Phase Monitor Relays (3-Phase Monitors) provide cost-effective protection against premature equipment failure caused by voltage faults on 3-Phase premature equipment failure cause by voltage faults on 3-Phase systems (Wye or Delta). The SLU Series multi-mode phase monitoring relay, was designed for the convenience of electrician's, maintenance managers and engineers. A single SLU Phase Monitoring Relay can be easily adjusted for the voltage, imbalance percentage and time delay requirements to protect against unbalanced voltages or single phasing regardless of any regenerative voltages. Both Delta and Wye systems may be monitored. In Wye systems, connections to neutral are NOT required. The SLU-100 Series is UL Listed under U File Number E55826. NOTE: Not recommended for generator or variable frequency drive applications. Call technical support for application assistance.