2
■
Humidity
In order to maintain the insulating properties of the PLC, relative humidity should be kept
within the range of 35% to 85%. In particular in the winter, when heaters are turned on and
off, sudden changes in temperature may be experienced resulting in condensation which can
lead to shorts or malfunctions. Where there is danger of such a change in temperature, power
should be kept on during the night and condensation should be prevented through such
measures as installing a small heater inside the panel to maintain low heat.
(See Figure 2)
■
Vibrations/Shocks
The PLC is tested in accordance with the environmental (electricity and
electrons) the sine wave vibration test method (JIS C0040/IEC68-2-6)
and the shock test method (JIS C0041/IEC68-2-27), so that vibrations
and shocks in the general specifications will not cause malfunctions.
However, the system should not be installed in a place where it will be
subject to regular vibrations or shocks, especially to the PLC and the
panel.
The following methods may be used to reduce the effect of vibrations and shocks.
1
For vibrations and shocks that originate externally, the panel should be removed from the
source. Alternatively, the PLC and the panel should be protected with the use of rubber.
2
Isolate vibrations such as through the construction of the building, flooring etc.
3
Regarding shocks experienced during magnetic contactor
operation in the panel, the source of the shock or the PLC should
be protected by rubber so that the shock is not felt.
■
Atmosphere
When using the system in any of the following kind of places, connections
may be loosened or elements and parts may experience corrosion, and an air
purge should be implemented to avoid this.
1
Places where dust, salt, particles, soot or organic solvents etc are
common, and where the enclosure is sealed in such a way that the
internal temperature does not increase very much.
2
Where corrosive gases are common, an air purge (air purification)
of the panel should be performed, to pressurize the panel and
prevent the intrusion of air from outside.
3
Places with flammable gases may be a cause of ignition. The system
should not be used without a fire prevention mechanism in place.
■
Work Space
When installing the PLC and the panel, please consider their use, operability and
maintenance, and pay particular attention to the following.
1
Make sure that there is sufficient space to operate programs and to
replace the unit. Further, for the sake of saftey and maintenance,
installation should be as far as possible from high pressure or high
power devices.
2
Mount the PLC and I/O unit in a position in which the use of the
debugging tool and the connection and operation of peripheral
devices will be possible.
3
The PLC and I/O unit generally has a maintenance light, and this
should be easy for the operator to see, and in a position where it can
easily be reached.
4
For systems using the PLC as a control system, it is likely that there
will be future additions and alterations to the system, so approx. 10-
20% extra space should be allowed for this.
5
Where necessary, about 600 mm of space should be kept behind
the panel for the purpose of performing maintenance.
PLC Control Panel Electrical Conditions
The power supply, grounding, and noise make up the main elements of the electrical conditions. In the installation and wiring of the device, great care must
be taken to ensure that there is no danger to the human body, and that electrical signals are not obstructed (noise).
■
PLC Installation Site
For the sake of safety in maintenance and operation, installation
should not be near high current (more than 600V) or high power
devices. Where this cannot be avoided, installation should be as far
away from such devices as possible.
(See Figure 3)
●
Arrangement of PLC and Each Unit
(See Figure 4)
1
The CPU and other adjoining units should be special or input units
where noise generation is limited.
2
The coils and contacts in electromagnetic contactors and relays in
an external circuit are sources of noise. Locate them at least 100
mm away from the PLC.
A
bs
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ent M
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Power
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He
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ter
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(Ex
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ipment Arr
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PLC
Control P
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Control P
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P
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Fig
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3
. Ex
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s
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ipment Arr
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(Ex
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ipment Arr
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PLC
Control P
a
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Control P
a
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P
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Fig
u
re 4. Ex
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bu
ilt-in type
DC
I/O
Device
AC
I/O
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Termin
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CPU
P
o
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r Unit
DC Unit
DC Unit
A
C
Unit
A
C
Unit
Comm
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Unit
