Xycom 9465 PC/AT, Manual, Page: 48 / 87

Chapter 3 – Installation
3-33
Division 2 Locations
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Class I volatile flammable liquids or flammable gasses are handled, processed, or
used, but confined within closed containers or closed systems from which they can
escape only in cases of accidental rupture or breakdown of such enclosures or sys-
tems, or in case of abnormal operation of equipment.
•
Ignitable concentrations of Class I vapors or gasses are normally prevented by posi-
tive mechanical ventilation, but which may become hazardous due to mechanical
failure of those ventilation systems.
•
Location is adjacent to a Division 1 location.
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Class II combustible dust is not normally in the air in quantities sufficient to produce
explosive or ignitable mixtures. Dust accumulations are normally insufficient to in-
terfere with normal operation of electrical equipment or other apparatus. Combusti-
ble dust may be in suspension in the air as a result of the following: infrequent mal-
functioning of handling or processing equipment; combustible dust accumulations
on, or in the vicinity of electrical equipment; may be ignitable by abnormal operation
or failure of electrical equipment.
Groups
All electrical equipment that is approved for use in hazardous locations must include a
group rating. Various flammable and combustible substances are divided into these
groups as a function of their individual maximum experimental safe gap (MESG), explo-
sion pressure, and ignition temperature.
Component temperatures and the potential for spark based upon voltage, current, and
circuit characteristics, within electrical equipment, will determine what the equipment
group rating will be. A device approved for installation within Class I, Group A locations
may also be used in Groups B, C, or D.
Note
Approved Class I equipment may not be suitable for Class II installa-
tions. Class I includes Groups A, B, C, and D. Class II includes Groups
F, and G.
Power Switch
The systems do not have a power switch. The amount of input power required by these
systems classifies a power switch as an incendiary device because the voltage and cur-
rent across the make/break device are capable of creating a spark.
Hazardous locations’ regulations require that a power switch rated for ordinary locations
may be used if it is located in an area specified as non-hazardous. However, limits in ca-
ble length between the workstation and the power switch may apply. Otherwise the
switch must be compliant with Class I, Division 1 requirements (intrinsically safe).
These switches are built in a manner that prevents the possibility of a spark when con-
tacts are made or broken.
Use suitable UL listed and/or CSA Certified Class I, Division 1 switches in hazardous
locations. These switches are available from a wide number of sources. It is the respon-
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