I'm going to be installing a whole-house surge protector this week and I
need to have it connected to at the service panel via two 20 amp breakers.
Our panel has about 30 spots for breakers, about 2/3 of which are in use.
Since the surge protector says it's best to keep the wires from itself to
the breaker as short as possible, and since I'll be mounting the surge
protector under the bottom of the service panel, I'd like to add the two new
breakers at the bottom two free spots to keep them closest to the surge
protector. But this will leave unused spots in between with no breakers in
Is there any reason NOT to do this? Is there any reason I should only use
the "next available" slots for adding new breakers? Does doing this affect
the surge protection negatively at all?
A couple of thoughs:
Something tells me that by "as short as possible" they nean "not
20' away from the panel", they're not being critical over ~1 foot
difference in which breaker you use.
If you decide to stick with the lower-most slots (and there is
no reason not to, electrically speaking) you will have a slightly
tougher time removing the two knockouts, and by all means get a
visual confirmation that the bottom two knockouts align with
the lowest two usable spots on that side of the panel, sometimes
they don't! You end up needing to knock out an extra hole and
filling in the bottom one with a plastic filler plate.
Did you get an electrician journeyman's license while in state prison for
sexually assaulting that child? If not, what makes you think you have the
intelligence and knowledge to give wiring advice? Alcoholic moron.
Best is to place protector so that it creates a circuit from
each AC main to earth ground rod that is shortest. That
overall distance shold be less than 10 feet.
In addition, things such as sharp bends in the wire are the
equivalent of adding up to another foot to wire length. Sharp
bends should be avoided or minimized.
Leave leads long enough to be manuvered and manipulated.
But do not bundle up a lot of excess wire in the box since
those sharp bended in the extra wire only add to wire
length. Run the ground wire to make a connection closest to
the earth ground wire - so that maximum copper width and
minimum copper length makes a connection between both. Same
applies to how the wire exits to earth ground rod. It too
should be as direct as possible, seperate from other
non-earthing wires, no sharp bends, and short. The connection
from AC main bus through surge protector, down grounding wire,
to earth ground rod is best at less than 10 feet.
But install everything also to be convenient for you. The
protector on the side next to where earth ground wire connects
would be a better location. But installing it at the bottom
of the box is just as good if that works better for you -
Same with circuit breakers near bottom. No problem overall.
But most important is how that wire connects less than ten
feet overall to earth ground rod AND that all other incoming
utilities also connect to that same earth ground rod.
Vinnie Murdico wrote:
From my calculations, the service panel ground bus appears to be right about
ten feet from the ground rod on the other side of the wall (10 feet as the
cable probably runs, that is). The only problem is that I can't see all of
the ground wire because it exits the concrete block near the ground outside
heading down at a 45 degree angle. I hope that indicates that the original
installer knew about the "no sharp bends rule" <g>. It's possible they put
bends in the wire where I can't see it.
The other disconcerting thing is that I can't find the where the main ground
wire connects to the service panel's ground bus. There's a large lug at the
top of the ground bus, but nothing's attached to it. On the neutral bus,
there's a larger lug at the top with a large cable (#2 or #4?) wrapped in
white tape connected to it. This cable and the other two #2 or #4 cables
(which connect to the main "hot" bus) all exit through the back of the
panel, seemingly to go outside into the meter box. I'm now wondering *how*
my service panel is grounded. The ground wire that connects to the
grounding rod outside looks to be a #6 solid copper wire. The problem is, I
don't see that wire anywhere inside the service panel, and definitely not
connected to the ground bus. The only wires connected to the ground bus are
the regular #12 wires exiting the top of the box for the various circuits.
Should I be concerned about this? Can you think of how they would have
grounded the service panel such that I wouldn't see the ground wire entering
Thanks again for your tme and assistance!
On Wed, 3 Sep 2003 12:33:49 -0400, "Vinnie Murdico"
I'm guessing that the ground wire is strapped to the neutral wire
(white) inside the meter box. The ground bar inside the service panel
and the neutral are probably bonded together (grounded to the box).
If it were me, I'd want to know for sure.
Every utility company document I have read says not to earth
the meter box. Earthing wire must go directly to main
disconnect box. However others report their utility wants
ground to meter box.
Remember, that earthing was not originally installed for
surge protection. It was only installed for human safety - as
required by National Electrical Code. Characteristics of wire
used for human safety do not address sharp bends and passing
through metallic conduit - installation that would only
adversely affect same ground wire for surge protection.
Earth ground wire serves multiple purposes. Most electricians
only understand what the code requires. If earth ground wire
was installed short with no sharp bends, that was probably
more an accident than intentional.
