Why a newly installed ventilation system can perform worse than the old one

The unit has been replaced, the ductwork is new and the controller is modern. Yet rooms are noisier, some zones receive less air, and the operations team constantly adjusts settings manually. The quality of a unit does not prove the quality of its integration into the building.

Switching on equipment does not mean commissioning is complete

A rotating fan confirms only that it has started. Commissioning must verify that actual operation meets the design requirements: airflow rates, operating modes, controls and protective responses.

‘The equipment is functioning correctly’ and ‘the system delivers the required conditions’ are different conclusions. The first can be true even with poorly designed ductwork or incorrect balancing.

Total airflow can conceal a local shortfall

The system must distribute 2000 m³/h between four identical zones, each receiving 500 m³/h. Actual measurements are 850, 600, 350 and 200 m³/h. The total is the same, but the last zone receives only 40% of its design airflow, while the first receives 170%.

Measurements in the main duct alone will not reveal the problem. Balancing and resistance checks are needed. Simply increasing fan speed may further increase the excess airflow in the nearest zones.

Installation changes the design aerodynamics

On site, a duct is moved, a transition shortened or a bend placed closer to the fan. Uneven flow and turbulence near the inlet or outlet can reduce airflow, increase noise and raise power demand.

The as-built drawing must reflect the actual installation. Otherwise, the commissioning engineer is trying to explain the behaviour of a duct network that no longer exists on site.

An on-screen command and a physical action are different things

The controller may display ‘valve closed’ even though the actuator is incorrectly installed or the valve is allowing heat transfer fluid through. A sensor may show a plausible reading but be poorly positioned. Checks must cover the entire chain: command → actuator → change in the physical parameter.

The client should receive actual airflow rates by zone, operating settings, descriptions of control sequences, test results and a list of deviations. An initial archive of parameters will provide a baseline for subsequent operation.

Installation ends with components in place. The engineering outcome begins when measurements confirm that the whole system works.