Hey all! I’m working on my mock inspections and wanted to make sure I understand the grounding situation with this main panel.
This is a 100 amp main disconnect (first point of disconnect after the transformer. 2 hots and a neutral come into the box, and go through the breakers, then 2 hots and a neutral go into the conduit to the basement, where the sub-panel is at.
The sub-panel in the basement has an equipment grounding conductor that is routed into the concrete foundation (Ufer if I’m not mistaken). When I originally looked at the main panel, I didn’t see where a equipment grounding conductor was hooked up and routed to a ground rod, which is what I was expecting. Upon looking at the pictures again, I’m thinking that the braided wire on the bottom right of the main panel is bonding the system to the equipment grounding conductor in the sub-panel. The conduit is metal.
Am I right in thinking that this main does have a path to ground, and that it is traveling on the conduit to the sub-panel where that is bonded to the equipment grounding conductor that then goes into the Ufer ground?
Thanks for the help, I really appreciate it! Take care all.
Ufer grounds are for system grounding and are not part of the egc for a branch circuit. EGCs do not connect to Ufers. The Ufer should go to the service .
A metallic conduit can be the 4th conductor to the subpanel.
Thanks for the quick reply! Shoot, I had my terminology wrong. My mistake, I am wondering about the system grounding, not equipment grounding (thank you for the correction).
The main panel shown in the picture doesn’t have a ground wire going out to a ground rod. Just to confirm, the conduit can act as a conductor to the sub-panel that would be bonded to the system ground conductor into the Ufer. Is that correct?
Yes the proper terminology helps. The conductor to the CEE (concrete encased electrode) is a GEC and that must land in the 100 amp service disconnect. As stated the metal conduit can serve as the EGC to the sub-panel. The wire from the bushing to the neutral is a bonding jumper which in is this installation is not required but doesn’t hurt.
To reiterate, so that I’m understanding this correctly, this main panel does NOT have a proper grounding system because the GEC is not hooked up to the Concrete encased electrode within the 100 amp main panel.
In the main panel, the neutral wire to the bushing is acting as the equipment grounding conductor to the sub-panel.
Yes, what you’re calling the “main panel” is technically called the service disconnect and it is at this point or somewhere further upstream that the GEC must connect to the service neutral not downstream in the sub-panel as it is now. The metal raceway between the service disconnect and the sub-panel is the equipment grounding conductor (EGC).
The bare jumper wire is a bonding jumper that in addition to the locknuts is also bonding the metal raceway. Since that raceway is after the service disconnect the bonding jumper is not required.
Was anybody doing CEGEs in residential in the 60s? I know Mr. Ufer invented the system during WWII, but I’ve never seen one in an older residential structure. Isn’t this more likely a common ground rod electrode through the concrete floor?
I took a look at the 1965 and 1968 NEC a concrete encased electrode first appeared in the 1968 NEC but they weren’t really used in homes until decades later.
Interesting that this isn’t actually a Ufer, but just a ground rod cemented in concrete. Just figured I’d add the picture I got of the copper going into the foundation.
Good post on this by the way. That you put your own thoughts out there for feedback rather than asking someone else to just tell you what’s what is great initiative. You have a really good grasp of terminology for someone just at the stage of performing mock inspections. This is the way to get really good and thoughtful responses to your questions. Effort and initiative earns respect.
