sparks
ELECTRICAL NEWS
june 2014
lighting
25
MOST modern homes, boardrooms and offices
nowadays consider it a necessity to be able to dim
lights and even groups of lights within the same
room. This is mainly for the aesthetic value that
dimming adds to the living or working environ-
ment. Justifiably, during earlier times when the
National Grid was not under pressure, electricity
prices were of less concern and conventional
lamps were cheap to replace, it was not necessary
to consider the possible added benefits that the
dimming of lamps can provide.
This has now all changed. Our grid is constantly
under pressure, electricity prices are sky rocket-
ing and even conventional lamps are becoming
expensive. Fortunately, the LED revolution came
to the rescue and due to its very low energy con-
sumption, provides some relief fromhigh electric-
ity costs. However since dimmable LED lamps are
slightly more expensive than their non-dimmable
counterpart, buyers now have to decide whether
they actually want to dim the lights or not. How-
ever, if the‘non visual’benefits of dimming LED
lamps are considered, especially the additional
energy savings possibilities and the increased
lamp lifetime, it might be much an easier decision
whether or not to dim.
Figure 1
shows the measured energy consump-
tion versus measured light level of a conventional
The real benefit of dimming LEDs
By Dr Marthinus Smit, Shuttle Lighting
50WGU10 halogen lamp, a typical 10WGU10
LED lamp and a typical 10WMR16 LED lamp
with an electronic transformer. It can be seen
that, besides the obviously much higher energy
consumption of the halogen lamp andmuch
lower initial light output, its consumption curve
when dimming is very non-linear. The LED lamps,
on the other hand, not only show a much higher
initial (non-dimmed) light output, but also exhibit
a virtually linear consumption curve as the lamp
are dimmed. In order to better appreciate the
implication of these characteristics,
Figure 2
shows
the energy savings as a percentage of the initial
(non-dimmed) energy consumption versus the
percentage of measured light output. It can be
seen that if the lamps are dimmed to 50% lux
output, the halogen lamp saves only 26% energy,
very little considering that it consumes close to
50Wwhen not dimmed. This is due to the fact
that the majority of the energy is used to ignite
the gas and produce heat – the visible light out-
put is only a small percentage of total consump-
tion. LEDs are, however, an electronic component
that has inherent non-linear energy consumption
versus light output, which is the opposite to that
of a halogen or incandescent lamp. With LED light
sources, the energy savings are remarkable when
dimming, as can be seen from Figure 2.
When dimmed to 50% light output, the 10W
GU10 LED saves a staggering 62% energy, effec-
tively consuming only 3.8W. Due to the losses as-
sociated with the electronic transformer, the 10W
MR16 LED performs less efficiently but still saves
a very respectable 48% energy when dimmed
to 50%, effectively then only consuming 5.2W.
Results will differ frombrand to
brand and even possibly be-
tween different models within a
brand, but the general tendency
will be the same or very similar
for all LED lamps.
Interestingly, due to the high
lumen output of the LED lamps,
the MR16 measures around 400
lux (1m from source) and the
GU10 approximately 450 lux
compared to the a very low 150
lux of the halogen lamp when
dimmed to 50%.
When an LED is dimmed, the
current through the module re-
duces and the junction tempera-
ture correspondingly reduces
(typically non-linear).
This has a profound effect on
the lumenmaintenance of the
LED as can be seen from
Figure 3
, which shows a
graph of the expected LEDmodule lifetime versus
its internal temperature. Additionally, the driver
built into the LED lamp also suffers degradation
due to increased temperature but dimming the
lamp reduces the overall temperature. Ameasure-
ment of a typical 10WGU10 LED showed that the
aluminiumhousing temperature reduced from
about 40°C above ambient when at full intensity
to about 5°C above ambient when dimmed to its
lowest intensity – this much reduced temperature
has an obviously beneficial implication on the
lifetime of the lamp’s driver.
Thus, the energy savings are real when you
dim LEDs – the more you dim, the more you save.
The more you dim, the cooler the lamp operates
resulting in reduced lumen depreciation as well as
a longer lifetime of the LEDs driver.
However, always ensure that the correct dim-
mer type is used for dimming a particular LED. If a
dimmer is not matched or approved for a specific
LED it can result in reduced product lifetime.
Enquiries: 082 465 2299
TWO Eastern Cape TB hospitals – the Jose Pearson in Port Elizabeth
and Marjorie Parrish in Port Alfred – have been upgraded and are
now illuminated with the latest highly efficient LED lighting solu-
tions from BEKA Schréder, Eastern Cape.
BEKA’s ByronTeengs says,“Our client was requested to upgrade
the security lighting of both projects, which also included general
area lighting. The Department of Health required an energy-efficient
product and a maintenance-free installation.”
Teengs explains that the client designed all the lighting layouts
using the BEKA LEDflood-midi 88W and BEKA Schréder’s glass-
fibre reinforced polyester poles.“The selected products conform to
requirements for marine grade aluminium luminaires with an LED
light source and corrosion-resistant glass-fibre reinforced polyester
poles,”explains Teengs.
“A total of 176 BEKA LEDflood luminaires and 89 BEKA GRP poles
were supplied to both projects,”he says, adding,“BEKA Schréder is
proud of its association with this project and its partnership with
Ballenden & Robb Consulting.”
Enquiries: (041) 373-3886
TB hospitals lit with LED floodlights
TRIDONIC has modified its multi-functional
DALI TOUCHPANEL 02 unit and added new
functions and interchangeable layouts. DALI
lighting control is nowmore convenient and
more flexible than ever before. The mechanics
have also been improved and a guide LED has
been integrated.
DALITOUCHPANEL 02 combines the
A quantum leap in quality
functions of group controller DALI GC
with those of scene controller DALI SC
in a single module. It is therefore pos-
sible to send dimming and switching
commands to two DALI groups and to
program and retrieve up to four light-
ing scenes.
The panel has six freely definable but-
tons towhich interchangeable layout
cards can be individually assigned.The
individual buttons can be configured
separately usingmasterCONFIGURATOR soft-
ware (V2.6 or higher).The options include on/
off switching and up/down fading of individual
addresses, groups or broadcast. In addition,
predefined lighting scenes can be retrieved.
The software also enables the touch panel to
be configured for tunablewhite applications.
This means that freely controllable and dim-
mable white light can be produced along the
entire Planckian curve from 2 700 to 6 500K.
This control option can also be applied to
individual addresses, groups or broadcast.
DALI TOUCHPANEL 02 does not need a sepa-
rate power supply as power is supplied via the
DALI line. You can connect the touch panel to
the DALI circuit without have to worry about
the polarity. The control module is multi-
master-compatible somultiple control mod-
ules can be connected in parallel in a DALI
circuit. Typical applications include multi-
functional rooms such as meeting rooms with
different lighting zones.
The manufacturer offers a five-year system
guarantee for peace of mind.
Enquiries: (011) 923-9686
BEKA LEDflood-midi luminaires provide the security and area lighting at
Jose Pearson TB Hospital.
Figure 3: LED module lifetime versus temperature.
Figure 1: Measured light output versus energy
consumption of halogen and LED lamps.
Figure 2: Measured energy savings versus light output
of halogen and LED lamps.
