How to Choose the Right Ferrule for PT Series Push-in Terminal Blocks
Introduction
Push-in terminal blocks are widely used in modern industrial control systems for their fast, tool-free wiring and vibration-resistant connections. However, to achieve the best performance, selecting the correct ferrule (cold-pressed terminal) is just as important as choosing the terminal block itself.
This guide explains how to properly match ferrules with PT Series push-in terminal blocks, ensuring secure contact, electrical safety, and long-term reliability.
Why Ferrules Are Important for PT Series Terminals
PT Series push-in terminals rely on a spring-clamp mechanism to hold conductors firmly in place. When stranded wires are inserted directly without a ferrule, individual strands may spread, leading to:
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Unstable contact
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Increased contact resistance
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Risk of wire damage
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Reduced current-carrying capacity
Using a properly sized ferrule ensures:
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Clean, compact conductor insertion
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Uniform contact pressure
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Improved vibration resistance
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Compliance with industrial wiring standards
Match the Ferrule Size to the Conductor Cross-Section
The most critical factor when selecting a ferrule is conductor cross-section (mm²).
| Wire Size (mm²) | Recommended Ferrule Size |
|---|---|
| 0.5 mm² | 0.5 mm² ferrule |
| 0.75 mm² | 0.75 mm² ferrule |
| 1.0 mm² | 1.0 mm² ferrule |
| 1.5 mm² | 1.5 mm² ferrule |
| 2.5 mm² | 2.5 mm² ferrule |
| 4.0 mm² | 4.0 mm² ferrule |
⚠️ Important:
Do not oversize the ferrule. An oversized ferrule may reduce spring contact force and lead to loose connections.
Choose the Correct Ferrule Length
Ferrules are available in different tube lengths. For PT Series terminals:
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Select a length that fully covers the stripped conductor
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Avoid ferrules that extend too far into the terminal housing
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Typical ferrule lengths range from 8 mm to 12 mm, depending on terminal depth
Proper length ensures full contact without interfering with the spring mechanism.
Single vs. Twin Ferrules (When to Use Each)
Single Ferrules
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Used for standard one-wire connections
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Ideal for most control panel wiring
Twin Ferrules
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Designed for two conductors in one terminal
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Common in PLC signal distribution and jumper connections
PT Series terminals often support twin ferrules, but always check the terminal’s rated capacity.
Ferrule Material and Insulation Type
For industrial control applications, choose ferrules with:
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Tin-plated copper conductors for excellent conductivity
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Insulated collars to prevent short circuits
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Heat-resistant insulation suitable for control panel environments
High-quality ferrules improve electrical performance and simplify visual inspection.
Proper Crimping Is Just as Important
Even the correct ferrule will fail if crimped improperly.
Best practices include:
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Use a certified crimping tool matched to ferrule size
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Ensure uniform hexagonal or square crimp
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Avoid over-crimping, which can damage the conductor
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Avoid under-crimping, which causes loose connections
A well-crimped ferrule ensures optimal spring contact inside the PT terminal.
Application Example: PT Series in Industrial Control Cabinets
In automation control panels, PT Series push-in terminal blocks combined with properly selected ferrules offer:
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Faster installation time
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Higher vibration resistance
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Improved wiring consistency
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Reduced maintenance requirements
This combination is widely used in PLC wiring, machine control systems, power distribution, and smart factory installations.
Conclusion
Choosing the right ferrule is essential for achieving the full benefits of PT Series push-in terminal blocks.
By matching the ferrule size, length, material, and crimp quality to your conductor and terminal specifications, you ensure safe, stable, and long-lasting electrical connections in industrial control systems.
With high-quality PT Series terminals and proper wiring accessories, engineers can build more reliable and efficient automation panels.
