(5)U Fuel Oil Viscosity. On or after July 1, 1978, no person shall cause, suffer, allow, or permit the burning of any grade residual oil in any fossil fuel utilization facility with an energy input capacity rated by the Department as equal to or greater than 250,000,000 Btu per hour unless said facility is equipped with an automatic viscosity controller that shall control the viscosity of the fuel oil to the burners. The automatic controller shall be of a type approved by the Department. The Department may require a fossil fuel utilization facility with an energy input capacity rated by the Department as equal to or greater than 100,000,000 Btu per hour but less than 250,000,000 Btu per hour to be equipped with an automatic viscosity controller if, in the opinion of the Department, such is deemed necessary.