Transcript 11.L3 Lighting ABBE

Energy Performance
Certificates & Display Energy
Certificates
Lighting
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LIGHTING INSTALLATIONS
Introduction
Lighting is often the single largest electrical consumption and cost in
non air conditioned buildings. For example, lighting can account for
over 40% of electricity costs in naturally ventilated offices. Good
lighting design can reduce these running costs and can also reduce
internal heat gains, thus reducing the need for air conditioning.
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A luminaire comprises a housing, a reflector, a lamp and shielding
(either louvres, or a lens or diffusing material) and, for discharge
lamps, some form of control gear. The photometric efficiency is
measured in terms of its light output ratio. This is the ratio of the total
light output of the luminaire to that of the lamp(s) under reference
conditions. The higher the light output ratio, for a given light
distribution, the more efficient the luminaire.
The distribution and other characteristics of over 70 generic types of
luminaire are described in the Code for lighting.
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Terminology
Adaptation.
The process which takes place as vision adjusts to the
brightness or the colour of the visual field.
Average lamp life.
The time when half the number of lamps in a batch under test
conditions failed.
Ballast.
Also called control gear. Apparatus to start and control the
current through the lamp.
Connected load.
The total load connected to the mains including lamp and
ballast.
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Diffuser.
A translucent screen used to shield a light source and at the same time
soften the light output and distribute it evenly.
Discharge lamp.
A lamp whose illumination is produced by an electric discharge through
a gas, a metal vapour or a mixture of gases and vapours.
Efficacy (luminous efficacy).
The ratio of luminous flux emitted by a lamp to the power consumed by
it, e.g. lumens per watt. When the control gear losses are included it is
expressed as lumens per circuit watt.
Extra low voltage (ELV).
Refers to anything under 50V and generally considered harmless.
Electrical engineers term ‘mains’ voltage as low voltage (50V –1000V)
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(There is a further category, Safety Extra Low Voltage (SELV) which
refers to supplies also under 50V but supplied through an isolating
transformer.)
General lighting.
Lighting of a whole area.
High frequency electronic ballasts
(also called high frequency control gear).
Uses solid state technology to run the lamp between 20 to 40 kHz.
Illuminance.
The amount of light falling on a surface of unit area. The unit of
illuminance is the lux, equal to one lumen per square metre.
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Light output ratio.
The ratio of the total amount of light output of a luminaire, under
stated practical conditions, to that of the lamp.
Lumen.
Unit of luminous flux, used to describe the amount of light given by a
lamp or falling, onto a surface.
Luminaire (light fitting).
The correct term for a light fitting. An apparatus which controls the
light from a lamp and includes all components for fixing, protecting
the lamps and connecting them to the supply.
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Maintained illuminance.
The average illuminance over the reference surface at the time
maintenance has to be carried out by replacing lamps and/or
cleaning luminaires and room surfaces.
Power factor.
The ratio watts to volt-amps. It indicates the efficiency with which
power supplied by the generating station is used. The higher the
power factor the better, 1 (unity) being the maximum.
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Lamp Selection
The factors involved in lamp selection are:
— luminous efficacy (lumen output/watts input)
— rating (consumption watts)
— mortality (rated life of the lamp)
— lumen maintenance (lumen depreciation over life)
— operating position (in some cases this may affect efficacy)
— size (physical properties can affect optical efficiency of light control)
— control gear type and controllability (switching or dimming)
— colour appearance (appearance of the source in terms of ‘warm’ or ‘cool’)
— colour rendering
— starting, run-up and re-start times
— minimum starting temperatures.
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There are three main categories of lamps:
Tungsten filament lamps
Fluorescent lamps
High-intensity discharge lamps.
Each category has different operating characteristics and is
appropriate in different circumstances, depending on the relative
importance of cost, life, colour appearance, colour rendering and
efficiency.
It should be noted that the Building Regulations now require the use,
in most cases, of energy efficient lamps.
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Filament lamps
Filament lamps (of which GLS lamps are an example) are the most
common type of lamp. They are cheap but relatively inefficient, and
are available in many different shapes, colours and bulb finishes.
They can also have built-in reflectors to direct the light.
A major variation of the basic design uses a halogen additive to the
gas filling in the lamp. These incorporate a quartz envelope that
permits the use of a higher operating temperature, a more compact
lamp, a higher efficiency and often a longer life.
