Question About Bonding for Multiple Subpanels

[wirednewby]

Hi Everyone,

I would like to pick your brains. I want to make sure my assessment is correct as I'm a Newby apprentice.

I want to make sure I fully understand the options and the best course of action.

Here’s the setup:

• The main disconnect is located outside and is properly bonded with two ground rods.
• This main feeds the main house panel, which is treated as a subpanel—neutral and ground are separated, and it is not bonded.
• The main house panel (1st subpanel) feeds an older section of the house via a subpanel (2nd subpanel) installed in the 1980s. However, it was wired with only three conductors, two hots and one neutral. In this panel, the neutral and ground are connected on the neutral bar, and there are no ground rods at this location.
• This 2nd subpanel then feeds a 3rd subpanel in a detached building, also using only three conductors (two hots and one neutral). The 3rd subpanel has two ground rods, and while the ground and neutral are separated, the panel itself is bonded.

I want to determine the safest and most code-compliant way to correct this issue but running a separate ground wire to these subpanels isn’t feasible without major demolition.

Any guidance you can provide would be greatly appreciated!

 

[don_resqcapt19]

You really need to get an EGC to the inside panel that is only supplied by the two ungrounded conductors and a grounded conductor.

Assuming the second building feeder was installed prior to the 2008 code, you need to bond the grounding electrode conductor and the EGC to the grounded conductor. You need a path for clearing ground faults and that path is via the grounded conductor.