Have two twin 6 ft fittings over the workbench in the workshop. Quite old
- just basic units from TLC with chokes and starters.
One of them started to flicker, so I got two new tubes and starters from TLC. They are 25mm rather than the original 38mm, which TLC don't seem to do any more.
However, the light output from them is well down on the originals. Surprising given how tubes age. And one of them wouldn't strike fully - it was sort of even dimmer along most of its length.
The blurb does sort of say they give increased light levels with electronic ballasts. Which implies they're not as good with low frequency?
Is it possible to still get the older tubes? Given the relatively short times they're in use it would take a long time to get back the costs of electronic ballasts.
25mm = 1 inch = 8 x 1/8ths of an inch = T8
38mm = 1.5 inch = 12 x 1/8ths of an inch = T12
T8 are a more energy efficient replacement for T12.
You normally* need to replace the ballast when fitting T8 as they have a lower current requirement than T12. It does not have to be an electronic ballast, just one designed for T8 lamps. Properly set up, although a lower wattage, the T8 should give slightly more light than a T12.
Some electronic ballasts will run either equally well.
T8 has been the preferred size for about 30 years, but a quick Google suggests T12 are still available.
Yes. You can still get the T12 38mm ones but you have to blag your way into an electrical wholesalers - you won't find them in (m)any sheds.
The T8 tubes are allegedly more energy efficient with the right ballast but ISTR you have to change both at the same time. I recently had to find a couple of T12's in a hurry. Local firm got them for me next day.
I reckon the insulation in the coils breaks down in time. Just replaced an ancient T12 unit for my aunt that had been staggering on for ages and ended up with a sort of lava lamp effect[1]. I rescued the tube for a friend who has a selection of SRS (ie starter motor free) florries that only work with T12 tubes and it's fine.
Whole new units are quite cheap in TS.
[1] I don't mean lava lamp but one of those oil filled rotating discs mounted in a spot light that I can't remember the name of.
Implies they are a suitable replacement. No mention of changing the conventional ballast - just that an electronic one will be better. And I knew that. Sadly, electronic ballast on their own tend to be more expensive than complete fittings.
OK then the right sort of old school electrical wholesaler that still has a stock of the things lurking in some dark corner. They were once common in industrial gear and as such are still not too hard to find around Manchester - I was surprised to see some in a general hardware store whilst on holiday in North Lancashire. They are no longer common.
Not too many of them round here. Just the more usual chains. And, I'd say, with the cost of premises these days not many will keep old stock for long. They'll flog it to an Ebay trader. ;-)
After being stored unused, you need to run them for a few hours to get the mercury properly distrubuted. T8's have a noticable run-up period of several minutes in any case, before the mercury vapour pressure is in equilibrium with the amalgam resevoir (same reason as CFLs and T5's, but not as bad as either of those).
Very typical after a long period of no use. Dim potion is often tinged purple, due to no mercury being present and the argon is forming the discharge, which doesn't emit any UV to excite the phosphor.
That was true, but the EU now requires electronic ballasts to underrun T8 tubes to generate energy savings, instead of increased light output. You will find the total power draw of an electronic ballast plus tube is actually less than the marked power rating of the tube alone.
T8 lamps in the UK were very specifically designed to run on the original T12 magnetic ballasts and starters. The inductance of the two types of ballast is identical. (This doesn't work so well on European 220V mains as the exact match is only for 240V mains. It doesn't work with T8's in the US which have a lower power rating than European T8's and do require different control gear from their T12 cousins.)
Only if you can find someone with old stock. T12 tubes vary enormously in efficiency, depending on the phosphor used. Unfortunately, the more efficent they are, the poorer the colour rendering. That was the tradeoff with halophosphate tubes.
They aren't manufactured anymore and can't be imported into the EU (except special purpose lamps such as UV tubes), but you might find some stock.
You don't need to change a magnetic switch-start ballast. T8 tubes were designed to work on T12 magnetic switch-start ballast in 240V mains countries.
That document applies to US T8 tubes only, which are a different specification from the rest of the world. Their 120V mains spawned a wide variety of different control gear designs (because simple series ballast can't work on tubes over 2' long on 120V mains), and it was not possible to design a T8 retrofit which worked across the variety of control gear in use in the US market.
You are, as usual, brilliant. The offending one has come up in brightness after being used for a while. They are over work bench lights - so only switched on when that is in use.
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