Inspector's Guide: Reading a Motor Nameplate

Motor nameplates provide essential information that ensures motors are installed and operated safely and in compliance with codes. As an inspector, understanding this information is crucial for verifying installations.

1. Manufacturer & Model Number
   • Purpose: Identifies the motor for reference and verification.
   • Inspection Tip: Ensure the motor is listed and labeled by a recognized testing laboratory.
2. Voltage (V)
   • Purpose: Indicates the operating voltage.
   • Inspection Tip: Verify that the motor's voltage rating matches the supply voltage.
3. Full Load Amperage (FLA)
   • Purpose: Shows the current drawn at full load.
   • Inspection Tip: Use this to confirm correct sizing of conductors and overcurrent protection devices.
4. Frequency (Hz)
   • Purpose: Specifies the operating frequency.
   • Inspection Tip: Ensure compatibility with the system frequency (typically 60 Hz in North America).
5. Phase
   • Purpose: Indicates single-phase or three-phase operation.
   • Inspection Tip: Confirm that the motor's phase matches the supply.
6. Horsepower (HP)
   • Purpose: Denotes the motor's output power.
   • Inspection Tip: Use this to verify appropriate application and load handling.
7. Speed (RPM)
   • Purpose: Shows the motor's rotational speed.
   • Inspection Tip: Ensure the speed is suitable for the connected equipment.
8. Service Factor (SF)
   • Purpose: Indicates the motor's overload capacity.
   • Inspection Tip: Recognize that a higher SF allows for occasional overloads; ensure it's not used continuously beyond its rating.
9. Insulation Class
   • Purpose: Defines the thermal tolerance of the motor's insulation.
   • Inspection Tip: Confirm that the motor's insulation class is appropriate for the operating environment.
10. Enclosure Type (e.g., TEFC, ODP)
    • Purpose: Describes the motor's protection against environmental factors.
    • Inspection Tip: Ensure the enclosure type suits the installation location (e.g., TEFC for dusty environments).
11. Ambient Temperature Rating
    • Purpose: Specifies the maximum ambient temperature for safe operation.
    • Inspection Tip: Verify that the motor is suitable for the ambient conditions of the installation site.
12. Duty Cycle
    • Purpose: Indicates how long the motor can operate under specific conditions.
    • Inspection Tip: Ensure the motor's duty rating aligns with its intended use.
13. Code Letter
    • Purpose: Provides information on the motor's starting current.
    • Inspection Tip: Use this to assess the impact on the electrical system during startup.
14. Design Letter
    • Purpose: Defines the motor's torque and starting characteristics.
    • Inspection Tip: Confirm that the motor's design is appropriate for the application.
15. Efficiency
    • Purpose: Shows how effectively the motor converts electrical energy to mechanical energy.
    • Inspection Tip: Higher efficiency motors reduce energy costs and heat generation.

Here's an example of a typical motor nameplate:​

 

[e hilton]

Good information, but i question if all those items are appropriate to be checked by the inspector. RPM for example … why does the inspector care if the speed is correct? Where would you cross check to confirm it is correct?

 

[Scipio]

One question: isn't the FLA used only for the Overload protection, and the FLC rating in the NEC tables 430.248 and 430.250 used for conductors and the overcurrent ratings?

Andy.

 

[jar546]

Good information, but i question if all those items are appropriate to be checked by the inspector. RPM for example … why does the inspector care if the speed is correct? Where would you cross check to confirm it is correct?

As an inspector, I don't believe that we need to worry about speed. However, we have to consider voltage and current. With some electric motors, such as for fire pumps, we need to know the locked rotor current (LRC).

 

[SCBO1]

Good information