10. Controls & Power Supplies

10 Controls - General The nature of the system should be that under quiescent conditions the control equipment should be in either fully automatic or standby mode. In this mode the control equipment must be protected against improper use. 10.1 Control Panels Control Panels should comply with prEN12101-9. Consideration should be given to the location of control panels and control equipment. Most control panels complying with prEN12101-9 are only designed to operate at ambient temperatures. Therefore they should be located such that the risk of exposure to high temperatures is minimised (located separately from the fire compartment by a fire-resisting separation of at least 1 hour). 10.2 Manual Control Point prEN12101-9 sets out the operational and aesthetic requirements for a manual control point. The term “manual control point” is designed to encompass generic phrases such as fireman’s switch, call point, breakglass etc. Under prEN12101-9 the manual control point requires the manual control point to be deep orange to RAL 2011. Manual Control Points shall be provided at agreed fire service access points. For automatic systems the switches shall provide off/auto control and where appropriate off/auto/on control. For manual systems the switches shall provide off/on control. 10.3 System Activation Where permanent openings are not used the system shall be initiated by one or more of the following: a. Smoke detection; b. Rapid rate of rise heat detection; c. Multi-criteria fire detection; d. A sprinkler flow switch; e. A fire service action, such as a control switch or in the case of natural ventilation the use of breakout panels, pavement lights, stallboards and the like. All mechanical systems shall have a fire service override switch to allow them to turn on or turn off the system. Fire service action is not suitable as the only form of initiation for smoke control systems designed to assist fire-fighting access and/or protect means of escape. Operation in the case of a fire shall override any environmental controls associated with the smoke and heat control system for controlling the normal environmental ventilation arrangements for the loading bay, if fitted. 30 The installation of a smoke, rapid rate of rise heat, or multi criteria detection system shall conform to the requirements of BS 5839: Part 1. The type and location of detectors shall be selected to initiate operation of the system as early as possible. The detectors shall be located to minimise adverse effects from air movement caused by the environmental ventilation system. In some situations a delay may be built into the operating system to hold off operation of all or part of the system for a set period see sections 5.4 & 6.6 Where zoned control is required, the detection system shall be addressable and capable of locating the fire with an accuracy that allows the different zones of the smoke and heat control system to operate appropriately within the design. 10.4 Power Supplies There shall be at least two power sources: the primary power source and the secondary power source. The primary power source shall be designed to operate from the public electricity supply or an equivalent system. The secondary power source, for example batteries, generator or a secondary independent public utilities supply, shall be permanently available, tested and maintained. Each power source, on its own, shall be capable of operating those parts of the system for which it is intended. If the primary power source fails, then the power supply shall be automatically switched over to a secondary power source. Failure of one of the power sources shall not cause the failure of any other power source or the failure of the supply of power to the system. The power supply equipment shall either have inherent resistance to or be protected from mechanical damage. The power supply and related equipment shall be clearly labelled as to their purpose and be secured against unauthorised operation. Each power supply should provide the power requirements of the worst case scenario at design duty under ambient conditions. The power supplies to each component(s) should be protected against the effects of fire for the required period of time of activation or operation of the component(s). Electrical power for smoke ventilation fans can be provided by either: 2 independent electrical public utility supplies, or 1 electrical public utility supply and backup power supply (generating plant). Power supplies should be installed such that they remain operational when other supplies to the building are isolated in an emergency. All electrical services shall be installed by suitably qualified engineers in accordance with BS 7671:1992 (IEE Wiring Regulations). The electrical primary power supply to life safety and fire protection ventilation equipment shall be separate from all other circuits in the building so that the failure of other equipment does not render the installation inoperative. 31 Each connection to the power supply shall be via an isolating protective device reserved solely for life safety and fire protection equipment and independent of any other main or sub-main circuit. Such isolating protective devices shall be clearly labelled and identified as to their purpose. They shall be secured against unauthorized operation. The primary and secondary power sources, electrical distribution board, cables and control equipment supplying power to the fire-fighting equipment shall be protected against fire and water damage for a period of at least 1 hour. They shall be kept separate so that a failure in a cable or equipment, either by mechanical breakdown or damage by fire, in either supply does not affect the other supply. Protection against fire can be achieved through choice of cable, the cable route (e.g. through protected areas, or external to the building) or by the use of a fire-resisting construction. The primary and secondary power supply cables shall be terminated in a changeover device located within the fire resistant compartment housing the main control panel. The changeover device shall automatically effect a transition from the primary to the secondary power supply if any phase of the primary power supply fails. Whichever secondary source is provided, the distribution shall be organised such that the secondary supply remains live when the remainder of the supplies in the building are isolated in an emergency. All electrical wiring, actuators, control equipment shall be protected against fire, when the effects of fire will result in the failure or incorrect operation of the vents/damper/doors for the appropriate period of time. The cables for the power supplies shall comply with one of the following British Standards:- • BS 8519: Selection and Installation of Fire Resistant power and control systems for life safety and fire-fighting applications • BS 8434: Part 3 for fire fighting systems • BS 5839: Part 1 for Means of Escape systems The electrical cables and associated equipment shall be sized and fitted in accordance with manufacturer’s instructions. All electrical wiring shall be clearly labeled and identified. 10.5 Cabling & Areas of Special Risk BS 8519 entitled “Selection and Installation of Fire Resistant power and control systems for life safety and fire-fighting applications” considers areas of special fire risk and highlights research that has confirmed that where there are ventilation limitations and/or very large fire sizes (e.g. in underground car parks and loading bays) localised temperatures can reach as high as 12000C Such areas therefore need special consideration. Further information regarding areas that could be classified as area of special fire risk is given in BS EN 12485. 32 As a general principle, cables for life safety and fire-fighting systems should not be installed within areas of special fire risk. However, there will be occasions where this cannot be avoided. In these situations, the cables used should be Category 3 cables as defined in Clause 11 of the British Standard, and should additionally be protected by a fire-resisting enclosures that has been shown to be suitable for the anticipated maximum temperatures, with a survival time at least equal to that of the cable. Any fixings should have suitable protection, e.g. intumescent coverings, appropriate for the anticipated maximum temperatures.