Fire alarm cables provide power and signals to emergency lighting units and fire detectors, ensuring proper functionality during emergencies. This allows for timely evacuation and response to prevent loss of life and minimise property damage.
In this guide, we’ll be explaining all you need to know when it comes to fire alarm cables, including the different types,
What are Fire Alarm Cables?
Fire alarm cable is a specialised type of wiring designed specifically for use in fire detection and alarm systems. These cables are engineered to transmit signals between the fire alarm control panel and various devices such as smoke detectors, pull stations, sirens, and other alarm system components.
The key purpose of fire alarm cable is to make sure there is reliable communication within the fire alarm system, allowing it to detect potential fire incidents and alert occupants through visual and auditory signals.
Types of Fire Alarm Cables
There are several types of fire alarm cables, each suited to different applications and environments:
Non Armoured Fire Alarm Cable
This is the most basic form of fire alarm cable, used in many regular fire alarm systems. It is typically used in applications where external interference is not a concern.
SWA Fire Alarm Cable
Steel wire armoured fire cable includes a layer of steel to protect against electrical interference. It's often used in buildings with multiple floors, running from floor to floor or in vertical shafts.
Data Fire Cable
Data fire cable provides high data transmission rates and is designed to continue functioning under fire conditions, providing circuit integrity in critical systems. The LSOH construction has low emissions of smoke and corrosive gases when exposed to fire.
Each type of fire alarm cable offers unique features and protections, making the selection process critical to meeting the specific requirements of a fire alarm system. Understanding the distinctions between these cables is crucial for ensuring that the installed fire alarm system operates effectively and complies with local building codes and standards.
Key Features of Fire Alarm Cable
Conductor Materials
The effectiveness of fire alarm cables largely depends on the conductor materials used in their construction. Copper is the most commonly used material due to its excellent electrical conductivity, which ensures reliable signal transmission between the fire alarm control panel and the system's components.
Copper conductors can be solid or stranded; solid conductors are typically used in installations where minimal flexibility is needed, while stranded conductors are preferred for their flexibility, making them ideal for applications requiring the cable to bend around obstacles.
Aluminium, though less common, may also be used, especially in larger installations where cost-effectiveness is a priority. However, it's important to note that aluminium has a lower conductivity than copper and is more susceptible to corrosion, which can impact the long-term reliability of the fire alarm system.
Insulation and Jacketing
Insulation and jacketing are important features of fire alarm cables, as they protect the conductors from environmental factors and electrical interference. Insulation materials such as PVC (Polyvinyl Chloride) or FEP (Fluorinated Ethylene Propylene) are commonly used to prevent short circuits and electrical leaks.
These materials are chosen for their fire-resistant properties and ability to insulate the conductors effectively.
The outer jacket of the fire alarm cable provides an additional layer of protection against physical damage, moisture, and chemicals.
The choice of jacket material is determined by the cable's application; for example, plenum-rated cables require jackets made from materials that produce limited smoke and no toxic halogens when exposed to fire. Similarly, riser-rated cables are jacketed with materials that resist vertical flame spread.
Choosing the Right Fire Alarm Cable for Your System
Choosing the appropriate fire alarm cable is crucial for the effectiveness and reliability of your fire alarm system. The selection process involves several important factors:
System Requirements
Understand the specific needs of your fire alarm system. This includes the type of system (conventional or addressable), the devices to be connected, and the system's overall complexity.
Environment
Consider the environmental conditions where the cable will be installed. For outdoor or underground installations, the cable must be durable enough to withstand moisture, temperature variations, and potential mechanical damage. For indoor installations, factors like air circulation and fire retardancy of materials around the cable path are important.
Building Codes and Standards
Compliance with building regs and industry standards is mandatory. These regulations dictate specific types of cable for different applications, such as plenum or riser spaces.
Future Scalability
Anticipate future expansions or modifications to the fire alarm system. Choosing a cable with additional capacity can save time and expense in the long run.
Cable Sizing and Capacity
Determining the correct size and capacity of your fire alarm cable is essential for ensuring that the system functions efficiently without risk of overload or signal loss.
Calculate Load
Estimate the total current load of the devices connected to the circuit, considering both the operating current and the potential starting current.
Consider Cable Length
Longer cable runs may require a larger conductor size to compensate for voltage drop, ensuring that devices receive sufficient power.
Check Specifications
Refer to the cable manufacturer's specifications for maximum load capacity and recommended applications to ensure compatibility with your system's requirements.
Fire Cable FAQs
Do all fire alarm systems require the same type of cable?
No, not all fire alarm systems require the same type of cable. The choice of cable depends on the system's specifications, the environment where it's installed, and local building codes. For example, plenum areas require plenum-rated cables, while outdoor or underground installations might need cables that are resistant to moisture and physical damage.
Can fire alarm cables be run alongside power cables?
Fire alarm cables can be run alongside power cables, but certain precautions must be taken to avoid electromagnetic interference (EMI).
It's generally recommended to maintain a physical separation between fire alarm and power cables. If they must cross, doing so at a 90-degree angle is advised. For situations where close proximity cannot be avoided, using shielded fire alarm cables or conduits can provide additional protection against EMI.
What is the difference between shielded and unshielded fire alarm cables?
The main difference between shielded and unshielded fire alarm cables lies in the presence of a metallic shield around the cable's conductors in shielded cables. This shield provides additional protection against electromagnetic interference (EMI), making shielded cables suitable for environments with high levels of electrical noise.
Unshielded cables, lacking this shield, are more susceptible to interference but are adequate for installations where EMI is not a concern. The choice between shielded and unshielded cables should be based on the specific requirements of the fire alarm system and the installation environment.
