The system mainly consists of differential pressure control mounted on the way between the main water supply and the main water return, and automatic control valve mounted by-pass pipeline. The differential pressure control detects pressure difference between the main water supply and the return one and operates the automatic control valve to realize by-passing between the main water supply and the return one according to the result gained so as to keep required pressure difference.

Outside air unit control principle Air handling unit control principle Differential pressure by-pass control principle Heat exchanger control principle