Flourcent lights, leave on or turn off?

[petersonra]

I know it takes a bunch of energy to "start" a flourecent light, is it better to leave them on or tun them off and on several times a day for energy efficency?

It does not take all that much energy to start a fluorescent lamp.

But they tend to fail not so much by how many hours they run but by how many cycles. And it often costs more in labor to replace the lamp than the lamp itself, so it is best to limit how many times it is turned on/off.

 

[broadgage]

If flourescent lamps are turned on and off frequently, them the life of the lamps in hours will be reduced, perhaps substantialy.
This does not however normally increase the money spent on lamps.

Consider a lamp that with infrequent switching lasts about 16,000 hours, that is about 2 years if left on most of the time.
Now consider the same type of lamp wired to a motion sensor such that is switched many times a day, and is lit for 6 hours a day.
This might halve the lamp life to about 8,000 hours, however the reduced hours of use per day mean that the lamps should last about 4 years instead of about 2.

The person paying for the lamps and the labour is most unlikely to know or care how many hours the lamps have burnt for.
They would want to know how much is spent per month/year, which is halved in this example.
The fixtures and ballasts should also last longer, less heat build up and less wear and tear from re-lamping.

 

[donw]

I have read that you should specify programed-start ballasts (instead of instant-start) if using occupancy sensors. Manufacturers will not warrant the use instant-starts.

 

[Doug S.]

Wow, page 3 before we got to lamp types. :roll:
Don't forget the philosophical aspect of keeping food on your union-brother (bulb changers) table. :grin:
Who knew how tough a choice this could become!

For me, it basically comes down to... "Am I leaving the room? Is there anyone else in it?" Click. I have been programmed by my oppressive father. Just as my children are now! :grin:

My 2?
Doug S.

 

[TOOL_5150]

Wow, page 3 before we got to lamp types. :roll:
Don't forget the philosophical aspect of keeping food on your union-brother (bulb changers) table. :grin:
Who knew how tough a choice this could become!

For me, it basically comes down to... "Am I leaving the room? Is there anyone else in it?" Click. I have been programmed by my oppressive father. Just as my children are now! :grin:

My 2?
Doug S.

Yep. Mythbusters allready did all the calculations - its better to just turn em off.

~Matt

 

[LarryFine]

I have been programmed by my oppressive father. Just as my children are now! :grin:

So Grandpa does the disciplining?

 

[Brian Oshman]

My thoughts are similar to Bob's.

There is a reason that someone has calculated for the setting of sensors to go off approximately 8-15 minutes.

FYI- Something I will share with you from experience, these sensors will burn through bulbs like crazy. That is why they are set to 8-15 minutes. One shop set their sensors to go off in 20 seconds and they replaced bulbs at 6 times the usual rate. The cost of the bulbs, rate of the electrician and his equipment all have to be calculated in the 'real world' cost savings, if there is any.

Less air polution from power plants and more mercury and phosphorus polution in the ground from CFL's and tubes. Sounds like a good isea to me. I am really suprised that this type of lamp has been so embraced in the quest for reducing polution.

There is no such thing as free lunch.

 

[Brian Oshman]

I have been programmed by my oppressive father. Just as my children are now! :grin:

Wait until they start paying the bill. That is when they will get it.

I have threatened many times that I am going to pull the meter out of the socket and we're going to party like it's 1899.

 

[Besoeker]

If flourescent lamps are turned on and off frequently, them the life of the lamps in hours will be reduced, perhaps substantialy.
This does not however normally increase the money spent on lamps.

Consider a lamp that with infrequent switching lasts about 16,000 hours, that is about 2 years if left on most of the time.
Now consider the same type of lamp wired to a motion sensor such that is switched many times a day, and is lit for 6 hours a day.
This might halve the lamp life to about 8,000 hours, however the reduced hours of use per day mean that the lamps should last about 4 years instead of about 2.

The person paying for the lamps and the labour is most unlikely to know or care how many hours the lamps have burnt for.
They would want to know how much is spent per month/year, which is halved in this example.
The fixtures and ballasts should also last longer, less heat build up and less wear and tear from re-lamping.

I pretty much agree with that.
The start-up v continuous running isn't the real issue for costs - it's a red herring.
It's the how trade-off between energy saving and replacement costs pans out for frequent or infrequent switching. And I think there is no "one size fits all" answer.

 

[weressl]

I know it takes a bunch of energy to "start" a flourecent light, is it better to leave them on or tun them off and on several times a day for energy efficency?

The additional energy is insignificant.

The concern of frequent on/off switching of fluorescents has more to do with their life shortening. Fluorescent 'life' is given at 8 hours continuous burning.