Installing arc-fault/gfic breakers in main panel - neutral bar vs ground bar

Question

My main electrical panel is mounted to the exterior of my garage. The main panel supplies 125 amps to a sub panel within my house. I am looking to replace a few of the breakers on my main panel that feed the circuits within the garage. I've already removed some of the old wiring and breakers from the box, so that's my it looks a bit bare as it is now. I'd like to use dual function AFCI and GFCI breakers in the top right 2 slots where I've already removed 2 20 amp breakers.

I understand that the neutral pig tail coming out of the dual function breaker should connect to the neutral bar. My question is, on my main panel, the neutral bar and the ground bar are connected. Does that mean that I can connect the pig tail from the dual function breaker to either side of the panel? Or, with my panel, do I need to install all of my breakers on the left side of the panel, as I believe that's the neutral bar vs the ground bar on the right.

Answer 1

The usual setup is that a "main panel" will have neutral bonded to the case to make it also ground, and a "sub panel" will not have neutral bonded to the case so that neutral and ground are separate. That allows switching a main panel to be a sub panel (e.g., if a meter main is put in to replace a simple meter but the main panel inside the house is kept intact) or a sub panel to become a main panel (e.g., if an old main panel is being replaced starting with adding a sub panel and eventually removing the old main panel and making the sub panel the new main panel).

When you have separate neutral and ground, it is very clear what you need to do. When you have neutral bonded to ground, the normal usage is:

• Neutral wires can only go on neutral bars
• Ground wires can go on neutral bars or ground bars

With a meter main, at least with this one, there is no separate ground bar included with the panel - it simply isn't needed because, by definition, a meter main will always have neutral and ground bonded together. So instead there are neutral bars on both sides, and enough neutral screws for most installations.

Unlike some panels where one side may be ground and the other side neutral (with a ground bond screw), these two bars are connected together with a bar across the bottom - making them both neutral. The right side actually gets the feed from the meter section, then connects across the bottom to the left side.

Note though that while, as is very common, a true ground bar here can have multiple (2 or 3, depending on various factors) ground wires per screw, the neutral bar can only have 1 wire (whether neutral or ground) per screw.

Therefore, if:

• You have tandem/double-stuff breakers everywhere
• Very few double-pole breakers (because those only need one neutral for a pair of breakers)

then you may need additional ground bars because your neutral bars will be filled with all the neutrals plus some of the grounds. There are two locations identified for Series LX ground bars:

but since you have a big panel inside the house, you will not need any additional ground bars in your meter main.

Answer 2

You are correct. In your main panel (specifically where the disconnect from the meter is located). Ground and neutral are bonded together. You can land a neutral to either the neutral or ground buss because they are interconnected.

Anyplace else in your electrical system, you must keep ground and neutral separate (unless you have an old 3-wire feed to a sub panel which is no longer allows it could be grandfathered in.)

Normally, it would be recommended to keep them separate, even in your main, in case you ever want to install a new main and make your existing into a sub panel. However, since your meter is integrated in, that seems unlikely.