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Fluorescent light toubles

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Fluorescent light toubles

Posted by Kelly Marie on Jan 19, 2020 6:19 pm

My kitchen fluorescent lamp which is 6 foot 100 watt unit wouldn't light tonite the starter flickered but no sign of any tube activity. It was very cold in the kitchen so I put the boiler on which warmed things up nicely I tried the tube again and although a bit sluggish it lit ( maybe my swearing at it helped) my question is do you think it's just because the tubes old and doesn't like the cold  or is there something else going on? 

Re: Fluorescent light toubles

Posted by perspicacious on Jan 19, 2020 6:41 pm

I wasn't aware that 1800 mm tubes were available in 100 W variants Kelly.

I used to work for Thorn Lighting, well Smart and Brown lighting at the time, and recall their literature giving operating ranges for temperature with the 8 foot tubes being particularly susceptible to low temperature starting. For cold stores, down to - 30C,  shorter tubes were used along with Semi Resonant Starting (SRS) that did away with the "starter".

Regards

BOD

Re: Fluorescent light toubles

Posted by Kelly Marie on Jan 19, 2020 7:31 pm

Hi BOD it's an old tube around 8 or 10 years it's been up there  I think I need to try it again in the cold just to see if it plays up again 

Re: Fluorescent light toubles

Posted by Zoomup on Jan 19, 2020 8:05 pm

Yes Kelly old fluorescent tubes do not like the cold. They will strike, but take ages to give out full light in cold garages or lofts. Perhaps your fitting deserves a new tube and starter if you can still source new 6ft tubes. Or even better a brand new L.E.D. batten fitting that comes on instantly even in the cold weather. Is the tube really a 6ft 100 Watt tube or an 8ft long tube? An indication of an old well used tube is when the ends go black.

Z.

 

Re: Fluorescent light toubles

Posted by mapj1 on Jan 19, 2020 8:57 pm

the old inch and a quarter (T12 ) 5fts used to be run at 65/80 watts but I have not seen anything more than the  85W in 6ft. Modern slimline tubes (T8) would be 70W or so and run perfectly well in the old fittings.

In any case cold makes it hard for the mercury to get going, and if the tube is old and already failing a bit, it is likely to struggle more when it is cold.
Various tricks like starter wires - bringing earthed metal near the tube to form a 'Gabriel' electrode and get  bit of ionisation going sometimes help, and it is not uncommon to find  a tube that fails in one fitting has a bit more life in another, or  even that running a finger along the tube can draw a few microamps of arc and get it starting.

Longer term a new tube should be good at -5C or so,  yours may just be getting past it.
But as noted above, an LED fitting in the same place will be about half the current, for a similar brightness, so given the costs, the days of  just replacing tubes are probably numbered.
regards Mike

Re: Fluorescent light toubles

Posted by Kelly Marie on Jan 19, 2020 9:11 pm

Thanks guys if it gives me more trouble il get a new tube for it  the ends are a bit blackened so it seems likely that the tube is getting a bit past it  also il try running a wire along it and earthing it to the fitting to help encourage the discharge. I don't want to go down the LED route unless I have to

Re: Fluorescent light toubles

Posted by mapj1 on Jan 19, 2020 9:25 pm

If you have none at the local wickes or BnQ, then a local wholesaler should be able to get one
   TLC for example

I note they cannot do mail order, but can deliver from local branch to your address if you live within a certain  range, I suspect other places will similar.
regards Mike

Re: Fluorescent light toubles

Posted by AJJewsbury on Jan 19, 2020 10:45 pm

the old inch and a quarter (T12 )

Wasn't a T12 was an inch and a half? (and T8=1")
   - Andy.

Re: Fluorescent light toubles

Posted by mapj1 on Jan 19, 2020 11:29 pm

yes sorry, slip of the fingers, it was all in 1/8 of an inch units.
regards Mike

Re: Fluorescent light toubles

Posted by pww235 on Jan 20, 2020 10:40 am

Kelly Marie:
Thanks guys if it gives me more trouble il get a new tube for it  the ends are a bit blackened so it seems likely that the tube is getting a bit past it  also il try running a wire along it and earthing it to the fitting to help encourage the discharge. I don't want to go down the LED route unless I have to

Just out of interest....why not?

