Do you believe that frequent on/off substantially shortens fluorescent light life?

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Do you believe that frequent on/off substantially shortens fluorescent light life?

  • Reduces life substantially+wastes power as it uses a lot of power to start

    Votes: 4 11.8%
  • Reduces life but saves power

    Votes: 17 50.0%
  • No difference in life, but wastes energy

    Votes: 3 8.8%
  • Makes no difference

    Votes: 3 8.8%
  • Depends on the ballast

    Votes: 7 20.6%

  • Total voters
    34
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broadgage

Senior Member
Location
London, England
Frequent on/off switching reduces flourescent lamp life. This is a fact that may confirmed by reference to suppliers data or by observation of large installations.
Different types of ballast influence the extent by which lamp life is reduced, but it is significant with any type.
Instant start are usually the worst, and those that preheat the cathodes are better.

There is a power saving since the lamps consume no power whatsoever when turned off. The extra energy consumed in starting is very small, typicly only one or two seconds worth of normal operation.

Switching lamps off when not needed is almost allways worthwhile, the energy saving being greater than the loss of lamp life.
In many cases, the lamp life if measured in years, rather than burning hours, will be unaltered, or even extended.

Consider a premium qaulity flourescent lamp that lasts 25,000 hours with infrequent switching. If seldom turned off, it will last about 3 years.
Now consider the same lamp, turned on/off frequently, such that it lasts one third of the life, or about 8,000 hours. If it is lit for an average of 8 hours a day, then it will still last about 3 years. There is therefore no increase in the money spent on lamps, per year.
There would however be a substantial saving on electricity. Over 3 years, about 17,000 operating hours have been saved. With a 60 watt lamp, about 1,000 KWH have been saved over 3 years, depending on the power price, that could be $200.

So in the example given, switching off has saved in the region of $65 a year, per lamp, with no increase in lamp costs.
 

realolman

Senior Member
I just want to compliment broadgage on his post. I like the part about measuring in years rather than burning hours. I think very often just a slight change in perspective changes the importance and validity of many subjects or information.
Nicely done.
 
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iwire

Moderator
Staff member
Location
Massachusetts
I notice when I read an article in EC&M or other trade magazine extolling the virtues of any particular product that the authors background and affiliations are disclosed.

So ....... how about it 'Electric Light' are you willing to disclose your motives?

I just find it somewhat dishonest to ask a question like this without disclosing any bias you may have.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110505-0910 EDT

This is an interesting multiple choice question.

The question is:

Do you believe that frequent on/off substantially shortens fluorescent light life?

The last two can be rejected on the basis of general information. #4 is obvious. #5 might apply if the ballast did not excite the gas thru the emitting electrodes at the tube ends, but this type of ballast is uncommon.

Of the first three questions the first two use the word power and the third energy. Why aren't all three phrased with energy?

#3 can be rejected based on general knowledge. From general knowledge a difference can be expected. From logic and general knowledge if the duty cycle is reduced, then energy use is reduced.

#1
Reduces life substantially+wastes power as it uses a lot of power to start
#2
Reduces life but saves power
Both of these are somewhat meaningless with the word power used. If I substitute energy for power, then I favor #2 out of the 5 possible answers.

My own experience is #2 using the word energy.

broadgage provided a very good discussion.

.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Instructions with a CFL indicated that the lamp life was best when it was on for at least 15 minutes. Or at least that is how I interpreted the French, German, Spanish, and Chinese instructions. No matter how efficient the lamp or how long the life, the least energy used is when it is off.
 

Npstewart

Senior Member
I often question this when I put occupancy sensors in a commercial project to satisfy energy codes. I get a lot of complaints from electrical contractors when we spec occupancy sensors for a larger project with a lot of offices, ESPECIALLY exam rooms. We do a lot of medical in my area because I live in Florida (a lot of retirees. ). We often do 7,000 square foot build outs with several exam rooms. I think occuapncy sensors are great for this because the lights will go out 20 minutes after the doctor & patient leaves, and that room may not be used for another 4 hours. Many EC's want to install time-clocks in lieu of occ sensors.

Many electrical contractors state that occupancy sensors aren't required for patient care, however we dont interpret these in & out exam rooms as patients care.

In any case, I think the life shortening effects of the on & off of the lights is irrelevant when the cost savings is factored in.
 

Electric-Light

Senior Member
So ....... how about it 'Electric Light' are you willing to disclose your motives?
I already have a pretty good idea of the answer however, I am curious how people in the electrical trade perceive the effect today. That is my motive.
 
