240 Volts? Are you in Europe?
Perhaps you mean to say 240 Watts, in which case I don't believe it will work.
I found this power consumption comparison here at Tom's:http://www.tomshardware.com/reviews/radeon-hd-4770,2281-13.html
It looks as though it will draw about the same power as an HD4850.
If 240W is your supply, you may be able to run an HD4670, but I wouldn't count on it.