1 Scope
NOTE This standard establishes common requirements for low-voltage, three-phase, squirrel-cage AC induction motors furnished as an integral part of driven equipment supplied under any division of the Work. (1.1)
NOTE It applies to motors rated 1/4 HP through 500 HP, 200 V through 600 V, 60 Hz, regardless of whether the motor is started across the line or through a combination starter, soft starter, or variable frequency drive. (1.2)
1.3Equipment specifications for pumps, fans, compressors, conveyors, and similar driven machinery shall cite this standard for motor requirements rather than restating motor criteria.
1.4Where an equipment specification states a motor requirement that conflicts with this standard, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
1.5Motors shall comply with this standard, with Grounding And Bonding for equipment grounding, and with the applicable starter, drive, or control standard for the selected starting method. NOTE The following are outside the scope of this standard and are governed elsewhere. (1.6)
- Starting and control devices (contactors, overload relays, manual motor protectors) - see Combination Motor Starters.
- Motor control center assemblies, bus, and plug-in units - see Motor Control Centers.
- Variable frequency drive electronics, harmonic mitigation, bypass, and drive acceptance testing - see Low Voltage Variable Frequency Drives and Hvac Variable Frequency Drives.
- Medium-voltage motors rated above 600 V, which fall outside the low-voltage applicability of NEMA MG 1 Part 12.
- Motors certified by the equipment manufacturer as part of a factory-tested listed package (chillers, rooftop units, packaged pumps), which are governed by the respective equipment specification.
- Branch-circuit conductors and cables from the motor terminals to the controller - see Conductors And Cables.
- Power distribution upstream of the motor branch circuit - see Low Voltage Panelboards and Low Voltage Switchboards.
2 Referenced Standards
2.1Motors shall comply with the latest adopted edition of each of the following unless a specific edition is cited or a more recent edition is mandated by the authority having jurisdiction.
2.2Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
| Standard |
Title |
| ANSI/NEMA MG 1 |
Motors and Generators |
| NFPA 70 (NEC) Article 430 |
Motors, Motor Circuits, and Controllers |
| NFPA 70 (NEC) Article 430 Part VII |
Motor Controllers |
| UL 1004-1 |
Rotating Electrical Machines - General Requirements |
| ASHRAE 90.1 |
Energy Standard for Buildings Except Low-Rise Residential Buildings (Section 10.4) |
| 10 CFR Part 431 |
Energy Conservation Standards for Electric Motors (EISA 2007; DOE 2027 rule) |
| IEEE 112 |
Standard Test Procedure for Polyphase Induction Motors and Generators |
| IEEE 43 |
Recommended Practice for Testing Insulation Resistance of Electric Machinery |
| IEEE 841 |
Severe-Duty TEFC Squirrel-Cage Induction Motors (Petroleum and Chemical Industry) |
| NEMA ICS 2 |
Controllers, Contactors and Overload Relays Rated Not More Than 2000 V AC or 750 V DC |
| NFPA 70E |
Standard for Electrical Safety in the Workplace |
NOTE ANSI/NEMA MG 1 is the primary technical authority for this standard; it governs efficiency classes, frame dimensions, nameplate data, temperature rise, insulation class, service factor, starting current, and altitude and ambient derating. (2.3)
NOTE The current revision is published as ANSI/NEMA MG 00001 using a zero-padded document number; references to "MG 1" in this standard and in submittals mean the same document. (2.4)
3 Submittals
3.1The Contractor shall submit the following product data for each motor or motor type furnished under the Work, identified by the driven equipment it serves:
- Manufacturer's catalog data sheet showing HP, voltage, phase, frequency, full-load amperes, locked-rotor amperes or code letter, NEMA design letter, and frame size.
- Efficiency class designation (NEMA Premium / IE3 or NEMA Premium 4 / IE4) with nominal full-load efficiency at the rated load point.
- Enclosure type, insulation class, temperature rise, and service factor.
- Inverter-duty rating and conformance statement to NEMA MG 1 Part 31 for every VFD-driven motor.
- Nameplate facsimile showing all data required by NEMA MG 1 Section 10.40.
- Certified IEEE 112 Method B efficiency test report establishing compliance with the specified efficiency class.
