I have an interesting question. I have a hundred-year-old house with electrical panel updated a few years ago by a professional electrician. I went around last week with a circuit tester just to make sure all the outlets were wired correctly. The former homeowner had added several outlets herself and some had reversed polarity, mixed-up ground/hot etc., which I was able to fix pretty easily.
However, most of the outlets are showing no ground. I opened the service panel and it is 60A service, Square D breakers, and two neutral bus bars. I'm not sure if one is a ground bus and one a neutral though. I assume they go to the same place anyway, since this is the only service panel (no sub-boxes).
The wires going into the buses are both neutral and ground.
So, assuming the neutral and ground bus bars are bonded (so, electrically the same), would this fact cause the tester to show no ground to a receptacle?
What I mean is, if a box had separate neutral bus and ground bus, would the tester show a good ground, whereas a shared bus would show open ground?
If the shared buses are not the issue, What other ideas do you have which may be causing the open ground reading?