Emergency Power Disconnect; Orderly System Shutdown; Class 1, Division 2, Approval - Automationdirect.com DirectLOGIC DL205 Series User Manual

Chapter 2: Installation, Wiring and Specifications

Emergency Power Disconnect

1
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".
2
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,
3
which is often through the Triacs.
After an emergency shutdown or any other type of power interruption, there may be
4
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
5
use retentive memory locations, or include constants in the control program to insure a
known starting point.
6

Orderly System Shutdown

Ideally, the first level of fault detection is the PLC control
7
program, which can identify machine problems. Certain
shutdown sequences should be performed. The types of
8
problems are usually things such as jammed parts, etc.
that do not pose a risk of personal injury or equipment
damage.
9
WARNING: The control program must not be the only form of
10
protection for any problems that may result in a risk of personal
injury or equipment damage.
11

Class 1, Division 2, Approval

12
This equipment is suitable for use in Class 1, Division 2, Zone 2, groups A, B, C and D or
non-hazardous locations only.
13
WARNING: Explosion Hazard! Substitution of components may impair suitability for Class 1, Division 2,
Zone 2.
14
WARNING: Explosion Hazard - Do not disconnect equipment unless power has been switched off or the
A
area is known to be non-hazardous.
WARNING: All DL205 products used with connector accessories must use R/C (ECBT2) mating plugs. All
B
mating plugs must have suitable ratings for the devices.
C
D
2–4
DL205 User Manual, 4th Edition, Rev. B
Turn off
Jam
Saw
Detect
RST
RST
Retract
Arm