there is a neutral coming in from the service, that should be connnected
to the ground/neutral bus in the main panel. All neutrals should be
connected to that bus, one per screw. If you don't have enough screws
add an auxiliary one, and you can add ONLY GROUNDS to the added bus bar
(note: I don't know if this is Code or not but it is a good idea) and
you should also bond it to the original ground/neutral bus bar with some
heavy gauge copper wire (also just my idea of a proper installation.)
That way even without the bonding there is NO current flowing through
the backbox unless there is a ground fault somewhere - it goes direct
from the original bus straight to the service.
I have a book that says you can connect more than one ground under a
screw BUT NOT NEUTRALS but I don't know if current codes have changed
any or not. In any case it is a very bad idea to put more than one
neutral under a screw; if that were to happen, you'd need to shut off
the power to the whole house if you needed to remove one neutral from
the bus for whatever reason. Otherwise, you could end up with a
momentary open neutral on a live 120VAC circuit, and that can cause lots
replace "roosters" with "cox" to reply.
The enclosure is connected to the neutral bar (only in a service panel).
There should only be current on ground wires in abnormal events. It is
permissible for that current to go from ground bar, through metal
enclosure, to the bonding screw or jumper in a service panel, to the
service panel neutral bar. The return path for the ground system may
also include metal electrical wiring boxes and metal pipes with wires in
them. Ground wires land on a ground bar, or only in a service panel on
the neutral bar (the neutral and ground are connected together only in
a service panel).
Neutrals normally do have current on them. It is not permissible to use
any metal enclosures as part of the return path for the neutral. If a
ground bar has a direct wire connection to a neutral bar, connecting
neutral wires is still likely not permitted. The wire connection is
sized for short duration abnormal ground currents to trip a breaker, not
for long duration neutral return currents. Neutrals may land only on a
I don't think the code has changed anytime recently. The book is right
that the code explicitly does not allow more than one neutral in a terminal.
The book may be right or wrong on ground wires. More than one wire in a
terminal is not permitted unless the terminal is 'UL' listed for more
than one wire (110.14-A). If more than one wire is permitted, the label
for the panel should indicate that. As gfretwell said "depending on brand".
If I understand correctly, the neutrals and grounds can't be attached at
different points in the panel and if they are, a large shunt wire should
connect the two so that the path of any abnormal current flow it through the
large shunt wire between the two bus bars and not the metal of the circuit
I suspect that since the panel was not installed into a house with grounded
outlets, the bus bar serves both neutrals and grounds. However, it's clear
that the two grounded outlets that were added were not done by an
electrician or even a talented amateur.
It would seem then, if I have to remove a neutral for any reason the main
shut off has to be used to kill all power to the panel. That's always a
good idea, even though it causes havoc with some of the VCR's and other
electronics in the house. Better than dumping 220VAC through them, I
Thanks for your help.
Originally, gfretwell said "If you put a neutral on the supplimental
bars you are putting circuit current through the metal can and the
green bonding screw. (that is 250.6 for you code guys)"
And you said "Neutrals normally do have current on them."
OK, so let's forget about where they are "put", and look at the logic
of the end result.
If the neutral and ground bars are bonded, it would seem to me that
means they are unified, regardless of which one the wire lands on. IF
the bond takes place through a screw that touches the panel box, then
how is that not "putting current on the can?"
Not arguing. I actually learned all this stuff from you and others
here. But this is the first time it occurred to me that the neutral
current could be on the panel box because of the bonding as gfretwell
said. So I am still confused about that point (not the issue of
putting neutrals on ground bar). Can you explain why that bond (if
achieved through a screw to the box) does not put the current on the
box? I'm still confused!
Now I understand what you're saying because I see that in newer boxes the
ground bar is along the side and the neutral bar is physically about a foot
away above the circuit breaker stack.
I went to the local supply house but all they had was a Cutler Hammer
supplemental grounding bar (the set screws are all painted green) that
looked as though it might piggyback onto the existing neutral bus bar. It
doesn't. )-: I might be able to redrill and cut it to fit, but it seems to
be as bad a solution as doubling up the neutrals with more than one to a
I'm hoping now to find a supplier via the internet for the box. Hopefully I
can find a:
Square D QOC-20MW supplemental neutral bus bar
somewhere on the net. Any pointers to good on-line suppliers appreciated.
The Square D site (apparently now Schneider) had nothing listed under the
QOC-20MW product number. )-:
If it comes down to availability, I would just get whatever neutral bar was
available from the electrical supply. I know Lowes and Home Depot sell
ground bars, but I am not sure if they have the neutral bars. You will
probably need to drill and tap a few holes to mount it or use self drilling
sheet metal screws.
Thanks for the photo BTW.
