Lighting

As lighting is a major energy consumer in commercial buildings it is important to ensure you are using lighting as efficiently as possible.

Types of Lights

Many lighting types and systems are available; the following are some of the most common:

Fluorescent Tubes
Fluorescent tubes generally provide a cost effective, energy efficient lighting option. This is the most common form of lighting used in the commercial environment. Light is produced by passing a current through the low pressure mercury vapour in the tube. This produces invisible ultra violet light which strikes the phosphorous coating on the inside of the tube. It is the phosphorous coating that actually radiates the visible light. Different colours can be created by using different types of phosphorous material.

All fluorescent fittings use a ballast to limit the current in the tube. Older fittings only used a magnetic type ballast, however new fittings are now available with electronic ballast. These use less energy and should be used whenever a light fitting is upgraded or a ballast is changed.

The early fluorescent tubes where 38mm in diameter (T-12 tubes). Newer technology has produce T-8 (26mm tubes). These use less energy for the same light output and should be used whenever a new tube is required.

The latest development is the T-5 tube and fittings (16mm tubes). These cannot be interchanged with the T-8 or T-12 tubes, so if changing to this latest technology, new light fittings will be required. T-5 fittings only use electronic ballasts and produce more light output per watt than the older T-8 tubes. Therefore less energy is required to produce the same light, saving energy, CO2 emissions and money.

Fluorescent lamps: T-5, T-8 and T-12 (from top to bottom)

Compact Fluorescent Lamps (CFLs)

These are also fluorescent tubes; however the tube is folded up to form a lamp to fit into a standard light fitting. The CFL is designed to replace the old incandescent lamp and use about 20% of energy for the same light output and also last up to 10 times longer than an incandescent lamp. The costs of CFLs have reduced over recent years, as well as the size and shape making them more affordable to buy and easier to use. Wherever possible, replace the incandescent lamps with the Compact Fluorescent Lamps, particularly if the lights are on for extended periods.

Incandescent Lamps

This is the oldest and least energy efficient method of producing light and is where electric lighting started. The current design dates back from the 1920s and only a small percentage energy input produces light, with the remainder producing heat. The light (and heat) is produced by passing a current through a tungsten filament. The filament heats up to glow white hot, producing the visible light. Over time the tungsten filament evaporates, leaving the black deposits on the inside of the glass bulb, eventually failing. Where possible, these lamps should be replaced by CFLs as discussed above. It is very likely that due to poor efficiency of incandescent lamps, these lights will be banned from being sold in the near future. Typically an incandescent lamp will operate for 1000 hours

Halogen Lamps

These are also incandescent lamp technology, but modified to include a small amount of halide gas inside the lamp. This allows the lamp to run hotter without destroying the filament. The evaporated tungsten from the filament combines with the halide gas and is deposited back onto the filament when the light is turned off.

Efficiency of a halogen lamp is not much better than an incandescent lamp, and should only be used for display lighting, or outdoor floodlighting where the light is turned on for a short period of time. They should not be used for general lighting due to high energy use and maintenance costs.

These halogen lamps can be made very small making them useful for display and accent lighting, especially the low voltage lamps. However these need a transformer (both magnetic and electronic are available) and energy is lost in the transformer as well.

Latest technology in halogen lights is IRC. IRC stands for “Infra Red Coating”, which is a coating on the inner bulb to keep more heat inside the lamp, meaning less energy is required to keep the filament hot, while still producing the same amount of light. A 35 Watt IRC halogen provides the same light as a 50 Watt standard halogen, and last twice as long as well reducing both energy for lighting and energy on reduced air conditioning load.

Examples of Halogen lamps

High Intensity Discharge Lamps

High Intensity Discharge Lamps (HID) are lamps used for high spaces such as warehouses, factories and outdoor floodlighting such as streetlights.

Most common types are Metal Halide (white light), High Pressure Sodium (gold colour light) and Mercury Vapour (white light). The Metal Halide and High Pressure Sodium produce the highest light output per watt, which is why they are extensively used for street lighting. In the near future Mercury Vapour lamps will be discontinued due to their poorer efficiency and mercury content.

All these lamps work by passing a current through the gases inside the bulb, and just like fluorescent tubes, a ballast is required to limit the tube current. More efficient electronic ballast are becoming available and should be used whenever possible.