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Fluorescent lamps
Light is generated mainly from the phosphor coating on a glass
envelope. The phosphors convert invisible ultraviolet radiation from
a low-pressure mercury discharge to visible light.
Different blends of phosphor powders allow a choice of lamps of
different colour rendering and colour appearance properties.
A fluorescent lamp requires control gear for its correct operation and
most have near instantaneous switch-on. In some cases they can
take a short time before reaching full light output but this is rarely
more than one minute.
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Compact fluorescent lamps (CFLs) with built-in control gear are
intended as direct replacements for filament lamps, enabling the
lamp to be inserted in the socket vacated by the filament lamp and
operate without any external control gear.
A recent addition to the family of fluorescent lamps is the induction
lamp. It is similar to other versions except that the discharge is
generated by a magnetic field. Because this eliminates the need for
electrodes, which deteriorate with time, the lamp can have an
extremely long life, typically 60 000 hours. This makes it useful for
lamp positions that are difficult to reach. The lamps are compact in
size and have similar colour performances to other fluorescent
lamps.
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High intensity discharge (HID) lamps
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The commonly used types of HID lamp are sodium and mercury lamps.
They have the advantages of a large light output for their size, relatively
high energy efficiency and a long life. Light is produced directly by a highpressure gas discharge, although some mercury lamps also employ a
phosphor coating. The gas discharge (together with additives) determines
the properties of the light produced.
Applications for most types of HID lamp are limited by the colour
performance and their run-up and re-strike times. All HID lamps require
control gear that should be matched to the particular lamp. Standard types
of control gear and lamp combinations involve a time delay before full light
output is reached after switch on.
Also when a lamp is switched on while still warm, there will be a short delay
before the lamp re-strikes. Special control gear packages are available with
instant re-strike capability for some lamps.
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Incandescent tungsten filament lamps
The most common types are known as general lighting service
(GLS) lamps and decorative (e.g. candle) lamps.
The majority of luminaires (light fittings) in most homes use
incandescent tungsten filament lamps with an efficacy of only about
8 to 15 l/W.
Incandescence literally means light produced from heating,
achieved by passing an electrical current through a strand of
tungsten filament. The filament is delicate and eventually burns out
after about 1000 hours. Although some lamps are made to last
longer and sold as double life lamps, this is at the cost of light
output.
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Advantages:
Low purchase price
Excellent colour rendering
No ballast required
Immediate full light when switched on
Ease of dimming
Sparkle lighting effects can be created
Operates in any plane (universal operating position).
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Disadvantages:
Low efficacy – 8 to 15 l/W
Short life, usually 1000 hours
High running cost.
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Tungsten halogen (quartz halogen) lamps
These are versions of the tungsten filament lamp. Many tungsten
halogen lamps operate at 12 volts, (extra low voltage – ELV)
requiring a transformer that is now quite neat and small.
This light source is compact and can be focused and directed better
than any other, making it particularly appropriate for spotlighting.
Although they should not be regarded as having high efficacy,
tungsten halogen lamps produce 16 to 25 lumens per watt and last
longer than standard tungsten filament lamps.
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These are versions of the tungsten filament lamp. Many tungsten
halogen lamps operate at 12 volts, (extra low voltage – ELV)
requiring a transformer that is now quite neat and small. This light
source is compact and can be focused and directed better than any
other, making it particularly appropriate for spotlighting. Although
they should not be regarded as having high efficacy, tungsten
halogen lamps produce 16 to 25 lumens per watt and last longer
than standard tungsten filament lamps.
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Mains voltage tungsten halogen lamps can be dimmed with a simple
domestic dimmer of the right capacity, but some ELV lamps may
require a special dimmer depending upon the type of transformer
used. Running the lamp at lower than the rated voltage will lower the
filament operating temperature, preventing the halogen cycle* from
taking place, and causing the lamp to blacken.
The blackening can be removed by occasionally running the lamp at
full light output. The quartz lamp envelope should not be handled
with bare hands and manufacturers instructions regarding the
operating position of the lamp should be observed.
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Advantages:
Higher efficacy than conventional tungsten filament lamps
Brighter, whiter light
Life of 2000 to 5000 hours depending on type
Excellent colour rendering
No ballast required
Immediate full light output when switched on
Can be dimmed
Bulb blackening eliminated when run at full light output.
Disadvantages:
Transformer required for extra low voltage lamps
Requires careful handling
Operating positions of double ended types is limited to horizontal
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Tubular fluorescent lamps
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Fluorescent lamps have four to ten times the efficacy of
incandescent lamps and can last up to eighteen times longer,
depending on the type of lamp and its ballast. All fluorescent lamps
require a ballast to operate.
