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SynC · Editorial revision

HVAC Variable Frequency Drives

Revision5
EditedAug 26, 2026
StatusCurrent
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Current revision. This is editorial revision 5, the current text of this standard. Read it on the standard's page.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs

1 Scope

NOTE This standard covers low voltage pulse width modulated variable frequency drives procured as separate assemblies and field-connected to HVAC fan and pump motors. (1.1)
NOTE The following are outside this standard and are governed elsewhere. (1.2)
  • Drives rated above 600 V, which are medium voltage equipment with a different safety standard, enclosure practice, and switching topology
  • Drives built into factory-packaged HVAC equipment, where the packager owns the drive selection, its integration, and its warranty
  • Drive sections assembled into a motor control center lineup, covered by Motor Control CentersMotor Control CentersResolves to the current adopted revision.sync/motor-control-centers
  • Sequences of operation, setpoints, and control logic resident in the building automation system, covered by Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system
  • The driven fans, pumps, and cooling towers themselves, and their motors, covered by the standards for that equipment
1.3 Drives shall comply with UL 61800-5-1.
1.4 Drives shall be listed and labeled by a Nationally Recognized Testing Laboratory.
NOTE UL 61800-5-1 replaced UL 508C as the North American safety standard for adjustable speed power drive systems, and drive listings issued under UL 508C ceased to be accepted for new product on 1 February 2020. Its component fault-current testing is what establishes the drive's assigned short circuit current rating. (1.5)
NOTE Centrifugal fans and pumps follow the affinity laws — flow varies with speed, developed pressure with the square of speed, and shaft power with the cube of speed — so a unit running at 80% speed draws roughly half of full-speed power and at 50% speed roughly one eighth. That cubic relationship is the entire economic case for speed control on HVAC equipment. (1.6)
NOTE ASHRAE 90.1 limits chilled water pump power at 50% of design flow to 30% of design power for pump motors larger than 5 hp, and imposes comparable part-load power limits on variable air volume fan systems. On most commercial projects speed control is how the mechanical design meets the adopted energy standard rather than an enhancement above it. (1.7)

2 Referenced Standards

2.1 Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
UL 61800-5-1 Adjustable Speed Electrical Power Drive Systems — Safety Requirements, Electrical, Thermal and Energy
UL 508A Industrial Control Panels
NFPA 70 National Electrical Code (Articles 409, 250, and 430)
NFPA 70E Standard for Electrical Safety in the Workplace
NEMA ICS 7 Adjustable Speed Drives
NEMA ICS 61800-2 Adjustable Speed Electrical Power Drive Systems — General Requirements for Low Voltage Adjustable Frequency AC Power Drive Systems
NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum)
NEMA MG 1 Motors and Generators (Parts 30 and 31)
IEEE 519 Harmonic Control in Electric Power Systems
IEC 61800-3 Adjustable Speed Electrical Power Drive Systems — EMC Requirements and Specific Test Methods
IEC 61800-9-2 Adjustable Speed Electrical Power Drive Systems — Energy Efficiency Indicators for Power Drive Systems and Motor Starters
ASHRAE 90.1 Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings
ASHRAE 135 BACnet — A Data Communication Protocol for Building Automation and Control Networks
ASCE 7 Minimum Design Loads and Associated Criteria for Buildings and Other Structures
ICC-ES AC156 Seismic Certification by Shake-Table Testing of Nonstructural Components
ANSI/NETA ATS Acceptance Testing Specifications for Electrical Power Equipment and Systems

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for Engineer of Record review before any drive is released for manufacture:
  • Product data giving continuous output current, overload capability, input current, efficiency, dimensions, shipping and operating weight, and heat dissipation at rated load
  • Enclosure data giving the enclosure type, material, finish, cooling arrangement, and the manufacturer's required service clearances
  • Power wiring diagrams showing input, output, bypass, and disconnecting means with terminal designations
  • Control and communication wiring diagrams showing every analog input, digital input, relay output, analog output, and network connection with terminal designations
  • Point list mapping each drive parameter and status to its building automation system object or register, with the network addressing scheme
  • Harmonic analysis report covering the cumulative effect of all nonlinear load on the project
  • Motor compatibility verification comparing each connected motor nameplate against the drive rating and the installed cable length
  • Derating calculations for ambient temperature and altitude where either exceeds the drive's standard rating
  • Bypass contactor sizing and overload device settings where a bypass is provided
  • Seismic certification documentation where seismic certification is required
  • Product data for every accessory, including reactors, filters, and space heaters
Required Action Submittalscheckbox
☑ Product data with ratings, dimensions, weight, and heat dissipation
☑ Enclosure data with type, material, cooling, and service clearances
☑ Power wiring diagrams with terminal designations
☑ Control and communication wiring diagrams
☑ Building automation point list and network addressing scheme
☐ Harmonic analysis report
☑ Motor compatibility verification
☐ Ambient temperature and altitude derating calculations
☐ Bypass contactor sizing and overload settings
☐ Seismic certification documentation
☑ Accessory product data for reactors, filters, and heaters
3.1.2 The harmonic analysis report shall be prepared by the drive manufacturer or by a licensed power systems engineer.
3.1.3 The harmonic analysis report shall evaluate the aggregate of all nonlinear load on the project, and a report analyzing drives individually shall not be accepted in its place.
3.1.4 The harmonic analysis report shall demonstrate compliance with the total demand distortion limit selected in this standard at the point of common coupling, using the available short-circuit current at that point.
3.1.5 The Contractor shall reconcile the harmonic analysis report with the Engineer of Record responsible for the power distribution system before submitting it.

3.2 Closeout Submittals

3.2.1 The Contractor shall submit the following before the date of substantial completion:
  • Operation and maintenance manuals including the complete parameter reference and programming instructions
  • As-built power, control, and communication wiring diagrams reflecting every field modification
  • Factory production test reports and field acceptance test reports
  • Final programmed parameter settings for each drive, printed and as the manufacturer's electronic configuration file
  • Building automation integration report confirming that every monitored point reports correctly and every commanded point responds correctly
  • Warranty documentation listing each drive by tag, serial number, energization date, and warranty expiration date
  • Spare parts inventory listing manufacturer part numbers and reorder information
Required Closeout Submittalscheckbox
☑ Operation and maintenance manuals with parameter reference
☑ As-built power, control, and communication wiring diagrams
☑ Factory production and field acceptance test reports
☑ Final parameter settings, printed and as an electronic configuration file
☑ Building automation integration report
☑ Warranty documentation by tag and serial number
☑ Spare parts inventory with part numbers

4 Quality Assurance

4.1 Manufacturer Qualifications

4.1.1 Drives shall be produced by a manufacturer with not less than ten years of documented production experience with pulse width modulated drives in commercial HVAC service.
4.1.2 The manufacturer shall maintain a quality management system certified to ISO 9001.
4.1.3 The manufacturer shall maintain factory-trained startup technicians able to reach the project site within one business day of a scheduled request.
4.1.4 The manufacturer shall provide telephone technical support during normal business hours for the duration of the warranty period.
4.1.5 The manufacturer shall commit in writing to supplying replacement parts and firmware support for the drive platform for not less than ten years from the date of manufacture.

4.2 Manufacturer Source Limitation

4.2.1 The source limitation applying to the drives on this project shall be as indicated in the datasheet.
Manufacturer Source Limitationradio
● Single manufacturer for all drives on the project
○ Single manufacturer for each mechanical system
○ No source limitation
NOTE Drives from a single manufacturer share one parameter structure, one keypad convention, one configuration file format, and one set of network objects, so maintenance staff learn one platform and spare drives interchange across systems. Where a project mixes platforms, each additional platform carries its own training, its own spare inventory, and its own integration effort at the building automation system. (4.2.2)

4.3 Startup and Commissioning Personnel

4.3.1 Initial energization, motor auto-tune, and parameter programming shall be performed by a technician trained and authorized by the drive manufacturer.
4.3.2 The Contractor shall submit evidence of current manufacturer authorization for each technician before that technician begins startup work.
4.3.3 Personnel performing network integration and point verification shall be qualified in the selected communication protocol and in the project's building automation platform per Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system.

