How many 240 volt fluorescent (2 X 4 recessed, 4 tubes) fixtures can I connect to a 30 amp breaker using 4 mmsq cable?
Sounds like europe? Total Wattage divided by voltage = Amps or Volts x Amps = Watts. so 240V x 30A= 7200W. I would personally not hit that 7200 total watts and have the circuit totally loaded. so the wattage of the lamps is the determining factor as Niall said.