Electrical Enclosure Wire & Cable
Wire and cable are terms used to describe various items not necessarily associated with electrical, electronics, power, or communications. Without the adjectives, standards, specifications, and other industry regulations are even more confusing.
Electrical wire as a term includes single wires and a group of wires (Cable). One example of a cable is the four-wire cable used in-home wiring. Did you think there were only three wires in the electrical cable used for homes? Such cabling does exist, and one reason there are codes and standards for wire and cable.
Communication or signal cable is usually associated with the transmission of data or telecommunications signals. There is also video cable or AV cable.
Types of Electronic Enclosure Wiring
A single industrial enclosure could have multiple types of wiring.
- Power wiring
- Control wiring
- Signal wiring
- Fiber optic cables
Voltage and current are essential variables for selecting power wiring coming into the panel or enclosure to power all the electrical components, contactors, switches, fans, and electronic devices. The outer coating must prevent the voltage and current from coming into contact with other surfaces or humans.
Consideration for the routing of the cable to the cabinet is essential. Is it in open cable trays or conduits? Even with the wiring enclosed inside insulation, the current flowing through the wire produces heat. In an open wire tray, the cable can disperse some of that heat. Inside a conduit or piping, the heat has no way to dissipate.
The distance of the power wiring from its source is also a consideration, whether the cable will need to bend around corners in the conduit, cable trays, or wire troughs.
Conductors carrying voltage and current to heating, cooling or condensation devices used for environmental control in enclosures should be considered power wiring and design accordingly. These devices will have varying current requirements requiring careful consideration of both the wiring and terminations. Custom wire harnesses are often used for this type of power wiring.
Industrial control panels often use 120 volts or less depending on circuits and switches. Some wiring is 24 volts or even 5 volts for some computer applications.
Voltage and current are considered, but connections, bending, wire trays, and other routing variables come into play. A good panel design will have control wiring isolated from power wiring to avoid the interference emitted from the current in the power wiring affecting signals.
The type of control device and location within the cabinet also comes into play. The application of the devices can dictate the type of wiring that meets the specifications or regulations.
These smaller wires can be subject to abrasion in routing and heat from other components. All cabinet wiring may need to be fire resistant or not give off toxic gases when exposed to fire. This requirement would be right for control panels aboard ships or underground.
Sometimes confused with control wiring, low voltage signals are used to transmit electrical pulses or digital communications for data reporting. At the lower voltage levels, signal interference from both power wiring and control wiring is possible.
Signal wiring is often wrapped in protective metal braiding to prevent interference from other wiring and control circuits. Coaxial cable is for your home TV, and the internet is an excellent example of covered braided wiring.
Signal wiring used in aircraft and space vehicles need protection from interference, heat, and vibration. The Milspec, military specification for this type of wiring, is very strict.
Fiber Optic Cables
Fiber optic cables have improved protection from electromagnetic interference and enabled faster transmission of vast amounts of data. Many fragile glass fibers are wound together to make one optic cable.
Even though they aren't susceptible to typical signal interference as metallic cables, they need extra protection from damage and bending.
Types of Wire & Cable for Industrial Control Cabinets
It isn't straightforward to classify all wire and cable into types. Electrical and communication cable might be considered the primary categories. Data along optical cables transmit electrical signals or data using light. Data and communications cables have their standards and fall under the same electrical code's references for labeling installations.
Types of electrical cabling can range from conventional house wiring, higher voltage and current wiring for industry, to power transmission lines. Communications or data transmission cables designed to transmit data signals are much different than electrical wiring.
These cables range from twisted pairs and coaxial for networking, USB for computers, to fiber optic cables for transmitting large volumes of information across greater distances.
Each of the types has a multitude of specialized coverings and sizes based on applications and use. Electrical underground power transmission cables and undersea optical communication cables are at one end of the spectrum for size and protection. Aviation and aerospace are at the end of durability and specialization.
How are all These Types of Cable Manufactured?
