Economical switching on/off time interval for discharge lamps

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T.M.Haja Sahib

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The working life of a fluorescent tubelight depends on the number of hours it is burning per start.If it is frequently swithched on and off,its working life shortens.But how much is it true for the present day technology for flurescent lamps?Can the present day fluorescent lamps be switched on/off at an interval of 15 minutes or even less with little loss of life compared to its total design life?Is this true for other discharge lamps? Thanks.
 
You mean switching off a fluorescent lamp in a space not going to be occupied for at least 15 minutes is not economical?
 
There is no simple yes/no answer since it depends on the type of ballast, type of lamp, lamp cost, energy cost, labour cost, and on whether the lit space is mechanicly cooled.

If a space in unused for only a few minutes then it is probably worth leaving the lights on.

If a space is unused for 30 minutes or more it is probably better to turn the lights out.

15 minutes is arguable either way depending the factors listed above.

Although the lamp life in hours is reduced by frequent swtiching, this wont allways increase the money spent on lamps since they are lit for fewer hours a year.
Consider a lamp that lasts 25,000 hours with infrequent switching, if left on most of the time that is about 3 years.
Now consider the same lamp turned on only when required for say 6 minutes, 10 times a day, perhaps in a toliet or storeroom. This would drasticly reduce the lamp life, perhaps to only 3,000 hours. But the lamp is now only lit for an hour a day, or perhaps 300 hours a year, and should therefore last about 10 years instead of about 3 years.
The energy saving would be very considerable in such a case.
 
Thanks for your replies.

I also wanted to know whether the present day technology improved the reduction in working life of a discharge lamp due to moderately frequent switching on/off.
 
For a HECO customer in Hawaii or a Seattle City Light customer in WA?

There is a dramatic difference(1:3 or so) in energy cost. So you'll have to compare the ratio of cost per power cycle that results from reduction in lamp life vs energy cost.
 
bullheimer said:
an article i read in EC&M on compact flouros says frequent on/off is very detrimental to their life
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Especially so on residential Energy Star screw-in CFLs.

In order to get Energy Star, the lamp must start within a second. The theory is that if it takes longer, consumer gets frustrated and put regular incandescent back in.

Even a second is annoying to many, so most CFLs sold today start instantly, which is very detrimental to lamp life.

Commercial use CFL ballasts are programmed start and are much easier on lamps, but takes about a second and half to start. Because of the start time, these can't get Energy Star.
 
Electric-Light said:
Especially so on residential Energy Star screw-in CFLs.

In order to get Energy Star, the lamp must start within a second. The theory is that if it takes longer, consumer gets frustrated and put regular incandescent back in.

Even a second is annoying to many, so most CFLs sold today start instantly, which is very detrimental to lamp life.

Commercial use CFL ballasts are programmed start and are much easier on lamps, but takes about a second and half to start. Because of the start time, these can't get Energy Star.
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We are a spoiled populace. Because of the lag time to full brightness is why they do not qualify

for " Energy Star" ? It sounds like we need a better educated consumer if you can save dollars

and energy.
 
John120/240 said:
We are a spoiled populace. Because of the lag time to full brightness is why they do not qualify

for " Energy Star" ?
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No, the starting time. Proper rapid start takes about 1.5 seconds. This would encourage consumer to switch out for regular bulb thus defeating the purpose of energy saving. There are places where incandescent lamps provide the most saving, like it or not. Places like janitor's closet that doesn't get occupied more than 10-15minutes at a time and usually only occupied 2-3 minutes at a time suffer from long warm-up time. Since the usage per day is so little, LEDs would not make financial sense.

It sounds like we need a better educated consumer if you can save dollars

and energy.
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Places like laundry room and utility closets where lamps spend more "on time" getting accidentally left on than being used benefits the most from motion detector switches.
 
Also..... you're in India, so calculations are different.

The suggestions that work for USA based on our national average electricity cost, lamp cost, disposal cost and labor cost does not reflect the local situations in India.

In the US, cost of labor + disposal of old lamps per lamp exceeds the cost of new lamp.
 
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