These little bipin slide in lamps seem to be going up in price or being hard to get hold of. I'd have thought that we would be encouraged to use such low voltage devices,. I may be forced to change the whole lamp in my porch for something that takes more modern lamps, which seems silly to me. One shop locally wanted 8 quid for a tube we used to get for a couple of quid recently. Brian
8W T5 12" lamps are £2.27 on Amazon, with free P&P
... or 79p each if you buy ten.
They're not common high-street purchases anymore (if they ever were). As Colin says, mail order is your best bet, or perhaps one of the sheds.
Those short fluorescent tubes are not very efficient - the fixed power losses at the tube ends become a significant part of the total power consumption. There are some LED replacements for them, but they are even less common in this size.
Replacement T5 tubes for under-cabinet kitchen lights are in screwfix and toolstation, but beware minor differences in tube length...
3 quid plus VAT at TLC.
Their main use is for emergency lighting, but newer fitting use LEDs
T5 tubes are all standard lengths.
However, T4 tubes aren't. Come to think of it, OP didn't specify T5 or T4.
Just checked my spares cupboard, and you're right, it's the T4 ones that have caught me out before.
Also I have an inexplicably large quantity of spare long and short G23 tubes
They sure aren't. I have some that are 580 mm.
On 05/11/2014 09:25, Andrew Gabriel wrote: ...
These days, if I can't find something I want in a shop fairly quickly, I always look on line and almost invariably find it.
I have some supposedly 221mm filament tubes that don't fit the fittings in a display cabinet, but I am apt to blame the tolerances of the fittings as much as the lamps.
Wattage that is. I must proof read more..
I have now nicked one from a greenhouse. The lights are not for me of course, but for those who cannot see without light..grin. Brian
So how are they less efficient than, say the concertinaed bulb replacement types. Is it the electronic ballast that does the trick? Ats far as i can recall, they have heaters at the ends to stir it up and a simple way of giving higher voltage pulses to strike the tube and ehen it runs at normal voltages thereafter. The electronic ones seem to not have to heat the filaments, so presumably break down the strike voltage thing by using an invertor.
Brian
These seem to come in three lengths.The shortest are as used in torches etc, the one I wont is the middle length and the longer ones which also seem to come in 21 watt versions as well. Brian
Hmm, well I don't know the modern classification of this one its a fitting made by Thorn, out of metal, and it does tend to buzz rather. Brian
Just when you think its all simple, its not.
Not measured this one but it was the standard in its day, long before light fittings became Luminaires. Brian
Re your sig line, no frustration is trying to find your slippers in bare feet. Brian
That will be a T5 tube, which is a standard 12" 8W tube.
(T4 tubes always run on electronic control gear which won't buzz).
T5 means Tubular, 5/8th inch diameter. (Similarlay, T4 are 4/8th inch diameter.)
Original T5 tubes (which go back to the 1950's) are 4W, 6W, 8W, 13W (6", 9", 12", 21" respectively). They are not efficient, but continued to find uses where designers needed a thin light source or low power with longer life than a filament lamp.
20 years ago, a new set of T5 tubes were introduced in Europe to enable luminares to be better designed by using a smaller light source than the T8 tubes. These start at 14W and go up to 80W. The tubes have metric lengths which are all multiples of 300mm minus a fixed 37mm (for lampholders), to enable them to be used with modular kitchen units, modular ceiling lights, etc, which tend to all be multiples of 300mm in Europe. They are also used in the US now, although the logic of the choice of lengths is lost on them, and they quote the lengths to the nearest foot;-) There are two* power ratings in each size, a lower power higher efficiency tube, and a higher output but lower efficiency tube. For example, the shortest tube is just under 600mm, and is available as 14W or 24W. These new T5 tubes are only supported with electrconic ballasts. *Largest size has three different power ratings for historic reasons.
The heaters are only powered at tube start-up (and in some cases, dimming ballasts will power them at other times too).
When the tube is running, excess power is generated in the area just around the heaters (known as the cathode fall region which emits no light) and on the heater surface itself, and it is not necessary to apply power to them to keep them hot.
The power dissipated at the tube ends will be the same in the short 4W tube as it is in the longest (13W) tube in the same range. I don't have the figure to hand, but in these tubes I suspect that's over 1W at each tube end, so that's over 2W of the 4W which is very significant, whereas
2W from the 13W tube is less significant.HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.