Manual call point and warning devices design principles

We will explain manual call points and warning devices projecting principle in this issue.

Manual call points and design principles

Fire is detected firstly by people found in area. In order to give notice as soon as possible, manual call points are mounted and they are connected directly to fire detection and warning system. Usually manual call points and warning devices (sounder, flasher etc.) are located in same point. In this issue, we will explain how to design better these devices.

If we investigate EN/ 54-14 Standard, 6.4.5, 6.5.4 and A.6.4.4 article. Manual call points should be compatible with EN 54-11 standard.

• Manual call points should have distinguishable features from other buttons that are used for other purposes.

• Manual call points should be located on the escape ways, escape ladder opening doors (indoor and outdoor) and exits that are open to outdoor. When the manual call points are located. Special areas should be analyzed when the manual call points are located according to disabled people activities. Manual call points should be seen clearly, realized and easily accessible.

• Manual call points should be mounted at walking distance up to 30m. In disable people activities area this distance should be reduced. Manual call points should be mounted near to special fire risk. (Kitchen, stokehold etc.)

• Manual call points should be mounted on 1.4 m (+/-02.) height from the floor.

• In order to manage the scenarios process, manual call points should be mounted on all zones passing according to architectural, mechanical and electrical zone assigning.

• In order to prevent fault alarm signal by the impact effects, protection cover should be mounted in school, kinder garden and hospital etc. manual call points can be used as malicious in unsupervised areas. In these areas, an audible communication solution that is communicated directly with fire alarm panel should be made.

• About mounting place of manual call point below advices are recommended according to BS 5839-1 Standard. According to this; access distance to the button can be max 25 m. in the area where has doors opening directly to the. Manual call points should be mounted at access distance max. 30 m. If disable people live in the building, manual call points should be mounted at access distance max 25 m. (In order to easy access Mounting height should be 1, 2 m), mounting call point access distance, should be max. 16 m in the areas that have high risk.( kitchen, stokehold, explosives)

• Weatherproof manual call points should be mounted if they are used in dusty, humid area or outdoor (storage area, ports etc.).

Fire warning devices (audible and visual alarm devices) and design principles

After the fire detection, usually evacuation is provided usually via audible and visual devices by giving the alarm. Detectors, control devices and warning devices design process gets important in fire detection and warning systems designing process. Deficiency and faults are usually occurred in audible and visual warning devices designing process. Sentences in regulation and standards will be explained in this section. Also, audible and warning devices designing principal will be compiled.

If we firstly introduce the rudiments that are determined by standard; In CEN/ 54-14 Standard 6.6. Article;

"6.6.1 General The method of giving the alarm to the occupants of the building should comply with the requirements of fire alarm response strategy. In some cases the fire routine may require the alarm to be given initially to trained staff, who may then take charge of the resulting operations in the building. In such cases a general fire alarm need not be given immediately, but a facility for giving a general alarm should be provided. Any alarm intended to be perceived by untrained persons (such as the general public) should be at least by audible means. These may be alarm devices or a voice alarm system (such as the public address system). The system should be so designed that it is not possible for more than one microphone, speech module or message generator to be broadcast simultaneously. In areas where sound signals may be ineffective, e.g. where the background noise is excessive, where the occupants are deaf or where hearing protection is likely to be worn, visual and/or tactile signals should be used to supplement sound signals.

6.6.2 Sound signalsThe sound level provided should be such that the fire alarm signal is immediately audible above any ambient noise. The sound used for fire alarm purposes should be the same in all parts of the building. Limitations on the siting of alarm devices, sound levels to be achieved, and intelligibility and form of voice messages are given in A.6.6.2.

a) Audio frequency. Fire alarm audio should be in easily heard frequency interval. Usually the audio between 500 Hz and 2000, can be heard most of people.

b) In order to provide recommended audio volume, alarm device number should be enough. Even recommended audio volume is provided by one audio device at least two audio devices should be mounted in building. Audio level is not expected as enough in the room where the nearest audio device is separated with more than one door. In order to prevent high audio levels, numerous low level audio devices can be selected instead of small number high level audio devices.

c)Audio continuity. Fire alarm should be continuous. In the special case, batch audio, frequency and amplitude can be used. But the plant users should be trained about that against the fire strategy and visitors misunderstanding should be prevented.

