To Flow Switch or not to flow switch

The connection of Flow Switches to an alarm is a topic in residential and domestic fire alarm sprinklers that can be done in numerous ways. This blog explores the options and looks at what BS9251 recommends.

So what does the British Standard say?


The current British Standard when writing this piece is BS9251:2014. Section 5.13.2 of BS9251:2014 states:


"All systems should have an alarm device, consisting of an electrically operated flow switch that should be initiated by the flow of water to a single head with the lowest flow rate.


The alarm device should initiate a sprinkler alarm signal that should instigate the appropriate emergency procedures."


So we know from the British Standard that as a minimum every system must have an alarm initiating device, better known as a flow switch. These are commonly installed as part of a Domestic and Residential valve set which consists of a Flow Switch, Pressure Gauge, Lockable Isolation Valve and test point, as shown in the picture below.




Dependant on the category of system and type of building the sprinkler system is serving will have an impact on how the alarm signal from the flow switch should be configured. As confirmed in the commentary contained within BS9251:2014 for section 5.13.2, in some domestic and residential buildings the actuation of the fire alarm triggers immediate and total evacuation of the premises, other residential buildings are designed so that the initial alarm is sounded only in the dwelling where the fire starts, as only this dwelling needs to evacuate immediately. It is important that the configuration of the sprinkler alarm is matched to the building’s fire evacuation strategy.


Ultimately the Fire Strategy for the building will determine the emergency procedure that should be initiated in a fire condition. For example, a Care Home or Student accommodation may have an "all out" policy, meaning that in the event of a fire alarm in any part of the building, the entire building should be evacuated. Whereas, for example in many Apartment Blocks where each apartment is its own fire compartment, the policy may be a "Stay Put" policy where only the apartment in which the fire occurs requires to evacuate immediately. There is much discussion and criticism over the use of a stay put policy following the recent tragic event at Grenfell, however it is still a policy we see on many occasions so until this changes we must ensure the configuration of the sprinkler alarm meets with the emergency procedure for that building.


So what does the British Standard say the flow switch should be connected to? Section 5.13.2 continues to state:


"The alarm device should be either:


a) connected to an internal audible alarm; or


b) interfaced with an automatic fire detection and alarm system. Where the property is fitted with an automatic fire detection and alarm system to at least the minimum grade and category recommended in BS 5839, the sprinkler alarm device may be interfaced with this system. Any such interface should be in accordance with the recommendations given in BS 5839-1:2013 or BS 5839-6:2013 as appropriate. NOTE 2 BS 5839-1:2013, Table A.1 and BS 5839-6:2013, Table 1 provide guidance on the category of system for the relevant property types.


When the alarm device is interfaced with automatic fire detection and warning systems, actuation of the sprinkler alarm should be clearly distinguishable on any fire alarm control and indicating equipment."


It is important at this stage to understand what the flow switch in the specific environment is there to do. Alarm system designers need to take account of the fact that the sprinkler alarm might have more than one function, e.g. to initiate evacuation, to alert management and/or to alert the fire and rescue service. In some cases there can be benefits for reducing property damage, especially in unoccupied areas, if an external sprinkler alarm is installed in a prominent location where people can be alerted to a sprinkler actuation.


Owing to the burden caused by false alarms, many fire and rescue services have introduced measures to reduce attendance to alarms generated by automatic fire alarm systems. Therefore to ensure an emergency response to a sprinkler alarm, consideration needs to be given to clearly distinguishing a sprinkler-initiated alarm from a signal generated by automatic fire detection. Early consultation with the local fire and rescue service can assist in developing an appropriate solution.


So lets look at a Category 1 system first.


Lets say we have a single dwelling that has a Domestic and Residential Sprinkler system fitted to the requirements of BS9251:2014. It is likely that a single flow switch is installed connected to the incoming supply to the Sprinkler System. The property is likely to be fitted with an LD3 fire alarm system, providing smoke alarms in hallways and heat detectors in the kitchen. As always, there may be many parties involved in deciding how the sprinkler alarm should be connected, such as the local Fire Authority, Building Control etc and alarming requirements may differ depending on whether the property is housing vulnerable people. For example, if the property was housing a deaf person the audible alarm by itself may be insufficient, therefore visual alarms may be required as well. However for this example we will assume that there are no special circumstances or vulnerable people, it is a normal family home.


