How Are Terminal Strips Connected?
What are Terminal Strips?
Terminal strips, also known as terminal blocks, are devices used to connect electrical wires and terminate them. They consist of a length of insulating material with metal terminals inserted at regular intervals that wires can be attached to. According to EPLAN’s Help Portal, a terminal strip definition defines the device name, number of terminals, spacing and design as well as the electrical data.
Terminal strips are commonly used to provide convenient and reliable termination points for wiring, especially in electrical control panels and junction boxes. They allow multiple wires to be connected in an organized way and reduce the need for splicing individual wires together. Terminal strips help manage complex wiring schemes by breaking connections down to common connection points. They also allow easy troubleshooting and replacement of wires if needed.
Types of Terminal Strips
There are three main types of terminal strips:
Barrier Terminal Strips
Barrier terminal strips have a plastic divider between each terminal to prevent accidental contact between terminals. This helps prevent short circuits. Barrier strips are a safe option when connecting multiple wires in a compact area. They allow for high density wiring while maintaining electrical isolation.
Feed-Through Terminal Strips
Feed-through terminal strips allow wires to be connected on both sides of the strip. This enables signals to be branched and distributed. Feed-through strips provide flexibility in wiring architecture while consolidating connections to a common point.
Ground Terminal Strips
Ground terminal strips have extra large terminals designed for connecting ground wires. The oversized terminals can accommodate multiple wire gauges. Ground strips consolidate ground connections and allow easy access for maintenance and troubleshooting. They help organize grounding and protect against shock hazards.
Terminal Strip Construction
Terminal strips are constructed using various materials depending on their application and electrical load requirements. Some common materials used include:
Thermosetting plastic materials like epoxy resin (EP) are commonly used. EP offers high mechanical strength, electrical insulation properties, and heat resistance (source).
Thermoplastic materials like polycarbonate (PC) are also used. PC offers high impact strength, temperature resistance, and dielectric properties (source).
Terminal strips contain multiple contacts or connection points, typically ranging from 2 to 12 or more. The number of contacts depends on the terminal strip type and application. For example, a common 4-position barrier terminal strip contains 8 contacts spread across 4 positions (source).
The spacing or pitch between contacts is standardized, with common spacings being 3.5mm, 5mm, 7.5mm, 10mm, etc. Larger spacings allow for thicker wire gauges to be connected (source). The spacing must match the application requirements.
Connecting Wires to Terminal Strips
Connecting wires to terminal strips involves understanding proper wire gauges, stripping, and securing the wires correctly under screws or clamps.
Terminal strip wire gauge compatibility is important. The terminal screw or clamp needs to match the gauge of the wire being connected. Using a screw or clamp meant for larger gauge wire on a smaller gauge can result in a loose connection. Conversely, using a screw or clamp meant for smaller gauge wire on a larger gauge can damage the wire strands. Always match the terminal to the wire gauge for optimal connection.
Wires need to be properly stripped before connecting to terminal strips. Use wire strippers sized for the wire gauge to remove just enough insulation to connect to the terminal – typically 1/4 to 3/8 inches of exposed copper. Remove any stray wire strands or insulation fragments which could interfere with the connection. The bare wire should be cleanly exposed.[1]
Once stripped, the bare wire inserts under the screw or into the clamp on the terminal strip. Tighten the screw securely to hold the wire in place, but be careful not to overtighten, which could damage the wire. Alternatively, press the clamp firmly to lock the wire into position. Ensure the wire is held snugly by gently pulling on it, but avoid putting undue stress on the connection.[2]
Wiring Configurations
There are three main wiring configurations used with terminal strips:
Series Wiring
In series wiring, the circuit components are connected end-to-end in a daisy chain. The same current passes through each component in the circuit. Series circuits have only one path for current to flow. If there is a break in the circuit, current will not flow. Series wiring is commonly used for lights connected in a string.
Parallel Wiring
In parallel wiring, circuit components have individual connections to the power source and return. This creates multiple paths for current to flow. If there is a break in one path, current can still flow through the other paths. Parallel wiring is commonly used to connect multiple loads to the same power source.
Combination Wiring
Combination wiring uses both series and parallel connections in a circuit. Complex circuits often combine components in series and parallel configurations. For example, lights may be wired in parallel while switches are wired in series.
Terminal strips allow for flexible wiring configurations to create customized circuits. Following the terminal strip wiring diagram is crucial for proper operation.
Safety Considerations
When working with terminal strips, it is crucial to follow proper safety procedures to avoid electric shocks, shorts, fires, and other hazards. Some key safety considerations include:
Proper insulation – Wires connected to terminal strips should have insulation rated for the voltage they will carry. Insufficient insulation can lead to shorts and shocks. The terminal strip itself should also be made of an insulating material like plastic to prevent accidental contact with live terminals.
