This paper examines the control of supply water temperature from boilers and steam-to-hotwater converters using water-mixing valves. By analyzing the steady-state process gain, the appropriate mixing valve characteristics were identified. The range of gain variations that occur when supply water temperature and heat load vary are shown. Minimizing gain variations is an important criteria for valve selection and control system design and tuning. Steady-state gain analysis is shown to be a simple yet powerful technique for identifying and resolving potential control problems.

Units: SI