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MultiPlus-II External Transfer Switch application

1. Introduction

In this section:

This manual provides instructions for installing and configuring a system using an external transfer switch (contactor) instead of the built-in relays of the Multiplus-II.

This application significantly enhances the versatility, cost-effectiveness, and reliability of larger systems, particularly those of 60kVA and above.

Note that this setup is intended solely for generator-based systems and is not certified for use with grid-tied systems.

1.1. Advantages

  • Reduce installation time and costs: This significantly reduces costs and installation time, especially for large systems with multiple units in parallel. It removes the need to wire each unit's AC input and output terminals.

  • Reduce equipment costs: Combining MultiPlus-II 8, 10, or 15kVA units with an external transfer switch lifts their "no parallel" restriction. Otherwise, the more expensive Quattro 8, 10, or 15kVA units would have been required.

  • Flexible installation: MultiPlus-II units and batteries can be placed up to 20 meters from the main distribution board without running power wiring back and forth.

  • No Bypass Switch Required: Eliminates the need for a separate bypass switch.

1.2. Compatibility

This application supports all MultiPlus-II models rated at 5000VA and above.

Key specifications:

  • AC transfer rating: 100 or 400A.

  • Unit limit: Up to 12 MultiPlus-II units, with a maximum of 4 per phase.

  • System size: Up to 180kVA.

  • AC input: Supports only one AC input source.

  • AC input type: Generator AC input only, not for grid connection.

  • Firmware: Requires application-specific VE.Bus firmware, version S99.

  • Hardware: Additional hardware is required; refer to the Hardware requirements list.

1.3. Hardware requirements

  • External transfer switch: Standard contactor.

  • Ground relay: High current single-pole relay.

  • Ground help relay: Low-power 230V relay with a 24V coil, enabling the MultiPlus-II low-power control signal to drive the high-power ground relay.

  • Victron Current Transformer(s): One per phase, rated at 100 or 400A, for accurate current measurement and power management.

  • Four-pole circuit breakers and RCD: For circuit protection.

  • Electrical wiring: Refer to the Installation chapter for detailed instructions.