Purchase now: Allen-Bradley 1756-TBNH ControlLogix 20-Point Screw Terminal Block
Atlantechdrives provides you the 1756-TBNH, a heavy-duty 20-pin Removable Terminal Block (RTB) specifically designed for the Allen-Bradley ControlLogix 1756 I/O family. This module is the standard interface for connecting field-side wiring to your I/O modules, featuring NEMA-style screw clamps that provide a secure, high-torque mechanical connection for industrial environments.
- Pin Count: 20 Points
- Terminal Type: NEMA Screw Clamp
- Compatibility: Standard 1756 I/O modules (Digital and Analog)
- Wire Gauge: 22 AWG to 14 AWG (solid or stranded)
- Housing: Deep-well design for easy wire routing
Technical Engineering: The Reliability of the 1756-TBNH
The 1756-TBNH is engineered for maximum contact integrity. In a ControlLogix system, the RTB acts as the bridge between the field sensors/actuators and the sensitive electronics of the I/O module. The 1756-TBNH utilizes high-quality zinc-plated steel screws and pressure plates that prevent wire shearing and ensure a consistent clamping force. This is particularly important for high-current digital outputs (like the 1756-OB8) or precision analog inputs where any resistance in the connection could lead to signal inaccuracies or localized heating. Its «Removable» nature allows for the pre-wiring of the cabinet before the I/O modules are even installed, and more importantly, it enables «Hot Swapping» of faulty modules without the need to disconnect a single wire from the field.
Installation Advice: Torque and Wire Management
When installing the 1756-TBNH, following the manufacturer’s torque specifications (typically 5-7 lb-in) is critical to prevent stripped threads while ensuring a vibration-proof connection. We recommend using ferruled wires if you are using stranded conductors to prevent «stray strands» from causing short circuits between adjacent pins. Use the integrated wire-routing housing provided with the 1756-TBNH to organize the bundle toward the side of the chassis. It is essential to ensure the RTB is fully seated and the locking tabs are engaged before applying field power; a partially seated RTB can cause arcing that damages the gold-plated pins on the I/O module.
Maintenance and Hardware Durability
The 1756-TBNH is a passive mechanical part, but in environments with significant thermal cycling or vibration, the screws should be checked annually as part of a preventive maintenance program. Inspect the housing for any signs of cracking or discoloration, which could indicate an over-current condition or excessive heat at the terminal point. If you are operating in a corrosive atmosphere (G3 rated), consider applying a non-conductive protective spray to the screws to prevent oxidation. Keeping a few spare 1756-TBNH units on-site is standard practice, as they are often the parts most prone to physical damage during aggressive troubleshooting or cabinet modifications.
FAQs
Q: What is the difference between 1756-TBNH and 1756-TBSH?
A: The TBNH uses NEMA screw clamps, while the TBSH uses spring clamps for faster, tool-less installation.
Q: Can I use the 1756-TBNH on 32-point high-density modules?
A: No, 32-point modules require the 36-pin 1756-TBCH block.
Do you need more references from this brand? Explore our full catalog of Allen-Bradley here.
This NEMA-rated terminal block provides a secure field wiring point for discrete modules such as the 1756-IA16 AC input module.
