Safety Isolation System
ElectroGuard
Wire Length Considerations/Ordering Instructions
The total wire length for the 5 RLS to be wired to the Control
Module will be: 100ft + 400ft + 200ft + 600ft + 1,000ft = 2,300ft
b. Sum the full-load currents of all the motor loads to be
connected to the Safety Isolation System. To this value add
the current values of all resistive loads to be connected to
the Safety Isolation System. This value is the “combined
load full-load current.”
c. Find the horsepower or kilowatt rating of a single motor with
a full-load current value greater than or equal to the
“combined load full-load current” value determined in Step
“b”.
Per the table entitled Total Wire Length for Remote Lockout Stations on
page 12-18, the maximum allowable wire length for 14AWG wire is
4,600ft for the RLS to be wired to the Control Module. This portion
of the installation will be within the maximum wire length permitted.
Next, we need to check the wire length calculation for the RLS to be
wired to the Expansion Module.
For RLS # 6: wire length = 1000ft x 2 = 200ft
For RLS # 7: wire length = 850ft x 2 = 1700ft
For RLS # 8: wire length = 750ft x 2 = 1500ft
d. Select the Safety Isolation System that meets or exceeds this
horsepower or kilowatt rating at the required voltage and
frequency.
e. Sum the locked-rotor currents of all the motor loads to be
connected to the Safety Isolation System. To this value add
the current values of all resistive loads to be connected to
the Safety Isolation System. This value is the “combined
load locked-rotor current”.
f. Find the horsepower or kilowatt rating of a single motor with
a locked-rotor current value greater than or equal to the
“combined load locked-rotor current” value determined in
Step “e”.
The total wire length for the 3 RLS to be wired to the Expansion
Module will be: 2000ft + 1700ft + 1500ft = 5,200ft
Per the table entitled Total Wire Length for Expansion Modules on page
12-18, the maximum allowable wire length for 14AWG wire is
40,000ft for the RLS to be wired to the Expansion Module. This
portion of the installation will also be within the maximum wire
length permitted.
Ordering Instructions
g. Select the Safety Isolation System that meets or exceeds this
horsepower or kilowatt rating at the required voltage and
frequency.
1. Determine the Catalogue Number of the Safety Isolation System
based on the rating of the load(s) to which it will be connected as
follows:
h. Compare the ratings of the Safety Isolation Systems selected
in Steps “d” and “g”. Select the larger of the two systems for
your application.
If the Safety Isolation System is connected to a single motor load,
the horsepower or kilowatt rating of the system should be
determined as follows:
a. Select the Safety Isolation System that meets or exceeds the
horsepower or kilowatt rating of the load at the required
voltage and frequency.
2. Determine how many Remote Lockout Stations are required for
the application.
3. Determine how many Expansion Modules (if any) are required
for the application.
4. Pick suitable enclosure type(s) for the Safety Isolation System
Power Panel, Remote Lockout Stations and enclosed modules
(e.g., Expansion Modules, Pneumatic Isolation Module).
5. Determine what, if any, factory installed options are required for
the application (e.g. Pneumatic Isolation, Status Communication
to remote PLC, metering).
If the Safety Isolation System is connected to two or more
motors or one or more motors in combination with other loads,
the horsepower or kilowatt rating of the system should be
determined as follows:
a. Identify the types of loads (i.e. motor, resistive) and the values
of the currents of each of the loads (i.e. steady-state current
for resistive loads, full-load and locked-rotor currents for
motor loads) to be connected to the Safety Isolation System.
12-19
ALLEN-BRADLEY [ Allen-Bradley ]