5 Service Conditions

5.1 Maximum Ambient Temperature

5.1.1 Drives shall deliver their rated continuous output current at the maximum ambient temperature indicated in the datasheet.
Maximum Ambient Operating Temperaturerange
°C
40455055
5.1.2 Where the maximum ambient temperature exceeds the drive's standard rating, the Contractor shall apply the manufacturer's published temperature derating factors and shall select a drive whose derated continuous output current is not less than the connected motor full load current.
5.1.3 Derating calculations shall be submitted with the product data.
NOTE A standard drive rating is established at 40 °C, above which the heat sink and cooling fans can no longer hold semiconductor junction temperature inside its safe limit at full output current. Published derating curves generally give up 5% to 10% of continuous output current for each 5 °C above the standard rating. (5.1.4)

5.2 Installation Altitude

5.2.1 The maximum installation altitude shall be as indicated in the datasheet.
Maximum Installation Altituderange
ft
33005000660080001000013000
Per drawings — the site elevation given on the civil drawings (deferred by default)
5.2.2 Where the installation altitude exceeds 3,300 ft, the Contractor shall apply the manufacturer's published altitude derating factors.
5.2.3 Altitude derating and ambient temperature derating shall be applied cumulatively where both conditions are present.
NOTE Thinner air at elevation carries less heat away from the heat sink per unit volume and also reduces the dielectric strength of the air gaps inside the drive. Published altitude derating is commonly about 1% of continuous output current for each 330 ft above 3,300 ft, and it is independent of the temperature derating rather than an alternative to it. (5.2.4)

5.3 Humidity and Condensation

5.3.1 Drives shall operate over a relative humidity range of 5% to 95%, non-condensing.
5.3.2 The condensation control provided in the drive enclosure shall be as indicated in the datasheet.
Enclosure Condensation Controlradio
● None
○ Thermostatically controlled enclosure space heater
5.3.3 Where an enclosure space heater is indicated, it shall be supplied from a control circuit that remains energized while the drive is de-energized.
5.3.4 Where an enclosure space heater is indicated, its circuit shall be identified at the drive and at its source so that it is not de-energized during drive maintenance.
NOTE A drive enclosure in an unconditioned space — a penthouse, a rooftop, a parking structure, an attic plenum — cools with the surrounding air overnight and can drop below the dew point of the air trapped inside it. Condensation forming on energized power electronics is a recurring field failure, and it is the reason enclosure heating is tied to the space rather than to the drive's own duty cycle. (5.3.5)

5.4 Seismic Certification

5.4.1 The seismic certification required for the drive assembly shall be as indicated in the datasheet.
Seismic Certificationselect
Not required
Shake-table certification per ICC-ES AC156 with component importance factor 1.0
Shake-table certification per ICC-ES AC156 with component importance factor 1.5
Certification by analysis per ASCE 7
Per drawings — the seismic design criteria in the structural general notes (deferred by default)
5.4.2 Where seismic certification is required, it shall cover the complete assembly as installed, including any integral bypass, reactor, filter, and disconnecting means.
5.4.3 Certification of individual components tested in isolation shall not be accepted in place of certification of the assembly.

6 Drive Ratings

6.1 Input Voltage and Frequency

6.1.1 The nominal input voltage shall be as indicated in the datasheet.
Nominal Input Voltagerange
V
208230240460480575600
Per drawings — the electrical one-line diagram (deferred by default)
6.1.2 Drives shall be supplied from a three-phase source.
System Frequencyradio
● 60 Hz
○ 50 Hz
6.1.3 Drives shall carry input voltage variation within the tolerance indicated in the datasheet without tripping, de-energizing, or requiring operator intervention.
Minimum Input Voltage Tolerancerange
%
1015
6.1.4 Phase-to-phase voltage imbalance at the drive input terminals shall not exceed 3% of nominal.
6.1.5 Where measured imbalance at the drive input terminals exceeds 2% of nominal, the Contractor shall report it to the Engineer of Record and shall not energize the drive until the source is corrected or the Engineer of Record accepts the condition in writing.
NOTE A diode front end draws current only while its input line is at the crest of the waveform, so a small voltage imbalance produces a much larger current imbalance across the three rectifier legs. The resulting uneven heating shortens rectifier and DC bus capacitor life well before it produces a nuisance trip. (6.1.6)

6.2 Horsepower and Duty Rating

6.2.1 The horsepower of the connected motor shall be as indicated in the datasheet.
Connected Motor Horsepowerrange
hp
11.52357.5101520253040506075100125150200250300350400450500
Per drawings — the mechanical equipment schedules (deferred by default)
6.2.2 The drive duty rating shall be as indicated in the datasheet.
Drive Duty Ratingradio
● Variable torque
○ Constant torque
6.2.3 A drive with a variable torque duty rating shall deliver 110% of its rated continuous output current for 60 seconds.
6.2.4 A drive with a constant torque duty rating shall deliver 150% of its rated continuous output current for 60 seconds.
6.2.5 The drive's continuous output current at the selected duty rating shall be not less than the connected motor nameplate full load current, after any temperature and altitude derating.
6.2.6 The drive frame sizing policy shall be as indicated in the datasheet.
Drive Frame Sizingradio
● Drive rated for the connected motor horsepower
○ Drive rated one frame size above the connected motor horsepower
NOTE Centrifugal fans and pumps develop their torque demand along the cube of speed, so they present no starting torque requirement and the 110% variable torque overload covers acceleration and transient load. Positive displacement pumps, some cooling tower gear drives, and fans that must accelerate against an already-flowing duct system are the HVAC loads that draw on the constant torque rating instead. (6.2.7)
NOTE Selecting the next frame size up buys additional current headroom and lower semiconductor junction temperature at the same load. That headroom is what absorbs continuous operation above 90% of rated current, an ambient at the top of the drive's derating curve, an exceptionally long motor cable, or a high-altitude site. (6.2.8)

6.3 Drive Efficiency

6.3.1 The minimum drive efficiency class shall be as indicated in the datasheet.
Minimum Efficiency Class per IEC 61800-9-2select
IE1
IE2
6.3.2 The manufacturer shall report drive losses at 100% speed and 100% torque, and at the part-load operating points defined by IEC 61800-9-2, in the product data.
6.3.3 Drive losses at the design operating point shall be included in the mechanical room cooling load calculation.
NOTE A drive is between 96% and 98% efficient, which sounds negligible until it is converted to heat in a closed room — a 100 hp drive at 97% rejects roughly 2.3 kW into the space around it. Mechanical rooms sized without that load run hot in summer, and heat sink overtemperature trips follow. (6.3.4)

6.4 Short Circuit Current Rating

6.4.1 The drive assembly, including any integral bypass, disconnecting means, and protective device, shall be marked with a short circuit current rating per NFPA 70 Article 409.110.
6.4.2 The marked short circuit current rating shall be not less than the value indicated in the datasheet.
Minimum Short Circuit Current Ratingrange
kAIC
51014182230354265100
Per drawings — the available fault current stated on the electrical one-line diagram (deferred by default)
6.4.3 The available fault current at the drive line terminals shall be established by a short-circuit study and confirmed by the Engineer of Record.
6.4.4 Where current-limiting fuses are used to establish the marked rating, the fuse class and ampere rating shall be confirmed with the drive manufacturer and shown on the submittal.
6.4.5 The fuse class and ampere rating shown on the submittal shall be the fuses installed, and substitution of another fuse class in the field shall not be permitted.
NOTE A drive that has not been evaluated with a specific upstream protective device carries a low default short circuit current rating, commonly 5 kAIC. Available fault current at a mechanical room distribution panel frequently runs from 22 kAIC to 65 kAIC, so the marked rating is raised by listing the drive with a named current-limiting fuse — typically Class J or Class RK1. Installing a different fuse class breaks the listing that established the rating. (6.4.6)

