Excess Cooling on Fan Coil Units

Often the importance of individual sensors can be overlooked as they are so far down the chain that other problems get prioritised and there is simply not enough time to find them, not alone resolve them. However as can be seen in this HVAC fault detection case study, a single zone temperature sensor can have a significant knock on impact on energy, carbon and comfort levels. Using a building analytics platform to identify, prioritise and issue findings such as this one is the most cost effective and efficient way to keep your building operating well.


The OPNHVAC fault detection rules identified multiple zone temperature sensors reading at faulty levels of above 1000°C. The faulty sensors were being used to drive the control strategy for fan coil units in an open plan office space.

In addition, the OPNHVAC software was able to identify the impact these sensors were having on the HVAC system. It identified that the cooling values on the affected FCUs were going to 100% cooling during their daily operation. This in turn was adding unnecessary additional demand to the building's chilled water system.


The impact of the issue is quite obvious but impactful. The internal conditions affecting occupants comfort levels were impacted as well as an increased energy load being placed on expensive to run chiller equipment.

All of the above is quite serious when factoring in things like the life cycle of the main plant and increased energy loads. It shows that a simple sensor going faulty is not something to be ignored.


As the maintenance provider has all the information at hand for the issue on the OPNHVAC software, they are able to send the technician with the most appropriate skills to validate the findings and efficiently make the required repairs. The sensor can be replaced or repaired and the control strategy will kick back into the correct operation and thus resolve the issue. After the fix is made the OPNHVAC software will identify if the issue is still present or not and therefore automatically close off the issue for the building operators while also providing an additional layer of validation on the resolution to the problem.

Fan Coil Unit Analysis

Client Feedback

"Thanks to OPNBuildings the HVAC upgrade project for €1.1M was a success. Throughout the construction stage snags were easily identified, trouble shooted and addressed. On handover there was confidence the building was achieving air quality and thermal comfort and the necessary tools were in place to support the continuous improvement in building operation with fault detection and easy to use dashboards. OPNBuildings was the most important quality driver in this project and represented excellent value for money."

- Robert Ryan Facilities Project Manager at Ervia