flourescent advantages

[cookgm]

Can someone prove or dis-prove the old saying that is is less expensive to leave a flourescent light on all day rather than to repeatedly turn a flourescent light on and off.

I can not find anything on the internet to support this.  I would like some advice and possibly a reference to a web site that will give me the data.

Thank You.

[Nando]

I concur partially with magnetic ballasts, Not so with Electronic Ballasts.

I have designed electronic ballasts for fluorescent lamps.

The magnetic ballast when energized produce excessive currents until the tube filament is hot.

During the heating period the filament suffers a kind of surface stripping, which shortens the filament life, one can notice this with old tubes that flicker for some time until the filament is hot enough to continue emitting electrons between AC voltage cycles.

For this reason ones needs to minimize such ON/OFF switching.

Electronic ballasts if properly designed do last a lot longer because the circuit can have a heating cycle to push the filament to get HOT fast in about 100 milliseconds, instead of 2 to 8 seconds for the magnetic ballast.

The electronic ballast now have available many Integrated Circuits that do such ON/OFF steps to minimize the filament life reduction.

I did a study, unhappily many years ago, where the ratio of ON/OFF cycles versus lamp life was determined, I do not remember the data, I only remember that if the filament was properly heated prior maximum plasma current continuous setting, the life of the lamp was practically defined by the ON time of the lamp.

This represent about same ON/OFF cycles and ON time for total hours life.

This was done with the early tri-phosphor tubes.

Presently, the best way is to send a message to the tube manufacturers asking this question, they do have such data, for sure, since that is one parameter that is needed to determine the total fluorescent lamp life.

By the way, there is an electroless ( filament-less) fluorescent lamp that may have the patent about to end, it has a life of about 100,000 hours, but the electronic ballasts is more expensive -- it is a RF ( Radio Transmitter) where the fluorescent lamp is in the output coil field to excite the internal gas by induction.

The lamps for such systems are not sold individually, they are sold with the RF ballast, also they do have a problem with RF field producing a lot of RF interference which make them unsuitable for many environments.

Nando

[scottsAI]

Hello cookgm,

I agree with Nando's comments above.

But, as you have figured there are many ways to look at something.

If the Lamp is a CF and cost $2.00 and power cost 1kwhr = $0.10

The bulb cost 20kwhr of power.

Let's say the bulb is 23 watts, this equates to 20,000whr / 23w = 869 hr of electrical power.

Or 36 days.

If you leave the lamp on all day for 36 days, you will use enough power to equal the cost of the lamp.

Yes, the lamps die sooner if turned on/off a lot. But any bulb will except LED.

I have read about 2-4,000 on/off cycles will do in a CF.

Remember most CF are rated for 8-10,000 hr life (little more than 1 year).

The idea here is to use a balanced judgment of the on/off vs cost of leaving it on.

If your power is from a solar panel, then turn on/off to minimize the power use.

If you think you will be back soon like within 15min you may leave it on. Not all day.

If your lamp and power has a different cost structure then apply the numbers and figure out what you should be doing. It's your money!

Have fun,

Scott.

[Nando]

I need to correct this remark:

>      The magnetic ballast when energized produce excessive currents until

>the tube filament is hot.

It should read:

      The magnetic ballast when energized produces STANDARD TUBE currents until

the tube filament is hot. THIS CURRENT FORCES THE TUBE'S Filaments to operate cold.

Nando

[nothing to lose]

"it is a RF ( Radio Transmitter) where the fluorescent lamp is in the output coil field to excite the internal gas by induction."

Is that what I was doing when I used to duct tape a fluorescent lamp tube to my CB radio antenna and make it light when I transmitted?  

[BT Humble]

I picked up a box of 36W fluoro tubes at the recycling centre that had pretty obviously been taken out of a shop or office via a scheduled replacement.  They work just fine with this fluoro driver circuit, if you replace the TIP31C transistor with an MJE3055:

http://www.smallsolar.org/hardware/fluoro/circuit.htm

Hey, how do you like my new website? I expect it'll be a permanent work-in-progress. ;-D

BTH

[NT]

The OP is an old myth based on a simple misunderstanding. Very briefly, power use during starting on a glowstart ballast is around 3x run power, and starting takes maybe 3 seconds. So switching off then on is equiv to leaving it on for 9 seconds approx.

2ndly there is the q of tube life. Linear fls are typically rated for twice as long on electronic ballasts as glowstart. A £2 tube over 20,000 hours costs 1/100th penny per hour in tube purchase cost, which is a tiny fraction of its electricity run cost. So in no way is it worth leaving a fl on when it could be off. Ever.

NT