ABB 1MRS050729 Auxiliary Contact Block (1NO + 1NC)

Description

1MRS050729

The ABB 1MRS050729 functions as an add-on auxiliary contact block, designed to mount directly onto compatible ABB contactors (such as the Tmax or AX series) to extend their control circuit capabilities.

1MRS050729

Unlike standalone relays used to compensate contact shortages, it operates in perfect synchronization with the host contactor: when the contactor’s main coil energizes (closing or opening the load circuit), the ABB 1MRS050729’s auxiliary contacts mirror this action—providing real-time, reliable feedback or triggering secondary control actions. This integration eliminates the need for separate wiring between contactors and external relays, reducing installation time and the risk of wiring errors. The contact block supports low-voltage control signals (up to 250V AC/DC), making it suitable for tasks like sending status signals to PLCs, activating indicator lights, or enabling interlock circuits. By attaching directly to the contactor’s housing (via a tool-free snap-on design), it maintains a compact footprint—critical for crowded control panels—and ensures mechanical alignment that prevents contact bounce or delayed actuation. In the automation stack, the ABB 1MRS050729 bridges the gap between the main power circuit (handled by the contactor) and the control layer, ensuring auxiliary tasks are executed in lockstep with primary load switching.

Main features and advantages:

Choosing the ABB 1MRS050729 delivers tangible value that streamlines both installation and long-term operation. Engineered for industrial durability, its contacts are made from silver-nickel alloy—resistant to arcing and wear, ensuring a mechanical life of 10 million operations and an electrical life of 1 million cycles. This longevity translates to fewer replacements, reducing maintenance costs and minimizing downtime in high-cycle applications (like assembly line motor starters). For engineers, the tool-free snap-on mounting eliminates the need for specialized tools or drilling, cutting installation time by up to 40% compared to retrofitting with external relays. The block’s compatibility with ABB’s most popular contactor lines also simplifies inventory management: teams don’t need to stock multiple auxiliary blocks for different contactor models, reducing procurement complexity.

Additionally, the ABB 1MRS050729’s 1NO + 1NC contact configuration offers flexibility for diverse control tasks—from monitoring contactor status (via the NC contact) to triggering auxiliary equipment (via the NO contact). Unlike generic auxiliary blocks that may not align with contactor mechanics, its precision-engineered mounting ensures zero actuation delay between the main contactor and auxiliary contacts, critical for safety interlocks where even a 10ms lag could lead to equipment damage. Its compact design also saves space in control panels, allowing engineers to add auxiliary functionality without redesigning enclosures—a key advantage for retrofits in older facilities.

Application fields:

The ABB 1MRS050729 excels in industries where contactor signal expansion is mission-critical. In manufacturing, it’s used with ABB Tmax contactors to add status feedback for robotic cell motor starters, ensuring PLCs receive real-time confirmation that a motor is energized before initiating a production step—preventing costly misalignments. In water and wastewater treatment plants, it’s paired with AX series contactors to enable interlock circuits for pump systems: if one pump’s contactor fails, the ABB 1MRS050729’s NC contact triggers an alarm and locks out the backup pump until the fault is resolved, avoiding system overload. In commercial buildings, it supports HVAC motor control by adding indicator light signals for maintenance teams—alerting them when a fan or compressor contactor is active, simplifying troubleshooting. Across all these use cases, the ABB 1MRS050729 ensures continuous reliability in harsh environments, from dusty factories to humid treatment plants, thanks to its wide operating temperature range and corrosion-resistant terminals.

Related products:

ABB 1MRS050730 – 2NO contact configuration for applications needing extra normally open signals (e.g., dual-status monitoring).

ABB 1MRS050731 – 2NC contact configuration for redundant safety interlocks (e.g., emergency stop circuits).

ABB 1MRS050732 – High-current variant (10A) for auxiliary loads like small fans or heaters.

ABB 1MRS050733 – LED-integrated version for visual contact status (ideal for control panels with limited indicator space).

ABB 1MRS050734 – Compatibility adapter for older ABB SACE contactors (enabling retrofits with 1MRS050729).

ABB 1MRS050735 – Sealed variant (IP65) for outdoor or dusty applications (e.g., solar farm inverter contactors).

ABB 1MRS050736 – Low-temperature version (-40°C to 60°C) for cold-storage or outdoor industrial sites.

ABB 1MRS050737 – Quick-connect terminal variant for tool-free wire changes (reducing maintenance time).

Installation and maintenance:

Before installing the ABB 1MRS050729, confirm the host contactor is compatible (ABB Tmax T2-T6, AX09-AX80 models)—incompatible contactors will cause misalignment and contact failure. Ensure the contactor is de-energized and the main power is locked out to prevent electrical shock during installation. Clean the contactor’s mounting rail (where the auxiliary block attaches) to remove dust or debris, which can prevent proper seating. When snapping the block onto the contactor, apply even pressure until you hear a “click”—this confirms secure mounting; a loose fit will cause actuation delay. For wiring, use stranded or solid wire (max 2.5mm²) and torque terminals to 0.8–1.2 Nm (per ABB specs) to prevent loose connections and arcing. For ongoing maintenance, inspect terminals quarterly for corrosion (especially in humid environments) and tighten if needed. Test contact continuity annually using a multimeter: energize the contactor and verify the NO contact closes (0Ω resistance) and the NC contact opens (infinite resistance)—replace the block if continuity is inconsistent.

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