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Old 24th Mar 2019, 10:49 pm   #121
julie_m
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Default Re: The demise of the fluorescent tube

There is still some life left in fluorescent tubes. They were always fairly efficient light sources, especially the old ones with plenty of copper and steel in the ballast to reduce losses due to self-heating and magnetic saturation. Glow starters probably didn't do the tubes any favours, though ..... I'd expect longer life and greater light output with a good, modern switched-mode "ballast", especially if it applied proper pre-heating.

Nowadays, with everything pared to the bone, it's anybody's guess how efficient a fluorescent light fitting will be in practice; but they are still much better than tungsten filament lamps in terms of photons emitted per Joule of energy supplied.
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Old 25th Mar 2019, 4:03 pm   #122
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Default Re: The demise of the fluorescent tube

In industrial situations, fluorescents are rapidly going the way of the Dodo: a friend is professionally involved with facilities-management contracts and his company (which maintains hospitals, petrol-stations, bus-stations, train/aircraft-maintenance facilities etc) has always had a policy of 'lifing' all lamps: basically they don't respond to service-calls for a single fluorescent being 'out', they wait until at least 5% of them have failed then they negotiate some downtime and replace the lot.

[replacement generally involves a self-propelled scissor-lift: you can't have that driving around a factory, down a pedestrian underpass or across a petrol-station forecourt while the place is also open-for-business].

His guys used to have a few spreadsheets which were used to forecast lifetimes of different fluorescents (both tubular and CFL) based on brand, size and usage-pattern. Definitely a science not an art!

These days they're _always_ replacing fluorescents with LEDs when the time comes - driven by the demand of the operators to reduce power consumption [an open-24x7 motorway-service-station needs a lot of lighting!] and so the operators can boast of their 'green' initiatives.

I for one am glad to see the back of linear and compact-fluorescents!
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Old 30th Mar 2019, 12:44 am   #123
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Default Re: The demise of the fluorescent tube

The future is LED for large or modern premises with a significant lighting load.

It will however be regrettable when fluorescent lamps become unobtainable for use in heritage fittings or older premises.
I suspect that the more popular fluorescent lamps will be available for many years yet. The choice is however already declining.

Not only are T12 lamps now hard to find, but the more obscure colours are virtually extinct.
Tungsten ballast lamps for burning in series with a fluorescent lamp in place of the choke are now effectively unobtainable.
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Old 30th Mar 2019, 12:37 pm   #124
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Default Re: The demise of the fluorescent tube

Quote:
Originally Posted by emeritus View Post
I do wonder how reliable the LEDs will be in practice? We have had a number of our street lights upgraded to LEDs in the past year and about 5% are faulty, mainly by flickering on and off rather than failing completely. This affects both street lights and illuminated traffic island "Keep Left" signs.
I suspect that the LED modules are quite reliable as long as the heatsinking is up to the job, it is more likely the electronics driving them is the culprit, some designers do like to cut corners running devices very hot and forgetting that ambient temperature is not a constant.

Adrian
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Old 30th Mar 2019, 1:23 pm   #125
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Default Re: The demise of the fluorescent tube

Interesting that T12 tubes are now banned from sale here. I was in New York recently and in shops such as Home Depot T12 tubes were readily available on sale.
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Old 30th Mar 2019, 6:42 pm   #126
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Default Re: The demise of the fluorescent tube

The newer thinner tubes do not work in my luminaries that have Crompton "Snapstart" starterless ballasts. Fortunately I have some spares that I bought when I thought the old ones were failing, but turned out to only need wiping with wax furniture polish.
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Old 30th Mar 2019, 7:45 pm   #127
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Default Re: The demise of the fluorescent tube

I haven't seen T12 tubes for sale for a long time actually.

Reason that they're readily available in the US, is that they have a lower ignition voltage. Their working voltage may be lower as well, not sure about it.

The ignition voltage is probably the reason T8 tubes don't work in the Snapstart models as well. Maybe put a few UV LEDs or a radioactive source behind the tube
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Old 31st Mar 2019, 12:34 am   #128
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Default Re: The demise of the fluorescent tube

Most types of T12 lamp do indeed have a lower starting voltage, many will start from line voltage without any starting pulse.
The running voltage of T12 and of T8 lamps is broadly similar, they usually work from the same switchstart chokes.

The lower domestic mains voltage in the USA limits fluorescent lamps to about 2 feet in length if they are to work from 120 volt circuits with a simple series ballast.
Longer lamps need either a step up transformer in the fitting, or a step up autotransformer ballast, or a higher voltage supply.

Non domestic premises in the USA may have lighting circuits at 208 volts, 240 volts, or 277 volts, or less commonly 480 volts.
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Old 31st Mar 2019, 2:23 am   #129
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Default Re: The demise of the fluorescent tube

Having done an audit on lumens/£, I bought a 2x58W 1500mm batten from Toolstation. triphosphor tubes, single electronic ballast. Thorn fitting, Osram tubes, cool white, 8000 lm, £36

Neither tube lit properly - pink at the ends, purple in the middle. Did not improve with running.

So I took it back for replacement; this was little better, uneven light and bands running up and down the tube. Again, Did not improve with running for an hour..

The second replacement was better, but it still had bands running up and down one of the tubes; these went away after 2 hours.

Are they all as bad as this now?

For comparison, a similar fitting in the French version of B&Q is only £8,68 single, £17.50 double. You may think we're being ripped off, I couldn't possibly confirm it.

