178B3811 by Danfoss

The 178B3811 is an HVAC drive produced by Danfoss within the VLT 6000 HVAC Drives series. Installed between the building power bus and a three-phase induction motor, it varies output frequency and voltage so fan and pump speed can track changing load demands in climate-control systems. This supports steadier airflow or water circulation and reduces unnecessary full-speed operation during part-load conditions. The unit is intended for variable-torque loads common in ventilation and pumping service, where speed changes help balance comfort targets with energy demand throughout the day.

This model accepts incoming power from 380-460 VAC lines and can deliver up to 45 kW (60 HP) to the connected motor, which suits large air handlers and cooling tower equipment. The electronics are housed in a Compact NEMA 1 enclosure for indoor installation where accidental contact with live parts must be limited. Parameter changes and local run commands are available from the front interface, and the drive comes with an LCP installed so no separate keypad is needed for normal setup or operation. For building automation, it supports LonWorks free-topology networking, which allows star, bus, or mixed wiring layouts without a rigid network arrangement. Its front-mounted controls also simplify routine adjustments because status information and parameter values remain visible at the cabinet door.

The drive is supplied without an RFI filter, so any required electromagnetic suppression must be provided externally. It is built as a standard unit, which indicates the base hardware configuration rather than a specialized variant. The power section has no protective coating, so the drive is better suited to clean indoor spaces than to areas with corrosive vapors or persistent moisture. This arrangement fits controlled mechanical rooms where airborne contamination is limited and external EMC measures can be planned as part of the overall installation. Danfoss lists the intended application as Graham, indicating a preloaded HVAC operating profile.