Light Emitting Diodes (LEDs)

LEDs are small, very energy efficient, using low power per light output, and run cool compared to other forms of lighting.

Light Emitting Diodes or LEDs have been around since the 1970s and have been used for small displays and indicating lamps. Recent technology changes have meant that higher light outputs are available and the colour range is also increasing.

Many manufacturers are experimenting with LEDs producing white light, and many different sized lamps are available to replace incandescent lamps, halogen lamps and even fluorescent tubes.

Cost of the LED lights is still very high due to low quantities being made and the technology of white light still being in its infancy.

Over the next few years technology will improve the white light LED, costs will come down and the LED will become more readily available.

Examples of LED lights

Lighting Control

Lighting is usually just controlled by an ON/OFF switch. The users of the area being lit are therefore totally responsible for turning these lights “ON” and more importantly “OFF”. Often light switches are “too far away” or reasons such as “I’m back here in half an hour” or “a work colleague will be here soon” are used for not turning the lights off.

Control of lighting is an important factor to ensure lights are not left on unnecessarily. Some ways that this can be done is through incorporating the following control features:

Occupation Sensor

An occupation or motion sensor turns on the lights automatically when someone enters the room, and turns off again after a period of non movement. These are ideally suited to areas that are not occupied continuously such as conference rooms, break rooms, toilets and individual offices.

Examples of Occupation Sensors

Daylight Sensor

A daylight sensor only turns lights on when the natural light level diminishes below the sensor light level set-point. Ideal for outside lights, or lighting in spaces that receive a lot of natural light. Often a daylight sensor in conjunction with a time clock is ideal for outside lighting, the light turns on at dusk and turns off at a set time, say 11pm.

Time Clock

A time clock allows lighting, or other equipment to be turned on and off at set times. As described above, these work well with a daylight sensor. Care must be taken to check the current time is correct, time is changed with daylight savings, and that the lights or not turned on too early or too long. If accurate dawn and dusk control is required, astronomical time clocks are available that automatically adjust daily for seasonal variations.

Light Switching - Labelling

Labelling of switches is important, especially in larger areas with multiple switches, and only part areas being used. More often than not all lights are being turned on as users do not know which light switch control what area.

Light Switches - Circuits

Having lights connected in multiple circuits allows users to turn lights on only in areas where lighting is required. The circuits should be arranged for flexibility, such as every second light in each row on a different circuit to allow only half the light to be turned on, without creating any dark areas. Arranging lights circuits in rows may leave large gaps between the lights. Although this should be carried out at design stage, as areas are refurbished, or change of use occurs, light circuits should also be reconsidered.

Energy Saving Tips

Lighting related energy saving tips can be found on the Energy Saving Tips page by clicking here: Energy Saving Tips

Maintenance

Relamping

Over time, the light output of a lamp reduces significantly and is called lumen depreciation. A fluorescent tube may still be going after 15,000 hours; however it will only produce half the light compared to a new tube.

The same applies to most other lamps, and a recommended practice is to relamp in batches, not one lamp at a time as the lamp fails. This is done for 2 reasons:

1. Replacing single lamps at a time significantly increases the cost due to multiple trips having to be made by the repair person.
2. When a lamp fails, it probably means that all the other lamps are nearing their end of life, the light output is much lower than from new lamps and the workplace will be much brighter, reducing the need for task lamps.

Fluorescent tubes and other lamps containing mercury should be disposed of in a safe manner: Medi-Chem Waste Services Ltd is the only company in New Zealand providing a “zero-to-landfill” service; please visit their website for further information: http://www.medichem.co.nz/fluorescent-waste.htm#bin

Cleaning

Lamps, reflectors and diffusers all get dusty and dirty over time. This reduces the light output considerably. Depending on the environment, regular cleaning will help keep the lighting levels to the required standard.

PCBs

Old fluorescent lights fitting may have capacitors inside the fitting containing PCBs (polychlorinated biphenyls). PCBs are a toxic chemical and must be disposed of safely. In New Zealand, Tredi New Zealand Ltd is the only company handling PCBs, please visit their website for further information: http://www.tredi.co.nz/pcb.html

Replacement of T-12 Tubes (38mm)

All T-12 (38mm) should be replaced with T-8 tubes (26mm) due to their age and inefficiency. This will provide a 10% savings, with the same amount of light output.

For safe disposal of old fluorescent tubes, please see the “relamping section” above.