Mike Dolt Enterprises
Mike Dolt Enterprises
User: LMAO, Location: Texas
Asked on: Friday, March 25, 2011 at 1:02 pm EDT
Answered on: Tuesday, May 14, 2024 at 3:16 am EDT
Question: Hi, I have a question regarding IEC; I am an engineer in a north American factory and we export our drives to Asia, Europe, America, Africa... I am pretty good at sizing cables based on NEC (just passed the PE); but since we deal with a lot of foreign countries I like to know more about IEC.I would really be appreciated if someone can explain how IEC is related to NEC. But I would really like to know is: if I follow NEC rules regarding calculating ampacities, can my calculation be transferred to IEC? I know the question is a little vague; here is an example: if I calculate the ampacity of cables used for incoming power into and outgoing power out of a "VFD", can the calculated ampacity be used to size cable in IEC (mm) instead of wire gauge and CMIL which NEC's convention ?Thanks,
Relationship Between IEC and NEC
IEC (International Electrotechnical Commission) and NEC (National Electrical Code) are electrical codes that provide guidelines for electrical installations. While they share some similarities, there are also differences between them.
Calculating Ampacities
The methods for calculating ampacities in IEC and NEC are similar but not identical. NEC
Ampacity calculation considers the current-carrying capacity of the conductor, the conductor material, the temperature rating of the insulation, and the ambient temperature.
IEC
Ampacity calculation involves the same factors as NEC, but it also considers the installation method (e.g., in air, conduit, or buried).
Transferability of Calculations
In general, ampacity calculations made according to NEC can be transferred to IEC, with some adjustments. However, it's important to note that: Conductor size
IEC specifies cable sizes in millimeters (mm), while NEC uses wire gauges and CMIL (circular mils). You will need to convert the calculated ampacity to the equivalent IEC cable size using conversion tables or software.
Installation method
IEC considers the installation method when calculating ampacity. If the installation method differs from the assumptions in the NEC calculation, you may need to adjust the ampacity accordingly.
Example
For your specific example of calculating ampacity for incoming and outgoing power to a VFD: Calculate the ampacity using the NEC method. Determine the equivalent IEC cable size using a conversion table or software. Check the IEC code to verify that the calculated ampacity is acceptable for the installation method and ambient temperature.
Additional Considerations
In addition to ampacity calculations, there are other factors to consider when using IEC instead of NEC: Voltage ratings
IEC and NEC use different voltage ratings for equipment and cables. Make sure to use the appropriate voltage ratings for the specific application.
Circuit protection
The requirements for circuit protection devices (e.g., fuses, circuit breakers) may vary between IEC and NEC.
Grounding: IEC and NEC have different requirements for grounding systems. Ensure that the grounding system complies with the applicable code.It's always recommended to consult with an experienced electrical engineer or code expert if you are unsure about how to apply IEC or NEC in your specific situation. Flag for review