ABB S203-C40 Three-pole Miniature Circuit Breaker, C 40 A

ABB’s S200 line includes the S203-C40, a three-pole MCB with the C tripping curve, catalogued as 2CDS253001R0404. A thermal element protects the cable against overload and an electromagnetic element against short circuit; the C characteristic leaves room for lamp, transformer and small motor inrush. Its 6 kA capacity under IEC/EN 60898-1 suits a three-phase 40 A feeder, for example to a pump or heater bank, among other board circuits.

Related devices can be found under circuit breakers; for loads beyond 63 A look at the SACE Tmax XT series.

Technical specifications

Loading limits of a 40 A S200 breaker

ABB defines the C release at 5 to 10 times the rated current; here that is 200 A to 400 A, with 0.1 to 30 s allowed at 5 x In. The bimetal element holds at 45.2 A (1.13 x In) for one hour and must trip inside one hour at 58 A (1.45 x In); the reference temperature is 30 C. The permitted operating current falls to 37.7 A at 40 C, 35.3 A at 50 C and 32.7 A at 60 C according to the ABB table. Grouping matters too, with factors of 0.9, 0.8 and 0.75 for two or three, four or five and six or more adjacent loaded devices.

Three-phase duty and add-ons

A 3P device handles a three-phase line through a single handle. Ratings are 400 V AC under IEC/EN 60898-1 and 440 V AC under IEC/EN 60947-2. Add-on parts that clip to the breaker: auxiliary and signal contact blocks, shunt and undervoltage trips, a motorised operator and the DDA 200 earth-leakage block. Allow 52.5 mm of rail width and the busbar slot, which takes busbars of 10 mm2.

Reading the type code

In S203-C40 the S200 housing is combined with 3 poles, the C characteristic and a 40 A rating. Quote 2CDS253001R0404 when asking for a price, so the exact type is supplied. Please check poles, curve, current, system voltage and prospective fault current for the project, and decide on side accessories first.

Key features of the S203-C40

• Three poles operated by one common toggle and one common trip mechanism, so a fault on any phase disconnects all three; this prevents three-phase motors from running on two phases after a single-pole trip.
• Thermal-magnetic release with a C characteristic, a balanced choice between protection of the cable and tolerance of inrush current.
• Dual rating under the household standard IEC/EN 60898-1 and the industrial standard IEC/EN 60947-2, which helps where both residential and industrial specifications apply to one board.
• Top and bottom terminals for conductors up to 35 mm², plus a busbar slot for distribution comb busbars.
• A full set of clip-on accessories for signalling, remote tripping and residual current protection, so one breaker type can serve many control schemes.

Choosing between B, C and D curves

The C curve chosen here gives magnetic tripping between 200 A and 400 A. To be sure the magnetic element trips fast on a short circuit at the far end of the cable, the loop impedance of the circuit must allow at least the upper value of that band to flow. This check is particularly relevant for long feeders to remote pumps or outdoor equipment.

Sizing with derating for hot panels

The 40 A rating applies at the 30 °C reference temperature. Inside a closed panel in summer the air around the breakers is often well above this, which reduces the current the device carries without tripping, as shown in the derating values above. The designer should therefore check three points together: the cable current-carrying capacity under the installation conditions, the design load current, and the breaker rating after temperature and grouping corrections. If the corrected current is too low, either improve ventilation, space out the devices, or select a higher rating with a correspondingly larger cable.

Installation and maintenance

• Mount on a 35 mm DIN rail and tighten the terminals to the specified torque; a loose terminal is a frequent cause of overheating in distribution boards.
• Use ferrules on fine-stranded conductors.
• Verify that the prospective short-circuit current at the board does not exceed the breaking capacity, or provide back-up protection coordinated by ABB tables.
• During periodic inspection, check terminals with a thermal camera under load and operate the handle manually to keep the mechanism free.
• Replace any breaker with visible heat damage, cracked housing or a handle that does not latch.

Applications in Oman and GCC buildings and plants

The S203-C40 is a common choice in final distribution boards for air-conditioning outdoor units, water heaters, pump sets, small compressors and three-phase sockets on sites across the region. Because ambient temperatures in rooftop and outdoor panels are high for much of the year, the derating table should be treated as a design tool rather than a footnote. Panels in coastal areas should be suitably sealed to protect the terminals and mechanism from humidity and salt.

Information to include in an RFQ

• Type S203-C40 and order number 2CDS253001R0404, with quantity.
• Required accessories, such as auxiliary contacts, shunt trip or residual current block.
• Prospective fault level of the board, if a coordination check is needed.

Documents and quotation

The linked ABB data sheet covers the S 200 and S 200 M miniature circuit breakers, with technical data, tripping characteristics, derating tables, accessories and dimensions. Ask Seven Star LLC, an independent supplier in Muscat, for a quotation stating type and quantity. No price or stock is shown on this page; please confirm the specification before ordering.