The cost of LED battens of equivalent output is prohibitive. Any saving in consumption will take many years; the light is used a few hours a week - if that.

cheers
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Old 31st Mar 2019, 2:41 am   #130
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Default Re: The demise of the fluorescent tube

I've seen Osram lamps perform badly (in the way described) at lower temperatures. Philips lamps usually work much better.
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Old 31st Mar 2019, 1:11 pm   #131
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Default Re: The demise of the fluorescent tube

Lamps that light very dimly with a pink or purple colour are almost always defective lamps, not a defective fitting or ballast.
Fluorescent lamps contain an inert gas, usually argon or krypton, and mercury vapour.
The amount of mercury must be sufficient, but an excess is fine. Due to the toxicity of mercury and the cost thereof, the modern trend is to reduce the mercury content to the absolute minimum.
Older lamps, and some cheap imports, contain a surplus of mercury. A small bead of liquid mercury may often be observed in such lamps.
With imperfect manufacture, some modern lamps end up without enough mercury to light correctly.

To be accurate, it is the partial pressure of mercury vapour and not the absolute amount present that is important.
A lamp with a marginal mercury content may light correctly if in a warm room, but glow a dim pink or purple in cooler surroundings. The warm temperature increases the mercury pressure.

In very high temperatures, the mercury pressure can become excessive which also impairs correct operation.
The partial pressure of mercury within a lit lamp is determined not by the average temperature but by the coldest part of the tube.
Various patented methods have been employed, and are still used, in order to produce a cold spot on an otherwise hot lamp and thereby reduce the partial pressure of the mercury and thus improve the performance in hot conditions.
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Old 31st Mar 2019, 2:10 pm   #132
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Default Re: The demise of the fluorescent tube

"The second replacement was better, but it still had bands running up and down one of the tubes; these went away after 2 hours."

I tell a lie; the bands are back on one of the tubes.
Broadgage, Marten - thanks for the info.

So it's out with the steps and back to Toolstation...
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Old 7th Apr 2019, 1:18 am   #133
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Default Re: The demise of the fluorescent tube

Just visited Chelmsford market yesterday. The original double 5' fittings are being replaced by the same number of single 5' LED fittings in the same locations. Despite what the stall holder told me the other week, the new ones don't appear to me to be significantly brighter (if at all) than the old (warm white) ones, but do have a higher colour temperature. I guess they will be cheaper to run.
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Old 13th Apr 2019, 7:26 pm   #134
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Default Re: The demise of the fluorescent tube

Hi I have a question about a CFL I have in my upstairs landing ive noticed that sometimes it seems to really struggle to start flickering dimly for maybe 30 seconds then other times it starts within 2 seconds it doesn't seem to have anything to do with temperature because I keep my house warm so any one got any idea? The mains voltage is steady here ever varying by more than a few volts so its not that
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Old 14th Apr 2019, 12:41 am   #135
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Default Re: The demise of the fluorescent tube

Probably the tube on it's way out. Usually one of the filaments fails, but it's only a miniaturised version of the full sized ones, so they'll likely exhibit similar end of life effects.
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Old 14th Apr 2019, 1:06 am   #136
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Default Re: The demise of the fluorescent tube

It might be worth trying some spray furniture polish. The CFL stick lamps in my shed used to be reluctant to start until I gave them this treatment, but they were just refusing to start at all rather than starting slowly.
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Old 14th Apr 2019, 1:37 pm   #137
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Default Re: The demise of the fluorescent tube

Thanks. I'll give it the furniture spray treatment see if that helps. It cold just be near end of life but I'll leave it until it fails completely. Fortunately I've got a box full of them so replacement won't be a problem.
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Old 14th Apr 2019, 3:09 pm   #138
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Default Re: The demise of the fluorescent tube

I believe CFL's have two heaters. If one is o/c the lamp may still strike but will take longer to warm up- and will look lopsided during warm-up.
As the heater filaments are mechanically quite rigid what you might have is a break in the filament- which sometimes manages to arc weld itself back together...then breaks again. This could give rise to inconsistent start-ups.

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Old 14th Apr 2019, 6:21 pm   #139
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Default Re: The demise of the fluorescent tube

Thanks philpot next time I put it on I'll look to see if it warms up lopsided and if it does I'll take it out and run it where I can feel the tube ends to see if one end gets hotter than the other. I'll report back tomorrow.
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Old 14th Apr 2019, 8:49 pm   #140
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Default Re: The demise of the fluorescent tube

Quote:
Originally Posted by 1100 man View Post
Can I have 6 off, 6 foot twin fluorescent fittings please? High frequency ones.

-Sorry, we no longer stock those.

Oh, how about a single 5' one then?

-No sorry, haven't got any of those either!

Oh, I'm guessing you haven't got any 250W MBFU lamps then (Mercury vapour)?

-Nope: but we can order those in.

So after nearly 70 years, the fluorescent tube is now obsolete Rather sad: I've always loved the technology and was fascinated by it as a small boy and have enjoyed installing it in small factories, offices & workshops ever since.

Luckily, replacement high frequency ballasts and T8 tubes are still available, so I will be able to keep older units running for a while yet.

I can't get excited about LED technology- It just doesn't do it for me like fluorescent does!

All the best
Nick
Just noticed you are a fellow Island resident, did you try Hurst first, I bet they still have some kicking about!
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