BS 5839-1 states that existing cables must only be reused if they are suitable, undamaged, and meet the performance requirements of the current system. To confirm this, the installer must carry out electrical tests equivalent to those performed on new fire-alarm wiring.
1. Continuity Test
Confirm all conductors run the full circuit path without breaks.
Ensures loops are complete and polarity is correct.
2. Insulation Resistance Test
Typically tested at 500 V DC (or a safe voltage for the circuits present).
Confirms insulation is intact and wiring is not degraded.
Prevents earth faults, short circuits, or leakage currents.
3. Earth Fault / Polarity Check
Verify correct polarity throughout the circuit.
Check for any earth faults that would affect system reliability.
4. Resistance / Voltage Drop Assessment
Measure resistance of the cable run to ensure:
Sounder circuits will meet required sound pressure levels
Detectors receive adequate voltage
Prevents excessive voltage drop due to long or degraded cable runs.
5. Visual Inspection (Very Important)
BS 5839 stresses a physical inspection to ensure:
Cable type is suitable for fire alarm use
No mechanical damage
Proper fire-stopping
Correct fixings and spacing
No exposure to heat, moisture, or chemicals
No mixing with incompatible services (e.g., high-voltage)
6. Cable Type Verification
You must confirm that the cable is:
Fire-resistant to the category required (e.g., "standard" or "enhanced" fire-resistant cables)
Correctly shielded if required (for interference protection)
If the existing cable is not a fire-resistant type and the system category demands it, it cannot be reused.
Summary
When retrofitting a fire-alarm system using BS 5839-1, you must test the existing wiring for:
Continuity
Insulation resistance
Earth fault and polarity
Resistance/voltage drop
Visual inspection
Correct cable type verification
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.