Pete

Re: Fluorescent light toubles

Posted by Kelly Marie on Jan 20, 2020 11:38 am

Hi PW235  The reasons for not wanting to go for LEDs is partly because I just don't like the look of them the flickeryness bothers me a bit the main reason is that this technology has been forced on us by the green brigade the only 2 greenies I've met in real life were so aggressive in telling me what I can and can't use they were both really nasty about it one was a bloke at work the other was a distant relative. Wwhen people get nasty with me like that I dig my heals in and won't do what they say. Incidentally I have a decent collection of incandescent bulbs now donated to me by friends who are going down the CFL/LED route. Also  a real bulb in my standard lamp over my chair gives a welcome bit of extra warmth 

Re: Fluorescent light toubles

Posted by Zoomup on Jan 20, 2020 4:33 pm

Kelly Marie:
Hi PW235  The reasons for not wanting to go for LEDs is partly because I just don't like the look of them the flickeryness bothers me a bit the main reason is that this technology has been forced on us by the green brigade the only 2 greenies I've met in real life were so aggressive in telling me what I can and can't use they were both really nasty about it one was a bloke at work the other was a distant relative. Wwhen people get nasty with me like that I dig my heals in and won't do what they say. Incidentally I have a decent collection of incandescent bulbs now donated to me by friends who are going down the CFL/LED route. Also  a real bulb in my standard lamp over my chair gives a welcome bit of extra warmth 

Yes I have also noticed with some L.E.D. lighting, there is a perceptible high frequency strobing effect. Tungsten lamps can be very useful when producing heat and light, especially if used with tropical fish in the lighting hood or over a terrarium as well.

Z.

 

Re: Fluorescent light toubles

Posted by pww235 on Jan 21, 2020 11:46 am

Kelly Marie:
Hi PW235  The reasons for not wanting to go for LEDs is partly because I just don't like the look of them the flickeryness bothers me a bit the main reason is that this technology has been forced on us by the green brigade the only 2 greenies I've met in real life were so aggressive in telling me what I can and can't use they were both really nasty about it one was a bloke at work the other was a distant relative. Wwhen people get nasty with me like that I dig my heals in and won't do what they say. Incidentally I have a decent collection of incandescent bulbs now donated to me by friends who are going down the CFL/LED route. Also  a real bulb in my standard lamp over my chair gives a welcome bit of extra warmth 

Interesting, I can't say I've noticed any flicker in LED products other than when they were still a relatively new technology.
Sorry to hear of those unfortunately horrid folks.

Pete

Re: Fluorescent light toubles

Posted by AJJewsbury on Jan 21, 2020 1:43 pm

I have occasionally noticed flicker from LEDs - not directly but by fast movement being made to look jerky (stroboscopic effect) - in my case when sharpening a knife on a carborundum stone. I guess that's the same effect as from the old fluorescents they were always warning us about (and the need to feed workshop lighting from all three phases etc) although the frequencies might differ. As far as I can gather some white LEDs work on a similar principle to fluorescents - i.e. UV rather than visible light is initially produced and that's used to make phosphor glow to produce visible white light. So in principle flicker from an LED shouldn't be any worse than from and old switch-start fluorescent - probably somewhat less noticeable as the basic LED frequency is likely to be higher than than the fluorescent's 50Hz - notwithstanding slight differences in the phosphor mix.
   - Andy.
 

Re: Fluorescent light toubles

Posted by Normcall on Jan 21, 2020 4:01 pm

If it's 6ft then they special starters as do 8 ft fittings.They also made 6ft fittings in matched pairs just to make difficult (lead/lag PF correction) which often need yet another starter. You will find it difficult to find 8ft tubes but 6ft should be available in good DIY stores.
Norman

Re: Fluorescent light toubles

Posted by Kelly Marie on Jan 21, 2020 7:32 pm

I hope that my mate has still got some 6 foot tubes in his stock room however the tube in my kitchen light seems to be behaving itself again now  the only thing I did to it was to take out the starter and refit it maybe that was enough. Normcall what do you mean about matched pairs are you referring to the twin tube fittings with a capacitor in series with one tube or something else? I know that in years gone by there have been some interesting circuit arrangement in use

Re: Fluorescent light toubles

Posted by Denis McMahon on Jan 22, 2020 8:31 am

AJJewsbury:
I have occasionally noticed flicker from LEDs - not directly but by fast movement being made to look jerky (stroboscopic effect) - in my case when sharpening a knife on a carborundum stone. I guess that's the same effect as from the old fluorescents they were always warning us about (and the need to feed workshop lighting from all three phases etc) although the frequencies might differ. As far as I can gather some white LEDs work on a similar principle to fluorescents - i.e. UV rather than visible light is initially produced and that's used to make phosphor glow to produce visible white light. So in principle flicker from an LED shouldn't be any worse than from and old switch-start fluorescent - probably somewhat less noticeable as the basic LED frequency is likely to be higher than than the fluorescent's 50Hz - notwithstanding slight differences in the phosphor mix.
   - Andy.
 

 
If I may add a personal observation or two.

I have noticed that LED lamps designed to be dimmable tend to have a flicker (which becomes more pronounced as you dim them) whereas non-dimmable types do not. I presume this is because they are designed so that the thyristor dimmer can chop the output waveform whereas non-dimmable types rectify the mains input - or something like that - does anyone have any intimate knowledge of this?