☐ Catalog data sheet (HP, voltage, FLA, LRA, design letter, frame)
☐ Efficiency class and nominal full-load efficiency
☐ Enclosure, insulation class, temperature rise, service factor
☐ Inverter-duty conformance to NEMA MG 1 Part 31 (VFD motors)
☐ Nameplate facsimile
☐ IEEE 112 Method B certified efficiency test report
3.2The Contractor shall submit the following informational submittals for review:
- Manufacturer's installation, alignment, and lubrication instructions.
- Bearing data including bearing type, lubrication method, and recommended regreasing interval.
- Statement of altitude and ambient rating, with derating calculations where the installed elevation exceeds 3,300 ft (1,000 m) or the ambient exceeds 40 °C.
☐ Installation, alignment, and lubrication instructions
☐ Bearing type, lubrication method, and regreasing interval
☐ Altitude and ambient rating with derating calculations
3.3The Contractor shall submit the following closeout submittals before Substantial Completion:
- Field acceptance test records including insulation resistance, rotation check, and no-load running current balance.
- Manufacturer's warranty certificate.
- Final lubrication record identifying lubricant type and quantity for each motor with external grease fittings.
☐ Field acceptance test records
☐ Warranty certificate
☐ Final lubrication record
4 Quality Assurance
4.1Each motor shall be listed and labeled by a Nationally Recognized Testing Laboratory under UL 1004-1.
4.2Each general-purpose motor 1 HP through 500 HP shall meet or exceed the minimum nominal full-load efficiency required by 10 CFR Part 431 and ASHRAE 90.1 for its horsepower, pole count, and enclosure.
4.3The manufacturer shall have produced motors of the specified type and rating for not less than five years.
4.4Motor efficiency shall be established by test in accordance with IEEE 112 Method B, and the certified test report shall accompany the product submittal.
NOTE The current federal minimum efficiency for general-purpose motors 1-200 HP is NEMA Premium (IE3) under EISA 2007 (10 CFR 431); the DOE 2027 final rule expands fractional-HP coverage and extends IE4 requirements to large machines, with staged compliance dates in June 2027 and January 2029. (4.5)
NOTE Specifying NEMA Premium (IE3) as the default satisfies current federal law and ASHRAE 90.1; the owner's sustainability standard may require NEMA Premium 4 (IE4) where lifecycle energy cost justifies the premium. (4.6)
5 Environmental and Service Conditions
5.1Motors shall be rated for continuous duty at the service conditions of the installed location without exceeding the temperature rise corresponding to the specified insulation class.
NOTE Standard-rated motors are suitable for an ambient not exceeding 40 °C and an installed elevation not exceeding 3,300 ft (1,000 m); these are the conditions assumed by NEMA MG 1 for standard catalog ratings. (5.2)
5.3Motors installed where the ambient exceeds 40 °C shall be furnished with Class H insulation or a special winding rated for the actual ambient.
5.4Motors installed above 3,300 ft (1,000 m) shall be derated, or furnished with a special winding, such that the temperature rise at the installed elevation does not exceed the limit for the insulation class.
NOTE Altitude derating is commonly missed because manufacturers quote standard catalog data; for mountain-region projects above 3,300 ft the temperature-rise margin shrinks roughly 3% per 500 m of elevation and must be verified in the submittal. (5.5)
5.6The applied voltage shall not vary more than ±10% of nameplate voltage, and the applied frequency shall not vary more than ±5% of nameplate frequency; the combined voltage and frequency variation shall not exceed 10% per NEMA MG 1 Section 12.44.
6 Electrical Ratings
6.1Motors shall be three-phase, 60 Hz, squirrel-cage induction type rated for the nominal system voltage serving the branch circuit.
6.2The nameplate voltage shall be the NEMA-standard utilization voltage for the system: 460 V for a 480 V system, 208 V for a 208 V system, and 575 V for a 600 V system.
NOTE 460 V / 3Φ / 60 Hz is the workhorse rating for commercial and industrial motors; small equipment is commonly 208 V, and dual-voltage 230/460 V windings are offered for 1-50 HP where field voltage flexibility is wanted. (6.3)
6.4Dual-voltage motors shall be shipped connected for the system voltage indicated, with the alternate connection diagram on the nameplate or inside the conduit box.
