Tech Thursday – EN54-23
January 10, 2013
What is EN54-23?
EN54-23 or to give it its full title “Fire detection and fire alarm systems – Part 23: Fire alarm devices – Visual alarm devices”, was produced to standardise the requirements, in terms of construction, robustness and performance of warning beacons used within a fire detection system. The purpose of the beacons being to warn personnel of a fire emergency so that they can take the necessary action. Throughout the term Visual Alarm Device (VAD) is used to refer to such beacons.
In the UK the Disability Discrimination Act (DDA) introduced to people the need to provide an alternative fire alarm signal for those who are deaf or hard of hearing. However, in addition, there has always been a requirement to provide the appropriate signalling where it would otherwise be difficult to hear a traditional fire alarm sounder/bell due to high ambient noise levels and/or where ear protection is routinely worn.
Whilst the requirement to provide a visual signal is therefore very clear, there existed little guidance on what performance level(s) such devices needed to meet. This is further compounded by manufacturers quoting a plethora of different performance figures using terms such as Joules, Watts, Lumens, Luminous Intensity, Effective Luminous Intensity, Peak Luminous Intensity or just “Brightness”! :
Joules : a measure of energy. This is typically used to quote the energy expended in a single, or sometimes multiple, flash(es) of a xenon strobe beacon. To determine how visible such a product is we need to know the efficiency of the flash tube and associated optics (including any de-rating for colour) as well as the flash waveform.
Watts : a measure of power – typically electrical power. Similar to the Joules figure quoted for a xenon strobe beacon, this may also be applied to any VAD such as LED or filament lamp. As we are concerned with the electrical power consumed by a visual warning device, in addition to the factors above, we also need to consider how efficiently the VAD converts electrical power to visible light.
Lumens : This is a measure of the total amount of light emitted by the VAD and is the light equivalent to the Watt (See our previous article on Light). Whilst this is good that we are starting to consider the light produced by the device as a whole, rather than power consumed, it is a little meaningless as is does not consider whether any of the light produced is directed in any useful manner.
Luminous Intensity – Candela (Cd): This is a measure of the light emitted in a given direction and for a steady burning light it is quite easy to measure. In common with Lumens above, it does not consider whether this light is targeted in any useful direction. To further compound matters, manufacturers nearly always quote the best measured figure and fail to quote in which direction that light was emitted.
Peak Luminous Intensity – Candela (Cd): This, along with Effective Luminous Intensity below, is typically quoted for flashing (non-steady) VADs. It is usually quoted as the maximum luminous intensity of a single flash, typically in whatever direction yields the greatest figure. It has a great problem in that with the short duration flashes from a VAD it fails to account for how the eye perceives the flash – a very short but very high intensity flash may actually appear less bright than a lower intensity, but longer flash due to how we see flashing lights and is therefore meaningless when comparing products or even products to specifications.
Effective Luminous Intensity – Candela (Cd) : In recognition of the issues with Peak Luminous Intensity above, Effective Luminous Intensity is defined by E. Allard as the “luminous intensity (cd) of a steady light, of the same spectral distribution as the flashing light, which would have the same luminous range as the flashing light under identical conditions of observation”. In other words, how bright does the flashing light appear to be compared to a non-flashing light. This necessarily takes into account the flash-rate, flash-pattern and individual pulse shapes and provides a figure that is easily compared across different types of light source. However, in common with the other measurements, this is usually quoted by the manufacturers in the direction that yields the most favourable result without considering whether the light is directed anywhere useful. To further complicate matters, there are numerous methods for calculating the Effective Luminous Intensity that may or may not yield the same numerical answer depending on the exact flash-rate, flash-pattern and individual pulse shape of the light being measured!
Brightness : Often quoted by LED product manufactures as “High-brightness”, “Ultra-bright”, “Super-bright” or other such meaningless descriptions. As there is no standard definition as to what these mean – even within a single manufacturer’s range – it is impossible to compare performance with a required standard.
All of this meant that comparison amongst products, let alone verification to a standard, was effectively impossible. Indeed, who would ever be able to confidently state that a proposed or installed VAD met the stated objective of being able to warn personnel of a fire emergency so that they can take the necessary action?
If luminous intensity (in its various incarnations) moved us from discussing consumption (Power or Energy) to what was produced (Light in a direction outside the VAD), EN54-23 wraps all of this up into a nomenclature that puts a numerical number to Coverage Volume – away from the individual VAD as a product and towards its application in the field. A good move in my opinion.
