Good post. But being the nit-pick I am, I challenge the following statement:
15 amp circuits usually use 14 AWG wire and 20 amp circuits usually use 12 AWG wire. 14 AWG extension cords are very common. 12 AWG extension cords are also available, but less common.
You’re correct. In a perfect world, people would use 14 gauge extension cords, and would install GFCI protection in damp or wet locations, we wouldn’t have any problems. Yet that wouldn’t account for voltage drop, not would those flexible cordsets be protected from physical damage, unless they were on bedroom circuits protected by AFCI units.
Unfortunately, homeowners and business persons rag-tag things together, without regard for the potential implications. I’ve seen scary things, such as a double male ended extension cord used to steal electricity from an adjoining apartment.
Although your point is valid in that extension cords are available in large size, the questions begs, who buys them? If they were a big seller, I’d have answered a lot less calls in my career.
Re Extension cord heating:
I had no facts or cites for my initial statement about unrolling extension cords, but my local fire department has several charred cords on reels from instances where residents called for help when they started smoking.
Ezstrete said: “If your home was properly wired the outlets in your room should be fed from at least two, and possibly three, different curcuits.”
Most electrical codes, and common practice, allow for five duplex convenience outlets, or a combination of five convenience duplexes and lighting fixtures on a single circuit, with separate dedicated circuits required for major appliances, and limited use circuits for small appliances (among thousands of other details too burdensome to repeat here). My own experience with older buildings, do-it-yourselfers, clowns, incompetents, and the like has discovered as many as fifteen duplex outlets and two major appliances wired into a single fifteen amp breaker (and they wondered why the damned thing kept tripping . . .). On the face of things, most of the advice here is correct – don’t turn everything on at once – but unless you know for sure how the place was wired, do yourself an inexpensive favor and hire an electrician to trace the circuits and make sure that the refrigerator and the bathroom didn’t somehow end up connected to the same breaker as the outlets in your room by some idiot over the years. Written electrical codes only work if someone reads them and actually does what they advise.
Q.E.D. said: “I’m sorry, but that just isn’t true. The plastic that the insulation is made from (usually PVC) is an excellent thermal insulator, so that the temperature gradient across it could be quite large. In other words, the copper conductor inside can be very hot, while the outside will remain relatively cool to the touch. Air-cooling is only effective if the heat is allowed to flow to the surface relatively unimpeded, as it is in metals.”
This resulted in some measured technical debate, which really wasn’t necessary – coiled or uncoiled, if the conductor is heating up the wire is overloaded, and will soon start a fire. The insulator is plastic, which melts progressively over time, normally, rather than as a single catastrophic event – sort of like one of those really fat candles that burn down about two inches before the side burns through and sends hot wax across the table. The melted plastic has no power of recovery, and each time the wire is overloaded the plastic melts a bit more, until finally it burns through. The easy test is always at the plug end – if the plug is warm to the touch after about an hour of use, then the extension cord isn’t big enough for the task and will eventually cause a fire. To a small degree a coiled wire can be argued to be more dangerous, but the argument there is sort of picking nits since the wire must already be overloaded to be heating up in the first place. If it burns the place down a day or two sooner by being coiled a jury won’t be much swayed by the impressive math demonstrating why there was a delay.
Gairloch
In a rental property the owners had an extention cord on a reel.
I noticed that the cord was sitting only a few feet from an outlet so that most of the cord was on the reel. I was curious to see the condition of the cord towards the center of the reel. It was just one solid melted mass.
I informed the property owners. I’m sure I prevented an accident.
YES IT DOES MATTER if one leaves the cord on a reel or other such device that tightly coils the cord.