Description
MERLIN GERIN
MASTERPACT
NW12 H1
CIRCUIT BREAKER
1250A
UI: 1000V UIMP: 12KV
UE ICU
(V) (KA)
220/440 ~ 65
480/690 ~ 65
ICS = 100% ICU
ICW: 65KA/1S CAT.B
IEC 60947-2 50/60 HZ
The Merlin Gerin Masterpact NW12 H1 is a high-performance air circuit breaker rated at 1250A, designed for robust overcurrent and short-circuit protection in demanding electrical distribution environments. Belonging to the Air Circuit Breaker category, this unit is suited for main switchboard and distribution panel applications aboard commercial and industrial vessels, where reliable protection of critical power circuits is essential to safe and continuous operation.
Key Features
✓ Rated current of 1250A with an impulse withstand voltage (UIMP) of 12kV and insulation voltage (UI) of 1000V, providing a high level of dielectric protection across the installation.
✓ Unconditional short-circuit breaking capacity (ICU) of 65kA at both 220/440V and 480/690V AC, with ICS equal to 100% ICU, confirming full-rated service breaking performance — certified to IEC 60947-2 at 50/60 Hz.
✓ Short-time withstand current (ICW) rated at 65kA/1s, Category B classification, enabling selectivity coordination with upstream and downstream protective devices in complex distribution systems.
✓ Compatible with main and secondary switchboards, motor control centres, and power management panels typical of marine electrical installations; voltage range covers standard shipboard distribution systems.
✓ Intended for switchboard-mounted installation in main electrical rooms or auxiliary equipment spaces; replacement or refurbishment of this breaker should follow OEM torque and alignment procedures to ensure proper contact pressure and trip function.
Marine Applications
✓ Main switchboard incoming or bus-tie circuit protection on merchant vessels, tankers, and bulk carriers operating high-demand electrical loads.
✓ Power feeder protection for propulsion-related auxiliary systems, including bow thrusters, cargo pumps, and HVAC distribution boards.
✓ Generator output breaker applications on vessels with multiple generating sets requiring selective fault discrimination across the busbar.
✓ Offshore platforms and support vessels where continuous uptime of electrical distribution is critical and high short-circuit levels demand robust breaking capacity.
✓ Retrofit and direct replacement duty on existing Masterpact NW-series switchgear installations aboard vessels undergoing electrical system refurbishment or compliance upgrades.
Why Marine Engineers Choose
The Masterpact NW12 H1 is trusted for its full-rated service breaking capacity (ICS = 100% ICU), proven IEC 60947-2 compliance, and its ability to withstand the fault levels encountered in high-power marine distribution systems — making it a reliable choice for protecting critical onboard infrastructure.
Ideal For
Merchant vessels, tankers, bulk carriers, offshore support vessels, cruise ships, ferries, and any commercial marine or offshore installation requiring high-capacity air circuit breaker protection at 1250A within main or auxiliary switchboard configurations.
Technical Support
Technical support is available for the Merlin Gerin Masterpact NW12 H1 air circuit breaker, covering onboard installation guidance, trip unit configuration, and remote troubleshooting assistance. Support extends to repair assessment and like-for-like replacement advice for NW-series switchgear applications.