Having said this, I would run a dedicated #4 AWG ground wire
from earth ground rod directly to breaker box. Since that
ground wire goes wherever, simply install a new dedicated
ground wire and be done with it. Don't know what your utility
wants, but code says that main disconnect box must be
earthed. Additionally, shorter ground wire means more
effective 'whole house' protector. Better to route through
foundation rather than up through joist or rim board, then
down to breaker box; less bends and shorter wire length. For
surge protection, better to route that the ground wire
separated from other wires.
That wire wrapped in white tape would be neutral. But there
should also be another bare copper ground wire from main
disconnect box to within 5 feet of where cold water pipe
enters earth - on earth side of water meter. That 5 foot on
cold water pipe required by code for human safety reasons.
Connection can be long, because that ground is for human
safety; not surge protection. But connection is required.
Also the incoming CATV wire and phone line premise interface
should also connect to that same earth ground rod at same
location. Again, a less than 10 foot connection each using
their own dedicated ground wire; typically 10 AWG insulated -
preferred color green.
From what was posted, reassess entire building ground system
also for human safety. volts500 posted a good summary of
inspection to meet NEC requirements, in this newsgroup
entitled "Grounding Rod Info" on 12 July 2003:
Vinnie Murdico wrote:
I installed the Intermatic IG1240RC tonight -- took all of about 10 minutes.
Took another hour to run the new ground wire, though <g>.
I left the original ground wire in place. That wire appears to be grounding
at the meter (as you suggested) since it comes out of the bottom of the
meter box and immediately goes into the concrete (stucco) exterior wall,
then comes back out of the wall near the ground and attaches to the
foundation rebar right there.
I ran a new #4 solid ground wire from the panel's ground bus through the
exterior wall on an angle pointing down (to "soften" the bends) to the
outside of the house, then down the outside of the house in PVC (to make it
neat and protect it), then had to make a slight "soft" bend to run
horizontal to the ground rod (which was closer to the service panel than the
foundation rebar connection). Previously I had bonded the foundation rebar
to the grounding rod with #4 solid wire as well to add additional
"grounding" to the whole system. Total length of the new run from bus to
rod was about 8 feet so I hope it will be a good ground path in case of a
What you just did was _install_ an objectionable current flow on your
electric grounding system...........this is something that should be
_discouraged_, not helped along. If you are a doubting Thomas (pun
intended) get a clamp-on ammeter and see how much current is now on that
wire.........there is now a parallel connection between the newly installed
wire and the neutral. (Intentionally installed) objectionable current flow
on the grounding system is not permitted by NEC Section 250.6. If you
decide to remove it, turn off all power first.
Thanks for this info. I checked the grounding wire I installed and indeed
it said there was about 200 mA on it (don't know if that's normal or
problematic). I've gone ahead and disconnected the ground wire I installed
and left everything as it was installed originally (except of course the new
surge supressor is still installed at the panel).
I guess the only question now is whether or not the utility's ground wire
from the meter runs a straight path from the meter into the wall, and down
to the foundation rebar connection. Since I can only see where it exits the
meter and enters the concrete block wall as well as where it exits the wall
and connects to the rebar, I don't really know how it travels (especially
since this is a concrete block wall).
Less desirable earthing connection is typically to meter.
That was acceptable in some places - more a legacy of old
practices. Many electric companies have now, with a brochure
to electricians, banned earthing to meter box and demanded
earthing to distribution box. Some have recently also
demanded a connection to gas pipe where pipe enters building.
IOW some utilities demand requirements in excess of NEC.
Earthing the distribution box - the single point ground - is
considered a better method even though both are permitted by
Code permits earthing either to meter box (once common) or
to distribution box (more standard with every decade). But
surge protection is enhanced when that earthing is into main
disconnect box; not to meter box. A single point ground is
volts500 is correct about a potential undesirable ground
loop. If the neutral breaks between distribution box and
meter, then undesirable and unacceptable currents flow through
both two ground wires. That could be a human safety problem.
Meter box ground is now known to exist - which was not known
before. BTW, that 200 ma may still exist even if one ground
is removed. Given a selection between two grounds, the
distribution box ground is a better choice. If no earthing is
suspected, then better to install new earthing, as you did,
even if that connection, unknowingly, makes a second earthing
connection. Earthing is that much more important compared to
any danger created by two earth ground connection.
Grounding is for human safety (the code and volts500
understands) and for transistor safety. Good grounding
principles dictate that all grounds meet at a common point.
That common point where AC electric grounds meet - from water
pipe, from earth ground, from meter box neutral, to all outlet
safety ground, and to all receptacle neutrals - is the
distribution box ground. Distribution box grounding makes
even the AC electric earth grounds meet at one point since
water pipe and GEC wires meet at same point in breaker box.