Normal people can hear between 10 dB (A) - 130 dB (A). (Table 1).

Table 1. Audibility Zone of people

Alarm audio level that is used in fire detection and warning systems should be determined by EN 60849 and at least 65 dB (A) is expected in any part of building. in order to wake sleeping people up fire alarm sound level should be at least 75 dB(A) at the edge of the bed According to CEN/ 54-14 Standard related sections. Sounders are evaluated as the measured audio volume in 1 m. usually produced between 100 dB (A) and 126 dB (A) levels. The audio level is reduced logarithmic (Table 2). ıf the distance to sounder is increased two times.

Table 2. Distance-dependent volume change

In this sense, according to selected sounder audio volume, generated volume at each point must be calculated. For example, When the 120 dB (A) sounder is used in 50m x 30m size area, audio volume on 50. m is approximately 82 dB(A). in the same area, if we want to create the same effect, we should use ten 100 dB(A) sounders. (Figure 1.)

Figure 1. Warning with 100 dB (A) sounder instead of 120 dB (A) sounder in the same area

As can be seen on this example, at least 82 dB (A) audio volume can be obtained in approximately 200 m2 area with one 100 dB (A) sounder. If the 120 dB (A) sounder is used, at least 82 dB (A) audio volume can be obtained in 20.000 m2. So, 20 dB (A) difference provides 100 times more effect.

In the hotel halls where the rooms are located; 75 dB (A) audio level is expected at the edge of the bed. Approximately 20 dB (A) audio volume lessen at the hotel room doors. By this means, 95 dB (A) should be created at facing the hallway of the hotel room. As the result, Sounders distance to room door should not exceed the 2 m. when the 100 dB (A) sounders are used in hotel hall. Also, Sounders distance to room door should not exceed the 4 m. when the 106 dB (A) sounders are used in hotel hall. By this means, smoke detectors c/w sounder or detector c/w sounder socket should be used in the hotel, dormitory etc. where the sleeping people inside.

Such as school, business center, shopping center etc. where there is no sleeping people, determined lower level 65 dB (A) is trying to obtain. This level is determined by EN 60849 standard. By this means, for example with 100 dB(A) sounder, 65 dB(A) audio is obtained in approximately 60m. in shopping centers. (Table.2)

Technical specifications, test methods and performance criteria are determined by EN 54-3 Because of this selected audible alarm devices should be based on the standard compliance.

In the areas where has high ambient noise and deaf people visual warning should be together with audible warning. Visual warnings light intensity should be 10 times bigger than ambient light level. This is determined by EN 842 standard. Visual warning devices should be installed in visible points

Light intensity of the illuminated warning devices can realize according to their emitting energy (Figure 2). For example, when the 15 Joule illuminated device is activated, a person who doesn't look through the source and 7, 5 m. away from this source can aware from the warning. If the same people are the same direction with the light source, in this case visual warning can be detected from 30 m. distance.

 

Figure 2. Visual warning device notice criteria

1. Area: realizing area without seeing 2. Area: Realizing area of people who is in the direction of the light source.

Visual alarm devices technical specifications, test methods and performance criteria are determined by EN 54-23 Because of this selected audible alarm devices should be based on the standard compliance. Apart from audible and visual warning devices selecting according to above explained information and criteria, IP protection class is selected according to ambient humidity and dust intensity. (Table 3.)

Table 3. IP protection class

Related articles of CEN/ 54-14 standard, EN 60849 standard audio level criteria, EN 842 standard light density criteria should be assimilated and calculated by project authors for correct design. Also compatible devices should be selected according to EN 54-3 and EN 54-23 Standard then IP protection class should be determined.

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