Product Overview
Downtime on a ControlLogix line rarely starts with the controller. It starts with a field-wiring connection. The Allen-Bradley 1756-TBNH is the removable terminal block (RTB) that plugs into the front of a 1756 I/O module and carries every field wire. It is a 20-position NEMA screw-clamp block from the ControlLogix series by Allen-Bradley / Rockwell Automation, and it must be ordered separately from the I/O module.
Because it is an accessory, the 1756-TBNH is exactly the part that goes missing from a spares shelf. When a terminal block is damaged during a rushed wire change, the whole I/O module stops working until a replacement arrives. That is a cost problem, not just a parts problem.
Technical Specifications
| Specification | Value |
|---|---|
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Series | ControlLogix |
| Module Type | Terminal Block (RTB) |
| Clamp Type | Screw-Clamp |
| Pins | 20-Pin Connection |
| Backplane Current (5 V) | 1,200 milliamps |
| Backplane Current (24 V) | 2.5 milliamps |
| Power Dissipation (Max) | 6.19 Watts |
| Wire Size | 20 AWG |
| Weight | 0.3 pounds (0.1 kilograms) |
| Dimensions | 5.51 x 4.41 x 5.71 inches |
| Operating Temperature | 32-140 F (0-60 C) |
| Enclosure | None |
What the Key Ratings Mean for Your Budget
The 20-pin screw-clamp layout sets how much field wiring one block can carry, so you avoid buying extra interface hardware for a single module slot. Screw-clamp terminations are reusable: you can loosen, re-terminate and re-torque the same block instead of scrapping it after one wiring change. That directly lowers the cost per maintenance event.
The 0-60 C operating range covers most clean, dry industrial enclosures without added cooling. The 0.3-pound weight and compact 5.51 x 4.41 x 5.71 inch footprint keep panel space and shipping cost low. Maximum power dissipation of 6.19 Watts is a panel heat-load figure worth noting when you plan enclosure ventilation.
Wiring Rules That Protect the Investment
The 1756-TBNH accepts 0.33-2.1 mm2 (22-14 AWG) solid or stranded copper wire rated 90 C (194 F) or higher, with 1.2 mm (3/64 in.) maximum insulation. Use 20 AWG per the catalog data. Keep every conductor in one block the same size, and use either all solid or all stranded wire. Never mix solid and stranded in the same block. Do not wire more than two conductors on any single terminal.
Screw torque is 1.36 Nm, and the maximum screwdriver width is 8 mm (5/16 in.). Correct torque prevents loose connections, which are a common cause of intermittent faults and repeat service calls.
Where the 1756-TBNH Fits
Every ControlLogix I/O module mounts on any ControlLogix chassis and needs a removable terminal block to connect field-side wiring. In ControlLogix architecture, input and output status is shared among multiple controllers in the same or different chassis using producer-consumer technology. That makes a healthy RTB a shared asset: one loose terminal can affect data used by more than one controller.
Typical duties include high-speed digital processing and process control. In oil, gas and industrial automation panels, keeping a spare 1756-TBNH on site is cheaper than an unplanned production stop.
Selection Checklist
Before ordering, confirm the module slot needs a 20-position screw-clamp RTB, verify your field wire gauge and type, and check that your screwdriver fits the 8 mm limit. Please verify current lifecycle status and availability with Oil AutoTech before ordering.
Contact Oil AutoTech today for pricing and availability.