The Coverage Volume quoted is the size of the space in which the VAD is effective. There are three categories of product (Ceiling, Wall and Open) and each quotes its coverage in a slightly different manner – see Product Markings below. From this figure we can readily compare differing products and from that design the configuration of one or more VADs within the real-world space we have to provide signalling for.
What are the requirements for an EN54-23 compliant Visual Alarm Device?
The performance and test requirements are quite rigorous – this is necessarily so in order that we can simplify the product classification and marking to allow straightforward system design. In summary, the requirements are as follows:
Coverage Volume
The VAD will classified in one of the following three ways:
C-x-y : Ceiling device
C : Ceiling
x : 3, 6 or 9 and represents the maximum height in meters that the product may be mounted.
y : The diameter in meters of a cylinder within which the product is deemed to comply
Example: C-3-12 denotes a ceiling device that is good for a 12m coverage cylinder when mounted at a height no more than 3m from the ground.
W-x-y : Wall device
W : Wall
x : Maximum height in meters that the device can be mounted on the wall. The minimum allowable height is 2.4m.
y : The width of a square room within which the product is deemed to comply.
Example: W-3,3-6 denotes a wall mounted device that may be mounted between 2.4m and 3.3m from the floor and is good for a volume of 2.4m x 6m x 6m.
Variation of light output
The measured performance of the VAD must not deviate by more than 25% over a 30 minute period.
Luminous Intensity Limits
The VAD must produce a luminous intensity of 1cd for 70% of all measurement points and not exceed 500cd for any measurement point.
Light colour
The emitted flashing light must be either Red or White. No guidance is given as to what Red or White are in terms of chromaticity.
Light flash pattern and frequency
The frequency must fall within the range 0.5Hz and 2Hz.
The maximum On time must be no more than 0.2 seconds.
For multiple pulse signals, pulse trains can be considered as a single pulse where the inter-pulse gap is less than 0.04 seconds.
Marking
The VAD must be marked with the following information:
EN54-23
Environment type (Type A or Type B)
Device category (e.g. W-2,4-6)
Name/trademark of manufacturer or supplier
Model designation/number
Terminal designations
Serial number/batch code to allow manufacturer to establish date and place of manufacture along with software revision if appropriate
Data
Within the datasheet/manual supplied with the device:
EN54-23
Environment type (Type A or Type B)
Device category (e.g. W-2,4-6)
Name/trademark of manufacturer or supplier
Model designation/number
Terminal designations
Serial number/batch code to allow manufacturer to establish date and place of manufacture along with software revision if appropriate
Rated supply voltage or ranges (AC or DC)
Power and current consumption
Supply frequency ranges if relevant
Coverage characteristics including how to orient the device if applicable
Flash pattern and frequency
IP Rating as per EN60529:1991
Any other relevant information pertaining to the installation, use or maintenance of the VAD
Synchronization – if appropriate
If multiple VADs are to be synchronized together, then the difference in flashes between two beacons must be no more than 0.02 seconds and thereafter drift to no more than 0.05 seconds over a period of 30 minutes.
Durability
In addition to the performance criteria above, the VADs must endure the following:
Work correctly at high temperatures: 16 hours at 55C for Type A / 70C for Type B
Endure high temperatures (off state): 21 days at 70C for type B
Work correctly at low temperatures : 16 hours at -10C for Type A / -25C for Type B
Work correctly at high levels of humidity:
Type A – 2 cycles of 25C >95% RH to 40C 93% RH
Type B – 2 cycles of 25C >95% RH to 55C 93% RH
Endure high levels of damp heat : 21 days at 40C 93% RH
Endure cyclic damp heat: Type B 6 cycles of 2 cycles of 25C >95% RH to 40C 93% RH
Work correctly when submitted to mechanical shocks
Work correctly when submitted to mechanical impact
Work correctly when submitted to sinusoidal vibration
Endure the effect of sinusoidal vibration
Endure the effects of corrosive atmosphere: 21 days 25ul/l SO2 at 25C and 93% RH
Work correctly when submitted to electromagnetic interference
Application
Loss Prevention Code of Practice CoP 0001 – Code of Practice for visual alarm devices used for fire warning provides recommendations for the planning, design, installation, commissioning and maintenance of VADs in and around buildings. It does not directly advise if VADs should be used but rather how they should be installed and guidance on their location.
I trust that this has been a useful guide – Whilst we have made all efforts to ensure the accuracy of this information, no liability can ne accepted for any errors or omissions contained therein. That said, do make contact if you would like further information or, indeed, if you have anything further to add!
