A little help on ARC fault wiring.

**Gary Burnett** · 02-18-2013, 05:26 PM

I inspected a new construction today with a main 200 amp and 90 amp sub panel (Yes it was in a submarine that was dry docked). All of the arc fault breakers were installed in the sub. When I read about installing these breakers they always say to attach the pigtail to the neutral bus bar. In a main panel, since the bus bars are tied together you can use either bar. In a sub panel, since the grounding bus is bonded and the grounded bus is floating, shouldn't the pigtails "really" be connected to the neutral (floating) bus and not the grounding (bonded) bus? I wore Google out earlier looking for an easy explaination where they would just say to attach to the XXXXX bar in a sub panel.
First Pic is the Panel
2nd Pic is the bonded bus (grounding)
3rd Pic is the floating bus (grounded or neutral)

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**Bruce King** · 02-18-2013, 07:04 PM

Originally Posted by Gary Burnett

I inspected a new construction today with a main 200 amp and 90 amp sub panel (Yes it was in a submarine that was dry docked). All of the arc fault breakers were installed in the sub. When I read about installing these breakers they always say to attach the pigtail to the neutral bus bar. In a main panel, since the bus bars are tied together you can use either bar. In a sub panel, since the grounding bus is bonded and the grounded bus is floating, shouldn't the pigtails "really" be connected to the neutral (floating) bus and not the grounding (bonded) bus? I wore Google out earlier looking for an easy explaination where they would just say to attach to the XXXXX bar in a sub panel.
First Pic is the Panel
2nd Pic is the bonded bus (grounding)
3rd Pic is the floating bus (grounded or neutral)

The pigtails should be connected to the neutral bus as you already know.
The installer tried to space the AFCI's for better cooling but should have planned for a neutral bus on each side and a ground bus off to one corner.

**Jim Port** · 02-18-2013, 08:29 PM

The arc fault neutral pigtail would attach to the same spot as a non-arc fault in a subpanel. The ones on the left are incorrect.

**Bill Kriegh** · 02-19-2013, 06:57 AM

Originally Posted by Bruce King

The installer tried to space the AFCI's for better cooling but should have planned for a neutral bus on each side and a ground bus off to one corner.

Maybe. There is no reason to space AFCIs in a panel. If they don't work like they're supposed to next to each other they need to go back and be exchanged. The 2014 NEC will likely require AFCIs on all resi 120 volt circuits and spacing won't be an option. I to see what the return rate will jump to when the rules get adopted.

And yes, the white wire are neutrals and do NOT belong on a ground bar.

**Gary Burnett** · 02-19-2013, 05:37 PM

The AFCI neutral pigtails are on the neutral bus, the neutral bus on the left also has bare EGC's terminated there.

Robert, The bus on the left is not a neutral bus. It is the grounding bus and is bonded to the panel. The only neutral bus is the one on the right.

It's kind of hard to make the work look pretty with all those pigtails. It is poor workmanship because it is wired incorrectly and was passed by the local inspector.

**Jim Port** · 02-20-2013, 10:43 AM

There are 3 bus bars as Robert states.

**ken horak** · 02-20-2013, 05:03 PM

Originally Posted by Bill Kriegh

Maybe. There is no reason to space AFCIs in a panel. If they don't work like they're supposed to next to each other they need to go back and be exchanged. The 2014 NEC will likely require AFCIs on all resi 120 volt circuits and spacing won't be an option. I to see what the return rate will jump to when the rules get adopted.

And yes, the white wire are neutrals and do NOT belong on a ground bar.

The 2014 NEC is adding Kitchens and Laundry rooms to the list of locations requiring AFCI protection.

**Jerry Peck** · 02-20-2013, 06:38 PM

Originally Posted by ken horak

The 2014 NEC is adding Kitchens and Laundry rooms to the list of locations requiring AFCI protection.

I haven't checked yet - is that "all" outlets in kitchens and laundry rooms, receptacle outlets only, receptacle outlets which are not GFCI protected, outlets which are not GFCI protected?

There are several options to what that wording could be requiring and it would be based on the actual specific wording in that section.

**Gary Burnett** · 02-20-2013, 07:05 PM

Robert and Jim,
You guys are correct that there are two bus bars on the left and one on the right. The top bus is grounding with bare grounds attached. The bottom one was probably installed by someone as a second floating neutral but (here goes) someone put a bonding jumper on that floating bar which caused it to sink! They are going to need to remove the jumper to the panel and move the grounding (bare) conductors up to the top bar to correct the goof up.
Here is a closer picture of the bonding jumper on the bottom bar.
Geez, I can't believe the eyes on some of you guys out there.