Bill, were the urns fitted with equipment-grounding cords? In some cases metal-sheathed, mineral-filled, 'cal-rod' heaters are particularly maddening leakage wise. If there’s no grounding included in the line cord, then humans sometimes get to complete the circuit. Until a GFCI trips, the ground current can be uncomfortable for some.
[This message has been edited by Bjarney (edited 05-22-2002).]