I understand that a residential service panel requires 2 sources for
grounding. I was looking at a newly installed panel the other day and I'm
not sure that it was installed correctly.
This panel has a neutral bar on both sides of the panel and ground bar on
the right hand side only.
At the electric meter on the side of the house, there are 2 bare copper
wires running down the wall into the earth. These wires were existing prior
to the installation of the new panel. They look like this:
When the new panel was installed, a new ground wire was run from within 5'
of the water meter to the neutral bar of the panel. The neutral bar is
bonded to the panel with a large green screw next to the incoming service
neutral lug. I believe that this part is OK.
However, this is the part that I'm not too sure about:
Above the panel, there a ground wire clamped to a water pipe. This wire was
there before the new panel was installed. The wire was pulled into the new
panel attached to the ground bar.
Does that wire count as a second grounding point for the panel or is it
essentially the same point as the new ground that was run from the water
meter to the panel?
Shouldn't I be seeing something that directly connects the ground wires at
the electric meter to the panel?
On Mon, 24 Mar 2014 15:56:16 +0000 (UTC), DerbyDad03
You really only need 2 electrodes if one of them is the water pipe.
As long as your grounding electrode conductor goes from the neutral
bar to the pipe, within 5 feet of where it comes through the wall and
there is nothing between that and the dirt (meter, filter or whatever"
that is your primary electrode. A water pipe has to be supplemented
with another electrode and it sounds like that is a rod or two
outside. (they usually get installed in pairs)
I can't see it but it sounds right.
Not necessarily. Old services used to only be connected to a metal water
service pipe. (Now you need a "supplemental" electrode for new services.)
A house might be built now with plastic water service pipe and a
"concrete encased electrode" (Ufer ground) used as the only grounding
You can connect grounding electrodes anywhere from the connection to an
overhead service drop (or at the connection to a service lateral) up to
the neutral bus at the service disconnect. But that is irrelevant here
- see below.
That is how connections to a water pipe service is made now. The
"supplemental" electrode is presumably 2 ground rods connected at the meter.
I presume the water meter is bonded and that is irrelevant to your
> However, this is the part that I'm not too sure about:
You used to be able to connect to a metal water pipe electrode anywhere
on the interior metal water pipe system. This was the grounding
electrode connection for the old service. It is not required now, but is
a little improvement. It is not a "supplemental" electrode.
Generally you want to connect all the grounding electrodes together and
make the connection to the service neutral at one point.
But "supplemental" electrodes can be connected several places, including
the meter. Ground rods are a pretty crappy electrode.
On 3/24/2014 4:24 PM, firstname.lastname@example.org wrote:
The problem is, as far as I can tell, both of them are the same water pipe.
I think this is what I should see, but I'm not sure that I do:
What I don't see is a connection from the ground rod(s) to the panel.
Please see the images below.
The first image is of the meter and the ground wires going into the earth:
This second image is of the panel. It shows the old bare copper wire
that is attached to the water pipe right above the panel. That is the
wire that is attached to the grounding bus.
It also shows the new black, insulated ground wire that runs back all
the way across the basement to the water meter.
I don't understand how the ground wires at the meter/rods are connected
to the panel as shown in the web image above.
Actually, I only have 2 grounds identified, but I can see where the
confusion might come from.
If you read the 2 text boxes related to the "bare ground wire" the upper
one says that the ground wire that is attached to pipe above the panel
"runs behind the joist" and the middle text box says that the bare ground
wire "emerges from behind the joist".
That is the same ground wire.
On Tuesday, March 25, 2014 11:07:28 AM UTC-4, DerbyDad03 wrote:
So you have one grounding electrode, ie the water service pipe
that comes directly into the panel.
According to Bud, the supplemental electrode(s) can be at the meter
and it sounds like that's where they are. The only part I'm confused
about is that you appear to have just two hots and a neutral coming into
the panel from the meter. So the neutral which is a current carrying
conductor would be what ties the grounding system together, ie it
connects the water pipe ground at the panel to the supplemental grounds
across a distance of 5ft, 10ft? whatever. Is that OK with code? Seems questionable to me. Bud?
That, my friend, is exactly what I find questionable too.
The homeowner has already called the owner of the company that installed
the panel and informed him that the circuit grounds and neutrals should not
be on the same lugs (my post from last weekend). The owner will be coming
out to fix it. He will order a new ground bus for the left side of the
panel and remove the grounds from the neutral bar.
The owner (electrician) told the homeowner that he can't believe that one
of his guys actually wired it that way. "He should know better!" Makes you
wonder what else this guy has wired that is still in use. If I hadn't of
been curious and and wanting to see how the new panel was wired, this one
would have gone unnoticed, probably until the homeowner tried to sell the
house and the buyer got it inspected.
Now I'm trying to find out if he has to fix the service ground connections
also. The homeowner doesn't want to call this guy back more than once.
On 3/25/2014 3:09 PM, email@example.com wrote:
In this case the most useful ground is the water pipe, which is
connected at the panel. Other comments below.
In this system there are 2 points of attachment. I don't think that is
OK in general, but in this case it is OK to attach the "supplemental"
ground rods at a separate place (the meter, if that is what is attached
You can have all the grounding electrodes (GEC) attached at the meter
(as at g's location). And the N-G bond ("main bonding jumper") is at the
service disconnect. That is code compliant, but seems a bit odd to me.
Like ferinstance if you had a neutral connection failure on the neutral
from the meter to the disconnect it wouldn't be too healthy. Comment?
(I have never seen one done that way, but basements are very common here.)
Minneapolis still has a municipal metal water system. If the GEC
(including water pipe) is connected at the panel, and the service
neutral opens at any point, the neutral current will be to the water
pipe, to other houses, and back to the service neutral. The neutral
voltage shouldn't float much.
Thanks for the responses.
I'm still confused how the situation we're discussing matches up with this
picture. Maybe it doesn't have to?
What I don't see is the connection from the ground rod to the panel. Does
the connection of the ground rod at the meter eliminate the need to connect
the panel to the ground rod?
If that's the case, then does that mean that the short ground wire to the
pipe just above the panel is redundant since a new ground wire was run from
the panel all the way back to the meter?
Seems to me that the section of pipe above the panel could easily become
not grounded if a section of pipe between it and the meter was replaced
with PEX, etc. I thought that was why you had to be bonded within 5' feet
of the meter now.
The NEC can be much more complicated than the picture. For instance in
new construction a Ufer ground is usually installed, which replaces the
ground rods (which are a POS).
Yes [to the water meter]
It is. The connection to the water pipe near the panel is likely the
connection that was made before the service was upgraded, and was just
easily connected to the new panel. Connection at that point used to be
kosher. Them pex guys are ruining the world.
I will tell my neighbor that he doesn't have to worry about the service
grounding situation. The owner of the company whose worker paired up the
circuit grounds and neutrals under the same lugs is coming out next week to
fix that situation.
If I have the time, I want to be there when he does the work and have my
neighbor ask him about the service ground. I just want to hear what he has
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