The city council of a city of the metropolitan class shall at no time draw warrants or create obligations against any of the funds provided in sections 14-501 and 14-502 in excess of the amount credited to such funds at the time of drawing the warrant or creating the obligation. The director of any department shall not draw or cause to be drawn a warrant or create or cause to be created an obligation against the appropriation to such director's department in excess of the amount credited to such department.