testing A type RCDs

This is what the instructions for my Megger MFT say:

"8.7 Type A (DC Sensitive) RCD test 

‘Type A’ RCDs are sensitive to pulsed DC as well as AC fault currents, and are tested with a pulsed waveform. The RMS current is √2 x the rated operating current of the RCD. As with the normal RCDs, these should be tested with 0° and 180° polarity. 

1. To select a Type A RCD see section 8.2 These are tested in exactly the same manner as those tested in section 8.3 to 8.6.

Note: Type A RCDs should be tested at 0° and 180° on 1/2xI, 1xI and 5xI

8.8 Type B (Pure DC) RCD test (not MFT1711)

‘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. 

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).

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 trest.

Notes: 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."

So there you have it: test type AC as such; test type A as such; and test type B as type A and then the smooth DC function separately.

This is what the instructions for my Megger MFT say:

"8.7 Type A (DC Sensitive) RCD test 

‘Type A’ RCDs are sensitive to pulsed DC as well as AC fault currents, and are tested with a pulsed waveform. The RMS current is √2 x the rated operating current of the RCD. As with the normal RCDs, these should be tested with 0° and 180° polarity. 

1. To select a Type A RCD see section 8.2 These are tested in exactly the same manner as those tested in section 8.3 to 8.6.

Note: Type A RCDs should be tested at 0° and 180° on 1/2xI, 1xI and 5xI

8.8 Type B (Pure DC) RCD test (not MFT1711)

‘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. 

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).

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 trest.

Notes: 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."

So there you have it: test type AC as such; test type A as such; and test type B as type A and then the smooth DC function separately.