Our vacuum is broken so this is a moot point just now. However, I have often wondered about this. When my father vacuums, he doesn’t turn the vacuum off when he’s done. He just unplugs it and then puts it away. Then when I get the vacuum and plug it in, it instantly roars to life. Is it all right to unplug the thing without turning it off?
I’d guess the feeling has been created from Windows 95. “It is now safe to turn off your computer”. You’re a real child of the modern age.
The power switch on the hoover cuts the power to the motor. So does unplugging it. No harm, no foul.
Unless there’s a microchip inside thats vulverable to the power surge caused when plugging something in, there’s no risk.
It doesn’t really have anything to do with computers, though. This has been going on since before I ever even used a computer. If it’s safe, then I’ll just be vaguely annoyed by it and not say anything to Dad, though. Thanks!
Most appliance manufacturers and electrical safety checklists seem to agree that you ought to switch off the appliance before plugging or unplugging it. And yes, this practice long pre-dates the modern personal computer industry.
But I don’t know exactly why it exists. It’s fairly obvious why it’s stupid to leave appliances like hand drills in the switched-on position, since if the movable parts happen to be touching something or someone while it’s unplugged, it could do serious damage when it unexpectedly roars to life upon being plugged in.
But this doesn’t apply so clearly to the case of appliances like vacuum cleaners. Nor do I know whether plugging and unplugging a switched-on appliance is more dangerous to the appliance (or the user) than plugging and unplugging a switched-off one.
Turn it off then unplug it. You will were out your outlets faster by unplugging items drawing current. It’s better to put the wear on the devices switch.
Power switches are designed to handle the big fat arc that can happen when you turn a high amperage device on or off. Wall sockets, while fairly tough, are at the mercy of whatever cheap powerplug you put in them. If the plug is prone to throwing chunks of metallic vapor around when yanked, it’ll coat the socket, and then the socket will be prone to arcing no matter how good a plug you use subsequently.
Switches are purpose built to act as switches. While sockets can be used as switches, that’s not what they’re designed to do.
It’s safe enough - but it’s bad practice with an inductive load like a vacuum motor
Rather dull linkypoo
Switches are designed to cope with the arcing - the contacts use materials that erode less - and they spring open as quickly as possible rather than sliding like a plug coming out of a socket
So your Dad is technically doing a *bad thing * (but unless you can see any pitting on the vacuum plug prongs, I wouldn’t worry too much)
Unplugging a high current draw, such as a powerful vacuum cleaner, causes arcing at the point of disconnect. The contacts in the switch on the appliance is designed to handle this arcing appropriately. The contacts in the outlet are not, and can suffer erosion and pitting as a result. This damage can result in increased contact resistance, which could present a potential fire hazard at some point due to resistive heating.
It’s a nitpick, but the motor in the vacuum is an inductive load. When you try to open a circuit having an inductive load the voltage across the opening will rise in order to maintain the current and it can draw a fairly long arc.
If you’ve ever unplugged a vacuum cleaner while it was running you might notice an arc of electricity coming out of the socket.
The switch on the vacuum is designed to interrupt an inductive arc. The wall plug can do that too but has a small chance of having the arc flash to a ground point, or the arc can discolor the socket.
Of course, if I could type faster I wouldn’t be repeating the two previous comments that I now see on my preview screen
Apart from wear issues, it’s bad practice from a safety standpoint even if the device in question doesn’t present a safety hazard. If you are in the habit of yanking the cord on one appliance to turn it off, you will probably do it with other appliances as well. Plugging in a turned-on vacuum cleaner is probably not going to do more than surprise you, but plugging in a turned on table saw isn’t a good idea. It’s better that you just be in the habit of turning things off before unplugging them, rather than having to make a judgment call on each item.
Of course, we have some things these days that aren’t equipped with power switches because the manufacturer is saving a buck or two, such as my inexpensive rice cooker. And a lot of DSL modems and routers. I find it mildly annoying to have to power cycle my DSL modem and router, which I wish to do occasionally, by unplugging the wall-wart connector and plugging it back in.
Not a safety issue?
Imagine a dude deciding he’s going to help Dad clean up a bit. He puts on a pair of sweatpants (work clothes!), gets out dad’s vacuum and sets up the optional hose attachment so he can sweep up the cobwebs before turning his attention to the carpets. He needs two hands to plug it in, and there’s nowhere to set the hose attachment so he rests it between his knees, up high oh his thigh. He leans over to plug in the vacuum…uh oh! Dad’s left it on! As he leaned forward to plug it in, the hose shifted CLOSER to his balls! The proximity of his sweatpants-covered balls to the magically-on hose allows for the vacuum to suck his manbits all the way up to his pelvis!
Doesn’t this sound like a safety issue? Or do I just watch too much Mr. Bean?
I have run into improperly grounded outlets.
No cite, but I imagine that when yanking out the cord of an appliance that draws as much current as a vacuum, you run the risk of shock and arcing hazards.
Also, I have noticed old cords were the insulation was pulled back away from the prong areas. I believe this is because folks unplugged the device a lot by grasping the cord and tugging, instead of grasping the molded plug. This leaves the normally covered wires exposed. (There is still usually another layer of insulation, green and white colored. But the little alarm in my head is lit looking at that situation.)
The aplliance makers spent the time and money to give us gizmos with on/off switches. And it’s not to charge us more for the product.
You get an electric arc to the outlet, if the aplliance is drawing a heavy current. It’s one of the reasons for damage to outlets, and the plug of the aplliance. It’s normally the outlet that recieves the worse damage.
OK, wait. So it seems that it is bad after all, to unplug without switching the thing off first.
No, you read too many Straight Dope columns. 
Yes. It is bad. Have dad knock it off.
See posts # 5,6,7,8,9,etc.