Service grounding

D

Darho

Member
Location
Cookeville
Occupation
Electrician
So concerning the post in facebook about service grounding. If you ground the meter can and rely on the neutral to be the bond jumper between the meter and the disconnect as the diagram illustrates. What happens if by chance you lose your neutral between the meter can and the disconnect? Where does the voltage return to. There is no ground conductor anymore so wouldn’t all grounded metal appliances then become charged by the current seeking to go to ground?
 
Darho said:
So concerning the post in facebook about service grounding. If you ground the meter can and rely on the neutral to be the bond jumper between the meter and the disconnect as the diagram illustrates. What happens if by chance you lose your neutral between the meter can and the disconnect? Where does the voltage return to. There is no ground conductor anymore so wouldn’t all grounded metal appliances then become charged by the current seeking to go to ground?
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Yes, everything connected to the grounding system will be energized, but the same thing happens if you lose your service neutral and that is much more likely than losing the neutral between the mete and the disconnect.

Also the current is not trying to go to ground, it is trying to go back to the source. On a grounded system the earth is a path back to the source, and some current will flow on that path.
 
Darho said:
So concerning the post in facebook about service grounding. If you ground the meter can and rely on the neutral to be the bond jumper between the meter and the disconnect as the diagram illustrates. What happens if by chance you lose your neutral between the meter can and the disconnect? Where does the voltage return to. There is no ground conductor anymore so wouldn’t all grounded metal appliances then become charged by the current seeking to go to ground?
Click to expand...
Even if there were a GEC connected in the main panel, if the neutral was broken, ahead of the main panel, everything would still become energized. A Grounding electrode will not do anything for a broken neutral.
 
electrofelon said:
Even if there were a GEC connected in the main panel, if the neutral was broken, ahead of the main panel, everything would still become energized. A Grounding electrode will not do anything for a broken neutral.
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In my area where the municipal water piping system is copper the grounding electrode conductor will serve as the neutral. If the neutral is lost current will flow through the municipal water system finding a way back to the source

There are countless bad neutrals out there and the neutral current is flowing on the copper piping system looking for a path back. The neutral for House A might be the neutral for House B and House C

Its at a point now when doing a service change, I will tell guys to put a amprobe on the water pipe GEC to check the current draw as guys are surprised when the old GEC is removed there is a large spark. Municipal water system carry a lot of current
 
Joe Villani said:
In my area where the municipal water piping system is copper the grounding electrode conductor will serve as the neutral. If the neutral is lost current will flow through the municipal water system finding a way back to the source
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Yea definitely in that case you would have a low impedance neutral. But that is not the purpose of the gec, to be a redundant neutral or a low impedance path back to the source.
 
Darho said:
What happens if by chance you lose your neutral between the meter can and the disconnect?
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While lots of grounding topics like lighting protection are not in the scope of the NEC, generally speaking what I try to avoid is the somewhat common situation where there is more than one Neutral - GES connection at a structure that only tie together (bond) via the system neutral (grounded conductor), changing the 'or' in the graphic to an 'and' say like this for example; I perfer to have all the grounding electrodes to have one 'window' to the neutral. I also look for legacy N-G bonds after the service disconnect, like accidental bonding screws in sub panels etc.
250-24.-e1.png
 
Joe Villani said:
In my area where the municipal water piping system is copper the grounding electrode conductor will serve as the neutral. If the neutral is lost current will flow through the municipal water system finding a way back to the source

There are countless bad neutrals out there and the neutral current is flowing on the copper piping system looking for a path back. The neutral for House A might be the neutral for House B and House C

Its at a point now when doing a service change, I will tell guys to put a amprobe on the water pipe GEC to check the current draw as guys are surprised when the old GEC is removed there is a large spark. Municipal water system carry a lot of current
Click to expand...
In my area the municipal water system is pex so there is no water pipe ground. You get the cold water ground from the ground on the electric water heater.
 
Darho said:
In my area the municipal water system is pex so there is no water pipe ground. You get the cold water ground from the ground on the electric water heater.
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If there is an interior metal piping system, you can bond it anywhere. If the interior piping is pex, then there is no need to bond anything. The EGC supplying the water heater will ground and bond the water heater
 
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