The main consideration here is that the sprinkler system's purpose is life safety, ie to give the occupants increased time to escape the property unharmed. Therefore when considering the alarm configuration we must ensure the primary purpose is to aid in the evacuation of the occupants. The LD3 Fire alarm system is designed to alert the residents of a fire and to allow them to evacuate immediately. However, consider this for a moment. If we install a sprinkler system in a property with an LD3 fire alarm system, and a fire starts in a bedroom. Lets assume the bedroom door is closed. There is a possibility that the sprinkler head will initiate and commence controlling the fire prior to the actuation of the fire alarm system. In this event, if the flow switch was not connected to the fire alarm system there is the potential that the occupants would not be alerted to the fire situation and the benefit added by installing the sprinkler system giving increased time to escape would be lost. However, if the sprinkler alarm had been connected to the domestic smoke alarm system, when the sprinkler system activated it would have set off the Domestic fire alarm and alerted the occupants to a fire situation allowing them to escape. In this scenario we would always recommend that the sprinkler flow switch be connected to the Domestic Smoke Alarm system. We would suggest this be done using a Switched input relay on the fire alarm system which is wired to the normally open or closed (dependant on manufacturers instructions,) connection on the flow switch.


The only draw back to a simple connection to the Domestic Fire Alarm system is that it is not easily distinguishable that it is a sprinkler activation rather than a smoke alarm activation. As a sprinkler alarm is treated by most fire authorities as a confirmed fire, in this scenario it would be difficult to establish whether the sprinklers had activated or a smoke alarm was causing the evacuation. However saying that, depending on size of property, location of fire, there is a likelihood that the occupants would know the sprinklers were active by hearing the escape of water.


So What about in a Block of Apartments?


In multi-storey blocks of flats the requirements for alarm initiating devices is different to a simple Category 1 system. BS9251:2014 Section 5.13.3 states:


"In multi-storey blocks of flats, the sprinkler alarm device may be configured to serve an alarm zone, rather than each individual dwelling, provided the following recommendations are met.


a) The alarm zone should cover no more than a single floor.


b) The individual dwellings should be fitted with an LD1 automatic fire detection and alarm system with a minimum of a grade D power supply, designed, installed and maintained in accordance with BS 5839-6:2013.


c) The sprinkler alarm device should be connected to suitable control and indicating equipment so that management are alerted and the emergency action plan can be initiated.


In multi-staircase buildings, the control equipment should clearly indicate the floor level and appropriate staircase"


In many recent new apartment blocks, it is common to see the floor arranged as a single zone meeting the requirements of BS9251:2014 section 5.13.3 a. In this scenario, each apartment should be fitted with an LD1 fire alarm system, ie a smoke alarm in each room with a heat detector in the kitchen. This configuration of the sprinkler system is common in new apartment blocks that adopt the "stay put" fire strategy policy as discussed earlier.


In this configuration, the sprinkler flow switch cannot determine in which individual flat the fire has occurred, it will only detect that water is flowing to that "zone" or floor, which is likely to have multiple apartments. However, with a "stay put" fire strategy, only the apartment in which the fire originates should evacuate immediately.


So in this scenario above, a multi-storey block of flats, with a sprinkler system arranged as a zone per floor, with LD1 fire alarms inside each apartment and where the fire strategy for the building has been decided as "stay put," what is the purpose of the flow switch and what should it be connected to?


