SKU: 1756-TBNH

Allen-Bradley 1756-TBNH ControlLogix 20-Pin Screw Terminal Block

The Allen-Bradley 1756-TBNH is a heavy-duty 20-pin NEMA screw-clamp removable terminal block for ControlLogix I/O field installations. Genuine factory original units are in stock now with expedited worldwide delivery options. Safeguard your automation uptime and wiring integrity today.

The Allen-Bradley 1756-TBNH is a 20-position Removable Terminal Block (RTB) engineered specifically for the ControlLogix platform. It provides a modular, pluggable interface between external field devices (such as sensors, limit switches, and actuators) and the internal circuitry of ControlLogix digital, analog, or specialty I/O modules. By decoupling the field wiring bundle from the structural I/O chassis card, the RTB optimizes maintenance processes and maximizes operational uptime.

Hardware Specifications

Parameter	Specification
Model / Catalog No.	1756-TBNH
Brand	Allen-Bradley / Rockwell Automation
Origin	USA
Weight	0.9 kg (packaged block profile)
Dimensions	3.5 x 13.0 x 14.5 cm
Module Type	Screw-Clamp Removable Terminal Block (RTB)
Total Positions	20 Pins / Terminals
Conductor Wire Range	22 AWG to 14 AWG ($0.32\text{ mm}^2$ to $2.1\text{ mm}^2$) Copper Only
Recommended Screw Torque	1.36 Nm (12 lb-in)
Insulation Rating	Conductor temperature minimum rating of 90°C (194°F)
Discontinued Date	June 30, 2016 (Legacy hardware support item)

Industrial Termination Design & Operational Benefits

The 1756-TBNH uses heavy-duty, NEMA-standard screw-clamp terminals housed within a rugged, finger-safe plastic enclosure. The mechanical clamping structure ensures reliable contact pressure, which helps prevent terminal loosening caused by physical industrial machine vibrations or local thermal expansion cycles.

Because it is a Removable Terminal Block, field technicians can disconnect an entire field wiring bundle from a failed or degraded I/O module instantly. The technician simply loosens the top and bottom mounting screws on the RTB housing, pulls the block away from the card faceplate, replaces the underlying I/O module slot asset, and reconnects the fully wired block. This completely eliminates the need to tag, label, desolder, or manually re-terminate up to 20 individual conductors during field replacements.

Frequently Asked Questions

Q: Can the 1756-TBNH be paired with every ControlLogix I/O module?

A: No. The 1756-TBNH is a 20-pin block designed only for modules that feature a 20-pin front-panel interface layout (such as the 1756-IB16, 1756-OW16I, or 1756-IF8). High-density modules with 36 pins require a different part number, such as the 1756-TBCH.

Q: Is it permissible to land two separate wires into a single terminal point on this block?

A: Yes, provided the conductors are of the same size and type, and their combined solid cross-section does not exceed the maximum 14 AWG physical mechanical constraint of the clamping cage.

Field Installation Guidelines

Chassis Alignment Pins: Ensure the alignment ribs molded into the back shell of the 1756-TBNH correspond properly with the tracking slots on the front cover of the paired 1756 I/O module before pushing it into place.
Torque Tuning: Always employ a calibrated manual torque driver set to exactly 1.36 Nm when securing the individual wire terminals. Over-tightening can strip the screw threads, while under-tightening can lead to intermittent high-resistance connections or wire pull-outs.
Cable Strain Relief Routing: Secure the heavy external wire bundle exiting the bottom of the RTB assembly onto the cabinet door swing paths using plastic cable ties or cable management bars to alleviate direct downward physical pulling force on the terminal connections.