Will my space heater kill me?
November 11, 2007 2:54 PM   Subscribe

Will my space heater kill me?

I just bought a new space heater. It's the type with the glowy orange coils. It works well, but I just noticed that the cord gets very hot where it is plugged into the extension cord. This seems weird to me. What could be the explanation for this? Is it something to be concerned about?
posted by boots to Home & Garden (13 answers total) 3 users marked this as a favorite
When you say 'hot', how hot?

Appliances that draw a lot of current (those style of heaters are a good example) then the wires will get hot. It is perfectly normal up to a point. Does the extension lead get hot, too?

Have you tried it without the extension lead to see if it acts the same?

Where are you? Is the heater fused individually (ie in the UK with a fused plug)?
posted by Brockles at 3:00 PM on November 11, 2007

It might be the extension cord that's getting hot. You need to check the current rating for your heater (it will be a number in "amperes" or "A") and make sure to use an extension cord whose current rating is equal to or higher.

If the extension cord is too small (by which I mean, the wires are too narrow), it will definitely heat up and it could cause a fire. Usually for space heaters you need a very heavy extension cord.
posted by Steven C. Den Beste at 3:21 PM on November 11, 2007

Space heaters draw a *lot* of juice. The cord on the heater is presumably designed for that, but the extension cord is another story.

A) run it without the cord

B) check the rating of the cord versus the power draw of the heater
posted by madmethods at 3:22 PM on November 11, 2007

Keep in mind too, it is always best to NOT use an extension cord if possible... Especially with items that draw a lot of current.
posted by HuronBob at 3:24 PM on November 11, 2007

You likely shouldn't be using this space heater with an extension cord. If you must, get the heaviest gauge cord you can in the shortest length possible.
posted by davey_darling at 3:25 PM on November 11, 2007

First off, you should be using what in most hardware stores is called an "appliance extension cord." This will have larger (typically 14 gauge) copper wires that can carry up to 1800 watts. The typical brown lamp extension cord only has the (smaller) 16 gauge wires. (Smaller wire gauge number means heavier wire).

It is not unusual for the plug connection of a high current device to get a little warm to the touch, but it should not be uncomfortably warm such that you can't hold it tightly in your hand. The reason it gets warm is that the connection between the plug and socket is not perfect. There is some finite resistance that produces heat just like it does in the heater coils, except that the resistance is much, much less. If the plug is not uncomfortably warm there should be no risk of fire.

You should examine the blades of the plug to see if they are bright and shiny. If not, polish them up a bit with a something like a Scotch Brite scrubbing pad. You can't easily polish the corresponding contacts in the socket and you don't want to push anything in there that might spread them and make the connection looser. But you can plug and unplug several times to try to polish the contacts.

This issue is more common in the U.S. which uses 120 volts than in countries such as the U.K. that use 230 volts. This is because in the U.S. you have to shove nearly twice as much current through the wires to get the same electric heater output.
posted by JackFlash at 3:47 PM on November 11, 2007

Here's an AWG chart, which you can use to determine how long and what gauge for what current.

It's probably less than you think, and you probably are in danger of starting a fire.
posted by Mr. Gunn at 3:50 PM on November 11, 2007

Don't use a regular extension cord with an electric heater. The kind you could use are the very heavy, very thick, very low gauge kind, 15 to 20 amp ratings preferred, which is probably higher than the heater but the heater tends to draw lots of current for a long time, as opposed to lots of current in short bursts, so the cord does not get to cool down. A hot cord worsens the problem. If you use an extension cord get the big hulking mega amp kind. They are big and ugly as sin, but you won't burn your house down.
posted by caddis at 3:53 PM on November 11, 2007

The heater will have a current rating on the back somewhere (in amps), telling how much current it'll try to draw. The extension cord will also have a current rating (possibly on the plastic tag you ripped off and discarded five years ago). Make sure the cord's rating is at least as much as the heater's.
posted by hattifattener at 5:36 PM on November 11, 2007

As JackFlash mentions, the reason for the plug/socket junction getting hot is resistance in the connection. If either side is dirty/corroded and if the plug and socket don't fit tightly, this is likely to happen. I would recommend a good quality, newer extension cord, with a large current rating, if you must use one. And, if the blades of the plug of the heater aren't shiny, gently polish them clean.

I have seen such a plug/socket junction get so hot that the plastic material it was made of melted, allowing the conductors to short, producing sparks and igniting the carpeting underneith.
posted by mmagin at 5:45 PM on November 11, 2007

For what it's worth, my space heater came with a warning that the cord may get hot when the heater is in use, but if it gets *really hot* that I should call an electrician.

No word on how hot *really hot* is, but apparently for my heater this sort of thing is normal.

I should mention, though, that I have a completely different kind of space heater than you. Mine is the radiator-looking kind.
posted by Afroblanco at 9:11 PM on November 11, 2007

I think JackFlash's guidance as to the difference between 'warm' and 'hot' is good. If you can hold it tightly in your hand, continuously, then you're OK: that's just warm, and electric appliances sometimes get warm. But if any part of the electric supply gets hot enough that you can't make a fist around it and hold it there, stop -- you're doing something wrong. The only part of the heater that should get too hot to touch are the heating coils and adjacent parts.

As others have said, make sure the extension cord you're using is rated for the current the heater draws. (If you only know the wattage on the heater, divide it by 100 for a rough idea of the current. It'll be a high estimate but will keep you safe.) Then buy an extension cord accordingly, and keep it as short as possible!

Never depend on the fuses in your house to save you. They're designed to work with the wiring in your walls, that was installed by an electrician according to code. They won't save you, and it's entirely possible to start an electrical fire, if you use under-rated extension cords, even if they're plugged into a perfectly good household electrical system.
posted by Kadin2048 at 9:36 PM on November 11, 2007

In addition to using a properly rated extension cord, do not cover the cord with anything.
posted by yohko at 12:04 AM on November 12, 2007

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