I am pulling new wires to upgrade and add circuits. There is a 3" knockout previously used on the back of the service panel lower portion covered by a round metal plate. I want to use this to bring new wires in. The service panel is on an outside slump block wall and the slump block is already penetrated into the inside wide enough to pass a piece of 3" conduit. I have opened up the sheetrock on the inside. I want to do what is necessary to pass inspection. I figured on using a chase nipple and nut to secure conduit to back of panel. If this is correct then what do I do to secure the conduit on the other side of the wall on the inside?
I accomplished my objective. I don't foresee any code issues. I used a 2 1/2" x 10" nipple, 2 locknuts and 2 plastic bushings. I tightened down one locknut as far as it would go and inserted this end of the nipple into the slump block from the inside of the house into the knockout in the panel. Attached the other locknut and bushing on the panel side and second bushing on the inside of the house end of the nipple. Feels very secure as it rests on a 2x4 perpendicular to the nipple in the wall.