Bosch CL200, User Manual

Page: 145 / 159

Installation
17–5
1070 072 145-102 (01.07) GB
17.2.4 Reference Conductor Not Connected to PE Conductor
If the reference conductor (N, 0 V) is not is not interconnected with the PE
conductor network, the introduction of a suitable earth leakage monitor for
the detection of ground faults will be required. This provides protection
against inadvertent Power-On in the case of insulation faults. As a result, the
power supply circuit becomes a SELV circuit (see also section 17.1). In this
context it must be considered that the earth-leakage protection may also be
rendered ineffective by virtue of connecting additional electrical equipment.
L1
L2
L3
N
PE
24 V 24 V
E E A A
0 V + 0 V +
Earth
leakage
monitor
E1
E2
NT200
17.2.5 Programming Unit and Earthing
In the majority of cases, programming units inherently feature a connection
between (equipment) ground and protective earth. This connection gives
rise to problems in situations where the power supply of the CL200 is equip-
ped with an earth-leakage monitor and the programming unit is connected to
the central processing unit.
Due to the non-isolated operation of the NT200 power supply module, the
earth fault in the programming unit continues via the central processing unit
and the NT200 power supply module to trigger the earth-leakage monitor. In
this case, the monitoring device should not cut power to the system automa-
tically but simply provide an indication or display of the earth leakage. The
maintenance personnel should be informed of this operating characteristic.