Lighting String Manufacturers Stats

[inzeos]

Broke open a few boxes of my 100ct Walmart incandescent strands to measure them and compare to the actual box specs.  Box states that they will draw 0.34 amps.  I measured them with my Kill A Watt EZ and I believe their actual draw is much closer to 0.21 amps.  Basing this off the fact that my when nothing is plugged into my Kill A Watt EZ it reads 0.14 amps, which I'm guessing is it's own baseline power consumption for it to work.

Am I write in thinking that the vendor is way over stating their products usage?

48 x 0.34A = 16.32A
48 x 0.21A = 10.08A

Makes a big difference when you do the math out over a large number of strings.

Going to measure a few more and eventually all of them for shits and giggles when the rain stops.

Kill A Watt EZ manual for reference;

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Leif

[inzeos]

Quick dump of my figures from a spreadsheet.

[chrisatpsu]

it would be wise for a company to state there product uses more energy than it really does. with people overloading their electrical sockets for just the christmas tree. if they keep to the printed warnings on the labels/box, they might prevent them from burning down thier houses.

kinda like it's safer to round up, than round down. 

[rimist]

Actual AC voltage varies, which causes the amps to vary as well

- Rimist

Sent from my HTC Glacier using Tapatalk

[rm357]

Whenyou first turn them on, lamps draw more current. As the filament heats up, its resistance increases, which reduces the power draw. Their rating probably accounts for the maximum current draw during the power-on surge.

RM

[inzeos]

Whenyou first turn them on, lamps draw more current. As the filament heats up, its resistance increases, which reduces the power draw. Their rating probably accounts for the maximum current draw during the power-on surge.

RM

So there is a chance that the Kill A Watt EZ meter is not sensitive or capable enough to capture and display that initial power draw?  Maybe my multimeter would do a better as it has some recording feature or so says the manual.

[tbone321]

I don't think that it's a matter of sensitivity and more a matter of design.  The purpose of the meter is not to measure peak current draw but to measure the average or constant current draw of what is plugged into it.  If your meter has a peak hold feature then that would give you the power up current.  The current rating on the box probably reflects the maximum current the string is expected to draw and probably takes into account start-up current, burnt out bulbs, and possibly voltage variations as well.

[deplanche]

I think you'll find that most stated capacities on things have a factor of safety built in.  Would you use a ladder with a 200 lbs capacity if you were 199 lbs and the ladder were to collapse right at the 200 lbs mark?  Probably not.  The number they put on there is the safe range for use.  If you go over that, you are doing so at a risk to yourself, even though you know the ladder can probably hold 250 lbs without a problem.

The lights are similiar.  They have likely tested many stings, come up with a statistical value for how much current is used, added onto that a factor of safety, and put that value on the box.  If you determine that it is using less, based on your own calculations or measurments, you are doing so at your own risk.  Not something recommended by the manufacturer or anyone on this site I am sure.