When furnishing a new space and during renovation, one wonders whether to opt for fluorescent or light-emitting diode (LED) luminaires. For conventional interior lighting, the advice is simple: both thumbs up for quality LEDs. In this article, we will compare the two technologies in the conditions of a dental practice. We'll reveal how the incomparable is often compared (especially when it comes to energy savings) and look at some frequently asked questions:

Dentistry is one of the most visually demanding activities - mainly due to the frequent shifting of gaze between large differences in brightness. In order to keep contrasts acceptable and to avoid premature eye fatigue for doctors and nurses, the intense illumination of the operating theatre must be compensated by patient lighting and general office lighting, followed by lighting for visual tasks outside the chair. These requirements far exceed the lighting values in, for example, offices or flats. Therefore, the luminaires used in dentistry outperform "ordinary" ones not only in terms of light output, but also in terms of glare prevention or better colour rendering.

Big energy and financial savings?

Let's compare the lighting of a model surgery using fluorescent and LED luminaires. In order to make a fair comparison, we are lighting at the same values, which correspond to the ergonomic minimum and further reduction of the luminaire power would already lead to excessive contrasts. Consider the lighting of a model surgery measuring 5 × 4 metres with a ceiling height of 2.6 metres. The reflectance of the ceiling is 0,7, of the walls 0,5 and of the floor 0,2. The maintenance factor (margin) is 0,8. Patient illuminance is 3300 lx at a height of 1.3 m, with an indirect component at the main luminaire of 50-60%. The total illumination is on average 1200 lx at a height of 0.85 m. The luminaire above the chair hangs at a height of 2.1 m and the supplementary luminaires are attached to the ceiling. Lighting for other tasks is not considered here. All prices in the following example include VAT.

Acquisition costs (approximate market prices):

Fluorescent tubes

LED

¹ indirect component 60 %, ² direct component only

Operating costs (approximate market prices): let's consider an electricity price including regulated services of 5 CZK/kWh and operation of lighting 10 hours a day, 5 days a week, 46 weeks a year. For luminaires with fluorescent lamps we assume replacement of lamps at a cost of CZK 5,500 in the 10th year of operation (after 24,000 h).

Technology Electricity consumption per month

Replacement of light sources (budgeted for 1 month)

The evolution of total costs for both options is shown in Figure 1.

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CONCLUSION: At the prices and wattages shown, LED dental luminaires will start to pay for themselves after 12 years of operation compared to fluorescent luminaires. After 15 years, however, many people are already considering a complete renovation of the practice. The example can easily be updated according to market developments. LED technologies are undergoing dramatic developments and can be expected to continue to increase in luminous efficiency. The purchase price of special luminaires is also falling, albeit more slowly than for general lighting. For fluorescent lamps, the potential for further efficiency improvements is already exhausted and no price decrease is foreseeable, rather the opposite.

LEDs don't heat, they shine with cold light?

Both fluorescent lamps and LEDs generate heat, although to a much lesser extent in the case of LEDs. Part of the current flowing through the lamp is always converted into heat. LEDs are very sensitive to heat and exceeding the permissible temperature leads to a drastic reduction in their lifetime. Cooling is therefore a key part of luminaire design. Underestimating heat gains - and not just from luminaires - when designing air conditioning can lead to unwanted temperature increases in the workplace.

Conclusion: LEDs also produce heat and overheating shortens their lifetime.

Are LEDs many times more efficient than fluorescent lamps?

Comparables need to be compared. The specific output of the light source (e.g. the fluorescent lamp itself or the LED chip) and the operating efficiency of the luminaire are related to each other as gross and net wages. The efficiency of an LED chip is not the same as the efficiency of a luminaire. Losses occur mainly in the optical system of the luminaire and in the power supply components. Confusing these 'efficiencies' (both in lm/W) - a common trick in advertising materials - can lead to unrealistic bids and an undersized lighting project that can become more expensive if the measured values do not comply with the requirements of the hygiene standard.

