MTL7779+ 28 V DC Rated Voltage 2-Channel Protection DIN Rail Mounting Zener Safety Barrier

The MTL7779+ is a high-performance 2-channel shunt-diode safety barrier (Zener barrier) from Eaton's Crouse-Hinds series MTL7700 range, specifically engineered to provide intrinsic safety protection for electrical circuits installed in hazardous areas. This passive device limits the voltage and current that can reach a hazardous area under fault conditions, preventing ignition of flammable atmospheres.

With a rated voltage of 28 V DC, switching current of 93 mA, and series resistance of 300 Ω, the MTL7779+ is the ideal solution for protecting circuits in Zone 0, 1, and 2 hazardous locations (gas groups IIC, IIB, IIA). The device features a compact 12.6 mm width and standard DIN rail mounting for easy integration into existing control cabinets.

Certified with multiple international approvals including ATEX IECEx KCS (KOSHA) and cCSAus, the MTL7779+ is the trusted choice for intrinsic safety applications in oil & gas, chemical processing, pharmaceutical, and other hazardous industries.

• 2-Channel Protection: Two independent intrinsically safe channels in a single 12.6 mm housing — maximizes panel space efficiency and reduces installation costs
• 28 V DC Rated Voltage: Provides safe voltage limiting for hazardous area circuits, preventing ignition under fault conditions
• 93 mA Switching Current: Adequate current handling for most field instrumentation including transmitters, sensors, switches, and indicators
• 300 Ω Series Resistance: Matches typical loop resistance requirements for 4-20 mA signal circuits while ensuring intrinsic safety compliance
• 250 V AC/DC Isolation (Um): Rated for connection to circuits with up to 250 V rms, allowing installation in standard industrial control systems
• Positive Polarity Configuration: Designed for positive ground applications — common in many industrial control systems
• Ultra-Slim DIN Rail Mounting: Compact 12.6 mm width for standard 35 mm DIN rail installation, saving valuable panel space
• Wide Operating Temperature: Functions reliably from -20°C to +60°C, suitable for most industrial environments
• Polycarbonate Enclosure: Lightweight, durable housing with excellent electrical insulation properties
• Multiple International Certifications: ATEX, IECEx, KCS (KOSHA Korea), cCSAus, and BASEEFA approvals for global installation flexibility

The MTL7779+ is a passive shunt-diode safety barrier that operates on the Zener barrier principle. It limits both voltage and current that can be delivered to a hazardous area circuit under fault conditions.

• Voltage limiting: Zener diodes clamp the output voltage to a safe level (28 V) if the safe-area voltage rises above normal operating levels
• Current limiting: A series resistor (300 Ω) limits fault current to a safe value (93 mA)
• Fusing: Internal fuses provide backup protection under severe fault conditions
• Grounding: The barrier requires a connection to a high-integrity earth ground to function properly

• The MTL7779+ is typically installed in the safe area (control room or panel)
• Field wiring from the barrier terminals connects to hazardous area devices
• The barrier requires a solid earth ground connection (typically < 1 Ω)
• Each of the two independent channels protects a separate field device

The MTL7779+ is specifically designed for intrinsic safety protection in hazardous area installations:

• 2-wire 4-20 mA transmitters (pressure, temperature, level, flow, pH)
• NAMUR proximity sensors
• Mechanical switches (limit switches, pressure switches, temperature switches)
• Solenoid valves (low-power)
• LED indicators
• Leak detection sensors

• Proven MTL7700 Series Reliability — The MTL7700 series has been the industry standard for shunt-diode safety barriers for decades, trusted globally for intrinsic safety applications. The MTL7779+ is built on this legacy of quality and reliability.
• Dual-Channel Efficiency — With two independent channels in a single 12.6 mm housing, the MTL7779+ protects two field devices while using half the panel space of single-channel barriers.
• Wide Global Approvals — Certified for use in virtually every major industrial market (ATEX Europe, IECEx international, KCS Korea, cCSAus North America, FM), the MTL7779+ simplifies global equipment standardization.
• Simple Installation — DIN rail mounting, clearly labeled terminals, and compact design make installation quick and intuitive. The polycarbonate enclosure provides durability without excessive weight.
• Easy Replacement — The MTL7779+ is designed as a direct replacement for older MTL700 series barriers, simplifying retrofit projects.
• Recommended by Equipment Manufacturers — The MTL7779+ is specifically recommended by Cooper Industries Japan K.K. for use with their leak detection sensors, demonstrating industry trust.

• A high-integrity earth ground connection is mandatory for proper Zener barrier operation
• Do not install in areas where condensation may occur
• Observe terminal polarity markings (positive and negative/ground terminals)
• The barrier must be installed in a safe area (non-hazardous location)
• Maximum cable parameters for IIC gas group apply to field wiring

Contact our sales team for volume pricing, datasheet downloads, or technical application support.