That's exactly what I did. Got a Cutler-Hammer grounding bus bar that
looked like it matched what was in the box, but it didn't. It has machine
screws, so I'll probably have to mount it with self-taps if I decide not to
return it. It will allow me to remove some ground wires that are now
mounted in the box's neutral bus bar and relocated them to the new ground
bar. Oddly enough, if I do that, it free just enough neutral holes so that
every breaker can have its own neutral bus bar set screw hole, which is
probably how the panel was designed (this is old, two wire constructions
from the 40's as you can see by the cloth insulation).
The scoop from Square D is that there are no supplemental neutral bus bars
for that model box, but the illustration inside the box differs and the
threaded screw holes on the front of the second bar say otherwise as well.
I doubt the guy who responded was even *born* when my model box was sold,
and I suspect their answer to a lot of questions like mine is "you need a
new box." I will check out Lowe's and HD before I decide what to do on the
off chance they have something the electrical supply house didn't.
Glad to see it made it through and that I am not under house arrest by
netcops. I think it's important when asking for potentially hazardous
advice to let people see what I am actually talking about because it may be
very different from what they think I am describing.
Thanks again for all the help,
roomIfor the additional breakers in the box but the neutral bus bar has no
more>room for the neutral and ground wires required. Is it permissible to put
more than one wire per set-screw hole on the neutral bus bar? Some sitesdI've
researched say yes, others say no. If no, what are the options
besidestreplacing the whole circuit breaker panel?gnTIA,"g--tBobby G.
I have no problems putting more than one wire into a hole in a bus bar and
tightening down a screw onto them. It has got to be more solid and safer
than a wire nut. However, if this is an old box with screws that you wrap
the wire around under the screw head, don't do it. Only one wire per screw
The solution to that situation would be to always kill the main breaker or
even the outside shut off below the meter when disconnecting any neutrals,
true? I'm just trying to figure out alternatives in case I am unable to
find a supplemental neutral bus bar.
Thanks for you input!
I wasn't going to do the pigtail/wire nut route. I'd rather pull the whole
box and put in one with a higher capacity and more features than start
spaghetti-ing up the box with wire nuts. Well, that's not exactly true.
But I certainly agree that two wires to a hole couldn't be any *worse* than
putting two neutrals into the same bus bar hole. BTW, it's not a screw head
type box. There are setscrews that lock wire into holes a little bigger
than 1/8" in diameter so there's more than enough room for two #12 wires.
Just doubling up a few would give me enough free spots for the neutrals I
need. But the best solution seems to be adding a third bus bar, if I can
Somewhat repeating gfretwell - ground wires can be doubled up but only
if the label indicates that is permitted.
Neutrals may NOT be doubled up - NEC 408.41
In a service panel you can add a ground bar which the label indicates is
acceptable and move ground wires to it. In a subpanel that doesn't help.
ONLY IF YOU KNOW WHAT YOU ARE DOING - you could take a neutral from an
A-leg circuit and a neutral from a B-leg circuit, wirenut them together
with a single wire to the neutral bar. It is easy to do this wrong.
FWIW, it looks like the reason it's done everywhere is that the "by the
book" solution is pretty drastic. As far as I can tell from what Square D
said, to gain more neutral holes, I'll have to change out the whole box.
That's a little too drastic a solution and I have a few options. One is to
disconnect the central A/C since we never use it. That would free some
openings. Another is to mount the supplemental Cutler Hammer ground bus bar
in the case, feed it with a large diameter wire from the existing neutral
bus bar and move the three or four ground wires now connected to the bus
(old house, very few grounded outlets) to the supplemental ground bus bar.
The third seems to be what most people do. Put two wires under a setscrew
and print up a big label for the box "Disconnect Main Breaker Before Neutral
Primarily because I'm still convinced there's a supplemental neutral bar for
this box somewhere in the world. The panel box illustration shows three
separate neutral bars for the box I have (but mine only has two) and the
frontmost bar has two threaded screw holes where a third bar could be
mounted, so I still hold out some hope I can find something that will work.
But I am reaching a point where I'm spending a lot more time than simply
mounting the new ground bus bar would take.
I don't like it much, either, I must confess. I haven't looked closely at
the box since I confirmed the new bar's holes didn't match the Square D's
(it was close!) but I don't see any way to use the machine screws that came
with the kit. I'm assuming that the correct place for the new grounding bus
bar is along one of the two vertical sides of the box, but I haven't seen
too many new boxes, so I'm not absolutely sure. There's not a heck of a lot
of room inside this box compared to some of the newer ones and I am worried
there won't be enough working room.
I first thought to mount it along the bottom, where there's a lot of free
space but in looking at the photos, I see that the existing ground wires
will be too short to reach and I'd have to wire nut some pigtails, something
I'm not keen on. There is a lot less working room on the sides of the box,
but if I mount it high enough, I can use the existing wire without having to
I have to admit, though, I am sorely tempted to take the four ground wires
going to the neutral bus and put as many of them under one screw as will
fit. That may or may not leave me enough open neutral connections on the
bar to accommodate the new outlets. From what I can tell, that's legit to
do with ground wires, but not neutrals.
Thanks for the advice!
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