General Tools and Instruments CA10 - Manual (Page 11)

Notes: 1) Be sure any surge suppression system used is properly grounded so it
can continue to protect loads during transient overvoltage conditions. 2) Before
measuring any parameter, remove any heavy loads from the circuit to avoid
producing an inaccurate test result. 3) Before measuring Z-E, be sure to
disconnect any RCDs from the circuit to avoid triggering them. 4) A ground
connection is required to test the impedance of conductors in 2-wire systems.
TESTING RESIDUAL CURRENT DEVICES (RCDs)
The CA10 can measure how much current it takes to trip an RCD, and how
quickly it responds to an event that should cause a trip. It does so by placing a
resistance across the circuit’s live and ground lines, generating a current
between them. According to UL, it should take no more than 30mA to cause a
trip. The CA10 measures and displays the triggering current (in mA) and the
response time (in ms).
To select the RCD test, press the FUNC button until RCD is highlighted. Then
plug the free end of the test cable into any outlet equipped with an RCD. To
initiate the test, press the TEST button. During testing, the display will show the
word TEST on the top line. If the device fails to be triggered, the analyzer will
stop testing automatically after 6.5 seconds.
The table below shows the normal measurement result of RCD testing. It also
lists possible causes of, and remedies for, an abnormal result.
Notes: 1) Before testing, remove any heavy loads from the circuit to avoid
producing an inaccurate test result. 2) A ground connection is required to test
RCDs in 2-wire systems. 3) Another common name for a residual current device
(RCD) is a residual current circuit breaker (RCCB).
11
Parameter
RCD reliability
and response
time
Normal
Measurement
Result
RCD trips within
specified time
Actual Result
RCD is too slow
to trip
RCD fails to trip
Possible Cause
of Abnormal
Result
RCD is installed
improperly
RCD is defective
Remedy
Check that installation
complies with
manufacturer’s
requirement and relevant
standards
Repair or replace RCD