Fluorescent light and starter question.

the starter is faulty. It should never interfere once the tube is lit, at l east after the first 2 seconds or so. Unless the tube is absolutely on its last legs, which you'd see by increasinly severe flicker every so often the n the starter kicks in. Then it runs ok for a bit then goes into flicker ag ain.

NT

no. There's far too much margin for that.

Well, 3 of the 6 could be considered so as they fail to even start the tubes from cold but the first two that caused the tubes to flick off now and again, may just be considered 'under spec' ?

Agreed.

Ok.

New tubes (now) so not that in this case.

And that's the ting ... I've been installing and maintaining such fittings for many years now and it's not the first time in the 20 years (or whatever) those fittings have been in the kitchen that one has started to misbehave and I've had to sort them.

The first and obvious trick is to swap stuff about between the two fittings, and / or just pull the starter once the tube is on etc.

It was just I was interested to find out what could cause a potentially good / new starter to start to misbehave but only after (it seemed) a few hours.

Now I'm a little clearer how the system works (thanks Andrew) I can see how a 70W tube could be 'pushing' a starter marked 4-80W (as it's actually likely to be rated as a 4-65W).

I'll put them back in and note the supply voltage when they are working fine and when they aren't and see if there is any correlation (when I believe there is more chance of them misbehaving if the input voltage is low).

All for the S&G's etc.

Cheers, T i m

The three most common failure modes for tubes at end of life are:

This was pretty much the only failure mode in all tubes until about about 10 years ago. With switch-start control gear, it shows as a blackened tube end which only glows orange and not white as the starter repeatedly tries and fails to start the tube. No white is because the filament is not emitting electrons when heated red-hot (no thermionic emission), so there's no conduction into the gas-fill, and the discharge can't start. Electronic control gear detects this by seeing the tube start to act as a rectifier and shuts down the tube to prevent it changing to operate as a cold-cathode tube which has a number of dangers.

Environmental regulations now require minimum mercury dosing of tubes for the expected life (typically 1/10th of what older T12 tubes used). Mercury is slowly absorbed into the electrodes and glass and lost from the gas fill. This causes tubes to dim with age, and eventually to run a dim pink when all the mercury has gone.

Tubes last much longer than they did and the phosphor efficiency drop causes them to dim and become unviable.

Air doesn't leak into tubes, even ones which are very many decades old.

Not any more. If you take into account losses in the fluorescent luminare (getting the light from the wrong side of the tube to where you want it, or losing it), they never were.

But isn't that often part of the whole 'lighting' process, especially in a domestic environment, having light shining in all directions (especially reflecting off the fitting / ceiling) and giving a much more overall (albeit less efficient) illumination to that space?

Working in a room with a single central light reminds me how nice it is to have a 'long' light source, when you start to try to work with a single point and are often in your own shadow. ;-(

Are you aware of any 6' LED fittings that offer the same light level and colour temp as the two TL-D 70W 840's I have now?

That's not even considering the chances of recovering the cost over the years I have left. ;-(

Cheers, T i m

FWIW there are thinner ones with better efficacy than T8 or T12 but their ouput v temp dependance is horrible

NT

Yes but that only goes to show that is you do the opposite of what harry says then there is a good chance you are correct.

Or just buy electronic starters and get the same result. ;-)

Cheers, T i m

You are talking of T5 tubes. T5 tubes are only rated for running on electronic control gear.

There are two ranges: T5HE (High Efficiency) are exactly the same efficiency as T8, when compared with T8 running on electronic control gear (although for historic reasons, I think T8 efficiency still has to be quoted for when running on magnetic ballasts, which is why it looks lower).*

T5HO (High Output) are lower efficiency than T5HE or T8 on electronic ballasts, but significantly higher light output for when that's required.

(There is also the old T5 tube range, 4,6,8,13W, but these are separate from T5HE and T5HO ranges.)

Also, as I hinted before, there's an important difference between fluorescent tube efficiency, and flourescent luminare efficiency. Fluorescent tubes emit light all around the tube (excluding in-line with the tube). That's not usually how you want light distributed, so refectors are used (that can be part of the luminare, or something like the ceiling - it doesn't matter). Reflectors are inefficient, and even with reflectors, much of the light is lost, typically 50% in the luminare and external reflectors such as ceiling, although it can be much worse.

