The most common type of smoke control system today is the ‘smoke shaft’ system.
‘Smoke shaft’ is the common term for ventilation systems in the lobbies of tall buildings, used to maintain tenable conditions in the common escape routes in the event of a fire in the building.
But what about its power supply and wiring? What specification applies? Read our blog post and download the SCS Guide to Smoke Shafts to find out.
It is essential to maintain the operation of the smoke shaft system with a secondary power source in compliance with EN 12101-10 and BS 8519. The primary power supply shall be from the normal electricity supply and the secondary power supply can be an alternative utility supply, generator, UPS or battery back-up source. The primary and secondary supply should be fully independent of each other to ensure a single fault will not result in the loss both supplies.
The secondary power supply shall be automatically switched or started in the event primary supply failure during fire conditions and be sufficient to maintain the system for the appropriate period of time. Automatic switching can be done by an automatic transfer switch (ATS) compliant to EN 60947-6 and must have a bypass switch to maintain essential power and service to the smoke shaft system during maintenance as given in BS 8519. Switches should be located near to the shaft system main control panel. When rechargeable batteries are used the power supply switching is built in to the power supply equipment in accordance to EN 12101-10. The power supplies should be sized accordingly to the shaft systems full duty load for the required operation period.
System isolation devices should be positioned in a secure location or have the provision to padlock them in the on position to prevent tampering and inadvertent isolation and disablement of the system.
Smoke shaft wiring
All electrical installations and wiring shall be in accordance to BS 7671 Wiring Regulations which refers to BS 8519 electrical installations for life safety equipment. Cabling shall be enhanced fire grade with a minimum fire survival time such as Prysmian FP range. Cabling requirements are split between power and control as defined in BS 8519. Generally power cable are large power cables or 3 phase supply and should be tested to BS 8491. Control are cable sizes up to and including 4mm2 and should be tested to EN 50200. Selection of cables should be in accordance to BS 8519 Table 1 Minimum fire survival time categories.
Electrical wiring should be of a suitable temperature rating for the application. For most residential systems FP200 Enhanced (PH120) or equivalent is suitable for sensors and devices, while FP600S is commonly used for power supplies to extract plant.