I am installing a new GE subpanel (main lug) in my basement. The
panel, rated for 125 amps, is fed off of a 100 amp breaker.
I noticed the following. The panel has slots for 24 breakers, and the
inside of the panel door says that 24 breakers are allowed. However,
the ground and neutral busses have 16 wire locations each, where each
location is a hole into which a ground or neutral wire is fed and then
screwed in place.
Why is this so? I mean, why would a panel allow 24 breakers and have
busses that are smaller than necessary? Does code allow for ground and
neutral wire locations to be doubled up? What if I want to install 17
breakers in the panel?
My work will be inspected with it is complete, so it must be completely
Some panels are designed and listed so that neutrals and grounds can be
connected to the same buss if so then it will say so on a label in the
panel. I had a panel like that in one house I lived in, but as I remember it
did not have a separate ground buss just 2 neutral/ground busses 1 on each
On other types of panels, it is not uncommon that you would have to purchase
an extra ground buss and install it but I never heard of having to buy more
I have also seen many a panel with 2 wires in one slot. Not sure if it is
If the panel is to be used as a sub panel, the ground and neutral busses
must be isolated, in many cases by adding a new and separate ground bar. In
any event, you can double up on the ground conductors, but not the neutrals
The panel is a subpanel, so I removed the metal bar that joined the
neutral and ground busses.
Should I install a secondary neutral bus and connect it to the existing
neutral bus? This neutral bus will need to float, I presume, so that
it does not allow current to bleed into ground.
Based on what?
If multiwire circuits (A-B-N) are used they use use 1 neutral and ground
for 2 poles. For separate circuits a neutral from an A circuit and a B
circuit can be wirenuted to a single wire to the neutral bar.
NEC 2002: 408.21 allows only one neutral per lug.
UL Std. 67 (Panelboard Standard) permits up to three 10 AWG equipment
grounding conductors to terminate on a single terminal, if the terminal is
marked for this purpose.
>>> any event, you can double up on the ground conductors, but not the
>> Based on what?
NEC 2005 moved 408.21 to 408.41, same wording. In the past I added a
note referencing 110.14D: "Termimals for more than one conductor ...
shall be identified", which, in effect, covers both provisions. [It is
annoying to get bit by UL provisions that are not in the NEC.] More than
1 ground wire per terminal can't be used unless indicated in the panel.
If a raceway needs a ground wire (like PVC) and carries multiple
circuits (say 20A, 30A, 50A) the code requires 1 ground wire sized for
the largest fuse/circuit breaker (in this case 50A).
You can wirenut in the panel, but I avoid that unless the neutral is
for two parts of a single branch circuit -- two home runs should be
avoided, but sometimes it is necessary for retro work. Also, we have a
doorbell transformer attached to our panel and it is placed on a lighting
circuit, so the neutrals are wirenutted together.
Check the specs for the panel - most studs on the neutral bus are designed
for multiple wires, depending on their sizes.
Our inspector didn't have a problem with multiple neutrals or grounds
using a single terminal.
However, I will mention this, though it is a bit off topic: he did mention
that trying to be too neat can be a problem! Running a bunch of neutrals
nice and neatly together from where their cables enter the panel to the
neutral bus can be an issue. Spread them out a bit so there is a bit of
air between them. A heavy load on a couple of circuits with closely located
neutrals in the panel can lead to a heat buildup!
"Never ascribe to malice what can equally be explained by incompetence."
Read the UL listing cover information. Most residential manufacturers say
that the bigger holes in the ground buss can contain more than one wire of
the same size. At least my SQD Homeline did.
I know of no requirement that they must provide you with the maxium number
of wires for the maxium number of breakers.
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