I'm having exactly the same problem an this:
-With only the supply cable connected, the test button does nothing
-If I connect the lighting circuit with a pull switch and 11w LE bulb, as soon as I pull the switch, the RCD trips
- If I connect the ring main and plug a drill in, plugging the drll in is fine but as soon as I ull the trigger, again the RCD trips
- I only hve a single nuetral bar
- The unit is badged 'CTI'
-With only the supply cable connected, the test button does nothing
-If I connect the lighting circuit with a pull switch and 11w LE bulb, as soon as I pull the switch, the RCD trips
- If I connect the ring main and plug a drill in, plugging the drll in is fine but as soon as I ull the trigger, again the RCD trips
- I only hve a single nuetral bar
- The unit is badged 'CTI'