# Thread: Fluorescent lights

1. Member
Join Date
Feb 2005
Posts
95

## Fluorescent lights

Quick question:
I have heard the fluorescents light will last a lot longer if they are left on with as little on/off cycles as possible Is this so? And if it is, does anyone have any idea how the constant "lights on" effects one's monthly electric bill?
I have a ton of them in my shop and am mixed as whether or not to leave them running or try to keep the electric bill down
Thoughts?

2. Senior Member
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If you did a bunch of math, you'd find that it costs about \$6 per month to operate one 8 ft tube, at a rate of 10 cents per kwh. That's leaving it on all the time. I've seen those tubes run for more than 5 years before failing, but if we take 5 years as the replacement time, then the cost of running them will be about \$360 per tube, plus replacement cost. Let's say they are \$10 to replace. So that's \$370 over 5 years. Per 8 ft tube.

Now let's say you switch them on and off many times per day. They'll still last 3 years or more. But let's say they only make it 2 years. Your cost of running them has jumped from \$370 to \$395 over the 5 year period. But that's if you still have them on for practically all of 24 hours per day. If you ran them for 8 hours per day, and they only lasted 2 years, then your 5 year cost of running and replacing them is then \$145. That's assuming a shorter lifetime than I'm used to seeing from them, a replacement cost of \$10 per bulb, which is a little higher than I can currently get them for, and an energy cost of 10 cents per kwh.

Now let's say that after 5 years the ballast had died, and that it's solely because you switched them on and off all the time, like you had nothing better to do. I can buy a ballast for about \$40, so that represents \$20 per tube, and if you add that to the cost of running the lights 8 hours per day, it still only costs \$165 to run one tube for 5 years.

So you leave them run all the time and it costs about \$400 per five years per tube, and if you switch them on and off all the time, but don't leave them run all night, it's about \$160 per five years.

The one reason I wouldn't always be turning them on and off is because if it's cold, they won't give a proper light right away.

3. Senior Member
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Not exactly on topic, but strangely, I have lost more ballasts than tubes in my shop in the last 6 years.

4. Senior Member
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## Weird Tubes

I have a high efficiency sign type tube system in my shop same tubes like 12 years? What am i doing wrong?

5. Senior Member
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I believe this "myth" comes from some office buildings where the lights are changed by union help. They probably need to have them on for at least 14 or 16 hours a day anyway so the savings in electricity is not as much.

I have seen those same buildings use electric heaters in the AC ducts to control the temperature in each area. The AC ran full blast 24/7 and the heaters reheated the air to a more comfortable temperature. 1950s thinking. I doubt that very many such buildings still do that. Likewise for leaving the lights on 24/7.

As my father often said, "Turn the lights off".

6. Senior Member
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Mar 2005
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## Turn the lights off....

Paul;
I couldn't agree more, Paul. A simple energy concervation means, yet it is dependent on trained, thinking people.
On the other hand, building owners/ tennants will spend big bucks to have "energy management systems" installed to turn lights & heat on & off automaticly....(good money to be made in energy consulting...)

As for heating & cooling, In many large buildings the lighting, equipment load (think maybe data centre, fashion store etc.) and tennant mix may be such that cooling is needed most, if not all, year round. Especially in a temperate climate. Some areas like office/ reception areas may need supplemental heat when the bulk of the load is for cooling. The cheapest way to do this is often with a duct heater...Duct or pipe revisions etc. are expensive and add to tennat improvement costs.

I agree that it would be better to have seperate heating units, zone control or some such affair but these are usually more expensive to install...

That's what I've experienced, anyway.
Rick

7. Senior Member
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## Corporate thinking revisited

Originally Posted by Paul Alciatore
I believe this "myth" comes from some office buildings where the lights are changed by union help. They probably need to have them on for at least 14 or 16 hours a day anyway so the savings in electricity is not as much.

I have seen those same buildings use electric heaters in the AC ducts to control the temperature in each area. The AC ran full blast 24/7 and the heaters reheated the air to a more comfortable temperature. 1950s thinking. I doubt that very many such buildings still do that. Likewise for leaving the lights on 24/7.

As my father often said, "Turn the lights off".
Paul,

Talking about the heating system, The university I worked at had chillers that produced 48* chilled water that was piped to every building on campus. They had a steam plant which piped live steam to each building also. They used the steam in little radiators at each room, inside the ductwork, to temper the air coming into the rooms by the thermostats. In the energy crisis of the 80's they came around and locked the thermostats at 80* in the summer (to save energy). To make it bearable we simply climbed into the ceiling and valved the steam off to the mixing boxes.

As for the lights burning in state buildings, the engineers figured the heat given off by the lights as part of the HVAC system to keep the buildings warm at night. No s**t!!!

8. Senior Member
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And shortly after my last post, what happens? I'm standing at the computer at the island in my kitchen and I hear a muffled pop and crackling sound. The light in the range hood is out. I walk over, and the smell hits me. It's the smell of magic electronic smoke. The failure is shown here:

Never witnessed such a failure before. Wonder if it would have gotten worse if I didn't hit the switch? It was pretty hot, I can say that...

-Mark

9. Member
Join Date
Feb 2005
Posts
95

## Wheeew

You guys are good. It was a bit OT but it still is a shop issue. It sounds as though there are still opposing thoughts on this. I didn't realize it would generate such a response! At any rate thanks to all who replied.
I think I will leave them on during the day as much as possible. I have been turning them on and off once each day but to tell the truth, I am a bit uncomfortable leaving just about anything running when I am not home. For us here in Arizona the cold flicker really isn't a problem and I guess I'll just leave them on as long as I am home and avoid as many on off cycles as I can.
Thanks for the input

10. Senior Member
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Illinois
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Wirecutter:
Heat from the lamp may have contributed to its failure. I found that with the compact fluorescents that if have if I burn them with the base up the heat from the lamp would cook the electronics and they would only last for about two months. Now this could well be just a problem that this particular Chinese manufacture is having.

Anyway I cured the problem by making a reflector/heat shield to go between the lamp and its base.

As far as being a fire hazard, it is probably pretty low. The offending part(s) will usually burn itself out rather quickly thus opening the circuit stopping any further current flow, and allowing it to cool down.

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