208 V / 3Φ / 60 Hz
230 V / 3Φ / 60 Hz
460 V / 3Φ / 60 Hz
575 V / 3Φ / 60 Hz
Dual-voltage 230/460 V / 3Φ / 60 Hz
Per drawings — motor and equipment schedule (deferred by default)
NOTE NEMA Design B is the standard low-slip squirrel-cage design suited to most pumps and fans; Design C provides higher starting torque for conveyors and positive-displacement loads, and Design D serves high-inertia loads. (6.5)
6.6The motor design letter shall be coordinated with the driven load so that the available starting torque exceeds the load torque throughout acceleration.
NOTE Specifying NEMA Design B for a hard-starting load such as a loaded conveyor or positive-displacement pump risks stall; verify starting-torque adequacy and specify Design C or D where the load demands it. (6.7)
● Design B (normal torque, low slip - general purpose pumps and fans)
○ Design C (high starting torque - conveyors, reciprocating loads)
○ Design D (high slip - high-inertia loads)
7 Efficiency
7.1Motors 1 HP through 500 HP shall be NEMA Premium (IE3) efficiency unless the Contract Documents require NEMA Premium 4 (IE4).
7.2Nominal full-load efficiency shall meet or exceed the value listed in ASHRAE 90.1 Table 10.8-1 for the motor's horsepower, pole count, and enclosure.
NOTE Representative NEMA Premium minimum efficiencies for 4-pole, 460 V, TEFC motors are 91.7% at 10 HP, 94.5% at 50 HP, 95.0% at 100 HP, and 95.4% at 200 HP. (7.3)
NOTE Failing to require an IEEE 112 Method B certified efficiency report means ASHRAE 90.1 and EISA compliance cannot be confirmed at equipment approval; the report is the only verifiable proof at submittal time. (7.4)
● NEMA Premium (IE3)
○ NEMA Premium 4 (IE4)
8 Enclosure
8.1The motor enclosure shall be selected for the installed environment so that the motor's protective rating equals or exceeds the exposure at its location.
NOTE Open drip-proof (ODP) enclosures are suitable only for clean, dry, sheltered indoor mechanical rooms; totally enclosed fan-cooled (TEFC) enclosures suit outdoor, wet, and dirty locations. Specifying an ODP enclosure for an outdoor, wet, or dirty location is a recurring error; such locations require TEFC (NEMA 3R or better) as a minimum. (8.2)
8.3Motors in corrosive or washdown environments shall be furnished with a NEMA 4X enclosure or stainless-steel construction with corrosion-resistant hardware.
8.4Motors in classified hazardous locations shall be furnished as explosion-proof, listed for the specific Class and Division of the area.
8.5Motors furnished under Hvac Fans, Hvac Pumps, and Fire Pumps shall use the enclosure type appropriate to their installed environment as defined in those standards and this section. Open drip-proof (ODP) - clean dry indoor
Totally enclosed fan-cooled (TEFC) - general outdoor/wet/dirty
Totally enclosed non-ventilated (TENV) - low-output enclosed
TEFC NEMA 4X / stainless - corrosive or washdown
Explosion-proof NEMA 7/9 - hazardous (classified) locations
9 Insulation and Thermal Rating
9.1Motor windings shall be insulated with Class F (155 °C) insulation system limited to a Class B (130 °C) temperature rise at the rated load and a 40 °C ambient.
NOTE Class F insulation operated at a Class B rise provides a built-in 25 °C thermal margin and is the de facto standard; this combination, not bare "Class B insulation," is what gives motors usable thermal headroom in service. (9.2)
NOTE Specifying only "Class B insulation" without the rise qualification yields a motor with no practical thermal margin and is a common pitfall; always pair the insulation class with the allowable rise. (9.3)
9.4Motors for high-ambient or high-altitude service shall use Class H (180 °C) insulation where required to maintain the thermal margin.
● Class F insulation / Class B rise (standard)
○ Class F insulation / Class F rise
○ Class H insulation / Class B rise (high ambient or altitude)
10 Service Factor and Starting Method
10.1Across-the-line general-purpose motors shall have a service factor of 1.15.
