Frenic HVAC

Slim, Stand-Alone Design

• First slim-body inverter design in Fuji Electric's HVAC lineup , same footprint across IP21 and IP55 protection classes, a first in the industry.
• No control panel required; the inverter can be installed independently, saving panel space and installation cost.

Purpose-Built Energy Saving Functions

• Linearization function– estimates target terminal pressure from load flow rate instead of holding a constant water conveyance pressure, cutting the "ineffectual" pump power wasted at low-demand periods.
• Wet-bulb temperature presumption control– automatically estimates wet-bulb temperature to interlock cooling tower fan speed with actual air conditions, instead of running fans at high speed by default.
• Temperature difference constant control– keeps the difference between cooling water inlet and outlet temperature constant, optimizing cooling water pump speed.
• Automatic energy-saving operation– continuously adjusts output voltage to minimize combined motor and inverter loss at constant speed.

Functions Built for HVAC Operation

• Standard 4PID control– one PID loop drives inverter output frequency; three additional PID loops (with optional OPC-AIO card) can control external systems such as valves or dampers.
• Fire mode (forced operation)– ignores inverter protection trips to keep fans and pumps running during an emergency such as a fire.
• Filter clogging prevention– detects fan filter clogging via output current and pressure sensor readings, reverses the fan briefly to eject dust, then resumes normal operation and raises a maintenance alarm.
• Pick-up operation function– smoothly picks up an idling, non-inverter-driven fan without needing to stop it first, useful when switching from commercial power to inverter control.
• Customized logic– build simple relay/logic sequences directly on the inverter (AND/OR gates, timers, arithmetic blocks) without an external PLC.

User Interface & Maintenance

• Multi-language LCD keypad supporting 19 languages plus a user-customized language option.
• Real-time clock (RTC) standard, with alarm history timestamps and up to four weekly timer schedules (including 20 flag holidays/year).
• Unit conversion function displays readings in the engineer's preferred units (m³/h, °C, kPa, mWG, mmHg, in-wg, psi, ppm, kW, RPM, l/min, bar, %, °F).
• Capacitor board outputs a life-prediction signal so maintenance teams know replacement timing in advance.
• Detachable control terminal block allows the unit to be swapped without disconnecting field wiring.

Communications & Network Options

• BACnet MS/TP and Modbus RTU standard, plus Metasys N2 support.
• Optional cards for LonWorks, Ethernet, DeviceNet, CANopen, CC-Link, and PROFIBUS-DP.
• USB port on the keypad for direct PC connection and diagnostics via Fuji's loader software.

Applications

• Cooling tower fans– wet-bulb temperature presumption control adjusts fan speed to actual air conditions rather than running at fixed high speed.
• Cooling water pumps– temperature-difference constant control keeps inlet/outlet delta-T stable, avoiding wasted pump energy.
• Chilled water pumps– linearization function converts flow-rate signals into accurate target pressure, replacing wasteful constant-pressure control.
• Supply and return fans– speed adjusts to duct pressure, discharge temperature, room temperature, and CO₂ levels for demand-based ventilation.
• Central plant / AHU systems– 4PID control and customized logic reduce or eliminate the need for a separate PLC in fan/pump sequencing.