How many CFLs does it take to ....

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Hi to all,

just picked up a "dimmable" CFL from K-Mart, a Mirabella brand 15 watt
spiral type  -  price was reduced from $20 to $8,  which is more like their
true value.

Connected via a standard triac (pulse fired) dimmer, it operates fairly well
with dimming down to about 10% of max brightness and just a little
flickering at one particular setting.

Using my  " RMS  Current Monitor"  and CRO to examine the current waveform
revealed it to be very spiky over the whole operating range.  At around mid
setting on the dimmer ( when the rms current draw was only 170mA)  -  there
were continuous, bi-polar peaks of ** 1.5 amps **  every 10 mS.

So the QUESTION is how many such CFLs can you safely operate from such a
dimmer  ??

Wall plate dimmers are typically rated at 300 to 500 watts with incandescent
loads and use a 4 amp or maybe 6 amp rated triac -  but  ONE  15 watt
"dimmable" CFL draws the same continuous peak current as a 250 watt
resistive load.

I know small triacs may well have a single peak current ratings of 30 or 40
amps -  but that is just for one surge that lasts only a few mS.

So what is the answer ??

Are users likely to experience failure of their dimmers if they run say 20 x
15 watt rated CFLs as the 300 watt power rating suggests you can   ???

Remember, doing the above will result is continuous current peaks of 30
amps.



.....   Phil




Re: How many CFLs does it take to ....



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**Wait for decent LEDs to fall in price. They eclipse CFLs efficiency-wise,
are easy to use and are very dimmable. Give it a couple of years.


--
Trevor Wilson
www.rageaudio.com.au



Re: How many CFLs does it take to ....

 "Phil Allison"

Hi to all,

just picked up a "dimmable" CFL from K-Mart, a Mirabella brand 15 watt
 spiral type  -  price was reduced from $20 to $8,  which is more like
 their true value.


** Oh dear  -   the thing has died already.

Got about 10 hours out of it before one end of the spiral has gone black  =
blown heater.

Back it goes .......



.....   Phil





Re: How many CFLs does it take to ....

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Mirabella shite.  Had so many problems with this brand it isn't funny.
False economy buying the crap.  Costs more to take back for a refund and not
worth the hassle.
Best just avoided in the first place.



Re: How many CFLs does it take to ....
On Dec 19, 6:57A0%pm, "Alan Rutlidge"
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Agree. Same with standard fluorescent tubes.  NEC are a better choice.


Re: How many CFLs does it take to ....
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Could the spikes be attributed to it being faulty?

Michael



Re: How many CFLs does it take to ....

"Michael C"
 "Phil Allison"
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** No.

The phenomenon of current spiking is *characteristic* of using a rectifier
with capacitor filter with a standard ( leading edge or pulse fired) triac
dimmer.

At some point in each half cycle, the triac suddenly conducts and applies
maybe 300 volts to the CFL resulting in the cap after the bridge rectifier
charging to full voltage in 50 - 100uS or so.  The only limit on the size of
the current spikes is the existence of a series resistor and the ESR of the
particular electro cap.

Using the same kind of dimmer with a normal 23 watt CFL  (ie  non dimmable)
results in a stream of current spikes of around 20 amps each !!!

This is why you must not use standard CFLs with a dimmer -  cos the CFL will
likely catch on fire and / or destroy the dimmer by causing the triac to
short out.




....    Phil



Re: How many CFLs does it take to ....
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We've been waiting a long time for that. LEDs are still behind in terms of
the light output per dollar and the quality of light.

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Only just from what I hear and only very recently.

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Re: How many CFLs does it take to ....



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**Did you see where I wrote: "Give it a couple of years"?

LEDs are presently as efficient as fluoros and are very dimmable. Better
still, they retain good colour balance throughout the range. Prices are
falling more rapidly than I thought possible. There are (at least) three
different varieties of white available. Then there are the multi-chip LEDs
where three primary colours are mixed, allowing an infinite variation of
colours.

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**Yep.


--
Trevor Wilson
www.rageaudio.com.au



Re: How many CFLs does it take to ....
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I wouldnt want to try it. I think the dimmer wouldnt survive it.
Happening repeatedly like that, I wouldnt want to try 2-3 even.

While on a similar subject:

Was at Haymans yesterday, and was talking about CFL and LED lighting.
The sales manager at our local branch is an experienced electrician
(but not expert on "electronics") and said that there had been
problems with people putting more than 4-5 + CFL's (wattage unknown)
in light sockets the same light switch, then having nuisance tripping
of the circuit breaker for the light circuit, at switch on, and this
was causing headaches for electricians being called in to "find the
fault", which, unsurprisingly, they couldn't.

This had increased recently with the Christmas and party season with
people using CFL's instead of bulbs in those "festoon" party light
strings, and turning on heaps of them at once. Some were worried that
the "CFL's must be faulty / dangerous / using more power than
incandescent" as they "never had this problem with the old bulbs".

