Functional testing of lighting
When it comes to commissioning a new building, it is crucial to ensure that all installations are working optimally. This is especially true for indoor lighting installations, where Functional Assessment (FA) plays a key role. FA is always in accordance with the Building Regulations 2018 (BR18) and DS/EN 12464-1. It was introduced in 2017 and covers both renovation projects and new builds. Here we dive into what functional testing entails and how it can be implemented.
Documentation for functional testing
First and foremost, the documentation is about verifying that light levels are met according to DS/EN 12464-1. Then there are the actual functions of the lighting system. This means daylight control or other control. There are many prerequisites for a functional test to be carried out. The most important ones are listed below:
The building is ready for use: Functional testing may only be performed once all craftsmen have delivered.
Lighting system and sensors are installed and ready: Functional testing can only be performed when the lighting system, daylight sensors and programming of both have been installed and are complete. If there are any sensors or luminaires that do not function as intended, they must either be reprogrammed or replaced on site. If this is not possible, it is the tester's right to note deficiencies in or under comments.
A well-executed functional test must include at least the following documentation:
Location: Project name and address.
Responsible: Company and the person who performed the functional test.
Standard: Which standard has been tested to, e.g. DS/EN 12464-1:2021.
Lux meter: Information about the lux meter used and its latest calibration.
Table of contents: An overview of the rooms and tests included and whether each room is "Pass" or "Fail".
Measurement assumptions: Prerequisites and conditions during measurements.
Lux logging: Lux measurements for selected rooms, with a minimum requirement of 25% of the rooms in the building.
Measurement results: Achieved results and requirements.
Overview drawing: Room drawings with measurement points.
Daylight sensors: All daylight or stand-alone sensors are tested for functional testing.
Dialux calculation: Attach the cross-check documentation.
Three key elements in functional testing
Illuminance:
Measuring lux values at selected points to determine the mean (Unmean) and regularity (U0).
Daylight shielding where possible or mathematical elimination of daylight impact.
Light control:
Check sensor placement and detection.
Control sensor lag time, ignition method, zoning and daylight control.
Checking if daylight control is activated can be remedied with a narrow-beam flashlight
Logging:
24-hour lux logging in selected rooms with active daylight control.
Practical Examples and Interpretations
Selection of Workplaces/Rooms - the 25% rule: BR18 prescribes that measuring points must cover at least 25% representative workplaces. This means that if there are 20 offices, at least 5 must be measured. All escape routes, corridors and stairs should always be tested.
Number of measuring points in each room: According to DS/EN 12464-1, the number of measuring points should be determined by a formula that creates a grid in the room. Typically, 2-3 measurements per zone can be sufficient as long as the lighting calculations are accurate.
Height when measuring: The height from the luxmeter to the luminaire has a major impact on the result. According to DS/EN 12464-1, there are different measurement heights depending on the room in question. Here is an example of a measured value at floor and handheld at a height of 0.85m.
Functional testing in daylight
Not everyone can offer functional testing at nightfall. Therefore, according to the Danish Technological Institute, if it is not possible to measure at night, measurements must be taken without direct sunlight and changing weather conditions. The measurement is taken with and without the artificial light on, and the two measurements are then subtracted. An example is shown below:
Measurement without the lighting system switched on: 271 lux
Measurement with the lighting system at full power: 805 lux
Result for measuring point 805 - 271 = 534 lux
Thus, for this respective measuring point, it will be approved for office lighting. There will immediately be some who consider the above problematic. This is understandable, but the method is accepted by the Danish Technological Institute and thus a solution. However, measurements in a completely dark room will always be preferable so that the varying daylight has no effect on the lux measurements.
Avoid functional testing
The client or contractor may be under time pressure and in rare cases choose to overlook or neglect functional testing before the building is commissioned. This is a bad idea. Functional testing is required by law and thus a functional test will form the basis for the building to be put into use. If the functional test is missing, the municipality or other body will not accept the building into use. Therefore, postponing the functional test saves neither time nor money. Waiting delays the approval of the building's commissioning.
Conclusion
Functional testing is a thorough and proven approach to reporting whether an indoor lighting system complies with current legislation before the building is put into use. By following this guide, you can ensure that your indoor lighting system works optimally and meets all the requirements of BR18, providing peace of mind for both clients and users. For best results, it is recommended to work with experienced professionals and use the latest standards and technologies in the field.
Lumega offers reporting with either the FA Method or in-depth reporting. Both services make it possible to deliver a thorough and documented proof of plant performance, which is essential for commissioning the building. For more information, please contact us by phone or email to book an appointment. Please note that functional testing is carried out on all types of lighting systems, including systems we have not supplied.
Relevant sources
BR18
DCL
DS/EN 12464-1