The little neons (the 1/4 inch glass tube ones) typically take a mA or 2 RMS, and go into explosive failure at about ten times this , the neon itself drops 60-80v depending on gas pressure inside, size the resistor on the remaining volts. For those I'd suggest 22k is bit low  for anything more than short bursts - 100 to  220k is more like it for long term reliability in UK mains, and 75 - 100k or so for 110V systems.  The panel mount ones usually have the resistors in-line already.


I have a number of unofficial home made boxes with neons to different plugs that everyone laughs at until it spots a fault like polarity or earth off - nothing more than a plastic box with a stuffing gland for the flex and plug, and some holes for the lights.

With 'power of opportunity' - gensets, line taps, leads from other buildings (don't ask) especially in parts of the world with less care than the UK, a quick sanity test can save expensive kit or even lives.


You can also do 3 phase rotation testing with a 3 Rs and one C  and a neon, if you know the mains freq. Or you can spend a fortune on shiny test kit and watch it get nicked as it crosses a border.

The little neons (the 1/4 inch glass tube ones) typically take a mA or 2 RMS, and go into explosive failure at about ten times this , the neon itself drops 60-80v depending on gas pressure inside, size the resistor on the remaining volts. For those I'd suggest 22k is bit low  for anything more than short bursts - 100 to  220k is more like it for long term reliability in UK mains, and 75 - 100k or so for 110V systems.  The panel mount ones usually have the resistors in-line already.


I have a number of unofficial home made boxes with neons to different plugs that everyone laughs at until it spots a fault like polarity or earth off - nothing more than a plastic box with a stuffing gland for the flex and plug, and some holes for the lights.

With 'power of opportunity' - gensets, line taps, leads from other buildings (don't ask) especially in parts of the world with less care than the UK, a quick sanity test can save expensive kit or even lives.


You can also do 3 phase rotation testing with a 3 Rs and one C  and a neon, if you know the mains freq. Or you can spend a fortune on shiny test kit and watch it get nicked as it crosses a border.