(Typical for BS 5839-1 Installations)
Note: BS 5839-1 does not always specify numerical values directly; it requires that wiring meets the electrical safety requirements of BS 7671 (IET Wiring Regulations). The values below reflect the standards normally applied in fire-alarm installation practice in the UK.
1. Continuity (CPC and Conductors)
Requirement: All conductors must show continuous, unbroken paths on the meter.
Acceptable value:
Resistance should be finite and stable (typically < a few ohms depending on cable length)
No open circuits
Correct polarity throughout
2. Insulation Resistance
Typical test voltage: 500 V DC
(Or 250 V DC if sensitive equipment is still connected.)
Minimum acceptable reading: ≥ 1 MΩ between:
Core to core
Core to screen (if present)
Core to earth
In many installations, engineers aim for > 2 MΩ to indicate healthy cable.
3. Earth Fault / Polarity
Must show:
Correct polarity on all circuits
No earth faults on any conductor
Earth fault current should be negligible (high resistance to earth).
Instruments typically show > 1 MΩ to earth.
4. Loop Resistance / Voltage Drop
Requirement: Voltage at devices must remain within manufacturer limits, typically:
Sounder circuits: not more than 10% voltage drop
Detector circuits: not below manufacturer minimum (often ~16–20 V depending on panel)
Acceptable cable resistance: Depends on the cable length and conductor size.
As a rule of thumb:
~0.8 Ω per 100 m for 1.5 mm² fire-resistant cable
~0.5 Ω per 100 m for 2.5 mm² cable
The test ensures the panel can supply enough current to the furthest device.
5. Visual Inspection Criteria
You must confirm:
Cable condition
✅ No crushing, cuts, rodent damage, scorch marks, damp ingress
✅ No joints unless using certified fire-rated connectors
✅ No unsupported spans or sagging
Routing
✅ Separated from high-voltage cables
✅ Protected where exposed
✅ Compliant with fire-stopping requirements
✅ No PVC cable used for critical paths
Fixings
✅ Metallic or fire-resistant fixings only
✅ Spacing compliant (typically every 300 mm–400 mm horizontally)
6. Cable Type Requirements (BS 5839-1 Summary)
BS 5839-1 defines two fire-resistant cable performance levels:
Standard Fire-Resistant Cable
Acceptable for:
Conventional systems in low-risk areas
Smaller buildings
Short escape routes
Examples:
Prysmian FP200 Gold
AEI Firetec Standard
Enhanced Fire-Resistant Cable
Required for:
Buildings where cables must sustain fire for extended durations
Critical areas (e.g., control rooms, multi-storey escape routes)
Systems needing operation during partial structural collapse
Examples:
Prysmian FP Plus
AEI Firetec Enhanced
⚠️ If existing cable is neither standard nor enhanced fire-resistant cable → it cannot be reused.
Simple On-Site Checklist
Existing Cable Reuse Checklist — BS 5839-1
Electrical Tests
☐ Continuity tested and satisfactory
☐ Polarity correct
☐ Insulation resistance ≥ 1 MΩ
☐ Earth faults clear
☐ Resistance/voltage drop acceptable for panel/device requirements
Visual Inspection
☐ Cable type confirmed as fire-resistant (standard/enhanced)
☐ No damage or deterioration
☐ Suitable fixings (metallic/fire-resistant)
☐ Correct segregation from LV/ELV
☐ Correct routing and protection
☐ Fire-stopping intact
Result
☐ Cable approved for reuse
☐ OR: Cable rejected (state reason)
Contact Information
For further assistance or if you have any questions regarding this procedure, please contact the Eurotech Technical Team:
Email: [email protected]
Phone: +44 (0) 203 141 0982
Important Notice:
This content is provided for informational purposes only and is intended solely for qualified personnel with appropriate training and expertise. Eurotech Fire Systems Ltd assumes no responsibility for the outcomes resulting from the use of this information. It is the user's responsibility to ensure all work is carried out in accordance with applicable regulations and standards.