On 2012-12-14, Andrew Mawson wrote:

"Adam Funk" wrote in message ...

I came across the claim somewhere recently that the proliferation of
DP isolating switches in domestic circuits might be dangerous, because
if the live contacts get welded closed, flipping the switch off will
misleadingly turn the neon indicator off and disconnect the neutral
but not the live.

How often does this problem actually happen?

Well I had it on a servo motor contactor on a cnc lathe week before last if
that counts. Switching 90 amps at 150v DC - there was a fault on the servo
driver, the contacts closed, vapourised themselves but still managed to weld
in the closed state on both poles! Made a very impressive bang, a smell like
Frankenstein recreating life, and blew up a very expensive servo controller!
Nothing left of the actual contacts - just the bar they mount on.
Fortunately it's a four pole contactor with only two used so I could just
use the other pair until a spare presents itself at a sensible price.

Sounds like a fairly unusual situation that made this happen?