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How this is calculated#

The tool looks up what a fire alarm circuit needs from NZS 4512:2010 Clauses 402.1 and 402.2. It gives the conductor size, the stranding, the insulation resistance and the fire rating.

1. Circuit. You pick the circuit: detector, alerting device, transmission, staged evacuation, data link or mains supply.
2. Clause. The tool picks the clause. Cl 402.1 covers detector and alerting device circuits. Cl 402.2 covers the rest.
3. Cores. You enter the number of cores in the cable. The size rule in Cl 402.1 reads it.
4. Conductor size. The tool gives the minimum conductor size and says whether it must be stranded.
5. Insulation resistance. From Cl 402.2 it gives the minimum insulation resistance.
6. Fire rating. It gives the fire rating, or says that this clause does not set one.

Worked example#

A detector circuit in 2‑core cable. The minimum conductor size is 0.75 mm². The conductor must be stranded. The insulation resistance must be above 5 MΩ. This clause sets no fire rating.

Limits#

• The tool reads Cl 402.1 and 402.2 only. Check the cable specification and the mechanical protection in Cl 402.1.
• Clause 402.2(g) is the other size driver. Read it in full.
• Check the earthing rules for zone circuit wiring in Cl 402.2(i).
• Check the separation and identification rules in Cl 402.2(k).
• The tool does not check voltage drop on the circuit.
• NZS 4512:2021 supersedes the 2010 edition this tool reads.

See also: Fire alarm battery, Detector spacing and the segregation checker.