electrical safety question

1) how many 100 watt equivalent bulbs can i safely run into a normal heavier guage orange household extension cord?

2) can it be unsafe to leave the extension cord plugged in and powering the safest number of light bulbs on for days and weeks at a time?

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Burf7 years ago

1) An extension cord, based on its gauge, can power an appliance of a certain wattage only at specific distances. As the cord gets longer, the current carrying capacity of the cord gets lower. For example, a 16 gauge extension cord less than 50 feet in length can power a 1625 watt (W) appliance. A 16 gauge cord that is longer than 50 feet in length can only power an appliance up to 1250W.
if your appliance indicates that it uses 5 amps at 125 volts, then its wattage rating is 625W (5x125). All extension cords sold in the U.S. and in most other countries, must have its rating printed on the packaging or on the cord.

2) It is never a good idea to leave any electrical device connected and unattended for an extended period of time. That said, if the cord is undamaged, used in accordance with its UL rating and recommendations, and undisturbed (you're not going to leave it someplace where earthquakes, floods, critters, human or otherwise can gnaw on it or damage it in some manner,) it should be able to safely withstand continuous use for months or even years.

hobbssamuelj (author)  Burf7 years ago
 yeah, the cord will definitely be less than 50 feet.

Its  kinda like the ol' saying: "A chain is only as strong as its weakest link".
You could be using a brand new extension cord, but what about the
REST of the wiring that goes from the  circuit breaker  box to
 the receptacle that  you plug the extension cord into?
Will there be anything else on the circuit? Are you SURE?
There's a possibility, especially in an older home, that some of the electrical
splices, and contacts have become oxidized over the years.Oxidized wiring
causes increased resistance which will result in excessive heat and possibly
an electrical fire.
So, its best to consider the condition of the whole electrical system first.

kelseymh7 years ago
You need to know the true wattage, not "equivalent", which is just misdirecting consumer-speak for light output (apparently normal people can't understand what "lumens" means).  Most CFLs listed as "100 watt equivalent" actually draw around 20 to 25 watts; look on the package for your bulbs to get the answer.

Once you have that information, Steve's math is what you should use.  Look on your extension cord to find out its maximum current (amps).  Indoor cords are usually 10A max; outdoor (thick orange) may be anywhere from 10A to 25A.

Power in watts is equal to voltage times amperage:  10A at 110V is 1100W.  So now you just have to do multiplication and division to answer your first question.
hobbssamuelj (author)  kelseymh7 years ago
 yeah, i knew they were true rated at 23 watts.  so, i guess the answer is a whole lot of cfls... essentially.
That depends on the cross section of the wire, and the supply voltage. Our stuff in the UK can usually run at 13A 240 V, or 3120 W, 31, 100 W bulbs BUT ONLY IF THE CORD IS FULLY EXTENDED AND VENTILATED. In the US, your usual cords seem flimsy by comparison to ours.

There is no safety implication PROVIDED there are NO hotspots in the cable. It MUST not be covered in anyway.