The ABB ACH550-UH-06A9-4 is a 3 HP variable frequency drive (VFD) from ABB's ACH550 series, a line dedicated specifically to HVAC applications. The ACH550 precisely controls the speed of pumps, fans, and compressors in HVAC systems, reducing energy consumption by up to 70% with payback times often under a year. The "UH" in the model code designates the North American configuration — setup and parts specific to US installation and NEMA compliance — while the "-4" indicates the 380–480 V AC three-phase voltage class and "06A9" is the 6.9 A output current rating. It ships in a compact R1 frame size with a standard UL Type 1 / NEMA 1 enclosure and an onboard keypad for setup and operation. ABB GroupMitsubishi

The ACH550 is a legacy/mature product line (ABB has since moved newer HVAC drive development to the ACH580 family), and this particular model is listed as discontinued by the manufacturer. It is rated 3-phase, 380–480 V AC, 50/60 Hz, 6.9 A, 3 HP. It remains widely available through the surplus, repair, and aftermarket channels, and is valued for its built-in HVAC functionality, BACnet support, and straightforward integration into building automation systems.

Factory Specifications

Key features carried over from the ACH550 platform include embedded BACnet, two built-in PID controllers, an interactive startup assistant, a real-time clock/calendar with built-in timers, tailor-made HVAC software, and built-in harmonic mitigation.

A couple of useful notes for documentation or appraisal purposes: the equivalent IEC-market model is the ACH550-01-06A9-4 (same drive, different regional setup), and the +B055 option suffix denotes an IP54 enclosure variant rather than the standard IP21. Current aftermarket/new pricing on this discontinued unit runs in the rough range of a few hundred to several thousand dollars depending on source and condition, so verify against live listings if you need a defensible appraisal figure.