Fault Detected - Failure of Intake & Return Dampers In Air Handling Unit

Like any mechanical component, Dampers in Air handling units which are controlled by motors to adjust the airflow or quantity of the air to any particular path can fail. When they do so they can have severe consequences on the effective opperation of the air handling unit and any downstream conditioning.


The OPNHVAC software identified a serious and potentially dangerous HVAC fault in a large air handling unit serving a large retail store. The AHU is a supply and return air packaged Rooftop Unit with mixing dampers. Heating is provided by two-stage gas burners and cooling by two-stage DX Coils.

The OPNHVAC software picked up the fault by analysing the damper component as well as the mixed and supply air temperature profiles during operation of the unit. The algorithms determined that the air handling unit was choked with reduced airflow, this in turn was causing the supply air temperature, heated by the gas burner, to rise to dangerous levels of 60°C.


Validation on this fault took place as soon as the maintenance engineer received notification of the problem. Although a maintenance visit was not due to take place for 3 months, the impact of the issue was deemed too severe so an emergency call out took place.

During the call out the engineer was able to conduct a manual investigation to validate that the temperatures in the air handling unit was high and also that the return and fresh air dampers were stuck in a near closed position. Due to the risk of severe component damage or even fire from the high internal temperatures the repair was carried out immediately.


Because the maintenance provider had all the information fed to them from the OPNHVAC software, they were able to send the technician with the most appropriate skills to validate findings and efficiently make repairs. The motor controlling the dampers was replaced and the air handling unit quickly returned to normal operation. Validation of the fix was made via the OPNHVAC platform as the fault was no longer detected as present during the automatic daily analysis from the software after the repair took place.

The impact of the fault and its subsequent repair were significant. As the supply air was not being fed into the serving space, the control strategy was continally looking for more heat. This meant the gas burners were firing for far longer than necessary resulting in waste gas consumption while the critical zone being fed by the air handling unit was not achieving its setpoint. Further, as indicated, the high heat in the air handling unit had the risk of causing further damage to components in the air handling unit.

43,256 kg CO2e

Avoided Emissions


Avoided Operating Cost


Avoided AHU Replacement

Client Feedback

" Within days of starting a trial with OPNHVAC we identified a number of operational and energy saving improvement opportunities within our buildings. After successfully using the software within two of our pilot buildings, we are now investigating the potential for further integration with other Ervia offices. Continuous Monitoring and Reporting enables the FM Department to measure and demonstrate the performance of our office led assets. "

- Dermot Walsh Facilities Energy Manager at Ervia