Main vs. sub panel for dedicated lines

lowrider574,352 posts

06-02-2021
10:37am


@jea48 @mesch
I have a new service panel and a subpanel. When the sub was installed, a second ground rod was added. Two different electricians installed the panels, both said two ground rods were required to meet PA code.

@lowrider57

Two rods yes. Both should be for the main electrical service panel.
(Reason for two as I described in my post above.)

If you would, go out side where the two ground rods are located and look if you see only one bare ground wire going into the house and not two ground wires.

The correct installation, the two rods shall be a minimum of 6ft apart from one another. The two rods are connected together with a ground wire that is then extended into the house and connects to the service entrance neutral conductor buss bar. The neutral bus bar is bonded/connected to the panel metal enclosure.
The two rods are counted as one Grounding Electrode, (NEC).
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I'm confused about the second (set) ground rod for the 2nd panel  issue. I'm familiar with installing two ground rods and connecting to the main panel. Sometimes a second panel (subpanel) is installed on a 2nd floor of a house for circuits in a bedroom, lights, etc... so are people suggesting we run a ground wire outside from there and connect it to a ground rod (or two)? 

A sub panel connection has different rules than a main panel. 

For a sub panel in an out building, separate building, a ground rod (Grounding Electrode) is required. The ground rod is connected to the equipment ground bar in the sub panel creating a grounding electrode system for the separate building.

For a sub panel located in the same building as the main electrical service panel the separate earth connection ground is not required. If not required why would anyone want it? The separate earth connection can/does cause more harm than good. In fact the separate earth connection can/will add noise to the branch circuit equipment grounding conductors connected to the earth connected ground rod.

This guy has helped over the years in writing parts of the National Electrical Code, (NEC).
Auxiliary Grounding Electrode. (NEC 250.54)
https://www.youtube.com/watch?v=gg4wBI7bWgI
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Thanks! I am currently away from home and will return by end of the month. I will have my electrician help me install the sub panel. I will use it for my audio system. I will get back to everyone once this has been accomplished. 

@jea48
Hi Jim, the service I mentioned is the one where you kindly offered advice. Installation was from the drop to a new meter, then inside to a Square D 100A panel, 60A subpanel.

This is a small Philly rowhome where outside the house is pavement. Now don’t freak out, this might be  Philadelphia code; both grounding rods are drilled into the basement cement floor near the rear wall. They’re 3’ apart, sunk into mother earth. I can only see one rod which is wired to the main panel. The 2nd rod is obscured behind my washer/dryer. I will look for the wire.

Question: why are two ground rods used?

I’m guessing the second rod isn’t wired to the subpanel because the main panel is ground, correct?