# CFL vs Incandescent

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• posted on April 28, 2008, 12:15 am
I remember one college project was to figure out how long you needed to turn out a standard the old 4 foot tubes before you would save money. Factoring in the cost of electricity lamps and the labor for maintenance to replace them, it turned out to be about 20 minutes. We had a fun statistics class back 35 years ago. The CF's would be far less. That start up surge is like 1/30 of a second and is about 10 times or less of the rated lamp consumption.

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Joseph Meehan

Dia \'s Muire duit
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• posted on April 28, 2008, 12:24 am
Joseph Meehan wrote:

For start up normal ilament lamps creates surge current at the moment it's on. Most any electrical load being inductive will do same.
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• posted on April 28, 2008, 2:04 pm

The inductance of a filament type bulb is negligible and doesn't cause any surge. In fact, with an inductor the effect is exactly the opposite. The faster the rise time of the incoming voltage waveform, the higher the impedance, which restricts current flow.
The current being higher at start up is only due to the fact that the filament resistance is lower when cold than when it's at operating temperature.
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• posted on April 28, 2008, 2:19 am

I remember doing calculations on 4-footers of 32-40 watt range also.
One more thing: There are older figures going around as to life lost per start that date back to 1970's-1950's, and/or are based on "glow switch" starters (which typically blink the lamp a few times before getting it on to stay on). 4-footers since the early 1970's at least have mostly not needed glow switch starters, due to use of ballasts that have starting means.
It appears to me now that a 4-footer can gain savings by being turned off for as little as a minute in comparison to being left on. It appears to me that this explains why I have seen a few instances of motion sensor switches to turn off the lights in rooms illuminated by 4-footers if nobody is there - even in a government building restroom!
As for CFLs - they cost more than 4-footers and consume less power than 4-footers, as well as not being as durable as 4-footers! Therefore CFLs often are better being left on rather than being turned off and back on 5 maybe 10 minutes later, while 4-footers are more in the category of turn 'em off when you leave the room!
As for effects of labor costs - I still see it being worth turning off 4-footers if they will probably stay off for at least 3 minutes, and CFLs if they will stay off at least 10-36 minutes or so (depending on CFL type and wattage, electricity cost rate, and labor cost).
- Don Klipstein ( snipped-for-privacy@misty.com)
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• posted on April 28, 2008, 11:55 am
I should have made it clear that those numbers were based on the available technology of the time and that today's technology is very different.
I can remember about the same time I was working at a very large discount store about the same time when the manager decided to replace all the lamps at the same time. The difference as amazing. It was sun glass time. It was one of the very few good things he every did. Lucky for me I worked for a lease department so I did not answer to him.
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Joseph Meehan

Dia \'s Muire duit
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• posted on April 28, 2008, 12:42 pm
never use spray polish anywhere near a CF.
I did a little of the mist must of entered the base vent holes, lamp has wood.
anyhow the ballast part erupted in a flame......
i now spray the rag and wipe the wood area.....
i was exciting:(
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• posted on April 28, 2008, 2:07 am
bonnie wrote:

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