Dimming LED lamps

09.09.2016

Application:  General lighting
Technology:  LED
Target Group:  Retail,  Shop owner,  General public,  Installer

Lamps that generate light with the aid of light emitting diodes (LEDs) are not always compatible with dimmers. Whether an LED lamp is fundamentally dimmable or non-dimmable must be specified on the packaging. But dimmable versions may also cause problems, mostly in combination with already installed brightness con-trollers for traditional lamps. This is on the one hand due to the electronics, and on the other due to the low wattages of the LED lamps that place special demands on a dimmer. Those considering the following information when selecting a dimmable solution can however also achieve the desired lighting results with modern, energy-saving lamps.

Energy- and cost-efficient OSRAM LED reflector lamps are a very good alternative to the high voltage reflector tungsten halogen lamps that from 1 September 2016 are no longer permitted to be “put into circulation” as part of the ban on inefficient light sources in the European Union (EU). Halogen lamps are more energy-efficient than incandescent lamps but in principle have very similar constructions: if the light switch is pressed, current flows through the wire in the lamp which then heats up to generate heat and light. Controlling the brightness is therefore relatively simple: a suitable dimmer ensures that less current flows through the wire which heats up less so that the lamp emits less illumination.

LEDs (light emitting diodes) are constructed in a completely different way – they are electronic semiconductors. This is why LED lamps feature electronics, comparable to a small computer, which are switched upstream from the LED to control type-conform, constant current supply among other functions. These complex electronic characteristics of the LED lamp must be taken into account when specifying the dimmer.

A further challenge for some dimmers are the low wattages of LED lamps. Earlier dimmers were designed for incandescent lamps. These are usually reduced to the desired brightness via a rotary switch installed on the wall. An LED lamp comparable with a 60 watt incandescent lamp for example requires much less installed load – only around nine watts – for the same brightness, and therefore has significantly less margin for light control. For this reason it requires a dimmer capable of mastering this challenge. If it cannot achieve this the lamp may flicker or generate noise, or in worst cases destroy itself or the dimmer.

Before replacing a tungsten halogen lamp by an LED lamp in a dimmable luminaire, the following information should therefore be noted:

  • Only operate LED lamps on dimmers where “dimmable” is explicitly specified on their packaging.
  • The dimmer used must be suitable for the specific LED lamp. Information about dimmers compatible with the lamp is specified on the websites of the lamp producers, for example at www.ledvance.com/dim.
  • The websites of dimmer producers (e.g. Merten, Gira and Jung) also provide compatibility lists or helpful online tools. If uncertainty exists about already in-stalled dimmers, consulting the building owner or an electrician is recommended.
  • Keep away from cheap light control systems and LED lamps often featured in online offers. The quality of such apparently “low-cost” providers is often inade-quate and results in poor performance and failures.
  • Only use lamps of the same type within a dimmer circuit if not otherwise speci-fied by the manufacturer of the dimmer – problems may occur as caused by the different LED designs of the lamp producers.
  • A dimmer should be used if the brightness is reduced once in a while. If however continuously less light is required, a lamp with a lower wattage is the right choice. The reason for this is that continuously dimming a higher-output lamp requires more energy than using a lamp with lower rated power.