Does the NEC Cover Wire & Cable Terminations?
Yes, the National Electrical Code does guide how wire and cable should be terminated, spliced, or connected to equipment. Following the guidelines provided by the NEC helps ensure the safety and operation of electrical equipment.
Errors in the installation and termination of wire, cable, and devices can result in injury, fire, or other costly damage. The recommended practices can save future maintenance, labor, and insurance costs.
A case of factory terminations and custom wire harnesses
A review of general guidelines and requirements for terminations, connections, and industry-specific requirements. In all cases factory designed and produced harnesses and connections will outperform those done in the field or manually when installing complex control and monitoring systems in enclosures.
The definition of factory-produced terminations and connections
In the field or even the assembly of electrical devices or electronics in control panel enclosures tools are used to make connections and terminations manually. The manual use of tools can provide safe and practical connections. Training is required for all termination tools, maintenance, and adequate space to utilize the tools.
When a wire is terminated to an electronic or electrical device when manufactured, you are assured of proper design, materials, and application of the terminating materials. The technician in the factory has many more options for appropriate attachment of the terminations and connectors.
The factory technician is also trained for that specific job and performs the process frequently where the installer in the field may or may not do the task every day. Factory tools are more robust than field tools and designed to do multiple terminations according to factory specifications.
The labor savings with installing factory-made terminations or custom wiring harnesses are considerable compared to the manual termination of the wiring or cable. The plug and play design customarily used with factory-made connections provide a simpler, safer, and time-saving alternative to onsite manual processes.
General Guidelines that apply to all applications
The national electrical code on wire & cable terminations requires you to follow the manufacturer's instructions when installing electrical equipment.
OEM or original equipment manufacturers depend on their engineers and technicians to design and install industrial control systems in enclosures. NEC and UL guidelines dictate the processes for producing the finished electrical control systems.
The use and application are critical. Manufacturers design devices utilized in certain conditions and industries. The product/device has instructions to be used following their intended use. Evaluation of the product's intended use is essential. Failing to follow these instructions or the manufacturers' guidance not only violates warranties but could result in harm to individuals or property.
UL listed products are required to provide the intended use and installation instructions for a tested device. UL listed means that Underwriters Laboratories has tested representative samples of the products based on their safety standards.
Is the URL listing important when following NEC guidelines? The listing is an excellent way to know that the installed devices are safely designed. It also ensures you can rely on the intended purpose and instructions for installation. Listing applies to completed products. Most components that are subcomponents being assembled in an enclosure or even a finished device are referred to as UL recognized.
Electrical connection requirements
When using the recommended connection devices and methods, proper tightening of the wire and cable is still required. If the device manufacturer has provided the connection or termination in a custom termination or wire harness, you can depend on the connection's integrity. If done in the field by an installer, they must ensure the connections are correctly tightened.
Properly tightened connections provide low-resistance to current and avoids heating, arcing, or pitting of contacts. A loose connection can lead to improper functioning of the device also.
UL 486-B, Wire Connectors refers to specific guidance on the proper tightening of a termination or amount of pull on the wire.
Requirements by industry can be different.
Any wire, cable, or terminations that can be factory-made will perform better than those during installation by manually using tools in the field. Custom made wire harnesses save time and labor while helping to ensure safety and proper operations.
Specific industries have different requirements based on local conditions—the more adverse the environment, the bigger the need for unique factory-made terminations and connections.
Do your terminations and connections adhere to the device specifications for the environment of intended use? Often even the devices chosen don't align with their recommended usage. Failing to use the specified materials and connection/termination methodology could result in catastrophic fire and injuries.
How do NEC requirements vary between industries?
Review the list of industries below and think about the operational environment. The list is not inclusive. Is the installation inside a factory, on/in a plane or ship, in remote locations and weather conditions, hazardous areas, or exposed to human contact?
- · Medical Devices
- · Aeronautics and space
- · Ships or submarines
- · Military
- · Oil & Gas
- · Energy & Power
- · Windmills
- · Solar
- · Lighting
- · Traffic & safety devices
- · ATMs
- · Manufacturing
- · Transportation - cars - trucks
- · Electric vehicles
- · Construction & farm equipment
- · Food services
- · Underwater
- · Commercial
- · Residential
Other categorizations for NEC requirements
Understanding the external conditions of electrical enclosures in the individual industries can lead you to find requirements specific to those industries.
- · Hazardous areas or materials
- · Submersible
- · Confined spaces
- · Weather conditions
- · Human exposure
- · Pest or rodent exposure
- · Water or washdown
One example of where a factory termination may be beneficial is shrink-wrapped with silicone or potted with other dielectric material. This type of protection from hazardous material exposure, water, and corrosion is challenging to accomplish manually in the field.
Our next article will go into detail or the specific requirements in primary industrial classification. We will also discuss the equipment used for factory installation versus in the field and use conditions.
Meanwhile, if you are in doubt about factory connections and terminations related to PTC or flexible silicone heaters used in any industry, check with our experts.
Need help with the Design of Custom Wire Harnesses?
DBK USA has experts standing by to answer your questions. Specialists on conductors, wire harnesses, and termination will answer your questions.
Feel free to call our custom wiring engineers directly at 1-864-607-9047