We will surely see more of these problems when inevitably people try
to flash strings of CFL 's, (with festoon light setups, in commercial
situations) - especially when incandescents become no longer available
and CFL's are used.
Doing this with a "musicolour" or light chaser - you would likely
destroy the output devices.

There has already been a post about suitable substitute bulbs (if
incandescents are gone) for this kit on this forum this week.



There had also been problems with plastics in non-UV stabilised light
fittings falling apart. In one case the plastic nut holding glass
front of an cheap oyster fitting had deteriorated and the glass bowl
had fallen onto the coffee table. From the description, it sounded
more like a circular fluro unit rather than a CFL - but both would
emit UV. This could possibly start happening if CFL;s are put into non
UV stable fittings originally meant for bulbs.

For that matter, are the standard white batten holders, used by the
millions in aussie homes for the past 30+ years made of  UV stable
plastics ?

Re: How many CFLs does it take to ....
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Definitely not! Ditto for fluorescent tube lamps. I work in a power
station where we use hundreds of fluorescent lights for general lighting
and the tombstones, starters and starter holders crumble into dust at
the slightest touch. Also the wiring becomes brittle and breaks off with
any movement. Those things are death-traps. It's easier and cheaper to
replace the whole light assembly than to try and fix them.

Re: How many CFLs does it take to ....

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Yes but the heat from incandescent bulbs seems to be just as big a problem
as the UV from FL's IME.
I have replaced *lots* of batten holders that have never seen a CFL. OTOH, I
still have some 30 YO tube fittings.

MrT.



Re: How many CFLs does it take to ....

"kreed"

While on a similar subject:

Was at Haymans yesterday, and was talking about CFL and LED lighting.
The sales manager at our local branch is an experienced electrician
(but not expert on "electronics") and said that there had been
problems with people putting more than 4-5 + CFL's (wattage unknown)
in light sockets the same light switch, then having nuisance tripping
of the circuit breaker for the light circuit, at switch on, and this
was causing headaches for electricians being called in to "find the
fault", which, unsurprisingly, they couldn't.


** I predicted thus would be the case a long time ago, in discussions I had
with Rod Elliot of ESP.

http://sound.westhost.com/articles/incandescent.htm#dim2

Typical 13 to 23 watt CFLs have a 4.7 to 22 ohm resistor in series with a
10uF to 22uF uF electro immediately after the bridge rectifer. When switched
on at the AC voltage peak, this generates a spike of current of about 20 to
30 amps per lamp that last about 0.5 mS or so.

With 5 or 6 in parallel, the current spike builds up to well over 100 amps
and may trip an 8 amp "thermal magnetic" breaker.  The magnetic function of
such breakers breaker is damn near instantaneous when the current exceeds 10
times the nominal rated value.


This had increased recently with the Christmas and party season with
people using CFL's instead of bulbs in those "festoon" party light
strings, and turning on heaps of them at once. Some were worried that
the "CFL's must be faulty / dangerous / using more power than
incandescent" as they "never had this problem with the old bulbs".

** With normal incandescent bulbs of no more than say 100 watts each   -  it
is possible to load and reliably switch a single lighting circuit right up
to the nominal 2kW limit.

With CFLs, the limit falls to around 100 to 200 watts -  at most.


We will surely see more of these problems when inevitably people try
to flash strings of CFL 's, (with festoon light setups, in commercial
situations) - especially when incandescents become no longer available
and CFL's are used.


** I think that is really out of the question  -  be much the same as using
a standard CFL on a pulse fired triac dimmer.

Doing that kills them real quick,  even if the dimmer is set all the way to
max.



.....    Phil




Re: How many CFLs does it take to ....

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I thought you could not use them on a Dimmer.
Sort of a similar reason you cannot use a Dimmer on a fluro, i.e. the Fluro
(CFL) needs a certain voltage to operate,
reducing it would lead to a higher current being made by the CFLS
electronics, leading to excessive current and burnout..
Allan



Re: How many CFLs does it take to ....

"Allan"
 "Phil Allison"
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** Care to explain why the word  "dimmable"  is on the packet no less than
*6 times* as well as on the point of sale advertising  ???




.....   Phil






Re: How many CFLs does it take to ....
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Dimmable CFLS were being discussed here and from what was said, they
are about
as impractical as an ashtray on a motorbike.


There are (and have been for years) ways to dim standard fluorescents,
none of them
anywhere as good as dimming with with incandescents and mostly
inefficient.
here is a document on it that I googled:
http://members.misty.com/don/f-dim.html


There are also special "dimming" ballasts for various installations.
From the "blurb" they work well, document is interesting reading
regardless.
http://www.lutron.com/CMS400/page.aspx?id3D%6491

I would note the comments on the Dimmable CFL too, the same sort of
problems (power factor and current surges) might possibly apply with
any (or other) electronic dimmable fluro ballasts.

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