Fast, flexible terminal blocks

Avoiding the need for hard wiring, the latest terminal blocks provide safe, secure connections with greater ease. Terminal block designs also offer more flexibility, space savings, accessory options, and integrated intelligence compared to prior designs. Although they are often overlooked, terminal blocks are a critical part of the electrical control system. See more photos and helpful terminal block resources.


Avoiding the need for hard wiring, the latest terminal blocks provide safe, secure connections with greater ease. Terminal block designs also offer more flexibility, space savings, accessory options, and integrated intelligence compared to prior designs.

Although they are often overlooked, terminal blocks are a critical part of the electrical control system, says TJ Landrum, product manager for DIN logic products, Eaton Corp . Important time and space-saving technologies are in wider use, Landrum says, including insulation displacement connections (IDC), push-in jumpers, and a vast array of integrated functions. “IDC allows for a secure connection with the flip of a screwdriver; the wires do not need to be stripped, and the risk of screws backing out is eliminated,” he says. This reduces installation time about 60%.

Other available control and protection features include fuse terminal blocks, circuit breaker modules, diode terminal blocks, and disconnect blocks. These “help integrate more functionality into a compact DIN rail assembly,” Landrum says.

In the last five years, Phoenix Contact also has observed greater IDC acceptance, and growth in what it calls hybrid terminal blocks. Larry Freeland, Phoenix Contact Clipline product marketing manager, says, “In our testing we’ve found IDC can be up to 80% faster than using a screw clamp connection with a manual screwdriver and ferrules. It is also up to 70% faster than spring-cage with ferrules and 50% faster than spring-cage without ferrules.”

Hybrid designs feature different connection technologies (such as IDC-to-screw, IDC-to-spring, and screw-to-spring connections) on each side of the terminal block. These are typically used when the machine builder or panel builder is not installing field wiring. The panel builder may use IDC inside the panel while building it and use screw connection for the conductors that come from the outside, which may be favored by the field installer, Freeland says. Other flexible, hybrid systems include interchangeable bridging system connections and an easier plug connection.

Plug and play designs are useful when large machines are broken down before shipping. “Pluggable connections simplify the process so the entire machine doesn’t need to be rewired on site,” says Freeland.

Smaller blocks, more choices

Opto 22 Snap Terminal Extenders

Opto 22 Snap Terminal Extenders provide bundled connections from I/O module terminals to custom break-out boards.

Over the past five years or more, terminal blocks have gotten thinner, narrower, and gained increased functionality such as added fusing, which eliminates the need for external fusing, according to Opto 22 ’s Arun Sinha, sales engineer, and James Davis, application engineer.
Terminal block makers have expanded portfolios by offering wiring harnesses, terminal extenders, other accessories, and, most significantly, control capabilities, they say.
“Controllers are now to the point where they are small enough to add to the DIN rail right there with the terminal blocks—as opposed to 5-10 years ago when terminal blocks served mostly as a termination point for field and control wiring,” they say.

Rockwell Automation has a long line of terminal blocks

Rockwell Automation has a long line of terminal blocks, including some with built-in intelligence.

Smaller terminal blocks with built-in intelligence also are making inroads as alternatives to screw connection technology as standards evolve, says Sarah Stepanski, product manager, IEC terminal blocks, Rockwell Automation.

Short circuit ratings

Standards that affect terminal blocks continue to evolve, and one influential change involves short-circuit current ratings (SCCR) for industrial control panels. As states adopt changes made to the 2005 National Electric Code Article 409, Stepanski says industrial control panels need to be marked with a short-circuit current rating.

“Since this rating can be determined by a test of the system or based on the short-circuit current rating of each component in the power circuit, the ratings for terminal blocks are in the spotlight, she says. Unless otherwise documented, the assumed maximum short-circuit current rating for terminal blocks is 10 kA. Many customers are looking to achieve overall system ratings between 25 kA and 100 kA, so this assumed rating may be a limiting factor,” she adds. Testing and documentation of terminal block ratings can help, she adds.

EN and DIN standards for high-temperature fluctuations, vibration, and corrosion also are important benchmarks, says Phoenix Contact’s Freeland.

