Your rant about non standard lengths of these T4 tubes is not correct!
The numeral in T4 , T5, T8,... always denotes the tubes diameter in unity of 1/8 inch, and the length varies for ALL of these different types - also in a standardized manner - over the wattage.
Then please explain:
- why no one sells T4 tubes to match the length I had - anywhere online that I could find, even overseas.
- Hardly any local lighting or hardware stores carry practically any T4 tubes spare, and the rare one that did had every size but mine (close though).
- No one makes T4 LED replacement tubes, yet they do for the other sizes that do have standardised lengths.
- Why many sites (inc wikipedia) confirm that there is no standard, and that it basically what I found when I searched.
Perhaps in Germany, but elsewhere there doesn't seem to be any standard.
Sorry for that , Dave!
In EU, there obviously exists a standard / norm , i.e DIN EN 60081.
I assume, that on other continents, there also exist corresponding standards, even in Australia.
The Chinese manufacturers may well stick to these definitions also.
I append a diagram about my assumption, and it turns out to be correct, there's a linear dependency between length and wattage for the T4 tube.
Only complication visible in this diagram, is the different efficiency of the gas filling, as there exist also e.g. HE and HO types, High Efficiency and High Output types, that alters the current density for the same diameter, obviously.
So you can not only select by diameter / wattage.
But I assume, that the absolute length of the tube is given on the package.. so when dealing with the replacement of an FL, you definitely have to measure the length of your old tube.
Maybe the bathroom lamp manufacturer used a no name lamp manufacturer, which did not obey any standards..
Please specify, which exact length your old tube has.. maybe there's a replacement from German company OSRAM, which would fit, even in LED replacement.
Again, thanks for illuminating that problem!
Frank