Comparing the ‘local loop’ value and the ‘+1.0Ω’ value should show the increase of 1Ω, within
the manufacturer’s tolerance.
• Either the test instrument or the supply socket is then switched off for a period of 5
seconds.
• After 5 seconds the FC2000 loop impedance switch is moved to the +100Ω position.
• The instrument or supply socket is then switched on.
• The earth fault loop impedance test is then carried out in the usual way. The measured
value is recorded on the instrument record sheet.
Comparing the ‘local loop’ value and the ‘+100Ω’ value should show the increase of 100Ω,
within the manufacturer’s tolerance.
Refer to section 4.4 for examples of how to apply tolerances.
Ongoing accuracy record
To give a more exact indication of the instrument accuracy it is strongly recommended
that the same dedicated power outlet is used each time for the checks. This will allow the
instrument to be compared with the:
• actual local loop value
• FC2000 ‘local loop’ value at that socket
• FC2000 ‘local loop + 1Ω’ value
and
• FC2000 ‘local loop + 100Ω’ value.
This process will give a reference against three Reference Values and provide a more precise
indication of the instrument accuracy.
The earth fault loop impedance tester is used to
1 Test and record the actual loop impedance from the dedicated socket outlet.
2 Test and record the FC2000 ‘local loop’ value.
3 Test and record the ‘local loop + 1Ω value.
4 Test and record the ‘local loop + 100Ω value.
Each of the above tests is repeated three times and the average value recorded as the
Reference Value for each test.
The Reference values obtained for tests 1, 2, 3 and 4 above (socket loop, local loop, local
loop +1Ω and local loop + 100Ω) then provide four reference points with which to compare
the instrument accuracy.
• The earth fault loop impedance tester is used to test the earth fault loop impedance at
the dedicated socket and the value recorded on the instrument record sheet.
• The earth fault loop impedance tester is then plugged into the FC2000 socket outlet
and the test carried out in the usual way. The measured value is recorded.
• Either the test instrument or the supply socket is then switched off for a period of 5
seconds.
• The FC2000 loop impedance switch is moved to the +1Ω position.
• The instrument or supply socket is then switched on.
• The earth fault loop impedance test is then carried out in the usual way. The measured
value is recorded on the instrument record sheet.
• Either the test instrument or the supply socket is then switched off for a period of 5
seconds.
• After 5 seconds the FC2000 loop impedance switch is moved to the +100Ω position.
• The instrument or supply socket is then switched on.
• The earth fault loop impedance test is then carried out in the usual way. The measured
value is recorded on the instrument record sheet.
• The measured values obtained for each of the four tests are then compared with the
reference values on the Record Sheet. The results should be within the manufacturer’s
tolerance of the Reference Value.
If the results show the instrument is accurately measuring the values, within the instrument
manufacturer’s tolerance then the instrument is suitable for continued use.
If any of the measured values are outside the manufacturer’s tolerance then the instrument will
need to be returned for calibration.
Refer to section 4.4 for examples of how to apply tolerances.
7 Residual Current Device Checks
The FC2000 provides a facility to check the accuracy of residual current device test instru-
ments relative to the testing of 30mA RCDs, the most common type used for additional
protection.
Note: Using the RCD test function will introduce a small fault current to the circuit being used
to power the check box for a period of 38ms in the same way that using an RCD tester on the
same circuit without the check box in-line would. It is therefore recommended that this function
is used on non-RCD protected circuits.
When the RCD/LOOP switch of the FC2000 is set to the RCD position the tests of:
• ½ × IΔn test at 15mA
• 1 × IΔn test at 30mA
• 5 × IΔn test at 150mA
can be carried out at the FC2000 socket outlet.
The FC2000 checks both the accuracy of the displayed disconnection time and the accuracy
of the tester’s output current.
Note: The FC2000 function for the 1 × IΔn and the 5 × IΔn test has a set operation time of
38ms ±1ms so the instrument being checked should display a value, subject to the instru-
ment manufacturers’ tolerance, of 37–39ms.