7 Enclosure and Cooling

7.1 Enclosure Type

7.1.1 The enclosure type shall be as indicated in the datasheet.
Enclosure Type per NEMA 250select
NEMA 1 indoor general purpose
NEMA 12 indoor dust-tight and drip-tight
NEMA 3R outdoor rainproof
NEMA 4 watertight
NEMA 4X watertight and corrosion-resistant
7.1.2 Drives installed outdoors or in an unroofed location shall be furnished in an enclosure rated NEMA 3R or better.
7.1.3 Drives installed where airborne fine dust, lint, metal particulate, or fibrous debris is present shall be furnished in an enclosure rated NEMA 12 or better.
7.1.4 Drives installed in a cooling tower enclosure, a wash-down area, or a coastal exterior location shall be furnished in an enclosure rated NEMA 4X.
NOTE Enclosure ratings above NEMA 1 close the enclosure to the room air the drive was using to cool itself, so the higher rating and the cooling arrangement are one coupled selection rather than two independent ones. A sealed enclosure rejects heat through its surface or through a sealed heat exchanger, which is why a NEMA 4X drive of a given horsepower is physically larger than the NEMA 1 version. (7.1.5)
NOTE Dust that settles on a heat sink insulates it. A layer thin enough to look harmless measurably raises junction temperature, and heat sink fouling behind a clogged intake is a leading cause of overtemperature shutdown in mechanical rooms that share air with a loading dock or a shop. (7.1.6)

7.2 Enclosure Material

7.2.1 The enclosure material shall be as indicated in the datasheet.
Enclosure Materialselect
Powder-coated steel
Type 304 stainless steel
Type 316 stainless steel
Fiberglass reinforced polyester
Manufacturer's standard (by default)
7.2.2 Enclosures in coastal exterior locations, cooling tower enclosures, and chemical treatment rooms shall be Type 316 stainless steel or fiberglass reinforced polyester.
7.2.3 Where the manufacturer's standard material is furnished, the material and finish system shall be stated in the product data submittal.

7.3 Cooling Arrangement

7.3.1 The cooling arrangement shall be as indicated in the datasheet.
Cooling Arrangementselect
Integral forced-air cooling
Integral forced-air cooling with filtered intake
Through-the-wall heat sink
Liquid-cooled heat exchanger
7.3.2 Where a filtered intake is furnished, the filter media shall be replaceable without de-energizing the drive.
7.3.3 Where a filtered intake is furnished, the drive shall include a filter condition indicator that reports to the building automation system.
7.3.4 Cooling fans shall be field-replaceable without removing the drive from its mounting.
NOTE A through-the-wall arrangement puts the heat sink on the far side of the enclosure wall, so the drive's losses land in an adjacent space instead of the room the drive sits in. Where several large drives are concentrated in one mechanical or electrical room, that relocation is what keeps the room cooling load from being set by the drives themselves. (7.3.5)
NOTE A filter that is never changed becomes a sealed panel. Without a condition indicator reporting somewhere a person looks, filter fouling is discovered by the overtemperature trip it causes. (7.3.6)

7.4 Mounting Arrangement

7.4.1 The mounting arrangement shall be as indicated in the datasheet.
Mounting Arrangementselect
Wall-mounted
Free-standing floor-mounted
Multiple drives in a common floor-standing enclosure
Per drawings — the mechanical and electrical equipment installation details (deferred by default)
7.4.2 Wall-mounted drives shall be installed with the bottom of the enclosure not less than 18 in. above the finished floor.
7.4.3 The Contractor shall verify that the supporting wall or structure will carry the operating weight of the drive, and shall provide structural backing where it will not.
7.4.4 Floor-mounted drives shall be set on a housekeeping pad or structural base.
7.4.5 The manufacturer's published service clearances shall be maintained above, below, and to each side of the enclosure.
7.4.6 Drives shall not be mounted directly above heat-producing equipment.
7.4.7 Drives shall not be mounted where the cooling air intake can draw in the drive's own discharge air.
7.4.8 Drives shall not be mounted where the enclosure or its required working space blocks maintenance access to other equipment.

8 Harmonic Performance

8.1 Harmonic Analysis

8.1.1 Whether a project-wide harmonic analysis is required shall be as indicated in the datasheet.
Project Harmonic Analysisradio
● Required at the point of common coupling
○ Not required
8.1.2 Where a harmonic analysis is required, it shall include every nonlinear load on the project, including drives, uninterruptible power supplies, electronic lighting drivers, and battery chargers.
8.1.3 Where a harmonic analysis is required, mitigation equipment shall not be released for manufacture until the Engineer of Record has accepted the analysis.
8.1.4 The total demand distortion limit applying at the point of common coupling shall be as indicated in the datasheet.
Total Demand Distortion Limit at the Point of Common Couplingrange
%
58121520
NOTE IEEE 519 sets the current distortion limit at the point of common coupling as a function of the ratio of available short-circuit current to maximum demand load current at that point. A weak point of common coupling, with that ratio below 20, carries a 5% total demand distortion limit; most commercial buildings land in the range from 20 to 50, where the limit is 8%. The limit is a property of the point of common coupling, not of any one drive, which is why an analysis of drives one at a time cannot demonstrate compliance. (8.1.5)

8.2 Rectifier Topology

8.2.1 The rectifier topology shall be as indicated in the datasheet.
Rectifier Topologyselect
6-pulse diode rectifier
12-pulse diode rectifier
18-pulse diode rectifier
Active front end
8.2.2 Where an active front end is indicated, the drive shall regulate input displacement power factor to not less than 0.98 across its operating range.
8.2.3 Where an active front end with regenerative capability is indicated, the drive shall return braking energy to the source rather than dissipating it in a braking resistor.
NOTE A 6-pulse diode front end draws characteristic harmonic current at the 5th, 7th, 11th, and 13th orders. Left unmitigated, the 5th order alone commonly runs from 20% to 40% of fundamental current, and total input current distortion from 80% to 100%. That current flows back into the building distribution and distorts the voltage waveform other equipment on the same transformer has to live with. (8.2.4)
NOTE Multi-pulse topologies cancel harmonic orders by phase-shifting parallel rectifier bridges — 30° apart for 12-pulse, 20° apart for 18-pulse — which brings total input current distortion to roughly 10% to 12% and 5% to 8% respectively. The phase-shifting autotransformer that produces the shift is bulky and heavy, and it corrects neither power factor nor regeneration. (8.2.5)
NOTE An active front end replaces the diode bridge with a controlled IGBT stage that synthesizes near-sinusoidal input current, holding total input current distortion below 5% and producing near-unity displacement power factor. It costs roughly 30% to 50% more than a 6-pulse drive and it switches on the line side, so it introduces high-frequency emission that a 6-pulse drive does not. (8.2.6)

8.3 Input Line Impedance

8.3.1 The input line impedance provided for each drive shall be as indicated in the datasheet.
Input Line Impedanceselect
3% impedance AC line reactor
5% impedance AC line reactor
Integral DC bus choke
None
8.3.2 Every 6-pulse drive shall be provided with an AC line reactor or an integral DC bus choke.
8.3.3 Where an AC line reactor is furnished as a separate component, it shall be listed for use with the drive and shall be mounted within the drive enclosure or immediately adjacent to it.
NOTE Adding series impedance ahead of a diode bridge widens the rectifier conduction angle. A 3% reactor typically pulls total input current distortion from 80% to 100% down to 35% to 40%, and it also limits the rate of rise of fault current reaching the rectifier and clips line-side transients before they get to it. (8.3.4)
NOTE Moving from 3% to 5% impedance buys a further, smaller reduction in distortion and costs roughly 2% additional voltage drop at full load, which reduces the voltage available to the motor at the top of its speed range. A DC bus choke sits after the rectifier and delivers comparable harmonic reduction, and on mid-range and larger drives it is frequently built in, in which case a separate AC line reactor adds impedance without adding much benefit. (8.3.5)

