1756-TBNH Allen-Bradley 20-Position ControlLogix Removable Terminal Block

Product Overview | Field Wiring Interface

The Allen-Bradley 1756-TBNH is a 20-position removable terminal block (RTB) for compatible ControlLogix I/O modules. It provides a screw-clamp interface between field wiring and the module's terminal connections.

Designed for industrial control cabinets, the 1756-TBNH supports organized field wiring and simplifies module removal during planned maintenance. Its NEMA-style screw-clamp construction secures compatible conductors at the terminal interface.

This component is an I/O accessory, not a standalone controller or signal-processing module. Confirm the exact I/O module compatibility before installation.

• Manufacturer: Rockwell Automation
• Brand: Allen-Bradley
• Product family: ControlLogix
• Part number: 1756-TBNH
• Component type: Removable Terminal Block (RTB)
• Terminal configuration: 20-position screw clamp
• Primary function: Field wiring termination for compatible 1756 I/O modules

Technical Data | Electrical and Mechanical Reference

Parameter	Specification
Brand	Allen-Bradley
Manufacturer	Rockwell Automation
Model	1756-TBNH
Series	ControlLogix
Module category	Removable Terminal Block accessory
Terminal arrangement	20 positions
Clamp mechanism	Screw clamp
Wire range	22–14 AWG (approximately 0.33–2.1 mm²), according to the supplied data
Conductor type	Solid or stranded copper; follow the manufacturer's wiring requirements
Conductor temperature rating	90°C minimum, according to the supplied wiring specification
Maximum screw torque	1.36 N·m, as stated in the supplied description
Maximum screwdriver blade width	8 mm (5/16 in.)
Maximum conductors per terminal	Two, subject to the applicable wiring instructions
Operating temperature	0°C to 60°C (32°F to 140°F)
Weight	Approximately 0.1 kg (0.3 lb, rounded in the supplied data)
Dimensions	5.51 × 4.41 × 5.71 in., as supplied; verify orientation and drawing dimensions
Enclosure	No separate enclosure
UPC	10612598171856

Data verification: The supplied source also lists backplane current and power dissipation values. These values may relate to a different component or may have been transcribed incorrectly. Do not use them as terminal-block ratings without confirmation from the applicable Rockwell Automation documentation.

Terminal Design | What Matters in the Panel

1. Twenty termination positions: Provides a defined connection arrangement for compatible field circuits.
2. Screw-clamp retention: Secures conductors when installers apply the specified torque.
3. Removable interface: Allows the terminal block to disconnect from a compatible I/O module during approved maintenance.
4. Separate field wiring: Helps organize conductors at the I/O module boundary.
5. ControlLogix integration: Supports the field-side wiring requirements of compatible 1756 I/O modules.

The terminal block does not determine signal type, channel resolution, input range, or output capacity. Those characteristics depend on the connected I/O module.

Compatibility Map | Choose by Module First

System Component	Compatibility Requirement
ControlLogix digital input module	Verify the module's specified RTB catalog number and terminal arrangement.
ControlLogix digital output module	Confirm the terminal block matches the exact module variant.
ControlLogix analog I/O module	Check the required RTB type and field wiring configuration.
ControlLogix chassis	The chassis supports the I/O module; the RTB attaches to the module's front interface.
Field instruments and actuators	Verify signal requirements, conductor size, terminal assignments, and electrical ratings against the I/O module documentation.

Selection rule: Do not select an RTB based only on the ControlLogix family name. Check the exact I/O module catalog number and its approved terminal-block options.

Installation Procedure | Safe and Repeatable Wiring

• Step 1 — Identify: Record the I/O module catalog number and confirm the required terminal block.
• Step 2 — Isolate: Follow site lockout procedures and verify that the relevant circuits are safe to handle.
• Step 3 — Inspect: Check the terminal block, screw threads, contact surfaces, and housing for damage.
• Step 4 — Prepare conductors: Use the specified copper wire size and temperature rating. Strip insulation to the length required by the manufacturer's instructions.
• Step 5 — Terminate: Connect each conductor to its assigned position. Observe polarity and channel identification.
• Step 6 — Tighten: Apply the specified torque using a suitable tool.
• Step 7 — Inspect: Check conductor retention, exposed copper, insulation clearance, and terminal labeling.
• Step 8 — Commission: Restore power according to site procedures and verify the corresponding I/O channel status.

Wiring precaution: The supplied description advises against mixing solid and stranded conductors in the same terminal block. Follow the applicable manufacturer instructions for conductor type, terminal loading, and any permitted combinations.

