Whenever possible, incorporating External Device Monitoring (EDM) and/or Adjustable Valve Monitoring (AVM) is highly
recommended to monitor devices under control (FSDs and MPCEs) for unsafe failures. See
on page 53 for more information.
Output Connections—The Safety Relay Outputs must be connected to the machine control such that the machine's safety
related control system interrupts the circuit or power to the machine primary control element(s) (MPCE), resulting in a non-
hazardous condition. When used, Final Switching Devices (FSDs) typically accomplish this when the safety outputs go to
the Off state.
The Safety Relay Outputs can be used as the Final Switching Device (FSD) and can be interfaced in either a Dual-Channel
or Single-Channel safety (protective) stop circuit (see
on page 18 before making connections and interfacing the Safety
Controller to the machine.
The level of the safety circuit integrity must be determined by risk assessment; this level is dependent on the configuration,
proper installation of external circuitry, and the type and installation of the devices under control (FSDs and MPCEs). The
safety relay outputs are suitable for Category 4 PL e / SIL 3. See
on page 51 for hookup examples.
Important: The user is responsible for supplying overcurrent protection for all relay outputs.
Overvoltage Category II and III Installations (EN 50178 and IEC 60664-1)
The XS/SC26-2 and SC10-2 are rated for Overvoltage Category III when voltages of 1 V to 150 V ac/dc are applied to the
output relay contacts. They are rated for Overvoltage Category II when voltages of 151 V to 250 V ac/dc are applied to the
output relay contacts and no additional precautions are taken to attenuate possible overvoltage situations in the supply
voltage. The XS/SC26-2 or SC10-2 can be used in an Overvoltage Category III environment (with voltages of 151 V to 250 V
ac/dc) if care is taken either to reduce the level of electrical disturbances seen by the XS/SC26-2 or SC10-2 to Overvoltage
Category II levels by installing surge suppressor devices (for example, arc suppressors), or to install extra external insulation
in order to isolate both the XS/SC26-2 or SC10-2 and the user from the higher voltage levels of a Category III environment.
For Overvoltage Category III installations with applied voltages from 151 V to 250 V ac/dc applied to the output contact(s):
the XS/SC26-2 or SC10-2 may be used under the conditions of a higher overvoltage category where appropriate
overvoltage reduction is provided. Appropriate methods include:
• An overvoltage protective device
• A transformer with isolated windings
• A distribution system with multiple branch circuits (capable of diverting energy of surges)
• A capacitance capable of absorbing energy of surges
• A resistance or similar damping device capable of dissipating the energy of surges
When switching inductive ac loads, it is good practice to protect the XS/SC26-2 or SC10-2 outputs by installing
appropriately-sized arc suppressors. However, if arc suppressors are used, they must be installed across the load being
switched (for example, across the coils of external safety relays), and never across the XS/SC26-2 or SC10-2 output
contacts (see WARNING, Arc Suppressors).
7.8.3 EDM and FSD Hookup
External Device Monitoring (EDM)
The Safety Controller’s safety outputs can control external relays, contactors, or other devices that have a set of normally
closed (N.C.), force-guided (mechanically linked) contacts that can be used for monitoring the state of the machine power
contacts. The monitoring contacts are normally closed (N.C.) when the device is turned Off. This capability allows the Safety
Controller to detect if the devices under load are responding to the safety output, or if the N.O. contacts are possibly
welded closed or stuck On.
The EDM function provides a method to monitor these types of faults and to ensure the functional integrity of a dual-
channel system, including the MPCEs and the FSDs.
A single EDM input can be mapped to one or multiple Safety Outputs. This is accomplished by opening the Safety Output
Properties window and checking EDM, then adding External Device Monitoring from the Safety Input tab in the Add
Equipment window (accessed from the Equipment tab or Functional View tab), and connecting the External Device
Monitoring input to the EDM node of the Safety Output.
The EDM inputs can be configured as one-channel or two-channel monitoring. One-channel EDM inputs are used when the
OSSD outputs directly control the de-energizing of the MPCEs or external devices.
• One-Channel Monitoring—A series connection of closed monitor contacts that are forced-guided (mechanically
linked) from each device controlled by the Safety Controller. The monitor contacts must be closed before the Safety
Controller outputs can be reset (either manual or automatic). After a reset is executed and the safety outputs turn
On, the status of the monitor contacts are no longer monitored and may change state. However, the monitor
XS/SC26-2 and SC10-2 Safety Controllers
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