FP Cables

Overview

FP cables are polymer-insulated fire-resisting cables commonly used in fire detection and fire alarm systems.

In the context of BS 5839-1:2025, they normally fall into one of the following groups:

cables conforming to BS 7629-1
cables conforming to BS 7846
other cables rated at 300/500 V or greater that provide the same degree of safety as BS 7629-1 cables of the relevant fire-resistance class

For fire alarm work, these cables are typically used on:

critical signal paths
ELV supplies from external power supply units
the final circuit providing low-voltage mains supply to the system

BS 5839-1:2025 also recognizes MICC as an alternative cable type for these duties.

What “FP” Usually Means in Practice

On UK sites, “FP cable” is often used loosely to describe modern fire alarm cable such as:

FP200-type cables
enhanced fire-resisting alarm cables
screened fire alarm cables used on loops, sounder circuits and interfaces

However, the important point for compliance is not the brand name. What matters is whether the cable used satisfies the relevant recommendations in BS 5839-1:2025 for:

acceptable cable type
standard or enhanced fire resistance
support
jointing
mechanical protection
segregation

BS 5839-1:2025 bases compliance on the cable’s conformity and performance, not simply on it being sold as “FP”.

Accepted Cable Types Under BS 5839-1:2025

For critical signal paths, ELV supply from an external PSU, and the final low-voltage mains supply circuit to the system, BS 5839-1:2025 recommends one of the following:

MICC to BS EN 60702-1, with terminations to BS EN 60702-2
cables to BS 7629-1
cables to BS 7846
other 300/500 V or greater cables providing the same degree of safety as BS 7629-1 cable of the relevant class

Standard vs Enhanced Fire Resistance

Standard Fire-Resisting Cable

BS 5839-1:2025 says that, for most fire detection and fire alarm systems, standard fire-resisting cables should be assumed to provide sufficient resistance to the effects of fire, provided there are also appropriate methods of support and jointing.

The 2025 edition defines standard fire-resisting cable as cable achieving 30 minutes survival when tested in accordance with BS EN 50200:2015, including the additional water spray test in Annex E. The standard notes that this corresponds to PH 30.

Enhanced Fire-Resisting Cable

BS 5839-1:2025 says enhanced fire-resisting cable should generally be used for certain higher-risk applications, rather than being treated as the default everywhere.

Enhanced fire-resisting cable is defined as cable achieving 120 minutes survival when tested in accordance with BS EN 50200:2015 and BS 8434-2. The standard notes that this corresponds to PH 120.

When Enhanced Cable Is Generally Needed

BS 5839-1:2025 recommends cable systems comprising enhanced fire-resisting cables for the following applications:

unsprinklered buildings or parts of buildings where the fire strategy involves evacuation in four or more phases
unsprinklered buildings over 30 m in height
unsprinklered premises or sites where a fire in one area could affect critical signal path cables serving remote areas that remain occupied during the fire
any other building where the designer, specifier or enforcing authority decides, on the basis of a fire risk assessment taking fire engineering considerations into account, that enhanced cable is necessary

So the compliant position is not “always use enhanced”. It is “use standard for most systems, and enhanced where Clause 25.4 points to it or where the fire strategy/risk assessment requires it”.

Minimum Conductor Size

BS 5839-1:2025 states that all conductors should have a cross-sectional area of not less than 1 mm².

Multicore Cable Use

Where multicore cable is used for fire alarm interconnections, BS 5839-1:2025 says none of the conductors should be used for circuits other than those of the fire detection and fire alarm system.

Electrical Characteristics

The designer still needs to select cable with suitable electrical characteristics, including:

voltage drop
current-carrying capacity
impedance
ability to transmit data where relevant

BS 5839-1:2025 says these characteristics should be in accordance with BS 7671:2018+A3. This is particularly relevant on addressable loops and any circuit carrying both signalling and power.

Support, Jointing and Installation

The 2025 edition is very clear that cable performance is not just about the cable itself. It repeatedly ties standard/enhanced cable selection to appropriate methods of support and jointing.

