Gemcell Australia

Back in the 70's E.L.O. was a band in the Top 40 chart; lighting troffers weighed about 10kg each, and nobody cared about energy savings as each twin forty consumed about 110 watts.

So you can't remember the seventies? Never mind, ELO has been digitally re-mastered and some of the troffers installed back then can still to be found in the ceilings of ageing buildings all around the country. Until recently, refurbishments happened about every seven years but excluded the installed lighting and the ceiling tiles. Today however, there are a swag of reasons why this approach isn't acceptable.

The oldest of the troffers were initially built for T12 40-watt lamps. Unless they had Rapid Start ballasts, they will still work with current generation 36-watt tri phosphor tubes, but the ageing paintwork and diffusers greatly reduce the amount of useful light that reaches the shiny new desks on the work area below. Many installations are slowly paying a high price for replacing the old ballasts one at a time as they finally expire. I don't know of any research into power factor longevity, but it is likely that a good number of old caps (designed for 0.8 correction) have silently given up the ghost. This won't affect the light output, but it doubles the line current in the luminaire to about 860 milliamps.

More recent installations weren't as clunky as the old battleships. In fact the budget troffer went the other way, providing as little colorbond metal as possible with a predictable lack of light output resulting despite the 83 watts it consumed. You don't have to look very far to find these installed, and they're still available though far less commonly sought after.

The ELO or Environmental Lighting Opportunity available today, is the chance to identify an old installation, and to present an argument to the client that a lighting upgrade is a good idea. Today you hear a great deal about T5 lamps. They are only 16mm in diameter and are shorter than the T8 lamps that they replace. As they have a more efficient construction, their 'Light Out' to 'Power In' ratio is up to 104 lumens/watt.

A twin-tube 28-watt troffer consequently puts out about the same light as the old ones did, but consumes just a little more than 60 watts; it has a possible lamp life of 30,000 hours on GE T5 Starcoat tubes and a Power Factor of almost unity. This means that less current flows in the circuit. When you consider that a one-for-one replacement of the installed lights is a "no-brainer" technically, the process becomes pretty simple. Although T5 tubes are shorter, the troffers still fit in a 1200 x 300 grid ceiling. You can even fit them in a continuous line as they no longer hang over at one end.

To close the sale you must convince the client that his office will look a whole lot smarter, that his staff will work more effectively under the new low glare installation, and that the upgrade will reduce the cost of energy bills.

In order to work out what the energy savings are going to be, you should take the following steps:

1. Work out the difference between the (instantaneous) energy consumed by the old and the new troffer. This could be from 22 watts to nearly 50 watts. Take 22 as our example.
2. Multiply this by the number of installed lights that will be replaced. Let's say 200-off for a typical office floor. The load is 4.4kW.
3. Now, if the lights are on 12 hours per day, 5 days a week, 50 weeks per year; that's 3,000 hours of burning time. Power consumed is 13,200 kWhrs annually. (Check the time clocks. It might be longer. If the lights are switched manually, they are often all turned on at 7am, off at 9pm or later and frequently left on overnight or on the weekend).
4. Find out from the power bill what the average energy cost is. Take the total bill excluding OPHWS, etc and divide it by the kWHrs logged for light and power. It is probably higher than you expected. Suppose it works out at 15 cents per unit.
5. Multiplying the energy cost by the power consumed and you discover that the new lighting will cut the power bill by $1,980 each year. In reality, it could save much more depending on all of the factors to be considered.

Where the monthly Demand component of the tariff is in kVA not kWatts, the improvement in power factor of the installation will reduce the electricity cost further. Add to this the obvious attraction of a modern low brightness louvre and it's no wonder the old tin boxes are finally disappearing.