EN 54-28-2016 pdf free download.Fire detection and fire alarm system – Part 28: Non- resettable line-type heat detectors
4 Product characteristics
4.1 General
4.1.1 Compliance In order to comply with the present standard, detectors NLTHD shall comply with the requirements of Clause 4, which shall be verified by visual inspection or engineering assessment as described in Clause 5 and shall meet the requirements of the tests.
4.1.2 NLTHD performance type To simplify/standardize/rationalize product marking (see Clause 8), the performance type of the NLTHD is described using the following format, Txxx-Vyy-Azzz, where:
— Txxx is the nominal alarm temperature in the range 54 °C to 160 °C;
— Vyy is the variance of the nominal alarm temperature in ± %, which is either 05 or 10;
— Azzz is the maximum ambient temperature in °C, i.e. the maximum environment temperature at which the sensing element of the NLTHD could be installed and operated without generating an alarm. EXAMPLE T085-V10-A066 means a NLTHD with a nominal alarm temperature of 85 °C having a variance of 10 % (i.e. a minimum alarm temperature of 76,5 °C and a maximum alarm temperature of 93,5 °C) which can be used for an application in which the ambient temperature is no greater than 66 °C. The difference between the maximum ambient temperature and the minimum alarm temperature is to be at least 4°C.
4.1.3 Environmental groups Different environmental groups are necessary to reflect the different service environment of the components of an NLTHD: The sensing element is in either environmental group II or III. The sensor control unit and the functional unit are in either environmental group I, II or III. NOTE Environmental group I covers equipment likely to be installed indoors in commercial/industrial premises but for which the avoidance of extreme environmental conditions can be taken into account in the selection of the mounting site. Environmental group II covers equipment likely to be installed indoors in commercial/industrial premises in all general areas. Environmental group III covers equipment which is intended to be installed outdoors.
4.2 Nominal activation conditions/sensitivity
4.2.1 Individual alarm indication Each sensor control unit shall be provided with an integral latched red visual indicator, by which the individual sensor control unit, which released an alarm, can be identified, until the alarm condition is reset. Where other conditions of the sensor control unit can be visually indicated, they shall be clearly distinguishable from the alarm indication, except when the sensor control unit is switched into a service mode. The visual indicator shall be visible from a distance of 6 m in the direct line of sight
perpendicular to the surface, in an ambient light intensity up to 500 lux.
If more than one sensing element is connected to the sensor control unit, there shall be separate alarm indication for each sensing element.
To confirm this, the detector shall be assessed in accordance with 5.2.1.
4.2.2 Signalling
The NLTHD shall signal the alarm and fault status to the control and indicating equipment.
If more than one sensing element is connected to a sensor control unit, there shall be separate alarm and fault signals for each sensing element.
To confirm this, the detector shall be assessed in accordance with 5.2.2.
4.3 Operational reliability
4.3.1 Maximum ambient temperature
The sensing element of the NLTHD shall be capable of withstanding long term exposure to temperatures as specified in 5.3.1.
4.3.2 Connection of ancillary devices
Where the NLTHD provides for connections to ancillary devices (e.g. remote indicators, RS 485 interface), open or short-circuit failures of these connections shall not prevent the correct operation of the NLTHD.
Where such connections are present the detector shall be assessed in accordance with 5.3.2.
4.3.3 Manufacturer’s adjustments
It shall not be possible to change the manufacturer’s settings except by special means (e.g. the use of a key, a code or a special tool or by breaking or removing a seal).
To confirm this, the detector shall be assessed in accordance with 5.3.3.
4.3.4 Software controlled detectors
4.3.4.1 General
For NLTHD, which rely on software control in order to fulfil the requirements of this standard, the requirements of 4.3.4.2, 4.3.4.3 and 4.3.4.4 shall be met.
4.3.4.2 Software documentation
4.3.4.2.1 The manufacturer shall submit documentation, which gives an overview of the softwaredesign. This documentation shall provide sufficient detail for the design to be inspected for compliance with this standard and shall include the following as a minimum:
a) a functional description of the main program flow (e.g. as a flow diagram or structogram) including;
1) a brief description of the modules and the functions that they perform,
2) the way in which the modules interact,
3) the overall hierarchy of the program,
4) the way in which the software interacts with the hardware.EN 54-28 pdf download.