System Lifecycle
HI 803 211 E Rev. 1.01.00 Page 99 of 110
9.1.6 Grounding Several Control Cabinets
Connect several control cabinets to a central, interference-free ground; individually ground the
control cabinets of a controller, if required.
Ensure at least 16 mm² cross-section for the connection between the central grounding points of
the control cabinets and the common central ground.
Cabinet frame
M 2500 busbar
Central grounding point
Central ground
Figure 36: Control Cabinets with Central Ground
9.1.7 Ungrounded Operation
In ungrounded operation, a single ground fault does not affect the safety and availability of the
controller.
If several undetected ground faults occur, faulty control signals can be triggered. For this
reason, HIMA recommends using ground fault monitoring for ungrounded operation. Some
application standards, e.g., DIN EN 50156-1:2005, prescribe the use of ground fault monitoring.
Only use ground fault monitoring devices approved by HIMA.
9.1.8 Grounded Operation
Requirements for grounded operation are proper ground conditions and, whenever possible,
separate ground connection, in which no parasitic currents may flow. Only the negative pole L-
may be grounded. The positive pole L+ must not be grounded since a potential ground fault on
the sensor wire would bridge the affected sensor.
L- can only be grounded at one point within the system. L- is usually grounded directly behind
the power supply unit (e.g., on the busbar). Grounding should be easy to access and well
separate. The grounding resistance must be ≤ 2 Ω.
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