"Mike Clarke" wrote in message
et...
Dave Liquorice wrote:

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.

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.

Mike Clarke


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.