Some HVAC people under previous home owners put in a sub panel box and ran the AC as well as some lighting and outlet circuits from the sub panel.
The bus bars on the two sides of the panel box were used for both the neutral and the ground wires just like in the main breaker box.
I assumed that it was right because they were professionals and should have had an inspection for the sub panel and the HVAC. I have been reading about how sub panel boxes should have separate neutral and ground bus bars.
Are there panel boxes which are not designed to be sub panel boxes and should only be used as main breaker boxes? The sub panel looks like the main box except the sub panel did not have a main shut off breaker in the sub panel.