+AD4- +AFs-TD+AF0- .. 24V 10A .. could easily generate and
+AD4- maintain copper arcs of about 3/4+ACI- between the
+AD4- switch contacts
I would think of more like 400V for a 3/4+ACI- arc.
Is it that the high wattage was ionising the
copper or otherwise altering makeup of the air gap?
John A.