Fire alarm Cable and wiring
explained
MICC, FP200, and the different cable types used in fire alarm installations — why the choice of cable matters, and what each type is suited to.
The cable in a fire alarm system is not merely a means of connecting devices — it is a critical component of the fire protection strategy itself. In a fire, the cable must continue to function long enough for the system to fulfil its purpose. The choice of cable type directly determines how long it can do that.
The Role of Cabling in a Fire Alarm System
A fire alarm system that fails at the moment it is needed most has failed in its fundamental purpose. The wiring that connects detectors, sounders, and the control panel must continue to function in a fire environment — at elevated temperatures and in the presence of smoke and flame — for as long as is needed to complete the evacuation of the building.
BS 5839-1 sets out requirements for the fire resistance of cables used in fire alarm systems, classified by the duration of circuit integrity they must maintain in a fire. For a summary of when different cable types apply, see also our dedicated guide to fire alarm cable types and our guide to red fire alarm cable requirements.
Cable types
MICC Cable — Mineral Insulated Copper Clad
What it is
MICC cable — commonly known as pyro cable or mineral insulated cable — consists of copper conductors packed in a compressed magnesium oxide mineral insulation and enclosed in a seamless copper outer sheath. It is one of the most fire-resistant electrical cables available and has been used in fire alarm and emergency systems for decades.
| Characteristic | Detail |
|---|---|
| Fire resistance | Extremely high — the copper sheath and mineral insulation are inherently non-combustible. Can withstand temperatures well in excess of 1,000°C. |
| Circuit integrity standard | BS 6387 Category CWZ — the highest available rating, covering high temperature, water, and mechanical shock during fire conditions |
| Typical applications | High-risk buildings, high-rise buildings, hospitals, buildings where the highest possible level of circuit integrity is required |
| Advantages | Unmatched fire resistance, extremely durable, long service life, physically robust |
| Disadvantages | Significantly more expensive than softskin alternatives — both materials and installation. Requires specialist tools and skills to terminate. Relatively stiff. Susceptible to moisture ingress at terminations if not sealed correctly. |
| Appearance | Bare copper or PVC oversheathed. Typically supplied on drums and cut to length on site. |
MICC cable is the gold standard for fire alarm circuit integrity and remains the specification of choice in the most demanding applications. Its cost and installation complexity mean it is typically reserved for projects where the fire strategy demands the highest level of circuit survivability.
Enhanced Fire Resistant Softskin Cable — FP200 and Equivalents
What it is
Enhanced fire resistant softskin cables — of which Prysmian FP200 Gold is the most widely recognised brand in the UK — are designed to maintain circuit integrity during a fire while being significantly easier and cheaper to install than MICC cable. FP200 has become the dominant cable type for fire alarm installations in standard commercial and residential premises in the UK.
| Characteristic | Detail |
|---|---|
| Fire resistance | High — designed to maintain circuit integrity during fire conditions. Tested to BS 8434-2 (equivalent to BS 6387 Category WZ at 650°C). |
| Circuit integrity standard | BS 8434-2 — typically 30 or 60 minutes circuit integrity at 650°C depending on specification |
| Typical applications | The standard cable for fire alarm detector, sounder, and control circuits in commercial, industrial, and residential premises across the UK |
| Advantages | Significantly cheaper than MICC; flexible and easy to route; uses standard cable termination techniques; widely available |
| Disadvantages | Lower fire resistance ceiling than MICC — not suitable for the most demanding applications |
| Common sizes | 1.5 mm² 2-core and 4-core are the most common in fire alarm applications |
| Colour | Typically red — immediately identifiable as a fire alarm circuit |
FP200 and equivalent products have become the standard specification for fire alarm wiring in the vast majority of UK installations. An earth fault on a fire alarm circuit is often caused by cable insulation damage — maintaining the physical integrity of the cable run is as important as specifying the correct cable type in the first place.
Choosing the right cable
Which Cable Does Your System Need?
The choice between MICC and enhanced softskin cable is a design decision that should be made at the system design stage, based on the fire strategy for the building and the circuit integrity requirements specified in BS 5839-1.
| Application | Typical cable specification | Reason |
|---|---|---|
| Standard commercial or office premises | FP200 or equivalent enhanced fire resistant cable | Meets BS 5839-1 circuit integrity requirements for most standard applications at reasonable cost |
| Residential premises — flats, HMOs | FP200 or equivalent | Standard specification for residential fire alarm wiring |
| High-rise buildings | MICC on critical circuits; FP200 may be acceptable on others — design dependent | Extended evacuation times mean circuit integrity requirements are higher |
| Hospitals and healthcare premises | Often MICC on primary circuits — design dependent | Inability to evacuate some patients means the alarm system must function for longer in a fire |
| Circuits powering suppression release | MICC or equivalent highest-rated cable | Circuit failure before suppression discharge could be catastrophic in a protected enclosure |
| External or underground circuits | Armoured fire resistant cable (SWA with fire resistant insulation) | Mechanical protection required in addition to fire resistance |
Cable colour and identification
BS 5839-1 recommends that fire alarm cables are coloured red throughout, or marked at regular intervals, to ensure they are readily identifiable. See our dedicated guide to red fire alarm cable requirements for what the standard actually says and the common misconceptions about cable colour requirements.
Cable containment and physical protection
The fire resistance of the cable itself is only part of the story. BS 5839-1 also requires that cables are adequately supported and protected from mechanical damage. Fire alarm cables should be run in dedicated containment and should not share containment with mains power cables or other services.