Fire-resistant cables have been developed for the purpose of increasing safety and decreasing the risk of fires in factories and other buildings. This article will explain what you need to know about these fireproof cables.
Certain circuits are required to continue operating during an emergency situation. The implementation of fire rated cables makes this possible.
Advances in technology along with modifications to the National Electrical Code (NEC) led to the development of fire resistant cables for fire alarm and other emergency systems. These fireproof cables must satisfy NEC CI requirements and must also pass IEC 60331.
Fire resistant cables don’t immediately shut off when a fire starts. Instead, power continues to travel through the circuit.
This power is directed towards fire pumps, elevators, smoke control equipment, fire alarm systems, and other emergency systems that are necessary to keep individuals safe during an emergency.
The NEC demands that these circuits remain operating for 2 hours during the emergency situation. This gives the extra time that might be needed for:
- People to evacuate the building;
- Firefighters to use their equipment to put out the fire;
- Communication during the emergency,
- Care facilities, such as hospitals, to evacuate ill, weak, or crippled patients.
In 2014 the NEC released Article 728, which provides all the guidelines and requirements for fire resistant cables. Since then, slight modifications were made and published in 2017.
Overview of fireproof cable requirements
Although an in-depth analysis is outside the scope of this article, we are going to give you a basic overview of what Article 728 contains.
Section 728.4 demands that “Fire-resistive cables, fire-resistive conductors, and components must be tested and listed as a complete system, must be designated for use in a specific fire-rated system, and must not be interchangeable between systems.”
Article 728 also covers:
- Installing fire rated cables outside of fire-rated rooms [728.5(A)-(H)];
- Mounting the system [728.5(A)];
- Raceways and couplings [728.5(C)];
- Cable trays [728.5(D)];
- How to incorporate boxes into the fire resistant system [728.5(E)],
- Supporting conductors and cables in vertical raceways [728.5(G)].
Complying with NEC Article 728 is absolutely necessary when installing fire resistant cables. You should read Article 728 for yourself to find out more about how to install fire resistant cables.
Fire resistant cable types
Let’s take a look at the different fire resistant cable types.
Mineral Insulated (MI) Cables
These fire resistant cables have existed since 1896. They can have a single or multiconductor design and are made of solid copper and magnesium oxide. MI fire rated cables pass UL 2196 testing and have an excellent reputation.
Here are some benefits of MI cables:
- A metal cover shields the wires from the damaging effects of oxidation. This feature is necessary for settings that are wet or use chemicals;
- MI cables won’t corrode, which reduces the likelihood of having to replace the fire rated cables. This promotes safety in circumstances, such as nuclear plants, where the task of replacing fireproof cables is dangerous,
- Because of its insulated design, MI cables will not burn. Instead, they will continue to deliver optimal performance even when confronted with high temperatures.
Although they have many advantages, MI cables are quite difficult to install. This challenging project requires an expert’s skills and knowledge. Specialized tools are also needed to give the finished job an attractive appearance.
Metal-Clad (MC) Cables
There are different varieties of MC cables but most of them are made of three insulated wires that are shielded by aluminum. They come in three common sizes:
- 10 gauge;
- 12 gauge,
- 14 gauge.
The benefits of MC cables are listed below:
- These fireproof cables are easier and safer to work with;
- They aren’t as expensive to install compared to MI cables;
- MC cables are made of flexible material, making them easier to install,
- They pass NEC requirements and have a 2-hour fire rating.
Fire resistant vs flame retardant cables
If you’ve been wondering, there is a difference between fire resistant and flame retardant cables. Despite their similar names, the two are not interchangeable.
As previously explained, fire resistant cables keep working during a fire. A flame retardant cable serves a different purpose, which is to hinder the spread of the fire by turning off and ceasing to operate.
Fire retardant cables have their own set of requirements and must pass the IEC 60332. Fire retardant cables are tested to ensure they will not spread the fire into other areas of the building.
The most important takeaway from this article is that you need to install fire resistant cables so that your building will be safer in case of a fire. You never know when the next emergency is going to occur, so get prepared now! You certainly don’t want to get caught off guard in a dangerous situation.