Wago Power Cage Clamp (PCC) terminal blocks

Wago’s Power Cage Clamp (PCC) terminal blocks offer one-twist terminations, reducing install times and operator strain.

Accommodation for larger conductors is another trend. Wago ’s terminal blocks with Wago Cage Clamps now run the gamut in sizes, says Michelle Goeman, product manager for terminal blocks and electronic interface, and usability has improved. Wago’s Power Cage Clamp (PCC) terminal blocks, for example, offer one-twist terminations, reducing install times and operator strain, she says.

Tighter connections for larger conductors help with variable frequency drives (VFDs) and motor controls, Goeman says, where the leading cause of failure is a result of loose connections. VFDs are not well served by screw-style terminal blocks, which are not inherently vibration proof and loosen with temperature cycling. “A major VFD manufacturer switched to PCC blocks instead of screw-style blocks in their VFD panels after having to re-torque the screw-style blocks before leaving the factory after validation testing,” she says.

Integration of various industrial networks and better engineering enables ease of use, along with better use of space, suggested Robb Black, vice president, Turck Network and Interface Division. “Our experience has allowed us to evaluate our customers’ specific needs for each of these networks.”

For instance, the Turck JRBS junction brick “was designed to meet customer demands in an easy-to-engineer package,” he says. The bricks simplify installation “while utilizing proven circuit design installed in thousands of Turck junction bricks currently in the field.” Black said development of this product resulted from evaluation of customer applications and requests.



Terminal blocks: Resources, application advice, products

Learning resources, application advice and terminal block product information follows.


Videos and more details

Videos on Phoenix Contact Clipline interconnection technologies .

Phoenix Contact Clipline terminal blocks .

More on Phoenix Contact SPTA, a compact, low profile, angled terminal block that provides space-saving connections for up to 10 A.


A Rockwell Automation video shows time saving connection technologies .

Wago offers:

E-learning on the Wago Cage Clamp Spring Pressure Connection Technology.

Wago Power Cage Clamp (PPC) system overview , variants, and more information.

Control Engineering Supplier Search offers terminal block resources .

Author Information

Mark T. Hoske, editor in chief , Control Engineering, can be reached at .

Vertical mount junction bricks ease installations

Turck JRBS junction bricks for FOUNDATION fieldbus provide quick and easy connection of multiple devices to the main fieldbus trunk.

Turck JRBS junction bricks for FOUNDATION fieldbus have 4, 6, 8, 10 or 12 ports and feature removable terminals for simple, efficient installation and wiring modification in tight spaces.

JRBS junction bricks are available with 4, 6, 8, 10 or 12 ports and feature removable terminals for simple, efficient installation and wiring modification in tight spaces. These terminals are located on both sides of the brick to enable easy access for wiring from either direction—and they securely screw (or clamp) into place—eliminating the risk of becoming disconnected in high vibration environments. They can be DIN-mounted vertically or horizontally.

JRBS junction bricks provide short circuit protection for all ports, as well as visual status with bright LED indicators located on each spur. This allows devices to be added and removed without disruption to the network. An optional overmolded, pluggable terminating resistor also is available for use with the three pole terminal blocks.

Applications include oil and gas, petrochemical, power generation and distribution, pharmaceutical, water processing and management. The bricks have IP20-rated housing and hazardous location approvals.

No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Leaders Under 40 program features outstanding young people who are making a difference in manufacturing. View the 2013 Leaders here.
The new control room: It's got all the bells and whistles - and alarms, too; Remote maintenance; Specifying VFDs
2014 forecast issue: To serve and to manufacture - Veterans will bring skill and discipline to the plant floor if we can find a way to get them there.
2013 Top Plant: Lincoln Electric Company, Cleveland, Ohio
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.

Bring focus to PLC programming: 5 things to avoid in putting your system together; Managing the DCS upgrade; PLM upgrade: a step-by-step approach
Balancing the bagging triangle; PID tuning improves process efficiency; Standardizing control room HMIs
Commissioning electrical systems in mission critical facilities; Anticipating the Smart Grid; Mitigating arc flash hazards in medium-voltage switchgear; Comparing generator sizing software

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.