Fluorescent Lighting

Fluorescent lighting can look good if chosen and installed well. But the all too common choice of a bare bulbed butt ugly glowstart fitting in the centre of the room with a tube chosen at random is a recipe for unpleasant lighting.

Fluorescent lighting is the most energy efficient lighting suited to widespread domestic use.

Types of fluorescent lighting

• Linear fluorescents have been with us since the 1930s.

• Circline tubes are a variation on the theme popular in the 1960s, and occasionally still found in homes.

• Miniature tubes have found use in emergency exit signs, torches, and small displays.

• HO high output and VHO very high output tubes are used in aquaria where high lighting density is required. These tubes have lower efficiency than standard tubes.

• CFL compact fluorescent lamps are designed to replace filament bulbs, and most have the ballast and lamp uilt into one package.

• CCFL cold cathode fluorescents are very thin tubes that backlight LCD monitor & TV displays. CCFLs are also used in scanners.

History

T12 tubes (1.5") were the only type of tube for many decades T8 tubes (1") have now mostly replaced T12s. T8s work happily in older T12 fittings. CFLs were developed to make fluorescent tubes work in the majority of domestic light fittings, which aren't large enough for 2' linear tubes.

Lamp sizes

Common British tube sizes include:

• 8' 125w & 100w (both T12)
• 5' 65w T12 & 58w T8
• 4' 40w T12 & 36w T8
• 2' 20w T12 & 18w T8

Less common tube sizes include:

• 6' 65w T12 (common decades ago) and 80w T12 (earlier standard)
• 3' 30/33w T12
• 21w
• 13w
• miniature tubes.... 4w, 6w, and ?

Good fluorescent lighting

Good fluorescent lighting needs the following points:

1 Hidden fittings & hidden bulb.

2 Uplighting

3 comfortable light level.

4 No flicker or flash

5 A tube of respectable quality. I like 3500K tubes, there are several good types to choose from, but there are also many unpleasant or poor light quality types of tube on the market.

6 Tubes of a size that makes keeping a spare practical.

For 1 & 2 - use trough fittings.

For 3 - Choose around a quarter the power you would use with filament bulbs.

For 4 - An electronic ballast fitting avoids all the flicker and flash of cheap glowstart fittings.

For 5 - see the next section

For 6 - 2 foot tubes are easiest to store, 4' are next best. I would not normally recommend larger tubes for domestic use.

Fluorescent tube types

There are many different versions of white, ranging from excellent quality to dire. Buying tubes at random can give you unsatisfactory lighting. Tubes are normally marked with their colour on on the glass at one end. Many shop assistants are unaware that there are different versions of white, or that the tubes are thus marked.

The Different Whites

Tubes marked simply as 'white' are not of the best quality, though not the worst. I can recommend 2700K and 3500K tubes, but I don't recommend higher colour temperature tubes for household use.

2700K is the colour of GLS filament bulbs, so it matches perfectly with traditional filament lighting. 2700K is a warm slightly yellowy white.

3000K is the colour of halogen bulbs, cleaner and crisper than 2700K. Some 3000K tubes don't have good CRI*, so if you want 3000K to match halogen its best to pick the more expensive triphosphor tubes rather than halophosphates.

3500K will not match other light sources, unless they're also 3500K fluorescent, but used alone they give a clean fresh and slightly cool look. These are my favourite halophosphate tubes for domestic lighting.

4000K look cold and anaemic, and 4500K and up are like the old fashioned 'cool white' tubes that once gave fluorescent lighting such a bad reputation. There are also proprietary numbering systems, such as the Philips system.

'Cool white' and 'daylight' are ill suited to domestic use.

Phosphor types

As well as the different shades of white, there are 2 phosphor families in use today: halophosphate and triphosphor.

The older halophosphate T12 tubes come in many versions of white, and have a wide range of CRIs from the 50s (really grim) to over 90 (excellent).

T8 Triphosphor tubes have consistently higher CRI than halophosphate, slightly higher lumen output per watt, and output doesn't reduce as much over time as halophosphates. These tubes also cost more.

• CRI = colour rendering index, a measurement of how well fluorescent tubes render colour. 100 is perfect, 50 is pretty grim.

Fitting & ballast Types

Glowstart

Glowstarts are the most popular ballast in Britain. They are easily identified by their starting behaviour, they flash badly during starting.

Glowstart fittings use a plug-in glowstarter with limited life. If a light malfunctions, replace the glowstarter first. If it still doesn't work, replace the tube.

Glowstarters

There are 3 or 4 main types of glowstarter, all of which look the same. All are a normally plastic can with a 2 pin base.

• Most glowstarters are rated for 20-65w, and are suitable for most lamps.
• 4-20w glowstarters are for the lower power tubes only
• 100-125w glowstarters are for 8' tubes only
• Series starters are for fittings that run 2 tubes in series.

Thermal

Thermal starters are now rare. The starters have 4 pin bases. They start with no flashing. If the light is switched off for a second they will generally not relight straight away. More modern 4 pin starter cans may contain a glowstarter.

Electronic

There are various types of electronic ballast. Nearly all start with no flashing.

Others

There are also some uncommon ballast types that are unlikely to be found in housing today.

See Also

Rewiring Tips Discharge Lighting Suppliers