I am rewiring my daughters home she just purchased. The home is 73 years old and I assume the wiring was added about 40 to 50 years ago. No grounded outlets at all. Thus the rewire job. I have almost completed the job, but have a few questions. I am installing a 200 amp service box. How many wires can I run through each hole in a header and can I run the main service cables through the walls. I am running out of space in the header above the service panel. The service panel is next to a walk through opening (no door) and I could run the service cableing through the header over the doorway and continue it through the adjacent walls and eventually through the exterior wall where the existing meter can is. The cableing will be three 3/0 wires and a ground wire (of what size I'm not certain it should be). Any help would be appreciated.