8.4 Supplemental Harmonic Filtering

8.4.1 Supplemental harmonic filtering shall be as indicated in the datasheet.
Supplemental Harmonic Filteringselect
None
Tuned passive filter at the drive
Broadband passive filter at the drive
Active harmonic filter at the drive
Active harmonic filter at the distribution panel serving multiple drives
8.4.2 Where the accepted harmonic analysis shows that the selected rectifier topology and line impedance do not meet the total demand distortion limit, supplemental filtering shall be provided.
8.4.3 The filter manufacturer shall confirm compatibility with the source impedance at the installed location before the filter is released for manufacture.
8.4.4 Passive filters shall be furnished with a means of disconnecting the filter capacitors from the source.
NOTE A tuned passive filter is a series inductor with a shunt capacitor branch resonant near one harmonic order, so a 5th and 7th trap does very little at the 11th and 13th. It also forms a resonant circuit with the source, and on a high-impedance source a filter tuned without regard to that interaction can amplify a harmonic order rather than attenuate it. (8.4.5)
NOTE An active filter injects a compensating current derived from the measured distortion, so it is not tied to particular harmonic orders and it can serve several drives from one distribution panel. Where drives are added to an existing panel over time, that shared placement is what avoids repeating filter cost at each drive. (8.4.6)

9 Bypass and Disconnecting Means

9.1 Bypass Arrangement

9.1.1 The bypass arrangement shall be as indicated in the datasheet.
Bypass Arrangementselect
No bypass
Two-contactor bypass
Three-contactor bypass with drive input isolation
9.1.2 Where a bypass is provided, mechanical and electrical interlocks shall prevent the drive output contactor and the bypass contactor from being closed at the same time.
9.1.3 The interlock arrangement shall fail such that a control failure or a wiring error prevents the bypass source from reaching the drive output terminals.
9.1.4 Where a three-contactor bypass is provided, the drive shall be capable of being isolated and serviced while the motor runs in bypass.
NOTE A bypass lets the motor run across the line at full speed while the drive is faulted or out for service. What it does not do is preserve any of the reason the drive was installed — in bypass the motor runs at one speed, starts across the line at 6 to 8 times full load current, and saves nothing. It also adds cost, enclosure volume, and a second set of motor protection to maintain. (9.1.5)
NOTE Where the driven equipment has a redundant unit and the building automation system can shift load to it, a drive failure is a maintenance event rather than a loss of service, and the case for a bypass is weaker. Where the unit is the only path serving its space or process, or where the Owner needs to run during drive service without shutting the system down, the bypass is what provides that. (9.1.6)

9.2 Bypass Transfer Control

9.2.1 The bypass transfer initiation method shall be as indicated in the datasheet.
Bypass Transfer Initiationselect
Not applicable
Manual transfer by operator selector switch
Automatic transfer on drive fault with manual return
Automatic transfer on drive fault with automatic return
9.2.2 Where automatic transfer is indicated, transfer to bypass shall complete within one second of the drive fault being detected.
9.2.3 Where automatic transfer is indicated, the drive assembly shall report the fault condition and the bypass status to the building automation system as separate points.
9.2.4 Unless automatic return is indicated in the datasheet, return from bypass to drive operation shall require a manual reset at the drive.
NOTE An automatic return that is not reset by a person will cycle a motor between bypass and drive operation for as long as an intermittent fault persists, and each transfer is another across-the-line start. A manual reset stops that cycle and forces someone to look at the fault, at the cost of the equipment staying in bypass until they do. (9.2.5)

9.3 Bypass Motor Overload Protection

9.3.1 Where a bypass is provided, an independent motor overload device shall be furnished in the bypass circuit.
9.3.2 The bypass motor overload device shall be as indicated in the datasheet.
Bypass Motor Overload Deviceselect
Not applicable
Electronic overload relay
Bimetallic thermal overload relay
Melting alloy thermal overload relay
9.3.3 The bypass motor overload device shall be sized and set for the motor nameplate full load current for across-the-line operation.
NOTE The drive's own electronic motor overload protection is in the drive's output path, so it does nothing once the motor is fed from the bypass contactor. The bypass circuit needs its own device, set for across-the-line full load current rather than for the reduced current the motor draws at part speed. (9.3.4)
NOTE An electronic overload relay carries an adjustable trip class, phase-loss detection, and an alarm contact that operates independently of the bypass contactor. A bimetallic or melting-alloy relay gives thermal protection with the trip characteristic fixed by the heater element and no alarm output. Where the project needs phase-loss detection or a bypass overload alarm at the building automation system, the electronic relay supplies it without adding a separate device. (9.3.5)

9.4 Input Disconnecting Means

9.4.1 An input disconnecting means capable of being locked in the open position shall be provided for each drive per NFPA 70 Article 430.102.
9.4.2 The input disconnecting means shall be as indicated in the datasheet.
Input Disconnecting Meansselect
Door-interlocked disconnect switch integral to the drive enclosure
Fusible disconnect switch ahead of the drive
Molded case circuit breaker ahead of the drive
Branch-circuit overcurrent device at the distribution panel
9.4.3 The input disconnecting means shall be rated for the drive input current and for the available fault current at its point of installation.
9.4.4 Where the disconnecting means is not integral to the drive enclosure, it shall be within sight of the drive per NFPA 70 Article 430.102, or a means of locking the upstream device open shall be provided at the drive.
9.4.5 Circuit conductors supplying the drive shall have an ampacity of not less than 125% of the drive rated input current per NFPA 70 Article 430.122.
9.4.6 Branch-circuit short-circuit and ground-fault protection shall be provided per NFPA 70 Article 430.130.
NOTE The DC bus capacitors hold a hazardous charge after the input is opened, so the discharge time marked on the drive governs when the enclosure can be entered regardless of which disconnecting means was used. A door interlock removes the input source as the door opens, but it does not shorten that discharge interval. (9.4.7)

10 Speed Control and Ramps

10.1 Operating Speed Limits

10.1.1 The minimum operating speed shall be as indicated in the datasheet.
Minimum Operating Speedrange
%
10152025304050
10.1.2 The maximum operating speed shall be as indicated in the datasheet.
Maximum Operating Speedrange
%
100105110115120
10.1.3 Where the maximum operating speed exceeds 100% of motor base speed, the Contractor shall obtain written confirmation from the motor manufacturer that the bearings and rotor balance are suitable at the elevated speed.
10.1.4 Where the maximum operating speed exceeds 100% of motor base speed, the Contractor shall obtain written confirmation from the driven equipment manufacturer that the impeller or fan wheel is rated at the elevated speed.
NOTE A totally enclosed fan-cooled motor cools itself with a shaft-mounted fan, so its cooling airflow falls with the cube of speed while its winding losses do not. At sustained low speed under load, that is what overheats a standard motor, and it is the reason a software minimum speed limit exists rather than letting the loop drive the motor to zero. (10.1.5)
NOTE Applications that genuinely need sustained operation at low speed and meaningful torque are served by an inverter-duty motor with a separately powered blower, which decouples cooling from shaft speed and removes the need for the minimum speed limit. (10.1.6)
NOTE Above base frequency the drive is in the field-weakening region and available motor torque falls in proportion to speed, while a centrifugal load's demand is still climbing with the cube of speed. The two curves cross quickly, so the usable overspeed range on a fan or pump is narrow and exists mainly for balancing. (10.1.7)

10.2 Skip Frequency Bands

10.2.1 The skip frequency band capability shall be as indicated in the datasheet.
Skip Frequency Bandsselect
Not required
One programmable skip band
Three programmable skip bands
10.2.2 Each skip band shall have an adjustable center frequency and an adjustable bandwidth.
10.2.3 Resonant speeds identified during startup shall be recorded and the corresponding skip bands programmed before the drive is placed in service.
NOTE A skip band tells the drive to pass through a speed rather than hold at it, which keeps a fan, a pump, or its supporting structure out of a mechanical resonance. Resonant speeds are a property of the installed assembly, not of the equipment as shipped, so they are found by sweeping the speed range at startup and watching vibration. (10.2.4)

