chuck wrote:
Check out this link for an explanation of how an SCR works.


http://www.allaboutcircuits.com/vol_3/chpt_7/5.html
The Silicon-Controlled Rectifier (SCR) - Chapter 7: THYRISTORS - Volume
III - Semiconductors

Good page. Thanks. I had class time on SCRs, but never messed with them
in the shop and that page brings it back very nicely.

Valid summary?: The only ways to shut down the SCR involve reducing the
current flow through the SCR, and the simplest is to have the shut off
switch shut off the full current and accept the reduced life on that
switch.

I suppose momentary short around the SCR, or a pulse, would also work,
but I don't see any simple and reliable way to do that. None that don't
make me cringe. Another reason to get the extra switch and make a high
water alarm.