Best grounding is single point. Meter box ground is
acceptable. Single point ground is lesser (an electrical
perspective based upon concepts beyond scope of this
discussion) if earth ground connects to meter box. Meter box
grounds were an old grounding method in some jurisdictions.
Still acceptable where some utilities have not come down
against it. But to also make your surge protector more
effective, the main breaker box is the best spot to earth. It
makes that connection to earth ground significantly short.
Vinnie Murdico wrote:
So let's assume that my meter box is the source of the main AC system ground
wire (which is certainly how it appears at this time). Since there's no
wire from the ground bus in the service panel connecting to the meter ground
or directly to earth, how (most likely) is my service panel connected to the
meter's ground wire? (I realize you can't see my setup, but I'm just
wondering what would be the most likely scenario for this "connection").
The only connections I can think of are the neutral (which is bonded to the
ground bar in the service panel) and travels out of the service panel and
back into the meter, and/or the case of the service panel itself which is
grounded to the ground bar and possibly connected to the meter by some
metallic condiut passing through the wall behind it to the outside metallic
meter box (maybe).
If the neutral exiting the service panel is the "ground connection" to the
meter, which then continues to earth via the ground wire, does the surge
supressor actually shunt a surge to the ground bar in the service panel,
which then sends the surge over the neutral back to the meter where somehow
the surge goes from the neutral to the grounding wire and then down to
earth? Is the ground wire at the meter possibly connected to the neutral?
Or, am I completely confused? <g>
Thanks again to everyone for all your input. This disucssion has been very
The neutral wire from breaker box to meter box would be path
for a surge to find earth ground. Yes, the surge protector
would still have an earth ground, just longer according to how
it was described.
If it becomes all too complex, then just leave the meter box
ground and don't use the new breaker box ground. However the
important point is you do have a short connection to earth
ground that provides earthing for human safety and earthing
for surge protector (transistor safety).
Grounding that is beyond scope of 'whole house' protector
but mentioned the grounding system is being examined:
Again, that breaker box ground must connect to cold water
pipe as described earlier. This only for human safety reasons
to remove electric currents from that pipe.
Because plastic pipe replaces sewer pipes, then some
jurisdictions also require steel bathtubs to have a dedicated
ground connection from that bathtub to breaker box ground.
This appears not to be a widespread practice, but can be a
good human safety feature.
Gas pipe ground - is required, by some gas companies, even
if incoming pipe is plastic. Ground connection is not to
earth breaker box via buried gas pipe. Ground is to remove
electric currents from gas pipe - and if, necessary trip the
corresponding circuit breaker.
Vinnie Murdico wrote:
Of course _all_ meter boxes must _absolutely_ be grounded [this is usually
accomplished (by default) at the factory by directly connecting the neutral
lug to the meter box metal enclosure.] Perhaps you meant to say that the
some electric companies do not require that the _connection_ to the system
grounding electrode conductor (GEC) to be to be made _at_ the meter (as
opposed to the main service disconnect?) That's just not true either. Many
electric companies require that the system grounding connection be made _at_
the meter..........in this case, as evidenced by the OP's configuration.
In _fact_, NEC(2002) Section 250.24(A) allows the premises wiring system to
be grounded at the meter, the service disconnecting means, or even at the
weatherhead (although not practical).
Here's one : http://www.tampaelectric.com/pdf/TEBSSESR.pdf
(see page 90) You'll also note that the lightning protector is installed
_at_ the meter, thus, keeping the surge _outside_ the building.......where
it should be.
While the NEC does not address sharp bends, it most certainly does address
conditions where the GEC is installed in a metal conduit by requiring that
the GEC be bonded to the metal conduit at _both_ ends..........this, in
fact, is very critical and the consequences of not doing so will _not_ be
evident until the system suffers a serious ground-fault or lightning
surge.........in either case it will be too late.
System grounding is a _very_ misunderstood topic, not only is it
misunderstood by many (mostly residential) electricians, but some engineers
also....._Power_ EE's excluded. If anyone wants to really understand
electric system grounding, the following book (as recommended by the
International Association of Electrical Inspectors, IAEI) should be
Changes to an existing grounding system should _never_ be made unless one
knows where and how _all_ connections are made. What you are proposing to
do will most likely result in a parallel (objectionable) current flow on
that #4 wire.......and not permitted by NEC Section 250.6. If the neutral
and the equipment grounding busbars inside the main panel are bonded
together (very, very likely), there's the parallel connection.....not good.
The solution is for the OP to purchase a protector that is intended to be
installed at the meter...........or definitely not install that #4 wire and
use what he has.........it will still be connected to grounding system via
his original set up. The solution is _not_ to remove the main bonding
jumper inside the main panel.
Well, he needs to find out..........chances are pretty good that if the
service is grounded at the meter that the lightning arrestor should also be
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