The purpose of Proportional Flow Control Devices, with Protection from Cross Connection via Hydronic Water, for use in Potable Water Installations is to control the flow of potable water based on the pressure of hydronic water from a hydronic system. The devices perform this hydraulically and have integral cross‐connection protection between the potable and hydronic water. These devices are typically installed in conjunction with a heat exchanger and a part of a hydronic system loop. 

The device consists of a single potable cold water supply inlet and outlet, and a single hydronic supply inlet and outlet, a means of dynamic flow control, an atmospheric vent, and two sets of three dynamic seals between the potable and hydronic flow paths.