On Fri, 05 Dec 2008 23:44:10 GMT, "BigWallop"
wrote:



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,

Do you have a Bovine Scatter diagram for that ?

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.


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 ?

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.