Frequency Drive - Communication:
1. The drive shall be provided with the following minimum standard Interface Features to
simplify its use, programming, and monitoring capabilities. The VFD shall include a
standard RS-485 communications port and capabilities to be connected at a future date to a
Johnson Controls N2 Metasys or Siemens FLN system at no additional cost to the owner.
The connection shall be software selectable by the user.
2. In systems where RS-485 communication is required, but a Johnson Controls N2 Metasys or
Siemens FLN system is not applicable the drive shall be capable of being provided with one
of the following additional communication protocols: (SELECT ONE if applicable)
a. LonWorks communication shall be available for factory or field installation within
b. Modbus communication shall be available for factory or field installation within the
c. Profibus communication shall be available for factory or field installation within the
3. As a minimum, the following points shall be controlled and/or accessible:
a. VFD Start/Stop
b. Speed reference
c. Fault diagnostics
d. Meter points
- Motor power in HP
- Motor power in kW
- Motor kW-hr
- Motor current
- Motor voltage
- Hours run
- Feedback signal #1
- Feedback signal #2
- DC link voltage
- Thermal load on motor
- Thermal load on VFD
- Heatsink temperature
3. Four additional Form C 230 volt programmable relays shall be available for factory or field
installation within the VFD.
4. Two set-point control interface (PID control) shall be standard in the unit. VFD shall be able
to look at two feedback signals, compare with two set-points and make various process
5. Floating point control interface shall be provided to increase/decrease speed in response to
6. Four simultaneous displays shall be available. They shall include frequency or speed, run
time, output amps and output power. VFDs unable to show these four displays
simultaneously shall provide panel meters.
7. Sleep mode shall be provided to automatically stop the VFD when its speed/frequency drops
below set “sleep” level for a specified time. The VFD shall automatically restart when the
speed command exceeds the set “wake” level.
8. The sleep mode shall be functional in both follower mode and PID mode.
9. Run permissive circuit shall be provided to accept a “system ready” signal to ensure that the
VFD does not start until dampers or other auxiliary equipment is in the proper state for VFD
operation. The run permissive circuit shall also be capable of sending an output signal as a
start command to actuate external equipment before allowing the VFD to start. 10. The following displays shall be accessible from the control panel in actual units: Reference
Signal Value in actual units, Output Frequency in Hz or percent, Output Amps, Motor HP,
Motor kW, kWh, Output Voltage, DC Bus Voltage, VFD Temperature in degrees, and
Motor Speed in engineering units per application (in GPM, CFM, etc.). VFD will read out
the selected engineering unit either in a linear, square or cubed relationship to output
frequency as appropriate to the unit chosen.
11. The display shall be programmed to read in inches of water column (in-wg) for an air
handler application, pressure per square inch (psi) for a pump application, and temperature o(F) for a cooling tower application.
12. VFD shall be able to be programmed to sense the loss of load and signal a no load/broken
belt warning or fault.
13. If the temperature of the VFD’s heat sink rises to 80;C, the VFD shall automatically reduce
its carrier frequency to reduce the heat sink temperature. If the temperature of the heat sink
continues to rise the VFD shall automatically reduce its output frequency to the motor. As
the VFD’s heat sink temperature returns to normal, the VFD shall automatically increase the
output frequency to the motor and return the carrier frequency to it’s normal switching
14. The VFD shall store in memory the last 10 faults and related operational data. 15. Eight programmable digital inputs shall be provided for interfacing with the systems control
and safety interlock circuitry.
16. Two programmable relay outputs, one Form C 240 V AC, one Form A 30 V AC, shall be
provided for remote indication of VFD status.
17. Three programmable analog inputs shall be provided and shall accept a direct-or-reverse
acting signal. Analog reference inputs accepted shall include two voltage (0 to 10 V DC, 2
to 10 V DC) and one current (0 to 20 mA, 4 to 20 mA) input.
18. Two programmable 0 to 20 mA analog outputs shall be provided for indication of VFD
status. These outputs shall be programmable for output speed, frequency, current, and power.