Don't kid yourselves that tungsten filament lamps are totally flicker free; they are not. Remember those "strobo-disks" you could once get to check the speed of gramophone turntables? They worked quite well under tungsten light.
Denis McMahon "There is always a better way."

Re: Fluorescent light toubles

Posted by Denis McMahon on Jan 22, 2020 8:35 am

Kelly Marie:
I hope that my mate has still got some 6 foot tubes in his stock room however the tube in my kitchen light seems to be behaving itself again now  the only thing I did to it was to take out the starter and refit it maybe that was enough. . .

 
It is more that possible that in a cold and occasionally damp environment some corrosion can take place on the contacts. You may well have fixed the problem for several years.
Denis McMahon "There is always a better way."

Re: Fluorescent light toubles

Posted by Denis McMahon on Jan 22, 2020 8:45 am

mapj1:
. . .
But as noted above, an LED fitting in the same place will be about half the current, for a similar brightness, so given the costs, the days of  just replacing tubes are probably numbered.

 
To achieve the same brightness you may need to replace the whole fitting with a complete LED design. Plug-in LED replacements for fluorescent tubes are available but, though they use less than half the power, they produce less light than the fluorescent tubes they replace. A 1·5 m replacement LED tube, for instance, gives barely more light than a 1·2 m fluorescent.

https://www.tlc-direct.co.uk/Products/LTT524DL.html

LED is still a developing technology and brighter version may well emerge in due course.
Denis McMahon "There is always a better way."

Re: Fluorescent light toubles

Posted by Normcall on Jan 22, 2020 11:22 am

The 'twin packs' of 6ft fittings were produced mainly for commercial projects. They were single 6ft fittings sold in pairs - one lead/one lag - to correct the power factor when used in shops/factories which often had 3 phase supplies and getting the PF as near to unity could save money.
Norman

Re: Fluorescent light toubles

Posted by Chris Pearson on Jan 22, 2020 9:07 pm

AJJewsbury:
I have occasionally noticed flicker from LEDs ...

Now you mention it, whilst drilling the fixing holes for a back box today and using a head torch for illumination (no mains lighting for obvious reasons) I thought of this and noticed that my drill appeared to be going backwards; so clearly, even battery powered LEDs must flicker.

Re: Fluorescent light toubles

Posted by perspicacious on Jan 22, 2020 9:19 pm

There's normally a switch on your drill to select forward Chris!

What is fun is on finding an anticlockwise HSS drill is to sharpen it, and give it to the apprentice to use.........

Seriously, I too have noticed stroboscopic effects from LED head torches.

Regards

BOD

Re: Fluorescent light toubles

Posted by mapj1 on Jan 22, 2020 10:23 pm

Rather than waste power on lossy resistors a lot of the cell saver designs of torches do the dimming from anything other than full brightness by chopping the current waveform, so half brightness is the same as full brightness for half the time. What I do not understand is why the makers elect to do this slicing at low audio frequencies, rather than hundreds of kHz, which is just as easy for the electronics and would avoid the worst of the weird optical illusions.
I do seem to be 'gifted' with the ability to see flicker more than most, and to me the overhead motorway variable speed signs flicker as well, and asking at work, most people have not noticed it, but those of us who do agree it is bloody annoying.
regards Mike

Re: Fluorescent light toubles

Posted by Chris Pearson on Jan 22, 2020 10:55 pm

mapj1:
Rather than waste power on lossy resistors a lot of the cell saver designs of torches do the dimming from anything other than full brightness by chopping the current waveform, so half brightness is the same as full brightness for half the time.

Which is an excellent example of how to spend a ha'penny.

Mike, you really are a mine of information. 🙂

So I just popped into my workshop and ran my lathe. Full power, no flicker at all. "Half power" definitely strobing. Doubtless if I gave you a list of the apparently stationery speeds, you would be able to tell me the frequency of my head torch.

Re: Fluorescent light toubles

Posted by mapj1 on Jan 22, 2020 11:04 pm

and so I'm sure can you without me - the lowest speed at which you see a fixed no of multiples of the chuck key holes,  and how many degrees they are apart at that many RPM, tells you the rotation angle and so the time between flashes and convert mins to secs for Hz.
or yo could use  a photo cell and a 'scope. It all rather depends what sort of workshop you have -mine has a lot of electronics stuff in it, the lathe however is down the garden as a concession to domestic pressures.
regards Mike

Re: Fluorescent light toubles

Posted by Kelly Marie on Jan 22, 2020 11:08 pm

One thing I have only use remembered is that curiously in the USA they seem to use series capacitors in there fluorescent fittings which seems odd given that florrys  for  110 volt mains don't have a choke as such it's an auto transformer  so why the series cap??

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