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4. Check RCD tester
A. CHECKING A RCD TESTER
RCD tester simulates a current between live and earth to trip
TEST BOX.
The disconnect time of relay is shown on RCD tester usually in
milli-seconds if TEST BOX and RCD tester select the correct
current and the correct time range.
Generally, the tester has several current ranges plus a ‘5l’
function which multiplies the current range set by 5.
As switches can switch off, it is important to check more than
one current range. Leaving the instrument on the same range
in every check.
If too much current is induced into the tester, the RCD will TRIP.
For example, If you are checking a circuit which should have a
30mA RCD and the faulty range of your tester is on the 300mA
range, this will open any trip up to 300mA.
Test with both a long and a short trip time to ensure that it is
correct. It is less important if the tester has a ‘positive/negative’
cycle switch. This will be better for timing measurement.
The unique features of the electronic trip of TEST BOX allow
all the above to be tested quickly and easily. Accurate timing
is ensured as the time period is not dependant on the current
transition and an over-current LED can be lit. The positive/
negative switch can be checked, as the time period will be
10mS longer than starting on the negative cycle.
If the TEST BOX RCD is "TRIPPED", it is almost no check the
correct operation of the tester. There is no indication of over
current and the timing accuracy is poor need to change current
range on the tester.
