cole de todos!”
RECURSOS HUMANOS
5. Competencias del Grado en Trabajo Social desarrolladas
longest life for lamps of this type. The advantages and disadvantages of the two types of tungsten lamp are shown in Tables 9.5 and 9.6. Where possible, GLSand tungsten- halogen lamps should be replaced with compact fluorescent lamps(20)(see also 9.3.4).
9.3.3
Tubular fluorescent lamps
Fluorescent lamps have high efficacy, long life, good controllability and relatively low cost. The older argon- filled 38 mm diameter lamps are largely superseded and should only be used for replacements in starter-less circuits. The modern range of krypton-filled, 26 mm diameter, triphosphor lamps are the preferred choice for switch-start circuits, suitable electronic start circuits, and electronic high frequency ballasts.
Because of their characteristics, fluorescent lamps are used for the majority of commercial lighting applications. Where appropriate, heat recovery should be considered by extracting air through the luminaires. This can improve the light output by maintaining the lamp at its optimum operating temperature (see section 8). The advantages and disadvantages of tubular fluorescent lamps are shown in Table 9.7.
9.3.4
Compact fluorescent lamps
Compact fluorescent lamps (CFLs) are available in various configurations, some types having integral control gear, others with a separate ballast.CFLs provide the equivalent light output of GLSfilament lamps for about 20–25% of the power. So that the lamp size and weight (of those with integral gear) can be kept to a minimum, some of these lamps operate at a low power factor. However, a wide range of luminaires designed specifically for compact fluorescent lamps is available and the extra available space usually allows the incorporation of power factor correction in these luminaires.
Before retrofitting CFLs in existing GLSluminaires(20), it is necessary to ensure that the light distribution and light output ratio is not adversely affected and that the operating position and temperature of the lamp do not significantly reduce its efficacy.
CFLs were originally developed as energy efficient replace- ments for filament lamps with ratings up to about 20 W. However, the same lamp technology has been applied to higher wattages giving light outputs equivalent to some linear fluorescent lamps. There are several formats including the short twin-leg and ‘2D’ variations. The shorter twin-leg construction means that these can be housed in more compact luminaires for general and localised lighting. The advantages and disadvantages of compact fluorescent lamps are shown in Table 9.8.
9.3.5
Mercury and sodium discharge
lamps
High pressure sodium (SON) and metal halide (MBI) lamps offer greater efficacies than high pressure mercury lamps Table 9.3Light sources meeting the criteria for general lighting given
in Building Regulations Approved Document L2(17)(reproduced from
Building Regulations Approved Document L2; Crown copyright) Light source Types and ratings
High pressure sodium All types and ratings Metal halide All types and ratings Induction lighting All types and ratings
Tubular fluorescent 26 mm diameter (T8) lamps; 16mm diameter (T5) lamps rated above 11W, provided with high efficiency control gear; 38 mm diameter (T12) linear fluorescent lamps 2400 mm in length
Compact fluorescent All ratings above 11 W
Other Any type and rating with an efficacy greater than 50 lumens per circuit watt
Table 9.4Light sources meeting the criteria for display lighting as given in Building Regulations Approved Document L2(17)(reproduced from
Building Regulations Approved Document L2; Crown copyright) Light source Types and ratings
High pressure sodium All types and ratings Metal halide All types and ratings Tungsten halogen All types and ratings Compact and tubular All types and ratings fluorescent
Other Any type and rating with an efficacy greater than 15 lumens per circuit watt
Table 9.5 Advantages and disadvantages of tungsten filament (GLS) lamps
Advantages Disadvantages
Low purchase price Low efficacy, i.e. 8 to 15 lm·W–1
Excellent colour rendering Short life, usually 1000 hours Immediate full light when High running costs switched on
No ballast required Ease of dimming
Sparkle lighting effects can be created
Operates in any plane (universal operating position)
Table 9.6 Advantages and disadvantages of tungsten halogen lamps Advantages Disadvantages
Life of 2000 to 5000 hours Lower efficacy than low and high depending on type pressure discharge lamps Excellent colour rendering Transformer required for low
voltage lamps
Brighter, whiter light Operating positions of double ended types is limited to horizontal No ballast required Requires careful handling Sparkle lighting effects can be
created Can be dimmed
Immediate full light output when switched on
Lighting design 9-7
(MBF). The colour rendering properties of the SONrange, particularly the SON-DLlamp has increased the range of applications from industrial use to some commercial applications. The efficacy of the MBI lamp is generally lower than the SONlamp but comparable to that of the SON-DLlamp.
