CHINT NM8N Moulded Case Circuit Breaker, 16-1600 A

A moulded case circuit breaker family from 16 A to 1600 A

The NM8N is CHINT’s moulded case circuit breaker (MCCB) series for AC power distribution up to 690 V, with DC versions listed up to 1000 V. It covers six frame sizes, 125, 250, 400, 630, 800 and 1600 A, with thermal-magnetic, magnetic and electronic release options, and an NM8NL residual current variant. Typical uses are main and sub-distribution boards, motor feeders and plant incomers where one breaker family has to cover a wide current range.

Technical specifications

Choosing the frame and release

Match the frame to the largest continuous load and the prospective short-circuit current at the board. The C to R breaking codes let one frame be specified for a weak supply or for a position close to a transformer. For feeders and incomers the thermal-magnetic TM release is the simple choice, while the electronic EN and the magnetic EM releases give adjustable settings on the larger frames. Motor feeders use the M, ENM or EMM releases, which are set for starting current, and the NM8NL variant adds residual current protection where the earthing system calls for it.

The catalog also covers accessories such as shunt and undervoltage releases, auxiliary and alarm contacts, rotary handles, motor operators and mechanical interlocks, so a changeover pair can be built from two frames of the same size. Check derating for ambient temperature and altitude in the catalog tables before sizing a breaker in a hot enclosure.

What to confirm before ordering

Send the frame, pole count, rated current, breaking code, release type, fixed or plug-in mounting and the accessories. For other makes in the same duty compare the Eaton NZMN1-A80 and the ABB Tmax XT, or browse the circuit breakers category.

How the CHINT NM8N works

The NM8N is a moulded case circuit breaker that protects a circuit against overload and short circuit. A thermal element reacts to a sustained overcurrent, and a magnetic element opens the contacts at once on a short circuit. Electronic releases do the same job with adjustable settings. The breaker can also be used as a switch to isolate a circuit for maintenance, since it is suitable for isolation. The wide range of breaking capacity codes lets one frame be used at different points of a network.

Where the NM8N is used

• Main incomers and sub-distribution boards
• Motor feeders with motor protection releases
• Plant and workshop distribution
• Commercial buildings and infrastructure
• Generator and transformer outgoing circuits
• DC circuits where the DC versions are specified

Selection checklist for the NM8N

• Rated current of the circuit and the frame that covers it
• Prospective short-circuit current at the board, and the breaking code C, S, Q, H or R
• Number of poles, 1P, 2P, 3P or 4P
• Release type, thermal-magnetic, magnetic or electronic, and distribution or motor duty
• System voltage up to 690 V AC, or the DC version
• Ambient temperature against the 40 degrees C reference
• Need for the NM8NL residual current version
• Fixed or other mounting and the accessories required

Installation, commissioning and maintenance notes

Mount the breaker on a flat surface in a board with enough space for the arc gases. Tighten the terminals to the torque in the instructions and use cables or busbars of the correct size. Set the adjustable releases to match the load and the discrimination study. Operate the handle a few times before energising and test the trip function where the design needs it. Inspect the breaker at intervals for heat marks, dust and loose terminals, and keep a record of any trips.

Requesting a quotation for the CHINT NM8N

Please send the frame, the rated current, the number of poles, the breaking code and the release type, with the quantity. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

NM8N breaking capacity codes

At 380 to 415 V AC the 125 and 250 frames reach 36, 50, 70, 100 and 150 kA for the codes C, S, Q, H and R. The service breaking capacity equals the ultimate value in the same table.

NM8N release units

For distribution the TM, EN and EM releases are offered, and for motor protection the M, ENM and EMM releases. The motor types are set for starting current.

NM8N endurance

The 125 and 250 frames have a mechanical life of 25,000 cycles with maintenance, and an electrical life of 10,000 cycles at 415 V AC and rated current.

NM8N residual current version

The NM8NL adds earth leakage protection to the breaker. It suits circuits where protection of people or fire protection is needed.

Breaker records for NM8N

Keep the release settings, the board location and the test results with the board documents.

Documents and quotation

The CHINT NM8N manual is attached. The full catalog is larger than the size we host, so the ratings above come from the CHINT catalog and should be confirmed against the current edition on the CHINT website. Send the complete designation and quantity through the quotation form for availability from Seven Star LLC.