Unsolved Puzzle of the Faulty Preheating Valve
In a recent development, a complex issue involving a leaking preheat valve in a building's air handling unit (AHU) has been successfully resolved, resulting in significant annual energy savings.
The problem originated from a combination of factors, primarily control conflicts, condensation from humidification, pressure and temperature fluctuations, and valve and piping wear. When the AHU's preheat valve and the humidifier were not properly sequenced or modulated, conflicting signals could cause the preheat valve to remain partially open or cycle improperly, leading to water leakage. Additionally, the humidifier's operation could increase air moisture, causing condensation on the cooling surfaces near the preheat valve piping, resulting in water accumulation and leakage.
The unique case was first identified on August 13, 2018. The heating valve was observed opening when the humidifier was running due to a shared pneumatic line. This issue went unnoticed by building operators as the AHU met setpoint and was not detected by traditional commissioning methods due to the infrequent preheating and humidification.
Collaborative efforts between Cimetrics and facilities personnel were instrumental in identifying and resolving the root cause of the problem. The repair of the pneumatic system was necessary to fix the leaking preheat valve issue. The repair has ensured that the preheat valve no longer leaks when the humidifier is required, as confirmed by data.
The key to resolving this issue lay in understanding the configuration of the building automation system (BAS). A thorough review found the configuration to be fool-proof, ruling out any errors in the BAS point configuration or sequence of operations as the usual suspects.
The fix has led to annual energy savings of $3,500, which are expected to persist year after year due to the root cause being fixed. This case serves as a reminder of the importance of proper coordination of AHU controls and maintenance to ensure valve integrity and prevent leakage issues caused by AHU preheat valve and humidifier interactions.
Finance specialists in the industry have highlighted the economic impact of the issue resolution, estimating annual energy savings of approximately $3,500. As technology advances, improved building automation systems (BAS) could potentially avoid such instances in the future, thereby reducing maintenance costs in the energy sector.
