I went to a class for machine embroidery. The machines were provided. The instructor said never use the no auto shut off on the same circuit as the sewing machine. The iron is constantly heating and while you are sewing which pulls power from the machine and could cause brown out. I never thought of it but the iron does sit there and constantly reheats using a lot of power to do so. If you are sewing while it does that then problems could happen. The auto shut off is annoying but it has it's purpose.