I recently bought an electric heater from argos. It is working ok but when switched on/off at the wall socket sometimes a spark is seen inside the socket. The house was re-wired a couple of years ago and is all properly fused etc.
Is this normal behavior for an electric heater / does it indicate a fault and should be replaced?
It's normal for a high power load, providing it's only whilst you are moving the switch. If the plug or socket gets hot or has any discolouration caused by having got hot, that needs invesigating. If it's a 3kW heater, the plug fuse is expected to get warm though.
Is the heater on or off when you switch it off at the socket?
How can you see a spark inside the socket when you switch off the socket or do you mean you can see the spark inside the unused half of a double socket or are you just pulling the plug out with the socket switch in the ON position?
The heater is on. I usually just turn it on/off at the wall. Is this inadvisable?
I see a light through the plastic socket cover and sometimes see the spark through the gap the switch sits in.
In a word yes. B-) Not overly important for small loads but heavy ones like heaters it is better to switch off on the appliance before switching off at the wall. If nothing else it saves damage to the sockets switching contacts by the arc that you see.
On Fri, 5 Dec 2008 05:59:09 -0800 (PST) someone who may be snipped-for-privacy@googlemail.com wrote this:-
What is the rating of this fire. 3kW?
With any reasonably high power electrical equipment there will often be a visible spark at the switchgear when it is switched off [1] [2]. This is generally nothing to worry about. However, if the heater has its own controls I suggest using them to switch the heater on and off. The spark will still be there, but it may not be visible (sometimes it is more visible in a heater though, there is not one answer to your questions).
The sparks (and arcs) on large switchgear can be very impressive indeed, there are films on the web.
[1] with AC electricity there are times when the current is so close to zero that there is no spark. Whether you operate the switch at that time is a matter of luck. [2] the spark is often still there even if it is not visible.
As long as it isn't as bad as this one, then I think you will be OK.
Toby...
Is this guy cutting or crimping?
I suppose that would be the case if the switch in the heater were more durable than the one in the socket. On the other hand a 13A socket is fairly cheap and easy to replace but sourcing a replacement switch for a heater could be more difficult, or even impossible for some Chinese imports.
There again, the heater switch gear may have been designed to withstand the arcing caused by switching off the heater element. Back EMF currents, even from a loosely coiled heater element, can cause higher amperage arcing across switch gear when the blades are snapped open, which the heater designer should account for when choosing the materials before equipment manufacture. I don't think anyone would recommend a heater that flashed blue and yellow sparks when they used it.
But, we all know that the 13 amp sockets in our houses are designed to withstand a minimum of 20 amps across the terminals and switching mechanisms, so it should be capable of accepting the load the heater draws, but its switching gear may not be able to handle the back EMF current. Especially if it is one of the cheaper brands which use minimal materials constructions to keep manufacturing costs down. And it is a pain in the rear orifice to keep swapping out the sockets in our houses.
True enough but I'd rather the switch in the appliance failed rather than hidden damage in a socket that could go undetected for years until the contact resistance goes up, a different heavy load is used, the contacts overheat resulting in a fire... Small risk but still a risk.
Do you have a Bovine Scatter diagram for that ?
Heating appliances are available in the supermarkets for less than four quid delivered from China, and the supermarket has made it's profit as well. How much do you think they've spent on the design and construction of the mains switch ?
The light from an arc like that is really very bright, easily bright enough to see through the plastic of a typical socket.
A few years ago one of the cats in the house where I was living "sprayed" on the wall above an electrical socket and it ran down the wall into the pattress box. I didn't see him do it and he had moved on before I noticed anything, but I heard a peculiar hissing noise and when I turned round I could see light shining from the socket -- through the face, off to one side of the holes -- and quite bright despite having passed through the plastic. It gave me quite a fright! And the smell of hot electrolysed cat piss is, shall we say, distinctive.
And if you have unswitched sockets, then you would only have the choice of the applicance switch(es) or pulling it out while running. At four quid (that *is* cheap), it is probably more sensible to blow the appliance switch than a socket.
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