10.3 Acceleration and Deceleration

10.3.1 The drive shall provide independently adjustable acceleration and deceleration ramp times.
10.3.2 The acceleration time shall be as indicated in the datasheet.
Acceleration Time from Zero to Full Speedrange
seconds
510152030456090120180240300
10.3.3 The deceleration time shall be as indicated in the datasheet.
Deceleration Time from Full Speed to Stoprange
seconds
510152030456090120180240300
10.3.4 Ramp times shall be set during commissioning for the installed load and shall not be left at the factory setting.
10.3.5 The ramp profile shall be as indicated in the datasheet.
Ramp Profileradio
● Linear ramp
○ S-curve ramp
NOTE A ramp time is a property of the connected load rather than of the drive. A large-volume supply fan accelerated over 30 to 60 seconds spreads belt and drive-train shock and holds down demand contribution; a pump decelerated too quickly on a long distribution loop generates a pressure transient several times design pressure, which is what splits joints and damages control valves. (10.3.6)
NOTE An S-curve profile rounds the transitions at the start and end of the ramp, removing the torque step a linear ramp applies at those two points. Where the coupling, belt drive, or piping restraint is the limiting element rather than the ramp duration itself, that rounding is what the S-curve buys. (10.3.7)

10.4 Sleep and Wake Function

10.4.1 The sleep and wake function shall be as indicated in the datasheet.
Sleep and Wake Functionradio
● Enabled
○ Disabled
10.4.2 Where the sleep function is enabled, the wake threshold and the sleep delay shall be adjustable.
10.4.3 Where the sleep function is enabled, the drive shall restart automatically when the speed reference exceeds the wake threshold.
10.4.4 Where the sleep function is enabled, its thresholds shall be reconciled with the building automation sequence of operations so that signal noise near the threshold does not produce repeated starts.
NOTE At the bottom of its speed range a fan or pump delivers almost no useful flow while still turning, so the sleep function stops the output entirely rather than holding minimum speed through unoccupied hours. The trade is that every wake is a restart, which is why the delay and the threshold matter more than the feature itself. (10.4.5)

11 Operator Interface and Control Wiring

11.1 Local Operator Interface

11.1.1 Each drive shall include a local operator interface that provides operating data and parameter access without connection to an external device.
11.1.2 The local operator interface shall be as indicated in the datasheet.
Local Operator Interfaceradio
● Integral alphanumeric display of not less than two lines by sixteen characters
○ Integral graphical display
○ Remote-mounted display at an accessible location
11.1.3 The local operator interface shall display drive status, output frequency, motor current, motor speed, input line voltage, DC bus voltage, heat sink temperature, and the active fault code with its description.
11.1.4 The local operator interface shall display the stored fault history and every parameter value without an external tool.
11.1.5 The drive shall retain not fewer than ten fault records, each with the fault code, the date and time, and the output frequency, motor current, DC bus voltage, heat sink temperature, and accumulated run hours at the moment of the fault.
NOTE The operating snapshot stored with a fault is what separates a failed cooling fan from a fouled filter from a room ventilation deficiency, after the fact and without reproducing the condition. A bare fault code records that the drive stopped and nothing about why. (11.1.6)

11.2 Hand-Off-Auto Control

11.2.1 The Hand-Off-Auto control method shall be as indicated in the datasheet.
Hand-Off-Auto Controlselect
Door-mounted three-position selector switch
Keypad mode selection
Mode selection commanded over the building automation network
11.2.2 Where a door-mounted selector switch is indicated, its Off position shall accept a padlock so the drive can be secured off without operating the upstream disconnecting means.
11.2.3 The drive shall report its current mode to the building automation system.
NOTE In the Hand position the drive follows a speed set at the keypad, in Auto it follows the external speed reference, and in Off it stops regardless of any external command. A door-mounted switch puts all three within reach without opening an energized enclosure, which is why the physical switch survives on equipment that is otherwise fully networked. (11.2.4)

11.3 Parameter Access Security

11.3.1 The parameter access security level shall be as indicated in the datasheet.
Parameter Access Securityselect
Multi-level password protection
Single-level password protection
No password protection
11.3.2 Where password protection is indicated, maximum speed, minimum speed, ramp times, and PID setpoints shall be protected against modification without the password.
11.3.3 Where password protection is indicated, the passwords in effect at substantial completion shall be delivered to the Owner with the closeout submittals.
NOTE Speed limits and ramp times are the parameters most often changed in the field to make a complaint go away, and a changed minimum speed or maximum speed silently rewrites the energy performance the system was designed for. Password levels separate the operator's daily access from the settings that carry design intent. (11.3.4)

11.4 Speed Reference and Control Wiring Terminals

11.4.1 The speed reference signal shall be as indicated in the datasheet.
Speed Reference Signalselect
4–20 mA current loop
0–20 mA current loop
0–10 VDC
2–10 VDC
Speed commanded over the building automation network
11.4.2 Each drive shall provide not fewer than two analog inputs, four programmable digital inputs, two Form C relay outputs, and one analog output.
11.4.3 The additional control input and output capability provided at each drive shall be as indicated in the datasheet.
Additional Control Inputs and Outputscheckbox
☐ Third analog input for an external sensor
☐ Second analog output
☐ Third Form C relay output
☐ Fourth Form C relay output for bypass status
☐ Safe torque off input
☐ External fault input from a fire alarm or smoke detection interface
11.4.4 The fault alarm relay output shall be wired to the building automation system in a normally energized, de-energize-on-fault arrangement.
11.4.5 Relay contacts shall be rated not less than 240 VAC at 2 A resistive.
11.4.6 The motor winding temperature input provided at each drive shall be as indicated in the datasheet.
Motor Winding Temperature Inputselect
Not provided
PTC thermistor input
PT100 RTD input
11.4.7 Where a motor winding temperature input is provided, the sensor leads shall terminate at the drive's temperature input rather than at a separate relay.
NOTE A 4–20 mA loop carries a live zero, so an open conductor or a failed transmitter reads 0 mA and the drive registers a loss-of-signal fault. A 0–10 VDC reference has no live zero, so an open conductor and a genuine zero-speed command produce the same reading. Where the sequence of operations depends on detecting a failed speed reference, the current loop supplies that detection without added logic. (11.4.8)
NOTE A normally energized fault relay de-energizes both on a drive fault and on loss of control power, so a drive that has died quietly still raises an alarm. A normally de-energized relay cannot report the second case, and a fan that stopped without telling anyone is discovered by the space it serves. (11.4.9)
NOTE An embedded thermistor or RTD measures winding temperature directly, where the drive's electronic overload infers it from output current and an assumed thermal model. The direct measurement is what catches a high-ambient motor, a blocked motor cooling path, or sustained low-speed operation that the current-based model reads as normal. (11.4.10)

12 Building Automation System Integration

12.1 Communication Protocol

12.1.1 The building automation communication protocol shall be as indicated in the datasheet.
Building Automation Communication Protocolselect
BACnet MS/TP
BACnet IP
Modbus RTU
Modbus TCP
EtherNet/IP
LonWorks FTT-10A
No network communication
12.1.2 Where a BACnet interface is furnished, it shall be listed by BACnet Testing Laboratories as a BACnet Application Specific Controller or higher.
12.1.3 The protocol selection shall match the protocol specified for the project's building automation system per Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system.
12.1.4 Network cable shall be shielded and shall be routed separately from power conductors per Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit.
12.1.5 The network cable shield shall be grounded at one end only.
NOTE Grounding a communication shield at both ends puts the shield in parallel with the building grounding system, and any potential difference between the two ends drives current along the shield. On a drive network that current is the switching noise the shield was installed to keep out. (12.1.6)

12.2 Monitored and Commanded Points

12.2.1 The drive shall make the following points available to the building automation system as read-only values: run status, output frequency, commanded speed reference, motor current, motor output power, DC bus voltage, heat sink temperature, fault status with the active fault code, accumulated run hours, accumulated energy, and input line voltage.
12.2.2 The drive shall accept the following points from the building automation system as commands: start and stop, speed reference, and fault reset.
12.2.3 Where network mode selection is indicated in the datasheet, the drive shall also accept Hand-Off-Auto mode selection as a command.
12.2.4 Additional monitored points shall be as indicated in the datasheet.
Additional Monitored Pointscheckbox
☐ Output voltage per phase
☐ Input current per phase
☐ Displacement power factor
☐ Calculated motor torque as a percent of rated
☑ Stored fault history with time stamps
☑ Cooling fan runtime and service alert
☐ DC bus capacitor service alert
☐ Filter condition indicator
☑ Drive operating mode
☐ Bypass status
☐ Enclosure space heater status

