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RCD Test Function
CAUTION
Although fully protected against over voltage to 550VAC this tester should only be
used on a 230V supply.
The KT63 PLUS will test all the most commonly encountered RCD’s of both standard (AC & A)
types and selective (ACS & AS) types across the full range of tests required by BS7671 (IET
wiring regulations 2018).
Test Requirements
Each RCD is tested to ensure that:
• It is not prone to ‘nuisance’ tripping it. It checks that it does not trip when a fault of half its
rated current is introduced. This is referred to as the x½ test.
• It operates with a maximum disconnection time of 300ms (AC&A type) when a fault at its
rated current is introduced. This is referred to as the x1 test.
• In the case of an RCD rated at 30mA there is an additional requirement that it operates
with a maximum disconnection time of 40ms when a fault of five times its rated current is
introduced. This is referred to as the x5 test.
For the reasons explained below all of the above tests have to be conducted at both 0° and
180° this means that four tests (or for 30mA RCD’s six tests) have to be made for each RCD.
The user friendly design of the KT63 PLUS simplifies the test process by enabling you to do
any of these tests by making just two function selections.
Sinusoidal Polarity (the 0° or 180° test)
RCD’s often operate with different reaction times depending upon whether the fault is
introduced during the positive or negative half cycle of the AC waveform. Therefore to
accurately determine the maximum response time of an RCD it is necessary to test it twice
at each given fault current, firstly with the fault introduced during the positive half cycle and
secondly during the negative half cycle.
The KT63 PLUS takes care of this for you by alternating the start point of consecutive tests
at any given setting. If for example you have selected a test at the rated trip current (x1) of a
100mA RCD, the first press of the test button will apply a 100mA fault current starting on the
positive half cycle (0°) and display the result. A further press of the test button will carry out
another test at the same current but starting on the negative half cycle (180°).
