Honeywell FS-TSDI-1624C 24V Safety Input FTA

Product Overview

The FS-TSDI-1624C is a high-reliability Field Termination Assembly (FTA) module designed to interface between field wiring and the Honeywell Safety Manager system. This module provides 16 current-limited digital input channels specifically approved for routing non-incendive field circuits into Class I, Division 2 hazardous locations. 

Core Technical Advantages

Class I, Division 2 Hazardous Location Safety

Engineered with precise energy-limiting circuitry, this module restricts igniting current to less than 100 mA per channel under worst-case voltage conditions. This design allows direct interfacing with field devices located in explosive gas atmospheres without the need for additional bulky intrinsic safety barriers.

Dual-Group Fuse Protection

The 16 channels are divided into two isolated groups of 8. Each group features a high-voltage rated 250 mA SOC SHV12 ceramic fuse on the common positive line, preventing field-side short circuits from disabling the entire module and isolating faults effectively.

Redundant Module Compatibility

The hardware architecture natively accepts dual connection paths, allowing a single FTA block to drive a redundant pair of safety input cards simultaneously. This architecture eliminates single points of failure between the field termination and the safety logic layer.

Technical Specifications

Class I Division 2 Loop Parameter Limits

To preserve non-incendive loop integrity, interconnected field wiring must comply strictly with the following electrical constraints:

• Max. Closed Loop Resistance: 250 Ω
• Min. Open Loop Resistance: 15 kΩ
• Hydrogen Environments (Group A & B): Max. Inductance = 8 mH | Max. Capacitance = 0.3 μF
• Non-Hydrogen Environments (Group C & D): Max. Inductance = 22 mH | Max. Capacitance = 7 μF

Installation and Maintenance

DIN Rail Mounting

Snap the module securely onto standard TS32 or TS35 DIN EN rails. The physical installation requires an absolute minimum rail length of 171 mm to guarantee stability and adequate side spacing inside the enclosure panel.

Field Connection Protocols

Connect field wires using copper conductors up to a maximum size of 2.5 mm² (AWG 14). Strip the wire insulation back exactly 7 mm (0.28 in). Secure the wire inside the terminal block by applying a precise tightening torque of 0.5 Nm (0.37 ft-lb) to avoid damage to the terminal frame.

Fuse Replacement Standards

If a group experiences a dead short circuit, verify loop integrity before replacing the fuse. Only use original manufacturer part numbers (SOC SHV12 250 mA) to maintain the certified non-incendive thermal thresholds. Note that the maximum sustained output current per fuse must not exceed 175 mA.

Engineering Advantages

Compact Footprint Optimization

Measuring just 170 mm in length, this module optimizes internal cabinet space compared to traditional terminal blocks combined with external fuse holders, providing high-density I/O allocation.

Reduced Total Cost of Ownership

By achieving Class I, Division 2 approval directly through internal current-limiting design, the assembly removes the requirement for expensive intrinsically safe galvanic isolators and dedicated grounding systems.

Global Safety Certifications

The module holds full industrial compliance stamps including CE, TÜV, UL, CSA, and FM, meeting the rigorous standards necessary for deployment in global refining, petrochemical, and chemical complexes.

Technical FAQs

Q1: Why is the maximum output current per fuse limited to 175 mA when the fuse itself is rated for 250 mA?
A1: The 175 mA limit enforces a safe engineering safety margin. This constraint prevents continuous operation near the thermal trip point of the fuse, preventing nuisance blowing caused by minor ambient temperature fluctuations or temporary current ripples.

Q2: What happens to the remaining 7 channels if one channel develops a short circuit to ground?
A2: If a short circuit draws current exceeding the fuse threshold on a single channel, the 250 mA common fuse for that specific group of 8 will open. This protects the system backplane but drops power to all 8 channels within that isolated group. The opposite group of 8 will continue running normally.

Q3: Can this module be used with non-certified standard digital input devices in hazardous areas?
A3: Yes, provided that the overall field circuit matches the non-incendive loop parameters (maximum loop resistance, inductance, and capacitance) defined for Gas Groups A-D. The current-limiting features of the FTA ensure that field wiring faults cannot generate a spark with sufficient thermal energy to ignite the atmosphere.