Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Todd,It is best to not rely on a particular width, but instead, set the safety gap with the TC cap and primary removed from the circuit. In this case set each gap so it barely doesn't fire with the variac at maximum voltage to the NST primary. THis will keep the voltage from getting higher than the "no load" secondary voltage from the NST. You can also set the main spark gap the same way but set it to just fire at the maximum voltage setting. If during normal operation, the safety fires too often, close the main gap a little and DO NOT be tempted to open the safeties any further. Of course as I'm sure you know, make any adjustments with power OFF.
Gerry R
Original poster: "Todd Reeve" <todd.reeve@xxxxxxxxxxxx>I am going to add a Terry Filter to my coil and I was wondering if someone could give me a ballpark width for the 2 safety gaps. I am running a 15kV 60 mA NST.Thanks.