UBW Molded-Case Circuit Breakers — 250 to 1200 A Frames

WEG’s UBW family covers medium to large distribution with frames from 250 A through 1200 A, delivering dependable thermal-magnetic protection (250–800 A) and high-function electronic trip options at 1200 A. The series is organized by interrupting class so you can right-size short-circuit capability to the available fault current at your site.

Where they fit

• Applications: main and feeder protection in switchboards/panelboards, MCC buckets, OEM control panels, machine sub-feeds.
• Environments: commercial buildings, institutional facilities, light/medium industrial.

Frame lineup & interrupting classes (480 VAC kAIC)

• UBW250 / UBW400 / UBW600 — Fixed Thermal / Adjustable Magnetic
  Classes: N (≈35 kA), H (≈65 kA), L (≈100 kA)
  Common ampere settings per frame (examples):
  • 250 A frame: 250 A
  • 400 A frame: 300–400 A
  • 600 A frame: 500–600 A
• UBW800 — Fixed Thermal / Adjustable Magnetic
  Classes: S (≈50 kA), H (≈65 kA)
• UBW1200 — Electronic Trip (no lugs supplied per datasheet), with or without Maintenance Mode
  Classes: S (≈50 kA), H (≈65 kA), L (≈100 kA)
  Typical settings: 800 A or 1200 A depending on the catalog variant.

Tip: choose N / S / H / L by matching or exceeding the site’s available fault current at the installation voltage (see your coordination study or utility data).

Key features

• Thermal-magnetic (250–800 A): fixed thermal overload + adjustable magnetic instantaneous for quick coordination in feeder circuits.
• Electronic trip (1200 A): precise protection curves; Maintenance Mode option helps reduce arc-flash incident energy during service.
• Three-pole configurations for three-phase distribution.
• Consistent form factor and terminal layout to simplify standardization across frames.
• Clear catalog scheme: frame size + class + trip type + poles (e.g., UBW600L-FTU600-3A, UBW1200H-ELS1200-3A).

Selection checklist

1. Available fault current (AIC): pick class N/S/H/L to meet or exceed kAIC at 480/600 VAC.
2. Ampere rating: select the thermal/long-time setting that matches the protected conductor/load.
3. Trip type: thermal-magnetic (250–800 A) vs. electronic (1200 A); add Maintenance Mode if your safety plan calls for it.
4. Terminations & accessories: confirm lug kits, wire ranges, and any shunt/aux contacts.
5. Compliance & settings: verify ratings, adjustment ranges, and tightening torques from the datasheet/submittal.

Advantages

• Right-sized protection: multiple interrupting tiers limit cost without overspecifying.
• Straightforward specification: intuitive catalog numbers and a uniform table layout.
• Service & safety options: electronic trip and Maintenance Mode at 1200 A for advanced protection strategies.

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