grounding and bonding of a residential service

[michaelv]

I am purchasing a home in Ravenna Township and during my home inspection the inspector and I noticed that the service was improperly grounded. Long story short I insisted it be grounded properly and the contractor the owner had out said it was fine. I still disagree. Here is the scenario. The service is 400 amps, has one meter base but two 200 amp panels fed through two separate 2 inch PVC conduits.There is an in-law suite on one side of the house and the home is all electric, so two of everything except hot water tanks. At the service entrance, which is overhead, there is only one ground rod which has a #6 bare conductor grounding the neutral at the meter base. There is no grounding/bonding conductors through the PVC pipes into either panel. In each panel the bonding screw is driven into the panel. Only one of the panels is taken to the cold water line. There is no bonding conductor from one panel to the other. The home has well water and PVC pipe from the well to the house. In my opinion there is no supplemental ground to the house and should have another driven rod. I also believe there should be conductors from the meter base connection point to the panels as well. Am I thinking correctly or are the bonding screws and one rod sufficient?

 

[GoldDigger]

... one rod sufficient?

One ground rod and no supplemental electrodes is sufficient only if that ground rod was (at some time in the past) measured to be less than 25 Ohm rod-to-earth resistance. Or if it was grandfathered in by different requirements at the time it was built.
From your reference to the contractor, I will assume that this is a new or just remodeled house?
Since, according to your profile, you are an electrician, why not just make the corrections yourself instead of hassling the contractor and seller about what may be a small issue?

 

[infinity]

I am purchasing a home in Ravenna Township and during my home inspection the inspector and I noticed that the service was improperly grounded. Long story short I insisted it be grounded properly and the contractor the owner had out said it was fine. I still disagree. Here is the scenario. The service is 400 amps, has one meter base but two 200 amp panels fed through two separate 2 inch PVC conduits.There is an in-law suite on one side of the house and the home is all electric, so two of everything except hot water tanks. At the service entrance, which is overhead, there is only one ground rod which has a #6 bare conductor grounding the neutral at the meter base. There is no grounding/bonding conductors through the PVC pipes into either panel. In each panel the bonding screw is driven into the panel. Only one of the panels is taken to the cold water line. There is no bonding conductor from one panel to the other. The home has well water and PVC pipe from the well to the house. In my opinion there is no supplemental ground to the house and should have another driven rod. I also believe there should be conductors from the meter base connection point to the panels as well. Am I thinking correctly or are the bonding screws and one rod sufficient?

If there is no OCPD at the meter then the conductors to the 200 amp panels are service entrance conductors and the 2" raceway should not have an EGC in it. Both panels should be connected to the GES. Depending on the age of the service at the time of installation it's possible that only one ground rod was required.

 

[Smart $]

If there is no OCPD at the meter then the conductors to the 200 amp panels are service entrance conductors and the 2" raceway should not have an EGC in it. Both panels should be connected to the GES. Depending on the age of the service at the time of installation it's possible that only one ground rod was required.

I essentially agree with your comment, but I can see where [red text] may be misinterpreted.

Based on the OP, the GES consists of the one rod and its GEC. Both panels are service equipment connected to this GES via the neutral. The conductor running from one panel to the water line is a bonding jumper. However, being the panels are separate service equipment enclosures, a bonding jumper to the cold water is required from both panels... but a common bonding jumper is permitted.

 

[dereckbc]

I really do not see a real problem here. Technically there should be two ground rods driven to meet today's code, but it does not add any real value or safety as it is impossible to get the earth impedance low enough to act as a conductor which if forbidden by NEC code.

Don't jump me, I know it is a well beaten down subject here. But for any low voltage systems under 600 volts earth resistance is irrelevant and has no real operational function. Even if at an extremely low impedance of 10 Ohms which is almost unheard of will not even operate a 15 amp breaker.

The purpose of the earth electrode in a residential service is for:

Primary to secondary utility faults like a shorted transformer, or accidental contact in storms.
Planned discharge path for lightning and static electricity.
Stabilize system voltages and short out line to ground capacitance so as not to stress cable insulation.
Minimize touch potential differences.

 

[suemarkp]

If the neutral to each panel is 1/0 or larger (assuming 400 KCMil Service entrance conductors and using table 250.66), then those are permitted to ground/bond each panel from a common point (the meter base where the GEC is connected per 250.142(A) and 250.164(D)(3)). You can also do it with taps to each panel, with each tap sized per the conductors that feed that panel.

I don't know of a requirement that each service disconnect must connect to the piping system. It just needs to connect to somewhere in the Service with a 1/0 copper conductor.

Agree that under today's rules you need two rods (or proof of 25 ohms), but that may not have been so in the past when the service was established.

 

[Smart $]

...

I don't know of a requirement that each service disconnect must connect to the piping system. It just needs to connect to somewhere in the Service with a 1/0 copper conductor.

...

Here...

250.104 Bonding of Piping Systems and Exposed StructuralSteel.

(A) Metal Water Piping. The metal water piping system
shall be bonded as required in (A)(1), (A)(2), or (A)(3) of
this section. The bonding jumper(s) shall be installed in
accordance with 250.64(A), (B), and (E). The points of
attachment of the bonding jumper(s) shall be accessible.

(1) General. Metal water piping system(s) installed in or
attached to a building or structure shall be bonded to the
service equipment enclosure, the grounded conductor at the
service, the grounding electrode conductor where of sufficient
size, or to the one or more grounding electrodes used.
The bonding jumper(s) shall be sized in accordance with Table
250.66 except as permitted in 250.104(A)(2) and (A)(3).

In the case presented, he has two service enclosures and two grounded conductors at the service (beyond the meter base).

Of course this is per current code. I have no idea whether there was any difference in the code in effect when built or modified.

 

[suemarkp]

It says enclosure singular, not plural. In many cases there is only one enclosure, but it is written vaguely for the case of multiple service equipment enclosures. Seems kind of strange to require it to go to ALL service equipment enclosures when it lists other single places you could land it (service neutral, GEC, or ground electrodes). It says grounding electrodes plural here too. Again, I would not think you'd have to bond the water to every ground electrode, just any one of them assuming the electrode bonding wire is of sufficient size between electrodes.

More poor writing in the NEC...

 

[Smart $]

It says enclosure singular, not plural. In many cases there is only one enclosure, but it is written vaguely for the case of multiple service equipment enclosures. Seems kind of strange to require it to go to ALL service equipment enclosures when it lists other single places you could land it (service neutral, GEC, or ground electrodes). It says grounding electrodes plural here too. Again, I would not think you'd have to bond the water to every ground electrode, just any one of them assuming the electrode bonding wire is of sufficient size between electrodes.

More poor writing in the NEC...

I'll agree it is poorly written and as such debatable. However, a prime reason for the majority of grounding requirements is integrity, and albeit as a result, a bit redundant... and this is one of those cases, even though the requirement is written in the singular sense of enclosure Take for example having to run a GEC to each of two service enclosures (disregarding GEC taps for the immediate discussion). While proper English dictates the plural sense is to be used or the possibility accounted for (such as the reference to "one or more" grounding electrodes), every reference outside the immediate requirement uses the singular sense of GEC.

 

[eprice]

It seems to me that the connection of the GEC from the ground rod to the grounded conductor in the meter base is in compliance with 250.64(D)(3). The fact that there is only one ground rod may, or may not be a problem, depending upon the past history of the installation as has been mentioned.