>Aren't X2 caps usually rated for AC volts, rather than DCV.  And there is
>some sort of significant multiplier involved (1.414 or perhaps 2.818?)  I
>don't think you can substitute a 250VDC cap for a 275VAC X2 cap in a 240V
>circuit without expecting some fireworks...

I believe X2 rated caps have insulation designed to withstand mains spikes
without going out in a blaze of glory and causing a fire. To this end I
think they use one of the self healing insulations so if they do flash over
internally then they will burn out the relevant bit, and heal the insulation
without problems.

If using any other sort of capacitor on mains circuits, just remember that
in the event of a problem, the national grid is as near to a perfect voltage
source as you are likely to find anywhere - read constant voltage, almost
limitless current in the event of a problem. In short you would be unwise to
use anything other than an X2 rated cap on mains, even for development work.

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