BS9251:2014 section 5.13.3 c confirms it should be connected to "suitable control and indicating equipment so that management are alerted and the emergency action plan can be initiated." Therefore in this instance the sprinkler flow switch is not the primary means of evacuation for the apartment. The evacuation of the apartment is being dealt with by the LD1 domestic fire alarm system which will raise the alarm in the apartment where the fire originates allowing the occupants to escape. We assume that the advice in BS9251:2014 to upgrade the alarm to an LD1 where a sprinkler system is arranged per zone rather than per apartment is the same reason in our Category 1 example, in that if is was an LD3 system the sprinkler could activate prior to the smoke alarm meaning the benefit of increased escape time would be diminished. By upgrading to an LD1 system the smoke alarm will raise an alarm prior to the activation of the sprinkler system allowing occupants to escape.


Therefore is the flow switch in this scenario worthless? The answer to that question is NO! The flow switch still has a purpose to play in alerting management, allowing the fire services to understand where a sprinkler activation has occurred and to potentially alert people where an unoccupied premises has had a sprinkler activation.


However the main question here is what to connect the flow switch to? The obvious answer would be the communal fire alarm panel. Normally in a multi-story block of apartments there would be a minimum L5 coverage of communal corridors for smoke detection purposes which would activate the required smoke ventilation strategy. If a communal fire alarm is installed then it would make sense to connect the flow switch. This would allow the fire brigade to see an activation of the sprinkler on arrival, and where management were based on site would allow them to be alerted as well. If the fire alarm was connected to a "red care" type system which dialled off site this would also aid in alerting management / fire authority.


If however there was no communal fire alarm system, maybe in smaller apartment blocks where there is no smoke ventilation required due to small travel distances, then what do we connect the flow switches to in this instance?


One option would be to install a fire alarm panel. This would serve the purpose above however an alternative method would be to connect to a FloWatch Sprinkler Monitoring system. The purpose of the FloWatch Monitoring system is the continuous supervision of critical elements of the system and to raise an alarm in the event of a failure which might impair the activation of the system, ie an isolation valve not in the fully open position or insufficient stored water within a storage tank. However the FloWatch 9251 monitoring system has the following features meeting the requirements of a BS9251:2014 in being suitable control and indicating equipment so that management are alerted and the emergency action plan can be initiated:


- 24 Hour Battery Back Up

- Fully addressable so will provide location and detail of event occurrence on the master panel

- Audible and Visual Alarms on the Master Panel to alert management

- Built in GSM Sim Card functionality which can send an email to a nominated email address in the event of a fault or system activation.

- 12 Month Alarm Log which will enable the user to see when faults / activations occurred and when they were rectified

- Ability to monitor Flow Switches and raise a suitable "Flow Alarm" providing a visual and audible alarm at the master panel

- NO/NC Output on alarm activation which can be used to interface with third party equipment to raise a separate alarm if required.


The FloWatch Sprinkler Monitoring system can also be connected to flow switches when connecting flow switches to a Fire Alarm system. Dependant on the type of flow switch used, many have dual output. Allowing the flow switch to be connected to a fire alarm for emergency protocol, and then connection to a monitoring system for providing an overall picture of the sprinkler system.


When specifying a FloWatch monitoring system, FloWatch will provide a full design for the sprinkler monitoring and can provide advice on alarm requirements. Even though flow switches can be connected to a FloWatch monitoring system, FloWatch will provide the best advice for the scenario which is normally the connection of the flow switch to a fire alarm system where present.


Conclusion


There is no magic one solution fits all scenarios when looking at the connection of Sprinkler Flow Switches. It is important to consider the following when deciding on an alarm arrangement:


  1. The Fire Strategy for the building. If one is not present it is worth having a professional Fire Risk Assessor review the building prior to the installation of the sprinkler system to establish current procedures and to provide a fire strategy for that building to allow this sprinkler designer to take this into consideration when deciding configuration.

  2. That life safety is the key to sprinkler systems and that the system / alarm should be configured in such a way that it does not produce detrimental effect on the ability to evacuate the occupants.

  3. Are there any risks to vulnerable people which may require additional alarms, for example are residents elderly therefore knowing exactly where the fire has originated may aid fire brigade or management therefore configure a flow switch per apartment to alert management or off site via a red care type system.

  4. Are the occupants impaired in anyway, such as hard of hearing and additional visual aids may be required.

  5. Consultation with any AHJ and their specific requirements.

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