i have a main service panel that was probably installed in the 70s or 80s. there is a bus bar on the right side that all of the white neutral wires terminate into. (there is also a bus bar on the left side, that is totally empty.) there are no bare copper ground wires visible anywhere in the box. the circuits all run from under the crawl space into exterior junction boxes on the siding, then up through metal conduit into the panel. i know some of the circuits are older, but some were added just in the last couple of years, and were done with permits. so how and where might the circuits be grounded?
The metal conduit is the ground. Commercial buildings require metal conduit and don't use any ground wires.
There has to be a ground or it wouldn't have passed inspection. Look for a copper rod in the ground around the front of the panel, or to a cold water pipe. That is how many are grounded.
If everything is wired for AC wire (BX) then you don't really need a ground, for the armored cable (AC) works as a ground. If everything is wired for NM (Romex) then yes it should have a bare copper ground. Now if the panel is the main service panel, you could wire in the ground and neutral together on the same neutral bar, but if its a sub-panel then all neutrals and ground need to be separate. Some older Romex has no ground wire in it. It kinda looks like a snake skin insulator on the cable or cloth rapping the wire. Maybe they ran a ground wire into the Junction box and put all grounds in the Junction box. That would save space in the panel.
It is possible the the copper wires were all stripped from the NM coating and attached to a copper rod or water pipe under the house, but it certainly isn't code to do that. Code requires the copper, white and black to all be attached to the appropriate bus in the circuit box, and then a bare copper wire running from the box to a copper rod driven six feet into the ground. The reason for the grounds to be in the box is because plumbing methods have improved and a simple plumbing repair with modern plastic pipe between the earth and the wires can result in no ground and someone touching a faucet getting electrocuted. Just so your home insurance will pay off in the event of a fire or an accident, you might want to check with the code dept. in your area and then have it changed to the box if required.