Fluorescent lamps and tungsten filament lamps work in entirely
different ways. The fluorescent tube contains an inert gas, usually
argon or krypton at low pressure, and a small amount of mercury.
When an arc is struck between the lamp’s electrodes, ultraviolet
radiation is produced, which excites a phosphor coating on the
inside of the tube to produce light at visible wavelengths.
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The quality of light that is produced depends on the precise mix of
phosphors in the coating. Older halo phosphate phosphors decayed
noticeably over the life of the lamp, but the newer troposphere and
multi-phosphor lamps lose less light output. The latest troposphere
lamps maintain most of their initial light output throughout their life.
Older tubular lamps 600 mm long and over were usually 38 mm
diameter (known as T12) but newer lamps are 26 mm diameter
(known as T8). Simply by replacing T12 by T8 lamps in switch start
luminaires will save up to 10% energy. Further improvements have
been made and now T5 fittings (16mm) are available with further
energy savings. Due to changes in building regulations, Part L2 now
requires this type of light fitting to achieve compliance.
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Advantages:
Low running cost
High efficacy
Very good to excellent colour rendering
Long life in normal use
Minimal reduction of light output through life
Prompt start and restart
Quick run-up to full light output
Up to 10% energy saving when replacing equivalent T12 on switch-start
circuits
Universal operating position.
Disadvantages:
Excessive switching shortens life
Ballast required
Can be dimmed but requires special ballast and dimmer.
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High pressure sodium lamps
Although not regarded as domestic lamps, high pressure sodium
discharge lamps combine high efficacy with very long life and are
particularly suited for floodlighting and illuminating larger exterior
areas that need to be lit for long periods.
They are not made for frequent switching and therefore should not
be operated by presence detectors for security lighting.
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Advantages:
Very low running cost
Very high efficacy
Very long life
Quick start
Universal operating position.
Disadvantages:
High purchase cost
Very poor colour rendering
Ballast required
Requires 1.5 to 6 minutes time to run up to full output
Delayed restart when hot on most lamps.
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Compact fluorescent lamps (CFLs)
New technology has reduced the size of fluorescent tubes,
and compact fluorescent lamps have been developed to
replace tungsten filament lamp applications in the home.
These new lamps give a light similar to tungsten lamps and
present a good opportunity to light homes with a fifth of the
energy required before. Although they cost more to
purchase than traditional GLS lamps (bulbs), CFLs make
savings in the electricity bill straight away. CFLs should be
installed in fittings that are heavily used (>4hrs/day), for
example in living areas and circulation areas, halls,
stairways, landings, common passages outside buildings
and areas that are likely to be lit continually.
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Virtually all tungsten lamps can be replaced with compact
fluorescents as the opportunity arises, except in some luminaires
which use crystal glass to create sparkle. An ever growing range of
compact lamps is available in various wattages, shapes and sizes.
Many of these lamps have a ballast built in, or an adapter enabling
them to fit directly into the standard bayonet cap (BC) or Edison
screw (ES) lamp-holders.
CFLs generally have five times the efficacy and last eight to twelve
times longer than a tungsten lamp of equivalent light output. When
cold, CFLs produce 40 to 60% of their full light output which is
reached after about two minutes. CFLs should not be used with the
standard domestic dimmer control but it is possible to dim the
separately ballasted four contact versions of the lamps with a
dimmable ballast and compatible dimming equipment.
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Low running cost
Replacement for tungsten lamps
Five times the efficacy of equivalent tungsten lamps
Average life of 8000 to 12 000 hours
Very good colour rendering with most lamps and some types
giving excellent colour rendering
Quick run up to full light output
Prompt start and restart
Four pin lamps can be dimmed with suitable ballast and dimmer
Universal operating position but light output may be reduced
with some types.
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• Disadvantages:
• Excessive switching shortens life
• Ballast required but is built in on some lamps
• Not suitable for use on standard domestic dimmer
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• LED Lamps
• Typically higher efficiency than
CFL
• Can be longer life
• Variety of colours available
• Low running cost
• Quick run up to full light output
• Prompt start and restart
• Universal operating position
• Brightness and pattern of light
often poorer
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Assessing Lighting Requirements
The role undertaken by a non-domestic energy assessor is to
provide an energy assessment as accurate as possible from the
information gathered on site.
