They don't need changing, they just fail, usually when the cathode wears out (due to electron bombardment). T5 lamps are electronically ballasted and show hardly any lamp lumen depreciation (loss of brightness), and the tri-phosphor lamps don't suffer much from phosphor depletion. You can easily get 2 or 3 years from a lamp, and with one switch on/off in any 24 hour period, live could be a lot longer, particularly if you have a 14W lamp on a 14 - 24W rated ballast etc.For as long as it turns on...
As the author of that article allow me to explain.skeletonw00t said:I saw in PFK this month it had a "top tip" to replace tubes every 12 months to "significantly increase the lighting over your aquarium" page 47... Seems there are still conflicting opinions on the issue of replacing tubes.
George Farmer said:As the author of that article allow me to explain.skeletonw00t said:I saw in PFK this month it had a "top tip" to replace tubes every 12 months to "significantly increase the lighting over your aquarium" page 47... Seems there are still conflicting opinions on the issue of replacing tubes.
That specific tip was in reference to a recent experience regarding an aquarium makeover.
The client had 4 x T8 fluorescents over their Juwel Trigon 350. I believe the Juwel ballasts are electronic, even the old T8 type.
The bulbs were old, at least 18 months. 2 x Hagen Power-Glo, 2 x Life-Glo.
I tested the PAR at the substrate using an Apogee meter.
With the old tubes it was less that 10umol in the corner.
With the new tubes it was over 20umol. Same brand and model type.
So as you can see that's over 100% increase in light by swapping old for new tubes. There was some hard water deposits on the old tubes but not a significant amount.
I can't comment on whether this applies to T5 and have every faith in Darrel's comments.
The life of a fluorescent lamp is measured in a number of different ways. Two measures tend to be employed: mortality (i.e. the number of operating hours elapsed before a certain percentage of the lamps fail) and lumen output (i.e. the depreciation of the lumen output over time). Both sets of data are useful measures. The rated life of tubular fluorescent lamps can range from 6,000 hours up to 60,000 hours, or more, depending on lamp type and control gear.
They can have a lifetime of up to 23,000 hours for normal T5 lamps (90% service lifetime at 12 hr switching cycle). Special long life lamps also exist where the life time is up to 68,000 hours with the same energy efficiency. Halophosphate lamps have a lifetime of only 6,000 hrs and are soon to be discontinued under the EuP Directive. All tri-phosphor lamps have a high CRI (typically >80) and are also 20-30% more efficient than halo-phosphor types with low CRIs. Better energy saving can be achieved when the lamps are operated on an electronic HF-ballast,........
Not if they're the Juwel 45W T5's with the oddball length.foxfish said:They cost a couple of £ each & you can experiment with different colours too