WCM8L-800 Molded Case Circuit Breaker 400V AC MCCB

The WCM8L-800 is an 800 A, low-voltage molded case circuit breaker used for overload and short-circuit protection in industrial and commercial power distribution. Housed in a molded insulating case, it is substantially larger and more robust than an MCB and is typically installed as a main or sub-main breaker in switchboards and distribution panels.

MCCBs handle much higher currents (typically 16 A–1600 A versus up to 125 A for MCBs), offer adjustable trip settings, and provide higher breaking capacities (often 25–100 kA). MCBs are fixed-trip DIN-rail devices for final circuits, while MCCBs are panel-mounted devices used as main feeders or large branch circuits where selectivity and coordination matter.

The thermal element (bimetal) provides inverse-time overload protection — the longer the overload persists, the faster it trips. The magnetic element provides instantaneous short-circuit protection at a multiple of rated current. In larger MCCBs like the 800 A frame, both the long-time (overload) and short-time/ instantaneous (short-circuit) thresholds are user-adjustable via dials or screws on the trip unit.

The "800" indicates a frame size rated up to 800 A continuous current. Within this frame, the trip unit can be fitted with a rated current (In) ranging, typically, from 400 A to 800 A. The frame defines the thermal withstand, terminal size, and breaking capacity, while the plug-in or fixed trip unit sets the actual trip current.

It is typically available in 3P (three-phase, no neutral) and 4P (three-phase + neutral) versions for AC 400 V systems. The 400 V AC rating is suitable for standard three-phase industrial distribution; confirm the exact voltage code on the nameplate because some frames are also rated for 690 V AC on certain variants.

Yes. The long-time (overload) trip dial typically adjusts In between 0.8–1.0 (or wider on electronic trip units), and the short-time/instantaneous dial adjusts between, for example, 5–10 In. Adjusting these lets the engineer coordinate the MCCB with downstream MCBs so only the faulty branch trips (selectivity), rather than the whole installation.

It is bolt-mounted onto a chassis or mounting plate inside a low-voltage switchboard, not snapped on DIN rail. Busbars or heavy cables are connected to the line and load terminals with specified torque. Adequate spacing for air termination, minimum clearances per IEC 60947-2, and access for operation and testing must be maintained in the cubicle design.

At 800 A, connections are usually made with laminated busbars or very large single/multi-core cables (typically 2 × 240 mm² copper per pole or equivalent). Use copper lugs crimped or bolted to the manufacturer's terminal size, observe the correct torque, and allow for cable bending radius and heat dissipation. Aluminum conductors require suitable bimetallic lugs to avoid galvanic corrosion.

It is used as the main incoming breaker in industrial switchboards, large commercial building substations, data center main distribution units, mining and plant distribution, and as a feeder to large motor control centers or transformer secondaries. It is also common in solar PV combiner and storage systems where high fault currents and selectivity are required.

The WCM8L-800 is built to IEC 60947-2 (low-voltage switchgear and controlgear — circuit breakers) and carries CE and other regional certifications. Maintenance includes periodic visual inspection, torque re-checking of terminals, mechanical operation of the breaker, and insulation resistance (megger) testing; many utilities also require primary/secondary injection testing of the trip unit at scheduled intervals (often annually or every 1–3 years).