UL1604 and Industrial Ethernet
Industry movement, in adopting Ethernet standards, entails conformance to various agency regulations not required in office environments. Industrial Ethernet products are designed and tested to the higher standards required for industrial equipment.
UL 1604 covers electrical equipment and accessories for controlling various equipment in hazardous locations. Such equipment should be UL 508 Listed as Industrial Control Equipment and have been investigated for risks to life and property in accordance with numerous standards. Unless battery-powered, the equipment installation must satisfy requirements in Article 500 of the National Electrical Code, NFPA 70.
Classes: Hazardous locations are those where fire or explosion hazards may exist due to the presence of certain substances. Class I areas pertain to flammable gases, vapors or liquids. Class II covers atmospheres having dangerous concentrations of dust. Class III applies to atmospheres containing fibers or flyings.
Divisions: Hazardous areas are further defined as either Division 1 (where the environment is normally dangerous) or Division 2 (where the risk is not normally present).
Zones: Class I hazardous areas are also specified by how prevalent the dangerous substance is during normal operation. The three areas are Zone 0 (risk is present and long-term), Zone 1 (risk is likely but intermittent) and Zone 2 (risk is unlikely).
Groups: For Classes I and II, product specification by Division and Zone varies by the materials group to which the equipment is exposed. (Class III equipment has no such specification). Class I has four gas groups: A (acetylenes), B (hydrogens), C (ethylenes) and D (propanes). Class II has three dust groups: E (metals), F (coal) and G (grains).
Temperature: Classes I and II (not Class III) specify the maximum ambient temperature that rated equipment can withstand without becoming a risk. Rated equipment receives a T-Code per the following table where values in parentheses are temperatures in degrees Celsius.
T1 (450)
T2 (300), T2A (280), T2B (260), T2C (230), T2D (215)
T3 (200), T3A (180), T3B (165), T3C (160)
T4 (135), T4A (120)
T5 (100)
T6 (85)
For example, a Class I, Div. 2 Industrial Ethernet switching hub is suited for an environment in which dangerous gases, vapors or liquids are potentially, but not normally, present. It is common to find Industrial Ethernet equipment qualified for all four groups (A,B,C,D) and rated T4A.
Markings: Finally, UL 1604 rated Industrial Ethernet products must have certain markings which commonly include:
listee name
model number
electrical input ratings (voltage, power, frequency)
terminal identification
location rating (eg: "Class 1, Div 2, Groups ABCD Haz. Loc.")
operating temperature code (T-Code)
date code of manufacture
notice of "Supplied from Class 2 Source"
fiber optic power (if applicable) in micro-watts
