Maintenance factors ensure that your luminaires continue to perform well long after they are installed. Find out what you need to know about them:
Because design engineers are busy professionals, the general public accepts that they use simple techniques in submitting specifications for the products they design. But there is some danger when you often use quick and easy methods. If we are not careful, they end up making these methods the “accepted norm” for no real reason.
A specific and very important example is the use of the maintenance factor of 0.8 when calculating the specifications of LED lighting . In fact, this has become a topic in the industry that is impossible to ignore when it comes to lighting design; the problem exists and is known to all. But we still have to face these issues…
Maintenance Factors are based on the fact that luminaire installations will gradually reduce the amount of light they emit over a number of years, due to lumen depreciation, dirt, failure and so on. .The Maintenance Factor is a percentage to which the total luminous power emitted from a luminaire measured at the beginning of the installation could decrease. It tells us how much we need to increase the luminous power from the beginning to maintain it at the required levels during the useful life of the installation. Led luminaires have an identified useful life time. This factor is used to identify the time that the luminaire will illuminate within the appropriate ranges and providing up to 80% of its light power. After that period,
In this way, if the lighting level required for the useful life of the project is 500 Lux and the maintenance factor is defined at 0.8 (or 80%), then to maintain lighting at the required levels, 625 Lux should be installed in the environment in question.
Here are 9 aspects of the maintenance factor that every lighting professional should know:
1. The maintenance factor is a key aspect in the lighting industry
The maintenance factor is an important consideration in the planning of lighting installations. The Society of Light and Lighting and the Lighting Code states that: “The lighting system should be designed considering a maintenance factor calculated in a general way, either for a certain lighting equipment, environment or for a specific maintenance program.”
2. A maintenance factor of 0.8 is not suitable for all projects
Although the 0.8 maintenance factor is a generally useful rule of thumb, it is an arbitrary number, and there is no reason that it should be used in all lighting projects. Each project is different, so the maintenance factor should be transformed to adapt it to the circumstances and to the lighting technology that is applied.
If we consider that the elements that make up the maintenance factor are key, then a number of factors can be seen that make up the final figure. The formula to determine the general maintenance factor for indoor lighting is:
MF = (LLMF x LSF) x LMF x RMF
MF: Maintenance Factor
LLMF: Lamp luminous flux maintenance factor
LSF: Lamp Survival Factor
LMF: Luminous flux maintenance factor of a luminaire
RMF: Environment maintenance factor
SMF: Maintenance factor of the surface of a luminaire
3. The luminous flux maintenance factor of the lamp is very important for LED luminaires
Factors such as RMF and SMF are affected by the location of the luminaires, whether for example in an industrial warehouse or an office. This would affect the LMF in terms of dust accumulation, with a direct effect on lighting levels. Pollution levels for luminaires and space can be viewed in the same way for LEDs as they are for fluorescent luminaires: both dust and dirt will affect light quality.
However, in LED lighting the Lamp Luminous Flux Maintenance Factor (LLMF) is particularly important and therefore its impact on the overall maintenance factor is also important. LEDs have a very long useful life , so it is highly likely that an office will first go through a renovation or refurbishment process before there is a need to replace an LED luminaire . (due to long lamp life)
4. The useful life is key to the calculation in terms of use and cost of energy
When developing specifications for LED luminaires, it is very important to indicate their useful life in the calculations as this will lead to decisions regarding the initial light output level and the number of luminaires installed. Consequently, it will have a large impact on the amount of luminosity required, and therefore, on operational and capital costs.
The power and durability of a LED is generally expressed as follows:
L80 B10 50,000 hours at 25C.
Here, L is the useful life, B is the chance of failure, and H is the hours of useful life.
5. Products may last longer on the computer where they were installed
The fact of having an adequate maintenance factor of the luminous flux of the lamp (LLMF) that allows finding the correct maintenance factor for a lighting project has other benefits in terms of planning the requirements of our clients. For example, if there are LED luminaires with a longer useful life, customers could analyze the need or not to have luminaires with a useful life of 50,000 hours in their lighting system.
Why plan for 12 or 15 years of operation if the client will be renting the office for only 7 years? If you change this value the LLMF will be modified and the amount of luminosity and the number of luminaires could be significantly reduced. This would save the customer money in both the short and long term.
6. Comparison of similar products is very important for both designers and end users
One of the main challenges for those planning a lighting system installation is the difficult comparison when developing the specifications of similar products.
For example, we found office luminaires that could be L80 B10 50,000 hours at 25C up to L70 B50 30,000 h at 25C. Even more, it becomes difficult for the same clients not to have consistent information in comparative figures when making a clear comparison.
It is essential to collect and unify a lot of information to formulate a correct maintenance factor.
7. The development of new norms can help in comparisons
In Europe many useful sources of information have been developed to help lighting specifiers quickly find the correct figure. One is the ENEC+ organization, which is developing standards for the certification process for the useful life and performance of LED products. The objective is to give the users of the products confidence and guarantee that what they are buying will work according to the detailed specifications. In addition, the ENEC+ will standardize the use of the L and B factors, making direct comparisons easier.
Another organization that has carried out in-depth research in this field is ZVEI, a European body for lighting and electrical industries, which issued a manual for “safe” planning with LED lighting.
8. Just because FM is above 0.8 doesn’t mean it’s wrong
Customers have a right to be wary of high maintenance factor figures. But just because it is greater than 0.8 does not mean it is wrong.
In the early stages of a project or in a retrofit, designers often work without all the necessary information. Yes, some intelligent approximations are expected. However, if there is a standardized method for verifying the LLMF and LSF and guidance on how to make the comparisons directly, there is no reason to use the 0.8 by custom.
Designers who use a maintenance factor of 0.88 correctly are often asked to use 0.8, even though this is the wrong figure. This practice, generally promoted, should be stopped.
9. A poor and oversized design wastes the benefits of LEDs
According to what is indicated by the Lighting Code: “The maintenance factor has a great impact on energy efficiency”. If we set too much lighting at the start of a project due to inadequate maintenance factors, then the customer will pay for that mistake through increased electricity bills.
It has been said many times that lighting is the great opportunity in the world of energy saving, and even more so in Argentina with the high costs of this service. Could it be that industry leaders have overestimated maintenance factors for a long time?
