What Is IEEE Standard 1349?

IEEE Standard 1349 is an IEEE guide for the application of electric motors in Class I, Division 2 and Class I, Zone 2 hazardous, or classified, locations. Published first in 2001 and revised as IEEE Std 1349-2011, it addresses a specific and commonly misunderstood question in industrial electrical engineering: under what conditions a motor that is neither explosionproof nor flameproof may safely be installed in an area where flammable gas or vapor could be present. The guide is sponsored by the Petroleum and Chemical Industry Committee of the IEEE Industry Applications Society, and it applies to three-phase and single-phase alternating current induction and synchronous motors rated 0.18 kilowatts, or one quarter horsepower, and larger.

A guide differs from a standard in IEEE terminology: it presents alternatives and good practice rather than mandatory requirements. IEEE 1349 does not classify areas or certify equipment. It supplies the engineering basis that owners, designers, and motor manufacturers use to evaluate a proposed installation against the rules set elsewhere.

Hazardous Area Classification

The framework comes from the National Electrical Code, published as NFPA 70. Class I locations are those where flammable gases or vapors may be present in ignitible concentrations. Division 1 covers areas where that condition exists under normal operation, while Division 2 covers areas where it exists only under abnormal conditions such as a container rupture or a failed ventilation system. The parallel zone system, adopted from IEC practice, splits the same territory into Zone 0, Zone 1, and Zone 2, with Zone 2 corresponding closely to Division 2. Because the flammable atmosphere in a Division 2 or Zone 2 area is present only rarely, the code permits general-purpose enclosures for motors provided the installation does not present an ignition source, and IEEE 1349 exists to interrogate that proviso.

Ignition Sources in General-Purpose Motors

The guide concentrates on two mechanisms. The first is external surface temperature: any exposed surface hotter than the autoignition temperature of the surrounding gas can start a fire, which is why equipment carries a temperature code, from T1 at 450 degrees Celsius down to T6 at 85 degrees Celsius, that must be compared against the specific gas group present. The scope of the 2011 revision makes clear that determining the maximum surface temperature under both normal running and abnormal conditions, such as stalled rotor or single-phasing, is the central analysis. The second mechanism is sparking, particularly at rotor bar to end ring joints in fabricated squirrel-cage rotors and at frame and enclosure joints where oxide films and loose fits can allow arcing. The guide describes surface temperature test methods and the construction features, including cast rotors and controlled joint design, that reduce both risks.

Adjustable-Speed Drive Applications

Motors fed from adjustable-speed drives receive separate treatment because non-sinusoidal voltage introduces harmonic losses that raise winding and frame temperatures above the values measured on sine-wave power, and because localized hot spots can exceed the average surface temperature that a conventional test reports. The guide covers testing and evaluation for non-sine-wave applications, including the need to verify temperature over the whole speed range rather than at rated speed alone, and it extends to life-cycle integrity, meaning the maintenance, repair, and rewind practices required for a motor to remain suitable for its location years after commissioning.

Applications

IEEE Standard 1349 has applications in a range of fields, including:

• Petroleum refining and petrochemical plant design
• Offshore platform and gas processing electrical systems
• Chemical and pharmaceutical manufacturing
• Grain handling, paint, and solvent processing facilities
• Motor manufacture, testing, and repair shop qualification
• Electrical safety auditing and hazardous area compliance review