On 2/26/2009 1:10 PM Jeff Wisnia spake thus:

David Nebenzahl wrote:

On 2/26/2009 11:06 AM Hobbyist spake thus:

When I switch my kettle off at the electric socket, a brief flash of
green light is visible behind the socket. Is this normal, or could it
be dangerous? Supposedly it's ok if the kettle plug is earthed?

Flashes of light accompanying switching something on or off are *never*
OK. Indicates arcing contacts, which can only get worse with time.

So, I'm using one of these Intermatic timers ahead of my home Bunn
coffee maker to remove power from it during the night. That saves us a
little electricity by not keep the water at brewing temperature all the
time.

http://www.intermatic.com/images/misc/TN111C.pdf

The Bunn is rated as drawing 900 watts and the timer is rated to switch
1750 watts resistive, almost twice as much as the resistive heaters in
the Bunn consume.

If I turn the timer dial by hand, when it switches power off I can see a
small spark through the opening the overide control knob protrudes through.

Yet, you say such flashes are *never* OK.

I don't agree. Have you ever closely watched the contacts of a relay
controlling a few hundred watts of load? When the contacts open there is
almost always a small visible spark.

Point taken; I guess it's a matter of degree. Some sparking with relay
contacts switching a large load are, as you say, normal. I think the
green sparks the O.P. saw were a little more dangerous. Hard to say
exactly where to draw the line; I'd say if there's a significant amount
of sputtering or sizzling sounds emanating from the device, it's not good.


--
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because it generates considerable business for me in consulting and
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"If this stuff worked, you wouldn't need me".

- lifted from sci.electronics.repair