CLIF-CBUSLC INTERFACE – INSTALLATION & COMMISSIONING INSTRUCTIONS
EN1Z-1026GE51 R0417 22
APPENDIX 1: EARTH GROUNDING
CLIF-CBUSLC and SELV
In order to avoid distribution of noise or earth ground potential
differences over networks or other connections, the CLIF-
CBUSLC is designed to be in compliance with SELV (Safety
Extra-Low Voltage).
Furthermore, SELV offers the greatest possible safety against
electrical impact.
To support SELV, all Honeywell external (CRT series) or
internal transformers comply with standard EN60742.
Earth grounding is therefore not recommended.
CLIF-CBUSLC and Standard EN60204-1
However, if compliance with EN60204-1 is required, note the
following:
General Information about EN60204-1
EN60204-1 defines electrical safety for a complete application
/ machine including controllers, sensors, actuators and any
connected/controlled electrical device.
EN60204-1 requires controllers to be powered by PELV
(Protective Extra-Low Voltage) and earth grounding of the
secondary side of the used transformers or earth grounding of
the system ground.
Earth grounding is prescribed to prevent unexpected start-up
of connected rotating/moving machines due to an insulation
fault and double earth grounding somewhere in the plant.
In order to fulfill PELV (if earth grounding is prohibited), the
use of an earth leakage monitor is also possible.
When is EN60204-1 Applicable to CLIF-CBUSLC
Systems?
Safety against electrical impact
– EN60204-1 is not mandatory; this is because electrical
safety is provided by the use of SELV and transformers
according to standard EN60742.
Safety against unexpected start-up of rotating/moving
machines
– If the application/plant does not contain machines that
can be harmful to the operator due to an unexpected
start-up, the standard EN60204-1 is not applicable.
If such machines are encountered, then EN60204-1 must be
followed. Grounding is required.
Earth Grounding of EN60204-1 Applicable
Systems
NOTE: Our recommendation is that each CPU be supplied
with electricity from its own dedicated transformer.
► If system protective earth grounding is planned, use a
cable as short as possible for grounding:
min. 1.5 mm² (16 AWG).
► For connection details, refer to the following examples.
Example 1
The following explains how to connect and earth multiple
CPUs (e.g., multiple CLIF-CBUSLCs, PANTHERs, TIGERs,
LIONs, etc. or any combination thereof) earth-grounded as
per EN60204-1.
NOTE: Use a noise-free earth ground inside the cabinet.
NOTE: If a field device that prohibits earth grounding is
connected to the system ground, an isolation
monitoring device must be used instead of earth
grounding.
► Connect earth ground to the respective terminal of the
CPU, see Fig. 24.
24 V~
24 V~
24 V~0
24 V~0
LINE
LINE
L
L
N
N
CPU 1
29 30
RS485-2 + RS485-2 -
COM
B
COM
B
NOISE-FREE EARTH GROUND
(ONLY ONE PER SYSTEM)
NOISE-FREE EARTH GROUND
(ONLY ONE PER SYSTEM)
COM
A
COM
A
74 7472 7273 7371 71
24V~ 24V~24V~0 24V~0
21
24V~24V~0
CPU 2
29 30
RS485-2 + RS485-2 -
21
24V~24V~0
I/O MODULE I/O MODULE
GND
FIELD DEVICE
24 V~
Y
RECOMMENDED
Fig. 23. Connecting and earthing multiple CPUs
(RECOMMENDED USE OF SEPARATE TRANSFORMERS)
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