The increasing popularity of free-standing and wall- mounted uplighters means that these high pressure lamps are now being used in office installations, although it is advisable to check the colour rendering characteristics before fitting an entire installation. Metal halide and high pressure sodium lamps operated on standard control gear have significant run-up and re-strike times, limiting their use with lighting control systems.
The advantages and disadvantages of SONlamps are shown in Table 9.9.
9.4
Control gear (ballasts)
All discharge lamps require a ballast to start and control the lamp and, possibly, power factor correction. Matching the control gear to the lamp achieves the optimum lamp performance and circuit efficacy. Until recently, ballasts consisted of a wire-wound choke with losses representing 10–20% of the total load. Low-loss wire wound ballasts are now available which are specifically designed to be more energy efficient.
High-frequency (around 30 kHz) electronic ballasts are available for a wide range of fluorescent and compact lamps(21). These can reduce losses by more than 50% and, as the efficacy of a fluorescent tube increases at high fre- quency, this provides further energy savings. Additional advantages are virtually instantaneous starting, the possibility of dimming, flicker-free lighting, softer starting conditions that increase lamp life and a power factor of 0.95. It should be noted that there have been cases of interference between some older types of high frequency ballast (operating at frequencies lower than 33 kHz) and infra-red computer mouses. This should not occur with later (33 kHz) ballasts.
Electronic ballasts for lower ratings of metal halide (MBI) lamps are being introduced. These provide faster warm-up
periods, instant re-strike, improved circuit efficacy and extended lamp life, but are more expensive than wire wound ballasts.
Ballasts for fluorescent and compact fluorescent lamps are now covered by an efficiency labelling scheme.
Building Regulations Approved Document L2*(17)defines high efficiency control gear as low loss or high frequency control gear that has a power consumption (including the starter component) not exceeding Table 9.10
9.5
Lighting controls
Effective control of electric lighting is the key to realising the potential energy saving from daylight. The control system for the electric lighting should reduce light output when daylighting levels are adequate, and when the space is unoccupied. The integration of daylight and electric Table 9.7 Advantages and disadvantages of tubular fluorescent lamps
Advantages Disadvantages
Low running cost Excessive switching shortens life High efficacy Requires ballast
Up to 8% energy saving when Can be dimmed but requires special replacing equivalent 38 mm ballast and dimmer
lamps on switch-start circuits
Long life in normal use Limited operation at low ambient temperatures
Minimal reduction of light output through life
Prompt start and restart with quick run-up to full light output Very good to excellent colour rendering
Universal operating position
Table 9.8 Advantages and disadvantages of compact fluorescent lamps (CFLs)
Advantages Disadvantages
Low running cost Excessive switching shortens life Replacement for tungsten lamps Ballast required (but built-in on
some lamps)
Five times the efficacy of Not suitable for use on standard equivalent tungsten lamps domestic dimmers
Average life of 8000 to Limited operation at low ambient 10 000 hours temperatures
Very good colour rendering Prompt start and restart, and quick run up to full light output Four pin lamps can be dimmed with suitable ballast and dimmer Universal operating position but light output may be reduced with some types for certain positions
Table 9.10 Maximum power consumption of high efficiency control gear as defined in Building Regulations Approved Document L2 (reproduced from Building Regulations Approved Document L2(17) ;
Crown copyright)
Nominal lamp rating / W Control gear power consumption / W Less than or equal to 15 6
Greater than 15, not more than 50 8 Greater than 50, not more than 70 9 Greater than 70, not more than 100 12 Greater than 100 15
Table 9.9 Advantages and disadvantages of SONlamps
Advantages Disadvantages Low running cost High purchase cost
High efficacy Moderate colour rendering limits use for general interior lighting Very long life Requires ballast
Universal operating position Requires 1.5 to 6 minutes to reach full output
Delayed restart when hot on most lamps
9-8 Part A: Designing the building
lighting requires planning, the correct choice of light source and the correct controls to facilitate it. Daylight in a building will not in itself lead to energy efficiency. Even a well daylit building may have high energy use if the lighting is left on because controls are inappropriate. Case studies have shown that in a conventionally daylit building the choice of controls can make up to 30–40% difference in lighting use.
