A fire alarm cable has an unusual job description. Almost every other cable in a building is expected to fail safely in a fire. This one is expected to keep working through it, long enough for the panel to sound, the exit signs to stay lit and everybody to get down the stairs.
That single requirement drives the whole construction.
What’s inside APAR’s fire alarm cable
The fire alarm cable is built as stranded circular class-2 copper, XLPE insulated, with an extruded PVC inner sheath, galvanised steel round wire armour, and an overall extruded FR-LSH PVC outer sheath in red. Each layer is doing something specific:
| Layer | Why it’s there |
|---|---|
| Stranded class-2 copper conductor | Fixed-installation stranding; easier to pull and terminate than solid at these sizes |
| XLPE insulation | Cross-linked, so it softens far less than PVC as temperature climbs |
| PVC inner sheath | Bedding, so the armour doesn’t bite into the cores |
| Galvanised steel round wire armour | Mechanical protection in risers, shafts and ceiling voids |
| Red FR-LSH PVC outer sheath | Flame retardant, low smoke and halogen, and instantly identifiable as a life-safety circuit |
The red sheath is not decoration. In a ceiling void with forty cables in it, an electrician needs to know at a glance which one not to cut. Colour is a safety feature.
The ratings
Voltage grade is up to and including 1100 V. Maximum conductor temperature in service is 90°C, and 250°C under short-circuit conditions, which are the standard XLPE numbers. Armoured and unarmoured versions are made, and the standard construction is unshielded multicore.
Where it goes
High-rise residential and office buildings, commercial complexes, schools and colleges, hospitals. Anywhere the detection and alarm system feeds smoke detectors, heat detectors, emergency lighting, exit signage and the fire command centre. In practice it’s the buildings with a lot of people in them and one staircase they all have to use.
Five things to settle before you order
- Which standard the project is tendered against. Fire alarm cable is built to the requirement written into the project specification, so the standard has to come from you or your consultant. Confirm it with APAR before the order is cut, not after.
- Armoured or unarmoured. Riser and buried runs earn armour. A short surface run inside a protected shaft usually doesn’t.
- Core count and size, with the loop length in mind. Voltage drop on a long detector loop is a real design constraint, not a formality.
- Whether the cable shares a route with power circuits. If it does, plan the separation before the conduits are cast in.
- What else on the site needs fire performance. The general building wiring around the alarm system has its own requirement, covered by the FR, FRLSH and FR-LSZH fire performance cables range.
One distinction worth being clear about
Flame retardant and fire resistant are not synonyms, and the difference decides whether a circuit survives. A flame-retardant cable resists spreading fire along its own length. A fire-resistant cable keeps its circuit alive while it’s being burnt. Detection and alarm circuits, emergency lighting and voice evacuation are the classic cases where circuit integrity is the requirement, and the specification should say which one it wants in plain words.
If a consultant’s drawing simply says “FR cable” on a fire alarm loop, ask what they meant. Nine times out of ten the answer changes the cable.