A routine maintenance visit identified multiple issues with the existing voltage optimisation (VO) equipment installed at the fire station. The site operates without a standby generator; however, UPS backup is available for essential services, offering limited resilience in the event of extended supply interruptions. Current supply protection was provided via a load breaker (L/B), although for optimal compliance and reliability this should ideally be upgraded to either a fused switch (F/SW) or an MCCB.
Condition of Existing VO Unit
On inspection, the VO system was found to be non-operational. Key issues observed included:
- The VO remained in inhibit mode, with the key switch failing to restore operation in auto.
- Contactor banks were not engaging; both C1 and C2 contactors were open, and associated MCBs were found switched off.
- Phase sequence was confirmed as L1 – L3 – L2, which can contribute to operational anomalies.
- Residual voltage readings indicated 13 V N–E and 13 V L1–E, traced back as feedback from the fire alarm panel.
- Solar PV generation was present on site, which can further complicate VO operation and system stability.
Given these conditions, the VO system was left safely in bypass mode as found. Persistent supply-side issues, particularly a voltage rise observed on L2, led to the recommendation for complete replacement of the unit.
Replacement Works
The failed VO system was removed and replaced with a new VM 400 3/5/7/9 Voltage Optimisation unit. The new unit was installed reusing the original terminations and bypass switching system to minimize installation downtime and site disruption.
In line with modern standards, the outdated auto/inhibit control system was fully decommissioned and removed. This ensures greater reliability and reduces unnecessary complexity, while the new VO provides stable, efficient, and fully automated regulation of incoming supply voltage.
Outcome
The installation of the VM 400 VO unit restores effective voltage regulation at the fire station, ensuring equipment protection, extended asset lifespan, and improved energy efficiency. The removal of legacy control circuitry reduces potential points of failure, leaving the site with a simplified, robust, and future-proofed solution.