Wire ratings – Wires must be the proper gauge to handle the expected electrical load without overheating. Oversized wires are preferable to undersized wires for most applications. Consult wiring charts to select the right wire gauge for your needs. Exceeding the current rating can damage wires and terminal blocks.
Enclosing terminal strips – Exposed terminal strips pose a safety risk, so they should be enclosed in a protective housing. Terminal block enclosures prevent accidental contact with live parts and protect connections from environmental contaminants.
Other important practices include using properly sized fuses or circuit breakers, labeling all wires, following all electrical codes, and exercising general caution when working with electrical systems. Proper installation and maintenance of terminal strips is necessary to ensure safe operation.
Terminal Strip Installation
Proper installation of terminal strips is crucial for safety and reliability. Here are some key considerations:
Mounting Options – Terminal strips can be mounted to DIN rails or directly to a panel or enclosure using screws. When mounting, ensure the terminal strip is properly aligned and secured. Allow space for wire routing and connections.
Spacing Guidelines – Maintain adequate spacing between terminal strips and other components for safe operation and maintenance. Many standards recommend at least 1 inch of space between terminal strips. Consult electrical codes for specific requirements.
Wire Routing – Wires should be routed cleanly to terminal blocks, avoiding excess length and sharp bends. Allow sufficient slack for any vibration or movement. Use wire ducts or ties to bundle and organize wiring. Route power and control wires separately when possible. Take care not to obstruct wire connection points.
Adhering to best practices for terminal strip mounting, spacing, and wire routing ensures a safe and reliable installation.
Maintenance
Regular maintenance is crucial for terminal strips to operate safely and reliably over time. Terminal strips should be periodically inspected, cleaned, and tested.
Inspecting connections involves checking that wires are securely fastened to the correct terminals. Any loose wires should be tightened to the proper torque specifications for the terminal. Also look for corrosion, damaged insulation, overheating signs, and other issues. Tug gently on wires to ensure a snug fit.
Cleaning helps prevent buildup of dirt, dust, oil, and other contaminants that can lead to conductivity issues or corrosion over time. Use a soft brush, compressed air, or approved cleaning agents to remove debris from the terminal strip and wires. Avoid harsh cleaners or abrasives that could damage components.
Testing strips involves using a multimeter to check for continuity, resistance, and voltage readings across different points in the circuit. Out-of-range values can indicate problems with connections, damaged terminals, or other faults. Regular testing provides an opportunity to detect and address issues before they lead to failures.
Following a thorough maintenance routine allows terminal strips to operate reliably for many years. Proper installation is also key – connect wires securely, provide strain relief, and use appropriate enclosures. With periodic inspection, cleaning, and testing, terminal strips can continue performing their important wiring distribution functions.
Troubleshooting
Some common issues that can occur with terminal strips include loose connections, corroded contacts, and faulty strips. Here are some troubleshooting tips:
Check for loose connections between the wires and the terminals on the block. Loose connections can cause overheating and intermittent electrical problems. Tighten any loose terminal screws and ensure wires are making solid contact with the metal terminals.
Inspect for corroded contacts on the terminal strip. Corrosion can build up over time, increasing resistance and impedance. Clean any corrosion off the terminals and wires with a wire brush or fine sandpaper. Replace severely corroded strips.
Test for faults in the plastic terminal strip itself. Cracks or carbon tracking can occur over time, leading to short circuits between terminals. Look for any burn marks or discoloration. Consider replacing old or damaged terminal strips.
For additional troubleshooting tips, refer to this helpful guide: https://issuu.com/elmex30/docs/maintenance_and_troubleshooting_of_terminal_blocks
Advantages of Terminal Strips
Terminal strips offer several key advantages over other wiring methods, especially when it comes to flexibility, serviceability, and expandability:
Flexibility – Terminal strips allow for flexible wiring configurations. Wires can be connected in parallel, in series, or in a combination of both. This makes it easy to create custom wiring layouts for different applications. Terminal strips are available in different sizes with various numbers of connection points to accommodate diverse wiring needs.
Serviceability – Wires are securely held by screws on terminal strips, but can also be disconnected easily for testing, troubleshooting or replacing components. This makes servicing and maintaining systems much simpler compared to permanently soldered wires.
Expandability – Additional wires and components can be added to terminal strips by using jumper wires between connection points. This allows systems to be easily expanded and modified without having to completely rewire. More terminal strips can also be daisy-chained together to add more connection points.
Overall, the flexibility, serviceability, and expandability of terminal strips make them an efficient and adaptable wiring solution for many electrical applications.