As lighting will be generally the single highest energy use on site,
assessing this energy use correctly is essential in providing an
accurate certificate.
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• From the conventions – Check Latest
• ‘If a building’s original lighting design is available and there is no
discrepancy between that and the observed lighting within the
building, the wattage and lux values, from that design, should be
entered using the ‘full lighting design carried out’ option in SBEM. If
complimentary values are not available (i.e. both values from the
same lighting design) the lighting design(s) must not be used.’
• ‘If the circuit wattage and lux levels can be accurately recorded by
the assessor (…) the option for ‘full lighting design carried out’
should also be used and the appropriate values entered. Wattage
and lux values must not be entered separately nor is it acceptable to
input assumed wattage or lux values from BSRIA publications or
other reference documents or to accept or use a software suggested
default value.’
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• ‘If the circuit wattage and lux values cannot be ascertained by either
of the above methods it may be possible to use the ‘Lighting chosen
but calculation not carried out’ option where the lumens per circuit
wattage must be entered, calculated in line with building regulations
guidance. This may not be possible for all zone activity selections.
The evidence of how the values for lamp lumens and circuit wattage
must be provided in the site notes.’
• ‘Lux level readings, taken by an assessor, may only be used for the
production of an EPC if the readings have been recorded in line with
the Society of Light & Lighting’s Code for Lighting 2009. Evidence of
achieving a complete blackout of windows and the required
calculations to establish the grid size for the measurements taken
must be provided.’
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• ‘If none of the above options are applicable the ‘lighting parameters
not available’ option should be chosen and the appropriate lamp
type for the zone should be selected.’
Mixed lighting in a zone in SBEM
• ‘Where a zone contains both general lighting and display lighting,
and for the selected activity SBEM assumes the presence of display
lamps, then the display lighting and the general lighting must be
entered as ‘display’ and ‘general’ lighting respectively.’
• ‘Where a zone contains both general lighting and display lighting,
and for the selected activity SBEM does not assume the presence of
display lamps, then the zone must be subdivided to create additional
‘display’ zones to represent the display lighting.’
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• ‘A suitable ‘display’ activity should be used for the ‘display’ zones
and appropriate lighting entries entered. The remains of the original
zone must have the original activity and only the general lighting is
entered into the zone(s).’
• ‘Where a zone contains a mixture of lamp types providing general
lighting (no display lighting) across the entire zone, such that simply
splitting the zone to reflect the lamp’s locations is not practicable,
then the following method should be followed.’
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‘1. The proportion of the zone’s area lit by each lamp type should be
established.’
‘2. The zone should then be split into a number of zones to match the
number of lamp types and for each lamp type the relevant proportion of the
zone area and all of the zone’s envelopes, including glazing, should be
entered into each relevant zone along with the appropriate respective lamp
type.’
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LIGHTING CONTROLS
Appropriate lighting controls can yield substantial improvements in lighting
energy efficiency These improvements arise principally from the utilisation of
available daylight to reduce electric lighting use and from switching off electric
lighting when a space is unoccupied. In addition they can increase user
satisfaction by allowing occupants to have more control over their working
environment through the use of localised switches.
To be energy efficient, lamps must be switched on to provide light only when
it is required, and switched off when it is not. Both automatic and manual
switching of lamps will adversely affect lamps by shortening their service life.
This effect is minimal; the energy cost saved by switching lamps off recovers
the cost of shortening lamp life within a few minutes. Provided that lamps are
to be left off for periods of more than two or three minutes it is always cost
effective to switch off.
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The most cost-effective control strategy for a particular space will
depend on the daylight availability and the type and pattern of
occupation. If sufficient daylight is available to meet lighting
requirements for a significant part of the day, energy savings can be
considerable. Research has shown that the probability of switching
on electric lighting on first entering a space correlates closely with
the daylight availability, but switching off rarely occurs until the last
occupant has left.
Daylight availability generally increases during daylight hours and is,
therefore, correlated with time of day Thus daylight availability
strategies are often linked to time switching technology.
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It is also possible to provide localised switching so that occupants can
decide when to switch off the lighting of their working area once the day
lighting is sufficient. Localised switching provides more flexible control of the
lighting of a worker’s space than a bank of switches mounted at the main
entrance of a space.
