175Z7291 by Danfoss

The 175Z7291 is a variable-frequency drive manufactured by Danfoss for the VLT 6000 HVAC Drives series. The unit converts fixed-frequency three-phase mains power into a controllable output so that centrifugal fans, pumps, and compressors in HVAC systems can run only as fast as the current thermal load requires. That variable-speed control also reduces abrupt starts and helps connected equipment respond smoothly to changing building demand during occupied and unoccupied periods. When installed in an air handler or chiller loop, it can support stable pressure control, quieter operation, and lower energy use than direct-on-line motor control.

Installation requirements are simplified by the Compact NEMA 1 enclosure because it can be mounted in most electrical rooms without additional drip or dust shields. The power section is rated at 30 kW / 40 HP, giving the drive capacity for 40-horsepower induction motors used in air handlers and similar HVAC equipment. A nominal input window of 380-460 VAC lets the drive operate on standard 60 Hz building feeders while still providing full torque at the motor terminals. Integrated electromagnetic suppression is handled by a Class A1 and B filter, which helps reduce conducted emissions to typical commercial EMC limits. The drive comes with an LCP, allowing parameter entry, fault review, and manual speed commands without a laptop.

From a configuration standpoint, the 175Z7291 ships as a standard unit, so no auxiliary I/O boards or application-specific hardware need to be installed for normal operation. Its electronics are supplied without conformal coating, which means the drive should be located in clean, dry areas where airborne contaminants are minimal. Communication expansion is left open because it is supplied without fieldbus options from the factory, although BACnet, LonWorks, or Modbus modules can be added later if the site requires networked control. The drive uses the Graham application variant, which aligns the default parameter set with common HVAC sequences such as supply-air static pressure regulation and return-fan tracking.