In industrial automation, control cabinets, and power distribution systems, din rail screw terminal blocks, spring cage terminal blocks, and din rail push in terminal blocks are the three most common types. Faced with different application requirements, how do you make the most suitable choice? This article will provide an in-depth comparison of the working principles, advantages, and disadvantages of these three types, offering a clear selection guide.
Din Rail Screw VS Spring Cage VS Push-In Terminal Blocks
Working Principle
Din rail screw terminal blocks: Electrical connections are established by tightening a screw, which uses vertical pressure to press the wire against a conductor. This is the most traditional and basic connection method.
Spring cage terminal blocks: These utilize a pre-compressed spring (usually a coil or disc spring). To connect, insert a screwdriver into the operating hole, push open the spring, insert the wire, and then remove the screwdriver. The spring’s return force will firmly clamp the wire.
Din rail push-in terminal block: This is the most convenient type. It has a cleverly designed spring mechanism. No tools are needed for connection; simply insert a stripped standard cable directly into the terminal hole, and the internal spring will automatically lock the wire in place. To disconnect, use a screwdriver or a special tool to press the release hole next to the cable.
Core Features
Screw terminals: Simple structure, reliable connection, and high tolerance for wire diameter.
Spring terminals: Vibration resistant, maintenance-free, and offer fast wiring speed.
Push-in terminals: Extremely fast wiring speed, requires only one tool (or even none), making them ideal for mass wiring.
Advantages
Screw Terminals:
Low Cost: Usually the most economical choice.
High Contact Pressure: Generates high contact pressure, suitable for high-current applications.
Intuitive and Reliable: Simple structure, connection status is clear at a glance, high engineer trust.
Spring Terminals:
Excellent Vibration Resistance: The continuous pressure of the spring compensates for loosening caused by vibration and thermal expansion and contraction, ensuring high reliability.
High Wiring Efficiency: Compared to tightening screws, releasing the wire by opening the spring is faster.
Low Maintenance Requirements: No need for periodic retightening.
Push-in Terminals:
Extremely High Wiring Efficiency: Eliminates the need for tightening screws or opening springs, providing the fastest wiring speed, saving up to 70% of wiring time.
Simple Operation: Reduces the technical requirements for operators and effectively avoids connection problems caused by insufficient or excessive torque.
Low Tool Dependency: Typically only a standard screwdriver is needed for wire removal.
Disadvantages
Screw Terminals:
Susceptible to vibration: Prone to loosening in vibrating environments, requiring regular inspection and retightening.
Slow wiring speed: Each terminal requires screwing, time-consuming and labor-intensive.
Risks exist: Poor connection or damage may occur due to stripped screw threads or improper torque (too loose or too tight).
Spring Terminals:
Higher cost: More expensive than screw terminals of the same specifications.
Requires specific tools and cables: Requires rigid cables, and precise wire stripping length is required. Using unsuitable tools (such as a screwdriver that is too fine) may damage the spring.
Poor visibility: Connection points are usually obscured, making it impossible to directly observe whether the wire is properly inserted.
Din rail push in terminal blocks:
Highest cost: More complex technology and structure, therefore the highest unit price.
Strict cable requirements: Typically only accepts rigid cables (such as single-core wires of 1.5mm² and below or multi-strand wires with cold-pressed connectors), and precise wire stripping length is required.
One-time suture removal: Although sutures can be removed, it is not as convenient as the previous two options and is not suitable for situations that require frequent suture changes.
How To Choose Based On Needs?
Application Environment
High-vibration environments (such as machinery, rail transportation, and ships): Spring terminals are the preferred choice, as their vibration resistance far exceeds that of screw terminals. Through-hole terminals also offer good vibration resistance due to their robust locking mechanism.
Static environments (such as distribution boxes and control cabinets): All three types are suitable, but cost becomes a significant consideration. Screw terminals are widely used due to their economic efficiency.
Compact space, high-density wiring: Through-hole terminals are typically smaller, enabling higher wiring density.
Types Of Wires
For thick-gauge, flexible/multi-strand wire: screw terminals offer the best compatibility; a reliable connection can be achieved with the appropriate copper lugs.
Standard rigid single-core wire: suitable for all three types of terminals.
Multi-strand wire with cold-pressed connectors: suitable for all three types of terminals and is the recommended approach.
Multi-strand flexible wire without connectors: spring terminals and straight-through terminals are generally not recommended for direct use, as the thin copper wires may not be effectively clamped or may break. Screw terminals are a better choice.
Wiring Efficiency And Cost
For projects aiming for the lowest procurement cost: choose screw terminals.
For projects aiming for the lowest overall installation cost (considering labor and time): through-hole terminals significantly reduce installation time; although the unit price is higher, the total cost may be lower. Spring terminals are the next best option.
For projects requiring frequent wiring modifications: screw terminals and spring terminals are relatively easier to disconnect.
Operation And Maintenance
Safety during live operation: Through-hole terminals are the safest because the operator’s fingers are kept away from conductive parts. Spring terminals are the next safest. When operating screw terminals under live conditions, there is a risk of the screwdriver coming into contact with a live conductor, so extra caution is required.
Maintenance convenience: Screw terminals require regular inspection and retightening. Spring terminals and through-hole terminals are essentially maintenance-free.
Current And Space
High-current applications (typically >100A): Screw terminals remain the mainstream choice due to their strong contact pressure and mature technology.
For low to medium current applications (control signals, sensors, drivers, etc.): Spring terminals and through-hole terminals offer more significant advantages.
Perguntas frequentes
Which Of These Three Terminal Types Is The Cheapest or Expensive?
Generally, screw terminals are the cheapest, followed by spring terminals, with through-hole terminals being the most expensive. The price reflects the technical complexity and convenience offered.
Which Is Better?Spring Or Screw Type Chooses For High Vibration Applications
Spring-loaded connections are undoubtedly the better choice. Their constant spring pressure effectively resists loosening caused by vibration, while screw-loaded connections will gradually loosen under such conditions, leading to connection failure or even safety accidents.
Which Terminal Operation Is Safer In A Live Environment?
Straight-in terminals are generally the safest because the operator only needs to insert the cable by hand, without any tools needing to come into contact with the live metal parts. While spring terminals require the screwdriver to be near the live part during operation, they are still safer than screw terminals, which require the screwdriver to be inserted directly into a live screw hole.
How To Determine Whether A Terminal Is Of Reliable Quality?
1. Check the material: Conductive components should use high-quality copper (such as pure copper), with a tin or silver plating to prevent oxidation; the insulating shell should use flame-retardant materials (such as PA66).
2. Check certifications: Look for internationally recognized certification marks such as UL, cUL, VDE, TÜV, etc. These certifications ensure that the product meets stringent safety and performance standards.
3. Check the brand and reputation: Choosing a well-known brand usually means more reliable quality control and after-sales service.
4. Hands-on testing: Perform wire clamping and pull-out force tests on the sample to feel its operability and clamping force.
Conclusão
No single terminal block is a “one-size-fits-all” solution. Screw terminals excel in their economy and versatility; spring terminals perform exceptionally well in vibration environments and maintenance-free applications; and through-hole terminals stand out for their wiring efficiency, safety, and space savings.
Your choice should be based on a comprehensive trade-off between your application scenario, cable type, budget, and long-term maintenance needs. In static, cost-sensitive power distribution projects, screw terminals are a reliable choice; in dynamic industrial machinery, spring terminals ensure long-term stability; and in automated panels requiring the installation of thousands of cables, investing in through-hole terminals will yield significant time and manpower savings.
Contact our technical experts today to find the perfect wiring solution for your next project!
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