T5 tubes do make it possible to design slightly higher efficiency luminares, because the smaller light source (thinner tube) makes it possible to focus more of the light output in the required direction than is possible with a T8 tube.

LED's on the other hand are by nature directional, so they start off avoiding the problem of light leaving the source in the wrong direction. They are (or can be) smaller sources too, which again helps with any focussing optics to get the light in the required direction.

• Also note that all T8 electronic control gear in the EU underruns the T8 tubes, as is rerquired by EU directives, so that power is saved rather than generating additional the light output which would be achieved if they ran at high frequency at full power. This doesn't significantly change their efficiency though.

Until the time you need to switch the light back on again. :-(

I've had the same sort of trouble with the last remaining fluorescent fitting that I couldn't upgrade to a "Quickstart"(tm) transformer ballast on account I couldn't get the older style compatible T12 tubes for this 5 foot fitting[1]. The problem is clearly down to s**te quality starter switches and I eventually sorted it out by buying enough of them from which to choose a working one (about 4 or so 'new' ones to add to my existing collection of two or three).

Even so, it takes some 5 to 10 seconds before the tube will strike, strangely, sans the disco strobe effect - it just sits there with the ends glowing (or not) before suddenly striking to full uninterrupted brightness. As a consequence, it tends to be left switched on for the whole evening.

The unavailability of Quickstart compatible tubes hit home over a decade ago with the shorter 4 foot variety so the last remaining 4 foot Quickstart fitting (in the basement) is now relying on the very last working compatible tube until it too finally expires (they last a bloody sight longer in Quickstart fittings - 16000 hours versus 7000 hours or so in a switch start fitting).

Fluorescent luminaires are the only sane choice in some locations such as kitchens (and my basement) for their non-glare, shadowless illumination properties. Until recently, they were still top dog for energy efficient lighting (still are compared to the older stock of LED Tubes being foisted on the great unwashed consumer in most retail stores).

However, once I start to see 125LPW (or better) 300 to 360 deg LED tube replacements, I'll upgrade the last of my fluorescent fittings. Until then, I don't see much point in wasting time and money on a mediocre 'upgrade'. Alternatively, large area ceiling panel luminaires might make a more suitable substitute for the humble fluorescent tube fitting. At the end of the day, it all boils down to their cost effectiveness.

-10 !

Unless you buy from a lighting specialist that can supply the latest

I was considering an LED tube upgrade for our 4 foot 36W cheap electronically ballasted B&Q fitting bought about two years ago now, when the 2nd tube in 18 months (replacement to the original, presumed low quality tube) started to give trouble. Switching the tube, end over end in the fitting gave less than a week's relief from the starting failure, culminating in the fitting 'going quietly Pop!'.

I wasn't impressed with either alternative of new ballast or a complete re-lamp with the unimpressively inefficient and over-priced LED tube options. However, persistence paid off and I bought a high quality Helvar ballast for just under a fiver delivered postage free[1]. At that price, it was the no brainer choice of repair.

However, the second tube had been so shagged by the Chinese ballast, the Helvar ballast refused to even try starting it. I had slightly better luck with the original but only in that it would light it up briefly before aborting further starting attempts (fussy microprocessor controller - I assumed).

My assumption proved to be correct but I did have to chance buying yet another tube, from Toolstation this time rather than my local lighting specialist from whom I'd bought the last one. In fact, I landed up buying yet another, cool white this time rather than warm white - I'd forgotten to take account of the kitchen's pale yellow colour scheme. At least I have a working spare, even if it is a little on the warm side for the kitchen's current colour scheme.

Would seem to be the very same item but a penny cheaper! :-)

If your fluorescent light fitting is a single 36W T8 tubed 4 foot luminaire, that should suit your needs nicely. It doesn't strike the modern T8 tubes as slickly as the ancient but very effective Quickstart ballasts did with the original T12 compatible tubes (250ms versus 900ms of the modern life enhancing microprocessor controlled electronic high frequency ballasts) but that's the price paid for a reduction from 52W consumption down to the 36W exactly of an electronically ballasted 4 foot T8 tube (I'd measured exactly 36W with both ballasts).

