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.2 Connect the Green (L2) terminal of the MFT to the upstream phase of an RCD on a separate phase.
.3 Press the TEST button.
.4 The MFT will display the trip time of the RCD.
8.12 Touch voltage display
The voltage to which an earth conductor may rise during an RCD test. The limit for touch voltage is 50 Vac or 25 Vac, depending on the
environment.
Touch voltage is caused by excessive resistance in the earth circuit when a load is placed between the live and earth conductors.
Touch voltage is displayed:
- at the end of an RCD test the voltage is below the safe limit
- before an RCD test is started if it would exceed the safe limit.
Touch voltage is calculated using the nominal trip current of the RCD x Earth resistance. For example:
RCD trip current = 30 mA
Earth resistance = 1000 Ω
0.03 A x 1000 Ω = 30 V
If the calculated touch voltage is less than the Touch voltage limit, the RCD test will proceed. If it is greater than the limit set, the test is
halted.
The Touch Voltage limit is set in section - UL 25 V, 50 V, 60 V
Notes: The touch voltage is always displayed using the nominal trip current of the RCD (ie 1xI).
If using the 1/2xI, 2xI or 5xI test ranges, the touch voltage will still be displayed for 1xI test current, as per IEC 61557-6.
2xI and 5xI can create real touch voltages during the test that are higher than the displayed value. If this voltage exceeds the touch volt-
age limit (UL) the test will be stopped.
Under these conditions the display will show the calculated touch voltage on the small digital segments and >50 V on the larger
digital segments, as below:
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