They shall also be programmable to provide a selected 24 V DC status indication. 19. Under fire mode conditions, the VFD shall be able to be programmed to automatically
default to a preset speed.
2.02 Construction – Disconnect, Fuses, and Enclosure
1. Contractor shall furnish and install the variable frequency drive with the appropriate
construction devices including disconnect, fuses, and enclosure as indicated on the drawings.
The drive manufacturer shall furnish the variable frequency drive construction. VFD trim
components shall meet design, types, sizes, and characteristics as scheduled/notes on the
Equipment Schedule drawings.
B. Construction – Disconnect, Fuses, and Enclosure:
1. Enclosure: Where noted on schedules or details a drive package shall be provided with
additional enclosure cabinets to hold additional drive system components. All optional
features shall be included within the metal NEMA 1 enclosure, or other NEMA type
according to the installation and operating conditions at the job site. The enclosure shall be
- Disconnect Enclosure
- Bypass Enclosure
- Special Enclosure
- Special NEMA Rated Enclosure
2. Integral Disconnect: Where noted on schedules or details a drive package shall be provided
with a lockable integral door disconnect handle. The disconnect shall be provided as a
- Drive Disconnect
- Drive and Main Disconnects
3. Pilot Lights and Selector Switches: These devices shall be provided on drive packages and shall be NEMA ICS 2, heavy duty type.
4. Fuses: On all drive applications the appropriate fuses shall be provided in a drive package. At a minimum fast acting drive fuses shall be provided to protect the semi-conductors in the drive. A fast acting drive fuse shall be provided upstream of the drive in a disconnect enclosure. In systems that apply bypass the bypass panel shall be provided with all necessary fuses. The bypass panel shall include a fast acting drive fuses, a main fuse, and a bypass fuse. The main fuse shall be installed upstream of the drive and shall be dual element time-delay type and shall protect the bypass circuitry but not the drive. The bypass fuse shall be installed upstream of the motor and shall be dual element time-delay type and shall be quick reacting to protect the motor from short circuiting during across the line operation.
5. Reactors and Filters: Where standard filtering features of the drive are determined to not be adequate enough to meet a particular projects needs, additional factory mounted filters and protective devices shall be provided. The appropriate type and number of devices shall be determined on a job by job basis and shall be provided in the appropriate size and type of enclosure directly mounted and wired to the main drive enclosure.
1. Contractor shall furnish and install the variable frequency drive with the appropriate type of bypass including connections, type, enclosure, and components as indicated on the drawings. The drive manufacturer shall furnish the variable frequency drive construction. VFD trim components shall meet design, types, sizes, and characteristics as scheduled/notes on the Equipment Schedule drawings.
1. Where noted on drawings or schedules the drives shall be provided with either manual or automatic style bypass. The bypass shall be added to systems where power disruption to a specific device is not acceptable. Specifically systems where standby equipment is not provided or where loss of device output is unacceptable. (SELECT ONE)
a. Manual Bypass: Provide a manual 3-contactor bypass consisting of a door
interlocked main fused disconnect pad-lockable in the off position, a door
interlocked drive fused disconnect pad-lockable in the off position, a built-in
motor starter and a four position DRIVE/OFF/BYPASS/TEST switch
controlling three contactors. In the DRIVE position, the motor is operated at
an adjustable frequency from the VFD. In the OFF position, the motor and
VFD are disconnected. In the BYPASS position, the motor is operated at full
speed/frequency from the AC power line and power is disconnected from the
VFD so that service can be performed. In the TEST position, the motor is
operated at full speed/frequency from the AC line power while power is
applied to the input of the VFD. This allows the VFD to be given an
operational test while continuing to run the motor at full speed/frequency in
bypass. In case of an external safety fault, a customer supplied normally
closed dry contact shall be able to stop the motor whether in DRIVE or
b. Automatic Bypass: Provide an automatic 3-contactor bypass consisting of a
door interlocked main fused disconnect pad-lockable in the off position, a
door interlocked drive fused disconnect pad-lockable in the off position, a
built-in motor starter and a four position DRIVE/OFF/BYPASS/TEST switch
controlling three contactors. Additionally, an internal electrical switching