12.3 Loss of Communication Response

12.3.1 The drive response to loss of network communication shall be as indicated in the datasheet.
Loss of Communication Responseselect
Maintain the last commanded speed
Run at a programmed fixed speed
Ramp to minimum speed
Stop the drive
Transfer to internal PID control
12.3.2 The communication loss timeout shall be adjustable and shall be set during commissioning.
12.3.3 The drive shall report loss of network communication as an alarm on the local operator interface and on the fault relay output.
12.3.4 The drive response to loss of communication shall be reconciled with the building automation sequence of operations so that the drive and the controller do not act on the same failure in conflicting ways.
NOTE A network failure, a controller reboot, and a controller isolated for maintenance are indistinguishable to the drive, and they are all common. What differs is the consequence of each response: holding the last speed keeps the space conditioned while the loop stops correcting, stopping the drive removes the load entirely, and falling back to a local PID keeps the controlled variable on setpoint provided a local sensor exists. (12.3.5)

12.4 Internal PID Control

12.4.1 Each drive shall include an integral proportional-integral-derivative controller capable of maintaining a process setpoint from a sensor connected directly to the drive.
12.4.2 Whether the internal PID controller is used shall be as indicated in the datasheet.
Internal PID Controlradio
○ Not used
○ Drive maintains the process setpoint from a local sensor
12.4.3 The process variable input for the internal PID controller shall be as indicated in the datasheet.
Internal PID Process Variableselect
Not applicable
Duct static pressure transmitter
Hydronic differential pressure transmitter
Temperature transmitter
Flow transmitter
12.4.4 Where the internal PID controller is used, its setpoint shall be readable and writable from the building automation system.

13 Motor and Cable Compatibility

13.1 Motor Insulation System

13.1.1 The insulation system of the connected motor shall be as indicated in the datasheet.
Connected Motor Insulation Systemselect
NEMA MG 1 Part 31 inverter-duty
NEMA MG 1 Part 30 general purpose
Existing motor with an unverified insulation system
13.1.2 Motors procured new for connection to a drive under this standard shall comply with NEMA MG 1 Part 31.
13.1.3 Where a drive is connected to an existing motor, the Contractor shall record the motor nameplate data and shall report the insulation system to the Engineer of Record before the drive is energized.
13.1.4 Where the connected motor does not comply with NEMA MG 1 Part 31, an output filter shall be provided.
NOTE An IGBT output stage switches between zero and the DC bus voltage in about a tenth of a microsecond, which applies a voltage step across the first few turns of the winding that a sinusoidal supply never produces. NEMA MG 1 Part 31 answers that with an insulation system rated for 1,600 V peak at a 0.1 µs rise time on motors rated 600 V and below. Part 30 general purpose motors are rated 1,000 V peak at a 2 µs rise time, and motors built before roughly 2000 frequently meet neither. (13.1.5)

13.2 Motor Cable Length and Type

13.2.1 The motor cable length shall be as indicated in the datasheet.
Motor Cable Lengthrange
ft
2550751001502003005007501000
Per drawings — the routing shown on the mechanical and electrical floor plans (deferred by default)
13.2.2 The Contractor shall compare the installed motor cable length against the drive manufacturer's published unfiltered cable length limit for the selected model, carrier frequency, and motor insulation system before the drive is released for manufacture.
13.2.3 Where the installed cable length exceeds that published limit, an output filter shall be provided.
13.2.4 Where a single drive feeds more than one motor, each motor cable run shall be evaluated separately against the published limit, and the filter shall be sized for the aggregate connected load.
13.2.5 Conductors between the drive and the motor shall have an ampacity of not less than 125% of the motor full load current per NFPA 70 Article 430.122.
13.2.6 The motor cable type shall be as indicated in the datasheet.
Motor Cable Typeselect
Building wire in metallic conduit
VFD-rated shielded cable in metallic conduit
VFD-rated shielded tray cable
NOTE The motor cable and the motor terminal winding present different surge impedances, so each switching edge partially reflects at the motor and adds to the incoming step. Published measurements on 480 V systems put the resulting terminal peak in the range of 1,400 V to 1,600 V beyond about 100 ft and 1,800 V to 2,000 V beyond about 300 ft, arriving thousands of times per second. Published cable limits are general figures for 480 V drives at 4 kHz to 8 kHz, and a specific drive and motor pairing can fall outside them in either direction. (13.2.7)
NOTE VFD-rated cable has a symmetrical ground conductor arrangement and a continuous shield, which gives common-mode current a low-impedance path back to the drive frame instead of through the motor bearings and the building steel. That return path is what reduces bearing current and keeps switching noise out of adjacent control and communication conductors. (13.2.8)

13.3 Output Filters

13.3.1 The output filter provided between the drive and the motor shall be as indicated in the datasheet.
Motor Output Filterselect
None
Output reactor
dV/dt filter
Sine wave filter
13.3.2 Output filters shall be listed for use with the drive and shall be selected for the drive carrier frequency and the installed cable length.
13.3.3 Output filters shall be installed within the drive enclosure or immediately adjacent to it, on the drive side of the motor cable run.
NOTE A dV/dt filter slows the rate of voltage rise and clips the terminal peak to roughly 1,100 V to 1,200 V on a 480 V system. It costs on the order of 5% to 10% of the drive and gives up very little efficiency, and it leaves the waveform recognizably a PWM waveform. (13.3.4)
NOTE A sine wave filter reconstructs a near-sinusoidal voltage at the motor, which removes the voltage-step stress entirely, quiets the motor, and lets a standard motor run on a drive. It costs on the order of 15% to 25% of the drive and gives up 1% to 2% efficiency, and its size and weight are what usually decide against it. Long cable runs, retrofit motors of unverified insulation, and acoustically sensitive fan rooms are where those costs buy the most. (13.3.5)

13.4 PWM Carrier Frequency

13.4.1 The PWM carrier frequency shall be as indicated in the datasheet.
PWM Carrier Frequencyrange
kHz
22.5458101216
13.4.2 Where the selected carrier frequency requires the drive to be derated, the derated continuous output current shall be not less than the connected motor full load current.
13.4.3 The carrier frequency programmed at substantial completion shall be recorded in the as-built parameter settings.
NOTE Carrier frequency is a three-way trade. Raising it smooths motor current and moves the audible switching tone toward and past the top of human hearing; it also raises IGBT switching losses, which forces a drive derating that grows with frame size and ambient; and it increases the common-mode current that drives bearing currents and cable-coupled noise. Where a large drive sits in a hot room, a high carrier frequency can cost more current headroom than the noise reduction is worth. (13.4.4)

13.5 Motor Bearing Current Mitigation

13.5.1 The motor bearing current mitigation shall be as indicated in the datasheet.
Motor Bearing Current Mitigationselect
None
Insulated non-drive-end bearing
Shaft grounding ring
Insulated non-drive-end bearing with a shaft grounding ring
13.5.2 Bearing current mitigation shall not be omitted on motors rated 50 hp and larger.
13.5.3 Where a shaft grounding ring is provided, it shall be accessible for inspection and replacement without removing the motor from its base.
NOTE An insulated non-drive-end bearing interrupts the circulating path through the motor; a shaft grounding ring gives the shaft a low-impedance path to the frame so the charge never reaches the bearing. They address different halves of the mechanism, which is why large motors in continuous service are frequently given both. (13.5.5)

14 Protective Functions

14.1 Motor and Output Protection

14.1.1 The drive shall provide electronic motor overload protection listed to UL 61800-5-1, with a selectable trip class, thermal memory retained through a power cycle, and compensation for reduced motor cooling at low speed.
14.1.2 The drive shall detect an open output phase and shall shut down before the remaining phases carry destructive current.
14.1.3 The drive shall detect a ground fault on the motor winding or the output cable and shall shut down.
14.1.4 The drive shall limit output current electronically and shall be protected by semiconductor fusing coordinated by the manufacturer.
14.1.5 The drive shall reduce output frequency and torque to prevent a motor stall on a sudden load increase, and shall shut down only where current remains outside safe limits after that reduction.
NOTE Speed compensation in the overload model is what makes electronic overload protection usable on a variable torque load. A shaft-mounted cooling fan moves far less air at 30% speed than at full speed, so the same motor current that is harmless at 60 Hz can overheat the winding at 18 Hz, and an overload curve that ignores speed will not catch it. (14.1.6)

