Heat integration across plants can be accomplished either directly using process streams or indirectly using intermediate fluids. Extensions to many plants of LP and MILP models previously developed for the two-plant case are presented. The targeting procedure first identifies the maximum possible savings for the whole system, and, subsequently, the minimum number of connections between the two-plant combinations required to obtain maximum savings is established. The location of intermediate fluid circuits to indirectly integrate the system is then found. Alternative solutions exist, which allow flexibility when the design of a multipurpose heat exchanger network is pursued. Finally, the optimal location of the circuits for cases of restricted operation is discussed.