Difference Between Cable Gland and Cable Terminal Post
It is in the field of electrical wiring and panel construction that small parts have the most impact on the safety and effectiveness of the installation. Two of those parts that are most often confused by beginners, and sometimes by skilled professionals, are the cable gland and cable terminal post. Both of them have an important function to perform in electrical installations but they perform totally different roles within them.
In this blog, we will explain the function of each part, how it differs from the other part, where it can be used and how to select the correct part for your needs. Whether you are an electrician, a panel constructor or you work in industrial electrical parts procurement, here you will find all the answers to your questions.
What is a Cable Gland?
Cable gland is a type of mechanical connector designed for fastening and sealing the cable into an enclosure, panel, junction box or equipment housing. It is primarily responsible for keeping the cable securely fixed to the enclosure, and at the same time providing protection from dust, moisture, vibration and mechanical stresses.
In general, a cable gland comprises of a body, sealing rings and a locking nut. When screwed in place, it provides compression to the rubber or elastomer seal surrounding the cable, thus making sure that the sealed connection is completely protected from external environment. This feature becomes critical in case of outdoor use or in case when the equipment is operated in harsh conditions such as humidity, dust, chemicals, and extreme temperatures.
The material of the cable glands varies depending on their application. Lightweight indoor plastic cable gland are usually made of plastic as this material provides not only sufficient protection but also excellent insulating and corrosion-resistant properties. On the contrary, metal cable glands are better suited for industrial applications when mechanical strength or explosion-proof rating is essential.
Key Functions of a Cable Gland
- Acts as strain relief to ensure that the cable does not get stressed or strained at the point of entry.
- Waterproofs the opening of the enclosure from water and any other contaminants (IP rated such as IP65, IP67, and so forth).
- Earthing continuity for some models (armored cable glands in particular).
- Keeps the cable from moving around and causing short circuits.
What is a Cable Terminal Post?
A cable gland, on the other hand, is not for sealing or protecting the point at which the cable enters; rather, it is meant to create an electrical connection. The terminal post refers to a connection point that is stationary and which is usually installed on a terminal block, busbar, or panel where wires are connected through screws, nuts, or clamps.
The terminal post serves to create a firm, low resistance connection point between the conductors. These are common on distribution panels, control panels, motors connections, battery banks, and switchgears where many wires require to be connected together, branched out, or terminated.
Terminal posts do not have anything to do with the environment sealing issues as it is only concerned with the electric performance of the device and ensuring the current flows smoothly from one wire to another without any unnecessary heating up of contacts, loss of voltage, or arcing.
Key Functions of a Cable Terminal Post
- Creates a junction between one or more conductors.
- Facilitates low resistance and stable current through the connecting wires.
- Facilitates easy detachment and attachment when necessary for maintenance or repairs.
- Frequently utilized with lugs, ferrules, or ring terminals to ensure a firm hold on stranded wires.
Cable Gland vs Cable Terminal Post: The Core Difference
| Feature | Cable Gland | Cable Terminal Post |
|---|---|---|
| Primary Purpose | Sealing and strain relief at cable entry points | Electrical connection between conductors |
| Location | Enclosure walls, panel entries, junction boxes | Terminal blocks, busbars, distribution panels |
| Protection Function | Protects against dust, water, and mechanical stress | No environmental sealing; purely electrical |
| Material | Plastic, nylon, brass, stainless steel | Brass, copper alloy, tin-plated metals |
| Typical Rating | IP-rated for ingress protection | Current-rated (amperage capacity) |
Where Are They Used Together?
In an ordinary control panel used in industry, there is an entry point of a cable through a gland which is fitted on the wall of the panel. The gland not only acts as a seal but also clamps the jacket of the cable to prevent any pulling or damage of the cable. Once within the panel, the different wires from the same cable are then connected to the terminal posts on a terminal block.
This combination is common in the control of machines, such as crane and hoist control panels. One example is a control panel which uses Crane Remote Control, which needs a correctly glanded cable entry point in order to waterproof and have reliable terminals inside the receiver panel. The use of either of the two or even lack of one can make the whole system unreliable.
Choosing the Right Component for Your Application
While choosing a cable gland, take into account the size of the cable, the surrounding environment (indoor or outdoor), and the IP class required. If you deal with indoor panels without mechanical strain, plastic Cable gland will serve their purpose both effectively and inexpensively. However, for outdoor, vibration-sensitive, and hazardous surroundings, it is more prudent to use metal glands.
In the case of choosing terminal posts, it is important to take into consideration the current carrying capacity, the quantity of conductors to be connected, and the wire size. It should always be kept in mind that improper torqueing of terminal connections is among the main reasons of malfunctioning electrical panels.
Don't Overlook Cable Management Accessories
Since glands and terminal posts deal with the process of sealing and connecting, the aspect of proper wire routing and management within the panel is equally as critical for sustainability purposes. It is at this point where the quality of cable ties comes into play.
A conventional nylon cable tie will suffice if the installation is within a building, but in the case of outside installations where the tie would be exposed to heat or chemicals, an SS cable tie should be used, considering that stainless steel is highly resistant to corrosion.
Although there is a small similarity in their names, cable glands and cable terminal posts play quite different roles in the entire electrical system. A cable gland will provide protection and secure the cable entry into the enclosure, while the terminal post will make the electrical connection once the cable is inside the enclosure. It is very important to understand the difference between these two elements in order to design and install electrical cabinets properly and avoid any safety and financial risks.
By choosing the proper components, including the appropriate cable glands and terminals, along with the cable ties and other related items, you will be able to create a reliable electrical system that will last long and require minimum maintenance. In case you need to build a simple junction box or an electrical cabinet for a crane remote system, this knowledge will come in handy.
Frequently Asked Questions (FAQs)
1. Is there a possibility that the cable gland may serve as a terminal post?
No. This is because a cable gland simply serves to secure and seal the cable where it enters the enclosure while the terminal post must serve to connect conductors.
2. Between plastic and metal cable glands, which is preferable for use in outdoor panels?
Plastic glands can be effectively utilized in light duty applications in outdoors where they will be exposed to weather conditions but with the appropriate IP rating. However, in heavy duty situations in outdoors, metal glands are recommended.
3. What causes the loosening of terminal connections?
The loose connection of terminals is due to vibration and expansion/contraction as well as poor installation practices such as improper torquing.
4. Should I use a combination of cable glands and terminal posts in my panel?
Yes, for most industrial panels. The cable gland will take care of cable entry to the panel, while the terminal post will be responsible for making the connection of the wires.
5. Which size cable gland is suitable?
The choice of the size of the cable gland depends on the cable diameter. Ensure you always refer to the manufacturer's size chart because a gland which is too large will not seal correctly, while a too tight gland may hurt the insulation of the cables.
Related Post: