I had to replace the burned out FL long straight tube in my shop light, and noticed the marking indicated "40 watt".
I was thinking - our twist CFLs that replaced the our 60 watt bulbs are only running about 14 real watts.
SO - are the traditional long straight tube FL shop lights actually using 40 watts, or is that just and equiv and the real watt usage is much less, just like the CFL ?
If not - then that means the long tube FL are as in-efficient as a normal bulb.
They use 40W, they will be producing the light equivalent to ~150W of incandescent lamps. Unfortunately, few people these days seem able to understand what efficiency really means, or calculate the MPG their car gets :(
Just a little gee whiz info I put a clamp on the hot side of the line cord of a regular 2 tube shop light and the whole thing, ballast and all is about 0.48-49 amps and a line voltage of 123 VAC so the whole thing is about 60 watts. I am not sure where the "40w" comes from. Maybe that was based on the old style magnetic ballast.
True RMS meter? The missing 20W could be hiding in a distorted electronic ballast waveform.
That might be true, the DL250 manual says
"AC readings displayed on this meter are average responding, True-RMS indicating. They are based on a true sinusoidal waveform."
ok - was curious enogh to break out my Kill-A-Watt meter... as the twin tube shop light is plugged into a switched outlet.
SO - the lamps are - F40RES SP41 40w
The meter shows the fixture with both tubes running -
124v .86amp 67watt 105va ..... that's 67watts total for BOTH running
The T8 tubes are 32W also, while the T12 are 40W. Not sure which you have in the fixture you measured.
Interesting. So I went out to my shop where I could conveniently measure on four identical cheap shoplight fixtures all populated from the same case of Sylvania Octron/Eco F032/T41/Eco 32W lamps. After a warmup period I measured: 56W, 57W, 57W, 60W. So there is some variation and all seem to be a bit below the 32W spec on the tube.
I'm guessing that is for the fixture - with two bulbs lit up -
BTW - looked up that various flavors of my F40's - looking for "lumens" and they appear to supply.... 2600 - 3150 lumens - so a lot of light for wattage used -
hmmm - single F40 straight bulb
2600 lumens / 34 watts = 76 lumens per watta stanard 60watt CFL
900 lumens / 14 watts = 64 lumens per watt
Watts are a measure of power consumption, not light produced. What you need to be looking at are lumens. Those old 40w 48" tubes lumen output varied, but 3200 lumens is a reasonable average. A 14w CFL produces about 800 lumens, which means you'd need 4 of them to produce the same light as an old tube.
BTW - the current 48" tubes are 32 watts for a similar lumen output.
40 watts per tube. I got 32 or 40 watt tubes rated over 3000 lumens each. The 12 watt cfl are under 1000 lumens each. You would have to match specs and do some math.
Greg
There ARE 32 watt t12's or something less than 40 watts.
Greg
Years ago I noticed how much brighter the new tubes were, and they didn't change ballasts, and they were 32 watts.
Greg
I have F40CW tubes in the one I tested.
If I get a few minutes I will check some other ones I have here with the clamp and the kilawatt. I think I have some old magnetic ballast fixtures.
As you can see from other replies, they may not be a true 40W, but they will use more power than the CFL. What you want to com pare though, is the light output to see if it is the same.
At work we replaced some 1000W light with brighter 128W fluorescent.
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