A customers downstairs lights keep tripping (they have advised me that this has been happening for the last 7 years that they have been living there). All lights are standard type lamps and there are no low voltage transformers used on these lights. The lighting circuit has 2 x wall lights, 4 ceiling lights and a outside light, there seems to be a 300+ volts shown at the kitchen switch (which operates one light with 4 x LED GU10 lamps). When this light is switched on the voltage drops down the 238 volts. The lounge switch which controls 2 x ceiling lights shown 238volts. Does anybody have any ideas ?