14.2 Input and DC Bus Protection

14.2.1 The drive shall detect loss of an input phase and shall shut down.
14.2.2 The drive shall not operate a three-phase input stage on single-phase power.
14.2.3 The drive shall shut down on DC bus overvoltage and shall extend the deceleration ramp automatically to avoid an overvoltage trip during a normal stop.
14.2.4 The drive shall shut down on sustained DC bus undervoltage.
14.2.5 The drive shall monitor heat sink temperature, shall alarm before shutdown, and shall report the alarm to the building automation system.
NOTE Losing one input phase does not stop a diode front end, it just forces the remaining two legs and the DC bus capacitors to carry the whole load with far more ripple. The drive keeps running and the damage accumulates, which is why phase-loss detection is a protective function rather than a diagnostic. (14.2.6)

14.3 Power Loss Ride-Through and Restart

14.3.1 The power loss ride-through capability shall be as indicated in the datasheet.
Power Loss Ride-Throughselect
Standard DC bus ride-through
Kinetic energy backup from load inertia
Extended ride-through capacitor module
14.3.2 The automatic restart behavior after a power interruption shall be as indicated in the datasheet.
Automatic Restart After Power Interruptionradio
● Enabled with flying restart
○ Disabled with manual restart required
14.3.3 Where automatic restart is enabled, the drive shall determine the residual speed and direction of the rotating motor and shall resume at that speed.
14.3.4 Where automatic restart is enabled, the restart delay, the number of restart attempts, and the attempt window shall be adjustable.
14.3.5 Where automatic restart is enabled, the drive shall lock out and require a manual reset after the configured number of attempts is exhausted.
14.3.6 Where automatic restart is enabled, its timing shall be reconciled with the building automation sequence of operations so that the drive and the controller do not command conflicting restarts.
NOTE Standard ride-through is set by the energy stored in the DC bus capacitors and lasts roughly 100 ms to 150 ms, which covers most utility reclosing events. Kinetic energy backup instead regenerates from the inertia of the spinning fan or pump to hold the bus up, extending ride-through to several seconds on high-inertia loads. (14.3.7)
NOTE Reapplying power to a still-spinning motor without matching its residual speed and phase produces an inrush and a torque step comparable to an across-the-line start. A flying restart measures the residual rotation first, which is what makes automatic restart safe for the belts, couplings, and the drive itself. (14.3.8)

15 Electromagnetic Compatibility

15.1 The EMC emission category shall be as indicated in the datasheet.
EMC Emission Category per IEC 61800-3select
IEC 61800-3 Category C1
IEC 61800-3 Category C2
IEC 61800-3 Category C3
No integral EMC filter
15.1.1 Drives serving residential, mixed-occupancy, patient care, or diagnostic imaging areas, or sharing a distribution transformer with them, shall be furnished to Category C1.
15.1.2 The Contractor shall verify that the system grounding at the drive location complies with Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding before relying on an integral EMC filter.
15.1.3 Where the drive is supplied from an ungrounded or impedance-grounded system, the Contractor shall confirm with the manufacturer whether the integral EMC filter is to be disconnected.
NOTE IEC 61800-3 sorts emission limits by the environment the drive is installed in rather than by the drive itself. Category C1 corresponds to the first environment, which includes residential buildings and anything sharing a low-voltage supply with them; Category C2 and Category C3 cover the second environment, with C3 assuming an industrial supply and a knowledgeable installer. (15.1.4)
NOTE An integral EMC filter works by giving high-frequency current a capacitive path to ground. On an ungrounded or impedance-grounded system that path does not exist as the filter assumes, so the attenuation is not delivered and the filter capacitors instead carry leakage current that can trip ground-fault protection or elevate enclosure potential. (15.1.5)

16 Testing

16.1 Factory Production Testing

16.1.1 The manufacturer shall perform production tests on each drive before shipment.
16.1.2 The factory test regime shall be as indicated in the datasheet.
Factory Test Regimeradio
● Certified production test report
○ Witnessed factory acceptance test
16.1.3 Production testing shall include a dielectric withstand test on all power circuits per UL 61800-5-1, an insulation resistance measurement on the input and output power circuits, a functional operation test through acceleration to full speed and controlled deceleration to stop, verification of the overload protection, verification of the input phase loss, output phase loss, DC bus overvoltage, DC bus undervoltage, and heat sink overtemperature functions, a communication interface functional test, and a visual and dimensional inspection.
16.1.4 Where a witnessed factory acceptance test is indicated, the Contractor shall give the Engineer of Record not less than two weeks notice of the test date.
16.1.5 Where a witnessed factory acceptance test is indicated, the Owner shall bear the cost of its own and the Engineer of Record's travel and attendance, and the Contractor shall bear the cost of the test itself and of any retest following a failure.
16.1.6 The manufacturer shall retain production test records for not less than five years and shall furnish them to the Owner on request.
NOTE Witnessing a factory test buys verification of programmed function and of a bypass automation sequence before the equipment ships, at the cost of travel and a schedule hold. Where the assembly is large, where the bypass logic is project-specific, or where a post-delivery failure would be difficult to correct on site, that verification is what the witness is for. (16.1.7)

16.2 Field Startup and Acceptance Testing

16.2.1 The field testing scope shall be as indicated in the datasheet.
Field Testing Scopeselect
Manufacturer startup with building automation integration verification
Manufacturer startup with independent acceptance testing per ANSI/NETA ATS
Manufacturer startup only
16.2.2 Before energizing any drive, the Contractor shall verify that input voltage at the drive terminals matches the drive nameplate and that all three phases are within 3% of nominal and within 3% of each other.
16.2.3 Before energizing any drive, the Contractor shall verify that the motor nameplate data matches the drive parameter settings.
16.2.4 Before energizing any drive, the Contractor shall remove all shipping restraints and packing material from inside the enclosure.
16.2.5 Before energizing any drive, the Contractor shall verify that all field wiring terminations are torqued to the manufacturer's published values.
16.2.6 Motor cables shall be insulation-resistance tested from the drive output terminals to the motor with the drive output conductors disconnected from the drive, and shall not be tested through the drive.
16.2.7 Functional testing shall verify every digital input and relay output, the analog speed reference across its full range, every network monitored point and every network commanded point, the Hand-Off-Auto selector in all three positions, the sleep and wake thresholds where enabled, and bypass operation where a bypass is provided.
16.2.8 Where a bypass is provided, functional testing shall verify manual transfer, the bypass motor overload setting, automatic transfer on fault where indicated, and that the interlocks prevent simultaneous energization.
16.2.9 Performance testing shall run each drive at minimum speed, at 50% speed, and at full speed, and shall verify stable operation, correct rotation, and smooth acceleration and deceleration at each point.
16.2.10 Performance testing shall verify that motor current at full speed does not exceed the motor nameplate full load current.
16.2.11 Performance testing shall identify any speed producing excessive vibration, and the corresponding skip bands shall be programmed before the drive is accepted.
16.2.12 The manufacturer's factory-trained technician shall perform initial energization, the motor auto-tune procedure, and parameter programming to the project sequence of operations.
16.2.13 The controls contractor shall attend startup at the same time as the manufacturer's technician so that point mapping is verified and corrected in one visit.
16.2.14 All field test results shall be recorded and included in the closeout submittals.
16.2.15 The Contractor shall bear the cost of any retest required after a failed test, including the cost of the Engineer of Record's attendance at that retest.
NOTE Startup and network integration are the same event viewed from two trades. Scheduling them separately means the drive is programmed without a controller to answer it, then the controller is pointed at a drive nobody can reprogram that day, and the difference is resolved on a return visit. (16.2.16)

17 Installation

17.1 Pre-Installation Coordination

17.1.1 Before any drive is set in place, the Contractor shall convene a coordination meeting with the electrical, mechanical, and controls trades and the drive manufacturer's startup technician to confirm equipment locations, service clearances, conduit routing, and communication cable routing.
17.1.2 Drive locations and raceway routing are as shown on the mechanical and electrical floor plans.
17.1.3 The Contractor shall confirm before installation that the mechanical room cooling capacity accounts for the drive losses reported in the product data.

