In an ‘aircon’ system there are a lot of heat exchangers to transfer energy from heated or cooled fluid to the air in your office. The flow through these heat exchangers is controlled by valves, driven by mechanical actuators (motors).

There are many types of valve and valve actuator. Some of them push against the pressure of the water to turn off the water flow to turn the Fan off.

A surprisingly common, but unseen fault, is that valves allow water to pass. As valves corrode over time, the spindles get stuck. On lower floors the pressure against which the valve actuator must act is larger. Cheaper valve actuators (which are more likely to be installed to save money), can provide insufficient force to close the valve. Actuators without positional feedback (which are also lower cost), can over time allow passing by a shift of their zero position.

In a Fan Coil Unit this puts Hot and Cold water in close contact. The energy loss caused by such direct transfer can be very large.

This problem is unseen. With specific tests, we can find it, and fix it