I have come across this recently. Before removing panel screws I utilize my ticker and check the screws. One inspection had this issue of the screws making the ticker activate. I did not open panel under and abundance of caution to myself. What would cause this and is it actually safe to open as long as all other precautions are followed? This particular panel did not have arcing noise, rust, circuits tripped etc.
A non contact detector is very prone to false alerts.
Put your finger near the tip of the ticker. That will usually stop any stray, false positives.
That is a completely inaccurate way to check for an energized cover or energized screws. Think about it - when you place that ticker on the sheathing of NMC, you get the same indication, however, you know that you can safely touch the NMC without fear of being shocked.
In the highly unlikely event that you ever come across a panel, panel cover or panel screws that is/are actually carrying current, you would be much more likely to reveal that with a volt-meter or wiggy.
That’s exactly what I would expect - flash, explosion, etc. But it’s pretty unlikely that the screw would be energized without tripping a breaker or creating a fire show.
All above is what I am thinking. In reality, I open the panel door and look at the breakers and such and dont get zapped. Again, I did not remove out of an abundance of mine and clients safety. I did not hear any buzzing or see tripped breakers so I would assume its safe to proceed.
Although highly unlikely, it is possible that the entire panel enclosure could be energized if was not properly grounded. If I had a condition where the proximity tester let up like in the photo I would grab a more accurate tester (Wiggy, DMM) and test it again.
This may or may not be true in the case where the panel itself is deficient in terms of possibly the lack of a MBJ or some other installation issue. If the current (as you know) is not able to return to the source it may just remain energized until which time it finds a path to the source.
Funny thing about electricity…it always tries to complete it’s task.