17.2 Power Wiring

17.2.1 Power wiring shall be installed per NFPA 70 and the drive manufacturer's published installation instructions.
17.2.2 Motor output conductors shall be installed in a dedicated raceway.
17.2.3 Motor output conductors shall not share a raceway, wireway, or cable tray with drive input conductors, other motor circuits, control conductors, or communication conductors.
17.2.4 Drive input and output power circuits shall be installed in metallic raceway.
17.2.5 Nonmetallic raceway shall not be used for drive input or output power circuits.
17.2.6 Where VFD-rated shielded motor cable is used, the shield shall be terminated at both ends — at the drive to its designated shield terminal or ground bus, and at the motor to the conduit box ground lug or the motor frame.
17.2.7 Fittings that maintain shield continuity shall be used at every raceway entry on a shielded motor cable.
NOTE The output conductors carry the full PWM waveform, so they radiate and capacitively couple into anything sharing their raceway. Nonmetallic raceway provides neither a shield around that coupling nor a high-frequency return path back to the drive, which is why the metallic raceway requirement is an electrical function here rather than a mechanical protection one. (17.2.8)

17.3 High-Frequency Grounding and Bonding

17.3.1 The equipment grounding conductor shall be sized per NFPA 70 Article 250.122 for the overcurrent device protecting the drive branch circuit.
17.3.2 A high-frequency bonding conductor of not less than 4 AWG copper shall be installed from the drive frame to the motor frame, routed with the motor conductors.
17.3.3 Grounding and bonding shall otherwise comply with Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding.
NOTE The equipment grounding conductor is sized for fault current at 60 Hz, where its impedance is essentially its resistance. Common-mode current from the inverter is in the hundreds of kilohertz, where the same conductor's inductance dominates and its impedance is far higher. The supplementary bond exists to give that current a shorter, lower-inductance path than the one through the motor bearings and the building steel. (17.3.4)

17.4 Control and Communication Wiring

17.4.1 Control conductors carrying analog signals, digital inputs, and relay outputs shall be shielded.
17.4.2 Control conductors shall not share a raceway with power conductors.
17.4.3 Control and communication conductors run parallel to power conductors shall be separated from them by not less than 12 in.
17.4.4 Where control or communication conductors must cross power conductors, they shall cross at 90°.
17.4.5 The control wiring shield shall be grounded at the drive only, and the far end shall be left unterminated.

17.5 Equipment Identification

17.5.1 Each drive shall be identified with an engraved phenolic nameplate or an equally permanent label bearing the equipment tag, the driven equipment served, the motor horsepower and full load current, the input voltage and phase, and the marked short circuit current rating.
17.5.2 Adhesive labels shall not be used as the primary nameplate.
17.5.3 Nameplates shall remain legible and attached for the service life of the equipment.
17.5.4 Arc flash warning labels shall be provided per NFPA 70E and the project arc flash study.
17.5.5 Label format shall follow the conventions in Low Voltage SwitchgearLow Voltage SwitchgearResolves to the current adopted revision.sync/low-voltage-switchgear.

18 Delivery, Storage, and Handling

18.1 Drives shall be delivered in the manufacturer's original packaging with the desiccant and humidity indicator intact.
18.2 The Contractor shall inspect the packaging on delivery, photograph any damage, and notify the manufacturer before accepting the shipment.
18.3 Where the humidity indicator shows that the packaging has been exposed to moisture, the Contractor shall notify the manufacturer and shall not energize the drive until the manufacturer confirms in writing that it is fit for service.
18.4 Drives shall be stored indoors between 0 °C and 50 °C at a relative humidity below 90%, non-condensing.
18.5 Drives shall not be stored where they are exposed to dust, chemical fumes, direct sunlight, or mechanical vibration.
18.6 Drives shall remain in their original packaging until immediately before installation.
18.7 Drives shall not be installed in an area where cutting, grinding, or drilling is still in progress.
18.8 Where storage will exceed six months before energization, the Contractor shall obtain the manufacturer's capacitor re-forming procedure and shall perform it before energization.
18.9 The Contractor shall bear the cost of capacitor re-forming and of any damage resulting from storage outside these conditions.
NOTE DC bus electrolytic capacitors lose oxide layer thickness while sitting unenergized, and re-forming restores it under controlled voltage rather than letting the first energization do it as a fault. Construction dust is the other storage hazard: a NEMA 1 enclosure is not sealed, and grinding debris that settles on a circuit board or a cooling fin does not come off. (18.10)

19 Warranty

19.1 Warranty Term

19.1.1 The warranty term shall be as indicated in the datasheet.
Warranty Termrange
years
1235
19.1.2 The warranty shall cover defects in materials and workmanship under normal use, beginning at the date of substantial completion or the date of Owner-accepted startup, whichever is earlier.
19.1.3 Where a warranted component is repaired or replaced, the repaired or replaced component shall carry a fresh full warranty term from the date of that repair, or the remainder of the original term, whichever is longer.
19.1.4 The manufacturer shall bear the cost of removing and reinstalling equipment displaced to reach a warranted repair, and of repairing collateral damage caused by the failure or by the repair.

19.2 Extended Service Coverage

19.2.1 Extended service coverage shall be as indicated in the datasheet.
Extended Service Coveragecheckbox
☐ Parts only
☑ Parts and labor including on-site repair
☐ On-site response by the next business day
☐ On-site response within four hours at any hour
☐ Annual preventive maintenance visit by a manufacturer-trained technician
19.2.2 Where an on-site response commitment is indicated, the response time shall run from the Owner's notification to the manufacturer's arrival on site.

19.3 Warranty Exclusions

19.3.1 The warranty shall not cover damage resulting from installation contrary to the manufacturer's published instructions.
19.3.2 The warranty shall not cover damage resulting from operation outside the rated voltage, current, ambient temperature, or altitude limits without the derating this standard requires.
19.3.3 The warranty shall not cover damage resulting from a source disturbance outside the input voltage tolerance indicated in the datasheet.
19.3.4 The warranty shall not cover damage resulting from modification of the drive hardware or firmware without the manufacturer's written authorization.
19.3.5 Where the parties disagree whether a failure falls within an exclusion, the Engineer of Record shall make the initial determination.

20 Spare Parts

20.1 Spare Drive Units

20.1.1 The spare drive units to be furnished shall be as indicated in the datasheet.
Spare Drive Unitsselect
None
One spare drive of the most frequently installed frame size
One spare drive of each frame size installed
20.1.2 Spare drives shall match the installed drives in model, firmware revision, and factory configuration.
20.1.3 Spare drives shall be stored per the delivery and storage requirements of this standard, including capacitor re-forming.
NOTE A spare drive earns its cost by covering the most common frame size on the project rather than by matching every installed unit one for one, because a larger drive will run a smaller motor while the reverse is not true. (20.1.4)

20.2 Spare Components

20.2.1 The spare components to be furnished shall be as indicated in the datasheet.
Spare Componentscheckbox
☑ One set of cooling fans for each frame size installed
☐ One operator interface for each drive model installed
☐ One communication interface card for each protocol used
☐ One set of semiconductor fuses for each frame size installed
☑ One set of control power fuses for each drive model installed
☐ One set of intake filter media for each drive with a filtered intake
☐ One enclosure space heater for each enclosure with a heater
20.2.2 The manufacturer shall furnish fan replacement instructions and the expected fan service life at the ambient temperature indicated in the datasheet.
NOTE Cooling fans are the shortest-lived component in the drive and the most common cause of an overtemperature shutdown after a fouled intake. Both failures are correctable the same day when the replacement is already on site. (20.2.3)