When comparing light sources or luminaires, their colour rendering index (Ra) should also be taken into account. In dentistry, the highest class of Ra ≥ 90 is used, for offices or residential interiors the medium class Ra ≥ 80 is used and for hallway or garage lighting Ra ≥ 70.

Conclusion: most of the LED luminaires with diffused light on our market are about 30-50% more efficient than comparable fluorescent luminaires.

Has the European Union banned fluorescent lamps?

The final approval of proposal No D059564/02, which tightens the ecodesign requirements for light sources and their power supply components, is expected. The following considerations are based on the assumption that the new Regulation will be adopted as proposed. As of 1 September 2021, the new Regulation should replace the existing Regulations 244/2009 (known as the "bulb ban"), 245/2009 and 1194/2012. Compact fluorescent lamps ("energy savers") with incandescent filament will suffer the same fate as incandescent lamps.

From 1 September 2023, T8 fluorescent lamps (Ø 25 mm) in lengths of 60, 120 and 150 cm (i.e. wattages of 18, 36 and 58 W) should be required to have unattainable efficiency. Thus, for older luminaires (including those above the dental chair), replacement fluorescent lamps will eventually not be available. In practice, it is possible to find 'ordinary' T8 fluorescent luminaires lasting well over 50 years. The Regulation is apparently trying to remove uneconomic luminaires with starters and chokes from service. Any replacement of T8 fluorescent lamps with so-called "LED tubes" would require the consent of the luminaire manufacturer.

The new regulation places reasonable requirements on thin T5 fluorescent lamps (Ø 16 mm) and therefore provides for their continued use. This type is referred to as the "pinnacle of evolution" of fluorescent lamps. The lifetime of T5 lamps is usually 30-40 years and their early replacement would be uneconomical.

The new regulation also specifies measurement methods and introduces requirements for the passing of lighting. Also on the horizon is a change to the regulation on labelling of light sources, which will redefine the A-G efficiency classes so that most fluorescent lamps and LEDs in use today will fall from the top A class to the lowest F or G classes.

Conclusion: the forthcoming restriction targets older types of T8 fluorescent lamps and does not affect newer T5 fluorescent lamps in more modern luminaires.

Can LED luminaires also be repaired?

Changing fluorescent lamps in the luminaire is usually done by the user. Replacing LEDs, on the other hand, usually needs to be entrusted to an authorised service centre. In some luminaires, the light source cannot be replaced at all. The manufacturer must provide this information in the instructions. The normal two-year warranty is extended by many LED luminaire manufacturers - for example to 5 years. However, given the expected lifetime of LED luminaires - often 50,000 hours (about 22 years), it is crucial that the manufacturer commits to ensuring the availability of spare parts for a certain period of time. LED technology is still developing rapidly and a wide variety of light modules are used in luminaires. If a type is no longer manufactured, there is nothing to replace it. Fluorescent lamps, on the other hand, are standardised and can be replaced by compatible types from different manufacturers.

The situation is similar for power components. In LED luminaires, especially if they are equipped with dimming, light tone change or remote control, the power and control components are usually tailor-made for the specific luminaire and cannot be replaced by any mass-produced type. Electronic ballasts for fluorescent lamps, on the other hand, are standardised and there are only a limited number of types in use.

Customers can therefore be advised to inform themselves about the possibility of replacing light sources and power supply components and their availability after the warranty period before purchasing the luminaire.

Conclusion: the dynamic development of LED technology brings some uncertainty about the long-term availability of spare parts.

Summary

For the customer who demands the latest technology, LED luminaires are the obvious choice. Even today, the more conservative customer can opt for cheaper fluorescent luminaires with slightly higher consumption and wait for the next generation of LED luminaires until the turbulent development calms down a bit, more standardisation of components emerges, and procedures in after-sales service and spare parts availability become more established. In addition, a significant improvement in the price/performance ratio can be expected for special LED luminaires in the future.