I already have a pretty good idea of the answer however, I am curious how people in the electrical trade perceive the effect today. That is my motive.

However you have not disclosed your affiliation and personal interest in the subject. That is intellectually dishonest to hide (if) biased interest. Especially when/if the survey - even if it is informal - will be used as a sales tool.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
about 1,000 KWH have been saved over 3 years, depending on the power price, that could be $200.

How many places are actually paying 20 cents/kW-hr. Can't be all that many. You could probably run a diesel genset at those rates.

I am reminded of some of the goofy assumptions people use to justify putting in VFDs and high efficiency motors. In many cases the payback time along with the cost of money for the upfront expenses means it is a loser.
 
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Electric-Light

Senior Member
How many places are actually paying 20 cents/kW-hr. Can't be all that many. You could probably run a diesel genset at those rates.

I am reminded of some of the goofy assumptions people use to justify putting in VFDs and high efficiency motors. In many cases the payback time along with the cost of money for the upfront expenses means it is a loser.

I haven't looked into commercial rates, but here is the residential rate for areas of California served by PG&E with most generous baseline usage allowance during summer for non-electric heated homes(i.e. gas furnace). For some reason,the allowance goes up 40% for SUMMER as well if your place is electric heated, so in PG&E served areas, it does make sense to install a heat-pump there, just so you can get lower rates during the summer.

0-582kWh @ $0.1223
582-756.6@ $0.13907
756.6-1164@$0.294
Portions in excess of 1164kWh billed at $0.40352
 

brian john

Senior Member
Location
Leesburg, VA
I did a PQ investigation about 10 years ago where the lamps were lasting 7-12 days. Utilizing a line disturbance analyzer (which was overkill). We found that the EMS was turning the light on and off about 1,200 times a night.
 

cadpoint

Senior Member
Location
Durham, NC
I notice when I read an article in EC&M or other trade magazine extolling the virtues of any particular product that the authors background and affiliations are disclosed.

So ....... how about it 'Electric Light' are you willing to disclose your motives?

I just find it somewhat dishonest to ask a question like this without disclosing any bias you may have.

However you have not disclosed your affiliation and personal interest in the subject. That is intellectually dishonest to hide (if) biased interest. Especially when/if the survey - even if it is informal - will be used as a sales tool.

Wow. I'll only assume that there's case history here that I don't know about! Or didn't pay attention too it!

I still see that any person still can't openly compose a line of thought here!
Why is that?



Wait let's digest the question and not the person for a moment. May I ?

I frankly thought it was generally known that flourscent have specific usage or as a function are generally understood why one's using this verses other illumination, but this was not a question! It did make me think about what was asked but didn't answer!

I found the query of the poll, if you want to call them that as being odd. I even thought of it as a misguided thought process or choppy sentence structure or what ever one thinks of this poll!

On a personal note!

From the poll, I'll digest that the OP is a designer from their profile and due the blank stark nature of the questions and possible responses makes me not think of them as a salesman!

I did not understand the call out, to quailfy the OP's position!
 
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chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
From the poll, I'll digest that the OP is a designer from their profile and due the blank stark nature of the questions and possible responses makes me not think of them as a salesman!

I also want to know EL's position.

I did not understand the call out, to quailfy the OP's position!
I got the call out. I PM'ed EL to find his stand due to the interesting nature of his posts but have yet to hear back.

Come clean my friend, who do you represent?
 

broadgage

Senior Member
Location
London, England
He's from London England... they got a wedding to pay for.:)

The going rate in London, at current exchange rates, is a little under 20 US cents a KWH.
As others post, many in the USA pay less than this, but some are already paying more.

Even at lower power prices, it will still be worthwhile turning off un-needed flourescent lamps.
 
The going rate in London, at current exchange rates, is a little under 20 US cents a KWH.
As others post, many in the USA pay less than this, but some are already paying more.

Even at lower power prices, it will still be worthwhile turning off un-needed flourescent lamps.

If he is in London, UK, then he is paying in Sterlins Pounds, instead of $'s!

Sure, if you want to support 'green' energy and want to generate your own your amortized cost can come out higher than that. So far the ONLY place you pay more than $0.2 in the US is in Hawai. The average US rate is around $0.1. http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html

'Conservation' of energy should be the reflexive thing what every thinking person would do. Figurateively speaking, if you have a hole in your pocket, where you can continously loose your money from, wouldn't you repair that? The only issue here is the awareness of difference between incandescent and fluorescent bulb behavior in response of switching; fluorescent has a much less 'switching life' than incandescent.
 
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