The macroscopic energy equations are developed and solved for regenerative air heater systems. The results of these solutions are used to show the effect of different control actions on the minimum metal temperature. The control actions that are studied are the use of a steam coil air heater, cold air by pass and hot air recirculation. The minimum metal temperature is presented for no control and the change in temperature due to the control action. The results are presented under a format that will permit the designer to evaluate the economics of different means of control.