Further improvements in energy efficiency can be achieved by using
automatic sensing of daylight levels, called daylight linking, or occupancy,
called occupancy linking. For spaces with negligible day lighting, a
combination of time switching and localised switching will cover most
situations, although care is necessary to ensure that dangerous blackout
conditions are avoided if lighting is automatically switched off For
installations with sparse and intermittent occupancy such as a warehouse,
localised switching will eliminate the need for the whole space to be lit when
only a small part is in use; occupancy detectors are particularly suitable for
such spaces, and may also be made an integral part of the security system.
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Local switches and dimmers
These are either permanently wired, such as wall- or ceilingmounted pull switches, or are remote control devices like those
commonly used to operate televisions and video recorders.
Permanently wired manual switches need to be positioned near to
the lighting circuit they operate, and should be easily accessible to
ensure that only the lights that are necessary are switched on.
Approved document Part L of the Building Regulations specifies that
the operating switch should be no more than 8 m (in plan) away
from the luminaire that it controls, or no more than three times the
height of the luminaire above floor level if this is greater.
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Time operated controls
These can be used to switch lights off when they are not required,
such as at lunchtime or at the end of the working day, or at a time
when it is estimated there will be sufficient daylight. A manual
override must be provided to allow users to switch lights on if
necessary. Time operated switches can also be used to control
lights in any situation with a regular period of operation. Lights in a
windowless circulation area, for example, can be switched on just
before people arrive in the morning and switched off at the end of
the day.
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Presence or occupancy sensor operated controls
These can be used to switch lights on as people enter a room and
off again after they have left. This avoids lights being left on
unnecessarily
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They can be used to operate task lighting, or lighting in rooms which are
used infrequently, such as storerooms. They can be particularly useful in
rooms where people are likely to have their hands full on entering.
The circuit will need to include a time delay to allow people to leave the
space safely and to avoid lights being constantly switched on and off.
Frequent switching of fluorescent lamps can shorten their life unless
appropriate control gear is used
Presence detectors can be ceiling- or wall-mounted, but the sensor must be
able to detect an occupant at all times. This may require more than one
sensor to cover an area. Sensors must also be sufficiently sensitive to
operate when required, but not too sensitive that they respond to
extraneous signals. An option is to combine a presence operated switch
with a manual switch. The occupant switches the lights on manually when
required, and the presence detector switches them off. This is sometimes
referred to as ‘absence sensing’.
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• Illuminance sensor operated controls
In areas where there is adequate daylight for part of the time, daylight
illuminance sensors (photocells) can be used to ensure that electric
lights are not left on unnecessarily. People will often switch electric
lights on first thing in the morning when it is still dark, but they are less
likely to switch them off later when daylight becomes sufficient,
particularly in shared spaces and circulation areas. Illuminance
sensors can switch or regulate luminaire light output, but regulation
(dimming) will require the appropriate control gear.
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If switch control is used, the switch-off level must be set to avoid
causing annoyance, i.e. switching off the luminaires when it will
hardly be noticed. If the sensor records the combined daylight and
electric light this will probably need to be at least three times the
required task illuminance. A time delay will be needed to avoid
frequent operation of lights in rapidly changing daylight conditions.
Dimmer control can provide a near constant illuminance and is
usually more acceptable to users, particularly in shared spaces.
Fluorescent lamps will normally dim down smoothly to a certain
level, after which they can become unstable and start to flicker. The
level at which this occurs will depend on the control gear, but it is
typically 10% of full light output.
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Central controller
Luminaires can be controlled by a dedicated personal computer or a
building management system. Depending on the sophistication of
the system and the wiring of the luminaires, almost anything is
possible. Switching can be related to time, daylight level and
occupancy, and luminaires can be linked into groups which can be
changed when necessary. Dimming is also possible if the luminaires
are equipped with appropriate control gear.
Luminaires can be controlled in particular sequences, so that room
lighting is operated independently of, but linked to, circulation
lighting. This can be used to prevent circulation lighting from being
switched off if rooms are still occupied, thus allowing people a safe
exit from the building. It is essential that adequate lighting is always
provided to allow people to exit a building safely.
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• ‘Intelligent’ luminaires
Luminaires are now available with their own
control sensors designed for occupancy and
illuminance monitoring. The sensors can
signal either a switching or dimming action, and can be
overridden with a hand-held infrared controller.
The luminaires can be programmed to provide a constant
maintained illuminance throughout the maintenance cycle
of the installation. Illuminance and time delay, which
operates when the occupancy sensor ceases to record
movement, can be adjusted manually by using controls
within the luminaire or remotely.
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