Field Diagnostics | Common Wiring Faults

The 1756-TBNH is a passive wiring accessory. It does not contain independent diagnostic electronics or generate channel alarms.

However, poor termination can cause intermittent I/O signals, unstable readings, or unexpected field-device behavior. A structured inspection can help isolate these issues.

• Intermittent input: Inspect conductor retention, terminal tightness, and field-device wiring.
• Missing output response: Verify terminal assignments, the output module's status, and the connected load circuit.
• Unstable analog readings: Check conductor identification, shielding practices, grounding, and signal wiring against the module manual.
• Recurring channel faults: Compare channel diagnostics with terminal inspection results before replacing the I/O module.
• Overheating or discoloration: Isolate the circuit and investigate loose connections, excessive current, or damaged components before returning the system to service.

Use controller diagnostics and the I/O module's indicators to distinguish a field wiring problem from a module or configuration fault.

Application Scenarios | Where This RTB Is Used

• Discrete signal termination: Connect compatible proximity switches, limit switches, and digital field devices.
• Output wiring: Terminate supported control circuits for compatible output modules.
• Process instrumentation: Provide field wiring connections for supported analog I/O modules.
• Machine control panels: Organize sensor and actuator connections in ControlLogix cabinets.
• Distributed I/O systems: Support field-side wiring in appropriately configured ControlLogix architectures.
• Maintenance and repair: Replace a damaged terminal block without changing the I/O module, when the installed module supports this exact RTB.

Global PLC Spare HUB's Insight

In control-panel maintenance, terminal-block selection and wiring discipline directly affect troubleshooting time. Engineers should verify the RTB catalog number before disconnecting an installed assembly.

Practical example: A digital input intermittently changes state while a machine runs. The technician checks the field sensor, reviews the controller input status, and inspects the terminal connection. A loose conductor may explain the symptom, but the technician should also verify the sensor supply and input module before concluding that the terminal block caused the fault.

For a planned replacement, photograph the existing wiring labels and document each terminal assignment before removing conductors. This practice reduces wiring errors during recommissioning and supports traceable maintenance records.

Engineering recommendation: Treat the 1756-TBNH as a module-specific interface component. Confirm compatibility, conductor requirements, and terminal torque using the relevant installation manual rather than relying on appearance alone.

Five Professional FAQs | Selection and Troubleshooting

Q1: How can a terminal-block replacement be validated before the machine returns to production?

Verify each conductor against the wiring diagram and terminal schedule. Check mechanical retention, polarity, and insulation clearance. Then test the affected I/O points and confirm normal operation under the site's commissioning procedure.

Q2: What information helps identify the correct terminal block when the original label is unreadable?

Record the complete I/O module catalog number, module series, terminal arrangement, and existing connector dimensions. Use the manufacturer's compatibility documentation to identify the correct accessory. Do not rely on dimensions alone.

Q3: Why can a wiring fault appear only when a machine vibrates?

Vibration may expose a weak termination, damaged conductor, or insufficient strain relief. Inspect the wire entry, terminal clamping, and cable support. Correct the underlying mechanical issue before repeating operational tests.

Q4: Is this component suitable for outdoor or wet-area installation?

The supplied information describes use in a clean, dry industrial environment and lists no separate enclosure. Provide suitable cabinet protection and confirm environmental requirements for the complete installation. Do not treat the terminal block itself as a sealed outdoor component.

Q5: What should be included in a spare-parts order for planned maintenance?

Include the exact catalog number, required quantity, compatible I/O module details, delivery destination, and requested lead time. If possible, provide a photograph of the installed module label. Confirm packaging, accessories, warranty terms, and shipment timing in the quotation.

Supply, Warranty and Logistics

• Product: Allen-Bradley 1756-TBNH ControlLogix removable terminal block.
• Package protection: Protective packaging suitable for industrial electrical components.
• Package contents: Confirm the supplied terminal block and any included accessories with the seller before ordering.
• Warranty: 12 months, subject to the seller's written warranty terms.
• Shipping carriers: FedEx, UPS, and DHL, subject to destination and service availability.
• Dispatch target: Within 24–48 hours after order confirmation, subject to stock availability and order processing.

Request a Quote | Confirm Your ControlLogix Configuration

Contact Global PLC Spare HUB for pricing, availability, and compatibility assistance for the Allen-Bradley 1756-TBNH.

Send your I/O module catalog number, required quantity, and delivery destination. Our team can review the requested configuration and provide a quotation for your maintenance or spare-parts requirements.

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