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xvii
Operating Environment Precautions
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measure for such problems, external safety measures must be provided
to ensure safety in the system.
• When the 24-VDC output (service power supply to the PLC) is overloaded
or short-circuited, the voltage may drop and result in the outputs being
turned OFF. As a countermeasure for such problems, external safety
measures must be provided to ensure safety in the system.
!WARNING
The CPU Unit refreshes I/O even when the program is stopped (i.e., even in
PROGRAM mode). Confirm safety thoroughly in advance before changing the
status of any part of memory allocated to I/O Units, Special I/O Units, or CPU
Bus Units. Any changes to the data allocated to any Unit may result in unex-
pected operation of the loads connected to the Unit. Any of the following oper-
ation may result in changes to memory status.
• Transferring I/O memory data to the CPU Unit from a Programming
Device.
• Changing present values in memory from a Programming Device.
• Force-setting/-resetting bits from a Programming Device.
• Transferring I/O memory files from a Memory Card or EM file memory to
the CPU Unit.
• Transferring I/O memory from a host computer or from another PLC on a
network.
!Caution
Confirm safety at the destination node before transferring a program to
another node or changing contents of the I/O memory area. Doing either of
these without confirming safety may result in injury.
4
Operating Environment Precautions
Do not install the Unit in any of the following locations.
• Locations subject to direct sunlight.
• Locations subject to temperatures or humidities outside the range speci-
fied in the specifications.
• Locations subject to condensation as the result of severe changes in tem-
perature.
• Locations subject to corrosive or flammable gases.
• Locations subject to dust (especially iron dust) or salt.
• Locations subject to exposure to water, oil, or chemicals.
• Locations subject to shock or vibration.
Provide proper shielding when installing in the following locations:
• Locations subject to static electricity or other sources of noise.
• Locations subject to strong electromagnetic fields.
• Locations subject to possible exposure to radiation.
• Locations near to power supply lines.
!Caution
The operating environment of the PLC System can have a large effect on the
longevity and reliability of the system. Improper operating environments can
lead to malfunction, failure, and other unforeseeable problems with the PLC
System. Be sure that the operating environment is within the specified condi-
tions at installation and remains within the specified conditions during the life
of the system.
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