Now have an equal appreciation for ensuring that my Stenner Pump does not run continuously (the other more often discussed concern amongst others here being to ensure the Stenner doesn't run when pool pump is off).
Long story short, consecutive util. co. power interruptions caused Woods Exterior timer to malfunction and continuously dose pool with MA. As luck would have it, I spotted the Stenner still running about 5 hours into 1st day of malfunctioning. Crazy low ph levels were addressed before any real damage could occur...but have taken steps to protect against that from happening again.
Considered changing to the WiOn wireless timer but actually found it easier to do minor dosing timing adjustment at the Woods Timer itself while I am outside tending to weekly pool chores vs. going inside to retrieve my cell phone or tablet to adjust via wireless device using the WiOn.
In view of any digital or mechanical timing device having the potential to go bad and cause the Stenner pump to just keep running (tho some have less potential than others), I stuck with the Woods Timer - they are only $19. With a multi-plug adapter connected to the Woods timer, one line out is to the Stenner and the other is now a line out to an exterior rated mini halloween effects strobe light. I spray painted the strobe shell green and concealed it on top of my pool equipment wall amongst the trumpet vine. It strobes with the daily 3 minute dose time about when I get up every morning.
Not a perfect solution but this inexpensive and simple set up dramatically increases the odds of spotting a timer malfunction and consequent acid overdose. The activated strobe light can readily be seen even in broad daylight, alerting me to a malfunction if I should see strobing past my scheduled dosing time.
I'm sure other safeguards arrangments could be set up but this works for me.
I remain a huge fan of automated acid dosing. Never had such rock solid, consistent ph levels with virtually no maintnence except for annual Stenner tube maintenance and filling up acid container once every six months.
Cheers to all.