Siemens UL 489, Operating Instructions Manual, Page: 330 / 352

25 – 5
25.3 Primary Injection Ground Fault Current Testing
Circuit Breakers With 3-Wire Residual Ground Fault Protection
Testing is accomplished by routing current through one phase of the breaker. The Ground Fault Mode switch must be in the up position
(summation symbol) in order for the residual ground fault detection to be tested.
Circuit Breakers using 4-Wire Residual Ground Fault Protection via the External Neutral Sensor (air core)
To test a WL breaker equipped with trip 4-wire residual ground fault protection, the ETU must first be activated by injecting 80-100A through
the breaker itself (Source A). Once the ETU is active, the test current can be injected through the external neutral sensor to verify its con-
nection and polarity (Source B). The external neutral sensor does not provide energy to the ETU to activate it.
Figure 4
The same test can be conducted using a single power source. The ETU must be activated by injecting a minimum of 100A through the
breaker itself. The external neutral sensor does not provide energy to the ETU to activate it. Multiple windings through the external sensor
can be added to create greater imbalances.
Figure 5
ETU
Source A
Source B
Secondary Terminals
X8-9 & X8-10
External Air-Core Sensor on
Neutral Bus
ETU
Source
Secondary Terminals
X8-9 & X8-10
External Air-Core GF Sensor
on Neutral or Ground Bus