Chapter 2: Installation and Wiring
2–4
DL205 Installation and I/O Manual, 2nd Edition
Emergency Power Disconnect
A properly rated emergency power disconnect should be used to power the PLC controlled
system as a means of removing the power from the entire control system. It may be necessary
to install a capacitor across the disconnect to protect against a condition known as “outrush”.
This condition occurs when the output Triacs are turned off by powering off the disconnect,
thus causing the energy stored in the inductive loads to seek the shortest distance to ground,
which is often through the Triacs.
After an emergency shutdown or any other type of power interruption, there may be
requirements that must be met before the PLC control program can be restarted. For
example, there may be specific register values that must be established (or maintained from
the state prior to the shutdown) before operations can resume. In this case, you may want to
use retentive memory locations, or include constants in the control program to insure a
known starting point.
Orderly System Shutdown
Ideally, the first level of fault detection is the PLC control
program, which can identify machine problems. Certain
shutdown sequences should be performed. The types of
problems are usually things such as jammed parts, etc.
that do not pose a risk of personal injury or equipment
damage.
WARNING: The control program
must not be the only form of
protection for any problems that may result in a risk of personal
injury or equipment damage.
Class 1, Division 2, Approval
This equipment is suitable for use in Class 1, Division 2, Zone 2, groups A, B, C and D or
non-hazardous locations only.
WARNING: Explosion Hazard! Substitution of components may impair suitability for Class 1, Division 2,
Zone 2.
WARNING: Explosion Hazard - Do not disconnect equipment unless power has been switched off or the
area is known to be non-hazardous.
WARNING: All DL205 products used with connector accessories must use R/C (ECBT2) mating plugs. All
mating plugs must have suitable ratings for the devices.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
A
B
C
D
Turn off
Saw
Jam
Detect
RST
RST
Retract
Arm