So today at work I was assisting a welder with welding track onto a trailer for a small childrens roller coaster we were re-furbishing, at our disposal was a Miller/Bobcat 225G 8 KW welder/generator used for welding (arc) the track to the trailer bed, and using one of the 120 outlets to power a grinder that I was using. The 120/240 plug is a 40 amp one, and when the load got to heavy on the plug that I was using (20 amp), it would trip one of the 40 amp breakers instead of the 20 for the outlet I was on. what im wondering is that is the two 20 amp breakers for the 120 volt outlets fed off of the two 40 amp breakers to the 120/240 plug. The engine was running at fast speed under practically full load (arc welder running) while grinding, could the welder load contribute to this?