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Fire alarm engineer inspecting an alarm panel in a commercial building

BS 5839-1:2025 Clauses 11, 25 and 26

Cabling & Monitoring

Fire-resisting cable context, common fault-indication times and circuit-integrity limits.

Cable selection and installation

  • Standard fire-resisting cable suits many general fire alarm circuits; enhanced performance is selected for defined critical conditions.
  • Segregate fire alarm cabling from other services and use supports that maintain integrity in fire.
  • Cable size must satisfy current capacity, voltage drop and any addressable data requirements.
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Fault indication

Open/short or removable-device fault
Indicate at the control equipment within 100 seconds.
Main supply failure
Indicate within 30 minutes.
Standby supply failure
Indicate within 15 minutes.

Circuit integrity

One circuit fault
Should not disable protection over more than 2,000 m².
Two simultaneous faults
Should not disable protection over more than 10,000 m².
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Source context: BS 5839-1:2025 Clauses 11, 25 and 26. This page paraphrases the app’s quick-reference material and does not reproduce or replace the standard.