Depending on the exact choice of T5 tube, energy savings of up to 45% are achievable (but this may bring with it a reduction in illumination levels).

The Technology
Conversion kits are available which will work in existing fittings containing switch start, mains frequency fluorescent tube ballasts. The kits convert the fittings to use energy efficient, high frequency ballasts and accommodate the smaller diameter T5 tube.

There are two main types of conversion kits (see picture below):

• Tube end type – kits which include a replacement starter and two separate components to fit over each end of the T5 tube. The tube is then slotted into the existing fitting.
• Baton type – one piece kits which slot into the existing fitting and into which the T5 tube is placed.

Application
The kits can be used on lighting in many commercial and office settings, as well as other locations such as schools.

The conversion kits can accommodate most tube lengths, and allow for changes from T12 and T8 tubes to T5 tubes. They are not currently available for 8 foot fittings.
The majority of the savings come from converting from mains frequency to high frequency ballasts. Savings will be significantly reduced if your existing lighting already has high frequency ballasts.

The following table describes the recommended lux levels for a selection of different tasks (Lux is a measure of the brightness produced by the lighting). Given the lux levels required, and the distribution of the light fittings, a selection needs to be made between standard and high efficiency T5 tubes so that the maximum energy saving is made without impairing lighting levels. A supplier should be able to assist with this process.

Commissioning procedures
The installation and commissioning of the plug-in retrofit conversion units and tube should be done in accordance with the manufacturer’s recommendations. It is however advisable to trial the retrofit units and tubes before switching all fittings to ensure that the specification has been accurate.

Ensure that the correct lighting lux levels are maintained and checked (see Application section).

If electrical wiring is altered electrical checks should include installation and commissioning to the current edition of BS 7671 IEE Electrical Wiring Regulations.

Common problems
Installing the retrofit units is a straightforward process, with few difficulties likely to be encountered.

Converting fluorescent tubes from T8 to T5 may cause a reduction in overall lighting lux levels, which, if lighting levels were previously only just acceptable, may cause them to become unacceptably low. In these situations it is important that in choosing between standard and high efficiency T5 tubes, the higher lumen tubes are selected, maximising the light output.

Some fittings may offer restricted physical access, which may influence the type of adapter chosen.

Similarly, in some mirror reflector light fittings, the presence of the baton type adapter’s “spine” can interfere with light output.

In all cases, it is recommended that a small trial installation is carried out before any bulk orders are placed.

Finding a supplier
A web-search is the best way to find a supplier for T5 retrofit conversion kits but satisfactory references should always be sought.

As an alternative, lighting is supported by the Government’s Enhanced Capital Allowances Scheme.
Individual lighting products are not included on the Energy Technology Product List, however manufacturers/supplier who successfully complete the Energy Technology List supplier assessment process do have their contact details listed on the ECA website and can be found at www.eca.gov.uk

The business case
The business case for a typical retrofit conversion unit, installed in an existing 1,500mm mains frequency switchstart fluorescent fitting, is as follows:

The T8 tube plus the mains frequency ballast would use a total power of typically 73W, whereas the T5 tube plus high frequency ballast uses typically 49W, a saving of 2W.

Assuming that the lighting is used 12 hours per day, 5 days per week, 52 weeks per year, a total of 3,120 hours per year changing the lighting would save 75 kWh per year. With a typical electricity cost of 7.9 p/kWh this would save £5.93 per year, leading to a payback period of approximately four years.

There are also savings as the tube life is increased, electrical circuit losses reduced and less demand on the air conditioning due to the lower heat output from more efficient lighting.

However, in this particular case, the light output would be reduced by 17% which may not be acceptable in some cases.

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