Mechanical Protection

BS 5839-1:2025 says that where cables are used with no additional mechanical protection, they should be:

MICC conforming to BS EN 60702-1 and BS EN 60702-2, or
steel wire armoured cables conforming to BS 7846

Cables that do not conform to one of those standards should be given mechanical protection anywhere physical damage or rodent attack is likely. The standard also says mechanical protection should be provided in areas less than 2 m above floor level, except in relatively benign environments such as offices and shops where cables are clipped directly to robust construction. In particularly arduous conditions, mechanical protection should be provided to all cables.

This is a major practical point in the field, because installers often assume that all fire alarm cable can simply be clipped direct everywhere.

Segregation and EMC

BS 5839-1:2025 says the circuits of fire alarm systems need to be segregated from other circuits to reduce the risk of:

insulation breakdown affecting the fire alarm system
fire on another circuit affecting the alarm wiring
electromagnetic interference
damage caused when other services are installed or removed from shared containment

The standard also says manufacturer recommendations on separation from other services should be followed. In addition, mains supply cable to control, indicating or power supply equipment should not enter through the same cable entry as ELV cables, and LV and ELV wiring should be kept separate within equipment so far as practicable.

Typical Advantages of FP-Type Cables

Compared with MICC, FP-type cables are generally:

easier to route
easier to terminate
faster to install
more practical for routine modern fire alarm work

That is a practical engineering observation rather than a direct BS 5839 recommendation, but it is why polymeric fire-resisting cables are so common on modern installs. The compliance position still depends on the cable meeting Clause 25 and the installation meeting Clause 35.

Common Field Issues

Wrong Assumption That “Enhanced” Is Always Required

A common mistake is assuming every fire alarm circuit must use enhanced cable. BS 5839-1:2025 does not say that. For most systems, standard fire-resisting cable is assumed to be sufficient, with enhanced cable used in the specific circumstances in Clause 25.4 or where justified by risk assessment.

Using a Branded “Fire Alarm Cable” That Does Not Actually Meet the Right Standard

Site language often reduces everything to “FP cable”, but compliance depends on whether it actually conforms to BS 7629-1, BS 7846, or provides an equivalent degree of safety as required by Clause 25.2.

No Mechanical Protection Where It Is Actually Needed

A very common issue is clipped-direct installation of polymeric fire alarm cable in vulnerable locations:

plant rooms
service risers
loading areas
warehouse edges
low-level routes
areas with trolley or forklift traffic

BS 5839-1:2025 makes it clear that non-MICC / non-BS 7846 cable should be given mechanical protection where physical damage or rodent attack is likely, and generally below 2 m above floor level unless the environment is relatively benign.

Poor Segregation

Running fire alarm cable alongside power or other services without regard to separation can create EMC issues, insulation risk and future maintenance problems. The standard explicitly addresses this.

Wrong Core Usage in Multicore

Another avoidable mistake is using spare cores in a fire alarm multicore for non-fire-alarm circuits. BS 5839-1:2025 says that where multicore cable is used for fire alarm interconnection, none of the conductors should be used for anything else.

Undersized Conductors

Using sub-1.0 mm² conductors for convenience or stock availability is not aligned with Clause 25.7.

Practical Guidance

When selecting FP-type cable for a fire alarm system, check:

Does it actually satisfy Clause 25.2?
Is standard fire resistance enough, or does Clause 25.4 push you into enhanced?
Is the conductor size at least 1 mm²?
Is the route vulnerable to impact, abrasion, vermin or low-level damage?
Is segregation from other services adequate?
Are support and jointing methods appropriate?

That is a more BS 5839-1:2025-aligned way of selecting cable than simply asking “standard or enhanced?”.

Summary

FP-type cables are widely used in modern fire alarm systems, but BS 5839-1:2025 does not treat them as a vague generic product category. It ties acceptability to specific standards and performance levels, and it makes clear that:

acceptable cables include BS 7629-1, BS 7846, MICC, and equivalent cables meeting the same level of safety
standard fire-resisting cable is sufficient for most systems
enhanced fire-resisting cable is generally reserved for the higher-risk cases listed in Clause 25.4
compliance also depends on support, jointing, segregation and mechanical protection
conductors should be at least 1 mm²
fire alarm multicore conductors should not be shared with non-fire circuits