Optical wire manufacturing uses a very different process than metallic wire cable in that molten glass drawn into the fibers rather than metal. The glass or optical cable must remain in a semi-molten state at very high temperatures to be drawn and annealed by external heating into thinner individual glass tubes.
Metal or copper wire is forced through dies of smaller dimensions and annealed by heat by passing electricity through the metal to create a thinner wire.
Focusing on the covering and labeling/coding of bare wire and glass filaments, we find the coverings aren't that much different. Some factories draw the metals, primarily copper, and cover it during the drawing process. Most of the covering wire methods or creating the cables originate with the bare drawn wire and extrude the specialized coverings onto the individual wires, stranded, or bundled cables.
Both types of wire and cable, once covered, must be identifiable by color or coding applied to their surface. These codes are set by multiple organizations internationally and nationally, depending on their end uses.
What are the Standards & Codes Used to Identify Wire and Cable?
There are as many different standards as there are types of wire and cables. The guiding standards or regulatory code pertain to labeling the covering during manufacture and installation. There are volumes of information with guidance on how each type should be labeled and installed. There are UL Certification, Mil-Spec requirements, NFPA and NEC, EIA, TIA, IEEE, NEMA, and SAE standards.
Looking at just one standard for PTFE insulated wire referred to as NEMA HP3 PTFE. The first designation or code on the wire is HP3, indicating that it has PTFE insulation. After a dash EE, a NEMA Type, a type intended for high-temperature applications suitable for 1000 volts RMS and high-frequency circuitry. The X is a type of construction, wrapped or extruded. The next letter is the conductor material.
We have mainly written about copper, but six different conductors are indicated with a B through G letter designation. Then comes the AWG nominal conductor size from 32 gauge to 4/0, indicated by letters A through Z. The number of stands inside the cable from 1 to 2109 designated by a letter. Color code is last ranging from 0 for black and 9 for white.
A typical number-coded onto the cable may look like this:
HP3 - EEXBGE9
Other standards may include wire specifications, shielding material, jacket material, and color-coding of the individual wires. Standard home and building cables have the type of wire, size, number of cables, with or without ground, voltage, brand, and UL if certified.
Type NM-8 14-2 WITH GROUND 600 VOLTS BRAND (UL)
Manufacturers also include part numbers and lot codes to the wire and cables for identification and traceability. Many print the brand's logo on the outside.
Terminations are Part of Wire Management
Wire management includes not only the types of wire and how they are mounted in the cabinet but also how each wire is connected to its destination. Wire for industrial control cabinets require terminations in terminal blocks or directly to devices. The terminations materials and fastening of the connectors are as important as the wire in ensuring safety and reliability. The terminations must protect the wire and not come loose from pulling or twisting.
If used for industrial automation applications one failed connection could shut down the entire production line. Connectors and the proper use or method of connecting them to wire are also covered under government and safety regulations.
If a wire must meet certain conditions and standards so much the connector. The soldering and shrink methodology used to attach the connectors is also covered. Look for UL certifications or NFPA 79 for guidance on compliance with national standards and rules covering installation.
One example of the rules in NFPA 79 under 13.1.2 Conductor Cable Runs states that conductors shall be run from terminal to terminal without splices or joints. The only exception is when connecting to motors or solenoids where the conductors are attached to pre-existing leads. Even then there are rules of how the splice should be made.
Premade Wire Harnesses for Cabinets and Devices
To ensure your wiring and connectors meet the right standard for your application custom wire harnesses are available for component manufacturers. A custom or premade harness saves installation times and ensures reliable certified connections that won’t fail during installation or use.
The connectors fasten to the wiring harness at both ends of the conductor ensuring they will not pull loose and are properly insulated. The connectors should be selected based on the termination requirements as well as the minimum fire and safety standards of the wire itself.
Continuity and pull testing are done on the wire and the termination minimizing time required to make such tests at the installation site.
Premade wire harnesses can be specified for single devices or designed for multiple connections throughout the electrical panels. Modern aircraft, trains, cars, and other vehicles all have premade wiring harnesses for rapid installation and reliability. Some home builders are beginning to use the same concept on prefabricated homes and eventually custom-built homes.
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