By Jeff Kuzniar
Innovative IDC terminal blocks eliminate the need for wire stripping and preparation, and reduce wire connection time.
 Rail-mounted ADO IDC terminal blocks. |
Insulation displacement connection (IDC) has become the latest trend in terminal block wire connection. IDC terminal blocks entered the market about 10 years ago. They eliminate the need for wire stripping or preparation and reduce wire connection time. These innovative products answer the industry's need for fast, reliable terminations and provide an alternative to standard screw-clamp and spring connection terminal blocks. In a recent study,1 11 percent of the respondents questioned as to the termination method they used, answered "insulation displacement." Interest in IDC terminal blocks will only grow as they continue to demonstrate reduced production time of high-quality, long-lasting connections.
IDC Terminal Block Benefits
 ADO mini-IDC terminal blocks for space-saving applications. |
IDC terminal block technology provides many application solutions, including reduced installation time and increased productivity and elimination of corrosion problems. IDC terminal blocks also eliminate the periodic retightening that is necessary with screw-clamp terminal blocks — a major benefit for maintenance in remote locations where equipment is difficult to access, such as in the heating, ventilating and air conditioning industries. They can also benefit original equipment manufacturers (OEMs). Some OEMs indicate that, after shipment, their products arrive at the customers' locations with screw terminals that need to be retightened prior to installation.
IDC terminal blocks eliminate wire connections that fail in vibration-intensive environments as well. Machine tool manufacturers that build equipment for the metal forming industry fall into this category. Examples of other industries include packaging, transportation and printing equipment.
Making the Connection
Connecting wire to an IDC terminal block is quick, easy and safe. There is no risk of under- or over-stripping the wire or of adjacent wires touching and affecting circuit integrity because insulation is never removed to expose the strands of the conductor. There is also no danger of applying excessive tightening torque, as is possible with screw-clamp terminal blocks. The use of unstripped wire eliminates the need for a ferrule.
 Figure 1. The steps for connecting wire to an ADO IDC terminal block, using an ADO semiautomatic hand tool. |
To install a wire using the company's ADO IDC terminal block and ADO semiautomatic hand tool, the operator first cuts the wire to length using the hand tool's built-in wire cutter. He then inserts the unstripped wire into the terminal opening on the side of the terminal block. After placing the tip of the hand tool into the recess on the top of the block, he presses the trigger to secure the wire, then releases and removes the tool. The action of depressing the hand tool trigger drives the wire into position. The operator cannot take the tool out of the block until the trigger has been pressed full cycle.
 Figure 2. Cross section of an ADO IDC terminal block showing the clamp and the terminal block housing gripping the wire. |
The insulation displacement connection has to be made thoroughly in order to disengage the semiautomatic hand tool from the terminal block. This technique ensures that the connection is independent of operator skill. It is not necessary to visually inspect the IDC wire connection. If the hand tool does not properly make the connection, it will not disengage (see Figure 1).
Insulation displacement connection is accomplished by the elastic pressure of the metal jaw or clamp built into the terminal block. Electrical contact is uniformly established and permanently maintained by the clamp's points of contact that perforate the insulation. The clamp, made of copper material, has two cone-shaped cutting lips that allow for centering the conductor and for cutting the insulating material by making two slots to reach the cable core. Both the clamp and the terminal block housing grip the wire, holding it solidly in place in a vibration- and corrosion-proof jaw (see Figure 2).
The insulation displacement mechanism bites through the insulation, providing an excellent connection that will not loosen during vibration. The gastight connection to the all-copper jaw prevents deterioration caused by chemicals, high humidity, salt air from coastal environments, and extreme heat or cold, ensuring a corrosion-proof termination.
Wire Entry and Size
The ADO IDC terminal blocks feature multiple wire entry — installation of two wires (wires must be the same gauge, each solid or stranded) into each termination. The second wire takes the place of the first wire by pushing it further into the clamp (see Figure 3A and B). Installing two wires into a terminal point offers two immediate benefits. It facilitates daisy chaining from one terminal block to another and simplifies jumping from one terminal to another terminal.
 Figure 3A and B. Multiple wire entry with ADO IDC terminal blocks. |
Most IDC terminal blocks accommodate a range of wire sizes. Also, polyvinyl chloride (PVC) insulation, which is commonly used for conductors, assures that contact pressure is held constantly high and does not degrade upon clamping or piercing.
Mixed-technology Terminations
Most manufacturers offer IDC terminal blocks with IDC connection technology on both sides. Some offer mixed-technology terminal blocks with IDC on one side and a standard screw-clamp on the other. These configurations allow for prewiring of the terminal block's IDC side at the factory, while providing the field installer with a familiar screw-clamp, if that is the preference.
The Future
IDC terminal blocks have an established foothold in the marketplace. They offer specific advantages over traditional terminal block wire connection including increases in speed and productivity, reliability, and vibration- and corrosion-proof connections. Manufacturers will continue to introduce new IDC terminal block products and continue to investigate other applications for this innovative technology.
Reference
1. Cahners Research, "Terminal Blocks Study," February 2000, Oak Brook, Ill.
JEFF KUZNIAR is engineering manager, Entrelec Inc., 1950 Hurd Drive, Irving, TX 75038-4312; (800) 431-2308; Fax: (800) 862-5066; E-mail: jkuzniar@entrelecusa.com; Web site: www.entrelec.com.
SPEC SHEET
End Applications: Remote locations and vibration/corrosion-intensive environments including those in the HVAC, packaging, transportation, petrochemical, automotive and machine tool industries
Related Products: IDC, screw-clamp and spring connection terminal blocks
Main Point: IDC terminal blocks have an established foothold in the marketplace. They offer specific advantages over traditional terminal block wire connection, including increases in speed and productivity, reliability, and vibration and corrosion-proof connections. They eliminate the need for wire stripping or preparation, allow for quick and easy connections, and are an alternative to standard screw-clamp and spring connection terminal blocks.
