8.10 Type B (Pure DC) RCD test (Not MFT1815)
‘Type B’ RCDs are sensitive to pure DC fault currents, as well as pulsed AC and ordinary AC fault currents.
First they are tested as Type A then Type B, using a pure DC test current.
Type ‘B’ RCD’s are only tested on the 1xI range. The result displayed in milli-seconds (ms).
1. Test the RCD in ‘Type A’ mode for 1/2xI , 1xI and 5xI if it is a 30 mA RCD. Test it in 1xI only if it is > 30 mA.
2. To select a Type B RCD press and hold the mode button
repeatedly until the symbol is displayed.
3. Connect the Red (L1), Green (L2) and Blue (L3) terminals of the MFT to the RCD Live, Neutral and Earth as below
(‘Type AC’ and ‘Type A’ RCD’s only need Phase and Earth connections).
RCD
g
L
N
E
MCB
4. Select the 1xI range on the left range knob, and the current rating of the RCD on the right range knob.
5. Press the TEST button.
6. The RCD should trip and display the trip time in ms. The “Touch Voltage” is displayed on the small digital
readout. The trip current in mA can be measured for Type B RCD’s using the ramp test.
NOTE : Only 1xI is available. Selecting other test currents will reset the test type to AC.
Only 10 mA, 30 mA, 100 mA and 300 mA test options are available on DC testing.
www.megger.com MFT1800 series
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Residual Current Device (RCD) or Ground Fault Current Interrupt (GFCI) testing
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