10.2HVAC fan and pump motors shall have a service factor of 1.25 where specified.
10.3VFD-driven inverter-duty motors shall have a service factor of 1.0.
NOTE A NEMA MG 1 Part 31 inverter-duty motor is rated at service factor 1.0; running a service-factor-1.15 standard motor above nameplate HP on a VFD voids the manufacturer's thermal model and is a frequent specification error. (10.4)
○ 1.0 (inverter-duty / VFD-driven)
● 1.15 (across-the-line general purpose)
○ 1.25 (HVAC fan and pump duty)
Across-the-line (full voltage)
Wye-delta (reduced voltage)
Autotransformer (reduced voltage)
Solid-state soft starter
Variable frequency drive (VFD)
11 Inverter-Duty Requirements
11.1Every motor driven by a variable frequency drive shall be rated inverter-duty in conformance with NEMA MG 1 Part 31.
11.2Inverter-duty motors shall withstand repetitive voltage spikes of not less than 1,600 V peak at the motor terminals per NEMA MG 1 Part 31.
11.3Inverter-duty motors shall be suitable for constant-torque operation over the speed range required by the driven load, up to the 1000:1 range contemplated by NEMA MG 1 Part 31.
NOTE Omitting the inverter-duty requirement on VFD-driven motors is a serious pitfall: reflected voltage spikes on long drive cable runs stress standard winding insulation and cause premature failure. (11.4)
11.5Where the cable run between the drive and an inverter-duty motor exceeds the drive manufacturer's reflected-wave limit, a dV/dt reactor or output filter shall be provided under Low Voltage Variable Frequency Drives. ○ NEMA MG 1 Part 31 inverter-duty
○ IEEE 841 severe-duty inverter-rated
● Not applicable (not VFD-driven)
12 Frame, Mechanical Construction, and Bearings
12.1Motors shall be furnished in NEMA T-frame dimensions unless the driven equipment requires an IEC metric frame for dimensional compatibility.
NOTE NEMA T-frame is the default for North American equipment; IEC metric frames appear on imported packaged equipment and differ in shaft height, bolt pattern, and shaft diameter, which causes field rework if mixed with NEMA-dimensioned bases without coordination. (12.2)
12.3IEC-frame motors shall not be substituted onto NEMA-dimensioned bases or couplings without verified dimensional coordination of shaft height, bolt circle, and shaft diameter.
12.4Bearings shall be anti-friction ball or roller bearings sized for the driven load and the coupling or belt arrangement.
12.5Motors 200 HP and smaller for general-purpose service shall have pre-lubricated, sealed bearings.
12.6Motors above 200 HP and high-speed motors shall have external grease fittings with relief provisions.
NOTE The conduit box shall be rotatable in 90-degree increments where the motor orientation is not fixed at the time of bid, so conduit can enter cleanly without a change order. (12.7)
12.8The conduit box shall be sized to accept the branch-circuit raceway furnished under Raceways And Conduit and the conductors furnished under Conductors And Cables, with motor leads not less than 18 in long. ● NEMA T-frame
○ IEC metric frame
● Pre-lubricated sealed (general purpose, ≤200 HP)
○ External grease fittings with relief (>200 HP or high speed)
● Rotatable conduit box (orientation flexible)
○ Fixed conduit box (orientation known)
13 Nameplate
13.1Each motor shall bear a permanently attached, corrosion-resistant nameplate stamped or engraved with all data required by NEMA MG 1 Section 10.40.
13.2The nameplate shall show, at minimum, the manufacturer, HP, voltage, phase, frequency, full-load amperes, full-load speed, NEMA design letter, service factor, insulation class, frame size, enclosure type, and nominal efficiency.
13.3The nameplate shall remain legible for the life of the motor and shall not be painted over during installation or finishing.
NOTE A permanently legible, corrosion-resistant nameplate is the primary traceability record for the motor throughout its service life; it is the first reference used during warranty claims, replacement-part ordering, and accident investigation, and a nameplate that has corroded, fallen off, or been painted over forces the owner to rely on as-built documentation that is rarely complete. (13.4)
14 Branch Circuit and Protection Coordination
14.1Branch-circuit conductors serving each motor shall be sized at not less than 125% of the motor full-load current taken from NEC Table 430.250, not from the motor nameplate FLA.
