Get To Know UL 1604

August 16, 2013
By Anonymous

What Is UL 1604?

Engineers who specify electrical products for industrial equipment tend to have a good working knowledge of UL ratings. However, one rating that gives many engineers trouble is UL 1604, which certifies electrical components for use in hazardous environments. We routinely field questions about UL 1604 and which products comply with it. Here are some answers.

The UL 1604 rating applies to most types of electrical equipment, circuits, and components operating in conditions that the National Electrical Code (NEC) defines as hazardous due to the presence of flammable gasses, combustible dust, or ignitable fibers. The NEC categorizes these conditions as Class I for gasses, Class II for dust, and Class III for fibers or flyings.

While referred to in North America as UL 1604, this standard has been supplanted by a global standard known as ANSI/ISA-12.12.01. The requirements are similar.

UL 1604 also addresses whether a flammable material is present as part of normal operating conditions, or is present only during abnormal operations. The NEC refers to these two scenarios as Division 1 and Division 2, respectively.

Finally, UL 1604 considers different types of hazardous materials according to their NEC codes. Codes A, B, C and D segment different gasses and vapors according to their ignition temperatures. Codes E, F and G segment dusts according to ignition temperatures and conductivity. Putting all the classes, divisions and codes together, here are UL 1604’s key provisions:

  • Apply to equipment, circuits, and components designed specially for use in hazardous locations the NEC classifies as Class I and II, Division 2 and Class III, Divisions 1 and 2.
  • Provide minimum requirements for the design, construction, and marking of electrical equipment for use in these locations.
  • Cover Class I, Division 2 equipment in which the circuits and components are incapable of causing ignition of a specified gas under normal operating conditions.
  • Cover equipment constricted to reduce or exclude the entrance of dust in Class II and Class III locations.
  • Apply under specific atmospheric conditions, including ambient temperature between 5 and 40 C, oxygen concentration no greater than 21% and nominal barometric pressure of 1 atmosphere.
  • Apply to portable battery powered equipment, other than flashlights, in locations defined as Class I and II, Division 2 and Class III, Divisions 1 and 2.

UL 1604 has other provisions too and excludes some electrical equipment covered by other standards. If you’re in doubt whether a specific component or piece of equipment is compliant, it’s a good idea to contact one of our application engineers.

Which Products Comply?

A wide variety of industrial equipment falls under the guidelines of UL 1604. So we’ve made the effort to develop and test a number of compliant electrical components. Among them are Panasonic Relays such as:

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