This was an issue aggravated by the use of cheap bi-pin switch started lamps in domestic service (kitchens, basements, sheds and the circular tubes used in hallways and landings). Each switch start attempt would sputter some of the thoriated coating off the cathodes/cum anodes, shortening the service life when used in such frequently switched applications.

The older (half century older!) Quickstart transformer technology not only gave an almost instant flicker free startup (200 to 300ms) but significantly reduced this sputtering effect which could double or even triple the service life of a tube used in a domestic kitchen over that using the cheap bi-pin switch start circuit, especially useful since it encouraged the occupiers to treat it as an instant start incandescent (but with a service life around an order of magnitude longer).

I lament the parsimonious mercury dosing of modern T8 lamps since it lends an unwanted "run up" characteristic, especially noticeable in the winter months, more associated with the mercury amalgam variants used in CFLs. The earlier fully dosed T12 tubes only showed the slightest hint of this with really low temperatures not usually seen in a domestic environment even in the winter other than for outhouse lighting.

In regard of both startup and run up time, modern electronically ballasted fluorescent luminaires(sp?) have taken a backwards step over the ancient Quickstart fittings. I guess that's the price you pay to save some 16 watt's of consumption on a 4 foot fluorescent fitting.

True enough, the phosphors have to deal with mercury poisoning as well as the degradation from UV radiation - the phosphor coating on LEDs doesn't have to contend with this so they last a lot longer (but nevertheless still slowly degrade over time).

In office and factory environments, fluorescent lamps were replaced en masse after clocking up the rated hours for the 80% of design lumens point, thousands of hours before the more gross and obvious failures would start showing other than for defectively manufactured lamps.

This was simply because changing out lamps by the gross was far cheaper both in electricity consumption to meet the minimum lighting standard required by regulations and the labour costs involved in relamping on an ad hoc basis as each individual lamp failed to produce its design lumens output one way or another.

For the general public, that's a fairly recent development, I first saw

The best efficiency tubes maxed out around the 90 to 100LPW mark.

For situations where a nice diffuse, shadowless lighting effect is desired, such as a kitchen or a shed come DIY workshop or a low ceilinged basement, that's not quite the deficiency it would seem. However, these days when such a lighting characteristic is deemed desirable, a better solution would be the use of ceiling mounted LED flat panels with a suitable diffusing cover to mute the horrendous glare typical of naked LEDs.

Sometimes cobweb or cockroach muck could cause change in voltage across the choke.

oke drop and the plasma drop. Plasma energy is generally low, hence choke i s the component taking most enrgy. Choke may develope intermittency due to failing insulation.failing insulation.

Just to make it clear to you- the plasma breaks due to high voltage induced due to choke in series with t he starter which breaks the circuit to cause it; before plasma breaks tube a high resitance in series with the choke. For your info I am not in Thailand or some stinking Thames river country, I am in Australia a clean intelligent country where early convict arrivals h ave long been dead!

Ok ...

Ok?

So no roaches there either then?

Ah, hence the thought re spiders living in your lights, interfering with the inductance. ;-)

Cheers, T i m

I asked a mate if I could borrow a 4-80W starter (thinking he'd have a spare) and he went out and bought me one, a 4-65W.

Anyroadup, I thought I'd give it a try and it seems to work fine so far but I'd have to see how long it lasts to be fair to the questionable ones (as they may have run for a week before the issues started).

Cheers, T i m

I think anyone with a working brain would put it back don't you? Even without it thought one can still fire a light up. Just arc the switch.

NT

s. Sometimes cobweb or cockroach muck could cause change in voltage across the choke.

choke drop and the plasma drop. Plasma energy is generally low, hence chok e is the component taking most enrgy. Choke may develope intermittency due to failing insulation.failing insulation.

h the starter which breaks the circuit to cause it; before plasma breaks tu be a high resitance in series with the choke.

ls have long been dead!

Ah, hence the thought re spiders living in your lights, interfering

Matey! one can survive with spider stings but has no such chance with plagu e from rats in Thames bank;-)