NOTE Sizing conductors from the nameplate FLA rather than the NEC Table 430.250 value generates RFIs because the installing electrician sizes per the code table; always coordinate equipment schedules to the table value. (14.2)
14.3Motor overload protection shall be set at not more than 115% of the motor nameplate full-load current for motors with a service factor of 1.15 or greater or a marked temperature rise not over 40 °C, and at not more than 125% for all other motors, per NEC 430.32.
14.4Branch-circuit short-circuit and ground-fault protection shall be sized per NEC 430.52 for the motor design letter and the protective-device type, recognizing locked-rotor inrush of approximately 600–700% of full-load current for NEMA Design B motors.
15 Testing
15.1The manufacturer shall perform routine factory tests on each motor including no-load current, locked-rotor current, and winding resistance per phase, with phase-to-phase resistance balanced within 2%.
15.2A certified IEEE 112 Method B efficiency test report shall be furnished for the motor model to substantiate the specified efficiency class.
15.3The Contractor shall perform an insulation-resistance (megger) test on each motor before energization and shall record a value not less than 1 MΩ per kV of rated voltage plus 1 MΩ, per IEEE 43.
15.4The Contractor shall verify direction of rotation before coupling the motor to the driven load.
15.5The Contractor shall record the no-load running current on each phase after the rotation check and shall confirm the phase currents are balanced within the manufacturer's tolerance.
15.6For motors larger than 100 HP, the Contractor shall perform a thermal scan after not less than one hour of loaded operation and shall record bearing and frame temperatures.
NOTE All testing and commissioning shall be performed under an electrical safety program complying with NFPA 70E, with arc-flash and shock protection appropriate to the available incident energy. (15.7)
☐ Insulation resistance (megger) per IEEE 43
☐ Direction-of-rotation check before coupling
☐ No-load running current balance
☐ Thermal scan after 1 hour loaded (>100 HP)
16 Installation
16.1Motors shall be installed in accordance with the manufacturer's instructions and aligned to the driven equipment within the coupling or belt manufacturer's tolerance.
16.2Direct-coupled motors shall be aligned for angular and parallel offset using a dial indicator or laser alignment tool, and the alignment shall be recorded.
16.3Belt-driven motors shall be installed with sheaves aligned and belt tension set to the belt manufacturer's recommendation.
16.4Each motor frame shall be bonded to the equipment grounding conductor in accordance with Grounding And Bonding. 16.5Motors with external grease fittings shall be lubricated at startup with the lubricant type and quantity recommended by the manufacturer, and the lubrication shall be recorded.
17 Delivery, Storage, and Handling
17.1Motors shall be delivered in the manufacturer's original packaging with shaft locks or bracing in place where provided for shipment.
17.2Motors shall be stored indoors in a clean, dry, vibration-free location with space heaters energized where furnished, until installation.
17.3Motors stored longer than the manufacturer's recommended period shall have their shafts rotated periodically and their insulation resistance verified before energization to confirm no moisture ingress.
18 Warranty
18.1The motor manufacturer shall warrant each motor against defects in materials and workmanship for not less than one year from the date of Substantial Completion.
18.2Severe-duty (IEEE 841) motors shall carry the manufacturer's standard severe-duty warranty of not less than three years.
18.3The warranty shall cover repair or replacement of the defective motor, including removal and reinstallation labor where the defect is attributable to the manufacturer.
● 1 year (standard general purpose)
○ 3 years (IEEE 841 severe duty)
○ 5 years (extended, owner option)
19 Spare Parts
19.1The Contractor shall furnish the manufacturer's recommended spare-parts list for motors larger than 50 HP, including bearings and, where applicable, space heaters.
19.2Where the owner's standard requires stocked spares, the Contractor shall furnish one spare bearing set for each motor size 50 HP and larger installed in critical process or life-safety service.
☐ Spare bearing set (motors >50 HP)
☐ Spare space heater (where furnished)
☐ Manufacturer's recommended spares list