Chiller Pump Control using Temperature Sensor Feedback

In commercial chilled water systems, one of the most prevalent system topology is the Primary/Secondary topology. In this topology, the primary and secondary circuits of the hydronic cooling system are hydraulically decoupled by a common pipe also referred to as the bypass. This allows the primary circuit to ensure minimum chiller flow without interfering with the secondary side. To maximize heat transfer and achieve optimal performance, the flow in the primary and secondary systems must equalize and thus leave no flow in the bypass line when the minimum chiller flow requirement is fulfilled. To achieve this goal in a robust and responsive manner a simple and cost-effective feedback method is proposed, where 3 temperature sensors constitute the control feedback for the primary pump control. Closed-loop stability is proven and automatic sensor calibration is proposed. The method is verified through lab test on a setup emulating by-pass of the Primary/Secondary topology.