Lighting controls should ensure that light is provided in the right amount, in the right place for the required time(22–24). Table 9.11(25) provides guidance on the selection and application of lighting controls. Further details on implementing lighting controls can be found in CIBSE LG10(4) and CIBSE Guide H(25), which also discusses human interaction with automatic lighting control.
There are many factors influencing the specification of lighting controls, including:
— occupancy pattern — available daylight
— type of lighting (i.e. can it be dimmed?) — the desired level of control sophistication — capital costs and the potential for saving.
Even with efficient lamps and luminaires, the energy used for lighting can be wasted in various ways(23). For
example, users cannot be relied upon to turn lighting off when they leave an area, or when daylighting has increased. Exhortation can be helpful in the short term, but the ideal solution is to provide manual ‘on’ switching and some form of automatic ‘off’ switching. Energy is also wasted where a large area of lighting is controlled by a small numbers of switches, or where the switches are not located in convenient positions. Clear labelling of manual switches will also help avoid energy being wasted.
The choice of the number of control zones is a balance between cost and energy saving. The more zones of electric lighting, the better the match between lighting and demand. Zones should start at the perimeter and work away from the windows, corresponding to the reduction in daylight factor (see section 4). It is generally cost-effective to have zones from 1.5–3.0 m deep since this coincides with the minimum module for one person.
The five basic methods of lighting control that can be used separately or in combination are:
— localised manual switching — time control
— reset control (timed off, manual on) — occupancy control (presence detection) — photoelectric switching and dimming. Table 9.11Recommended types of lighting control(25)
Type of space Recommended options for stated lighting type and occupancy
Daylit Non-daylit
High occupancy Low occupancy High occupancy Low occupancy Owned: e.g. small rooms for Manual by door Manual by door Manual by door Manual by door one or two people such as Flexible manual Flexible manual Flexible manual† Flexible manual† cellular offices Timed ‘off’, manual ‘on’ Timed ‘off’, manual ‘on’ Presence detection†
Photoelectric dimming†
Shared: e.g. multi occupied Flexible manual Flexible manual Flexible manual† Flexible manual areas such as open plan offices Timed ‘off’, manual ‘on’ Timed ‘off’, manual ‘on’ Time switching† Presence detection† and workshops Photoelectric dimming Photoelectric dimming†
Presence detection†
Temporarily owned: e.g. Local manual Local manual Local manual Local manual meeting rooms and hotel Flexible manual† Presence detection Presence detection† Presence detection bedrooms,where people expect Presence detection† Flexible manual† Flexible manual† to operate the lighting controls Timed ‘off’, manual ‘on’† Timed ‘off’, manual ‘on’† Timed ‘off’, manual ‘on’† when present Photoelectric dimming† Key control† Key control†
Occasionally visited: e.g. Not applicable Presence detection Not applicable Presence detection storerooms, book stacks in Full occupancy linking† Full occupancy linking† libraries, aisles of warehouse Local manual† Local manual†
and toilets Timed ‘off’, manual ‘on’† Timed ‘off’, manual ‘on’† Key control† Key control†
Unowned: e.g. circulation areas Photoelectric dimming Full occupancy linking Time switching† Full occupancy linking where people expect their way Photoelectric switching† Presence detection† Presence detection† Presence detection† to be lit, but often do not expect Timed ‘off’, manual ‘on’† Timed ‘off’, manual ‘on’† to operate lighting controls Photoelectric dimming†
Photoelectric switching†
Managed: e.g. atria, concourse, Photoelectric dimming Photoelectric dimming Centralised manual Centralised manual entrance halls, restaurants, Time switching Time switching Time switching Time switching
libraries and shops, where Centralised manual Centralised manual Programmed scene setting† Programmed scene setting† someone is in charge of the Photoelectric switching† Photoelectric switching† Full occupancy linking† lighting, but usually too busy Programmed scene setting† Programmed scene setting†
to control it; individual users Full occupancy linking† do not expect to control the
lighting
Lighting design 9-9