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I have a main panel that was converted to a sub panel when a new Main Panel was placed in a new addition to the house. So now, the subpanel appears to have two grounding wires connected along with the neutrals on the bus bar (middle right). The fat bare wire on the left is the Main Panel grounding wire that is not being used. Most of the grounding wires, in the subpanel appear to be grounded down the wall cavity to a copper pipe in the crawl space. All the outlets show a correct installation with a receptacle tester.

???Can this type of incorrect installation (ground to neutral bar) cause the following???: I've lived in the house for two years now. Recently, the living room lights have started to flicker once in a while. The power will shut off for about 1/2 second. This might happen 2-3 times before shutting off completely. No breakers get thrown. After 1-10 minutes or so, of me doing nothing, the power comes back on. These symptoms are now more and more reoccurring. This occurs even with nothing turned on except a surge protector, modem, and router. Maybe the breaker is bad and the grounding to the neutral bus bar is incorrect?

I plan to replace the subpanel (use modern parts), use a insulated neutral bus bar, a separate grounded-to-the box grounding bar that will ground to a copper pipe in the crawlspace. I'm not sure if I should connect the bare ground wire from the Main Panel to the grounding bar in the subpanel? The subpanel and main panel are in the same house and are about 20 feet away (20' wire travel).

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  • Your images are not showing up. – Craig Mar 16 '15 at 20:16
  • The images should be showing up now. – Andy Mar 16 '15 at 22:04
  • What make is your main breaker panel, if I may ask? – ThreePhaseEel Mar 16 '15 at 22:17
  • The main panel is a D-Square, I believe, with those flat wide metal power tabs for the breakers. And the breakers have two metal clips. One to grab (hinge on) and other other to grab the metal power clip. The metal clips on the breakers are external. – Andy Mar 16 '15 at 23:05
  • It's Square-D, but yes -- you're fine on that front. I was concerned that your addition was old enough that someone could have shudder installed a FPE Stab-Lok for your "new" panel... – ThreePhaseEel Mar 17 '15 at 0:07
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1) Replacing the subpanel is a very good idea -- FPE Stab-Loks are absolute junk that have a well-known propensity for failing to do their job when called upon, and also are susceptible to faults in the busbar-to-breaker contacts (high resistance/overheating) that are documented to cause the symptoms you're seeing -- this phenomenon can develop into a full-fledged electrical fire!

If a complete replacement of the subpanel is impractical for whatever reason, there is also the option of gutting the box and using one of the Eaton CH retrofit kits to replace the innards. Since your box is a mere, oh, 7" wide by 11" tall, this requires an Eaton RWCH6L125N retrofit interior, the matching cover (a CRWCH6ML of the appropriate size), and the appropriate Eaton CH breakers (it looks like you can use a CH220 and a CH250 along with a pair of CHT1515s, but I'd need to know more about what this subpanel feeds in order to specify for certain).

2) You will need to run a ground wire from the subpanel to the main panel, and separate the ground and neutral bars in the subpanel; however, you do not need a GEC + grounding electrode for a subpanel in the same building as the main panel, as such an installation falls under NEC 215.6:

215.6 Feeder Equipment Grounding Conductor. Where a feeder supplies branch circuits in which equipment grounding conductors are required, the feeder shall include or provide an equipment grounding conductor in accordance with the provisions of 250.134, to which the equipment grounding conductors of the branch circuits shall be connected. Where the feeder supplies a separate building or structure, the requirements of 250.32(B) shall apply.

  • The subpanel is suppose to feed an electric stove and possibly an electric dryer. But I switched it out to gas stove and dryer. For all I care, I can leave these wires just sitting there, not in use. The rest is just living room outlet, lights, refrigerator, kitchen outlets, lights, etc. Not to much power pull on these breakers. This is great info. I'm good with carpentry, so I'm hoping for a 9" wide box to fit in. The current box has studs on both sides on a very tiny wall. I'll see if I get lucky, if not, I can replace the insides like you mentioned. Thanks! – Andy Mar 16 '15 at 23:07
  • @Andy -- what size is the existing box? (I estimated it from the photo, but that's probably off by a bit.) – ThreePhaseEel Mar 17 '15 at 0:05
  • It's 7" at the opening but 8" at the sides. The interior walls recess quite a bit behind the drywall. So basically 8" wide and 11.5" tall (space required in the wall to install). – Andy Mar 17 '15 at 18:41
  • It looks like you'll be stuck with the retrofit kit then -- the largest type CH box that's 8" wide or less only has 4 circuits in it, and the same's true for type BR; there's nothing better in the Square-D lineup, even, for that matter. – ThreePhaseEel Mar 17 '15 at 23:44
  • @ThreePhaseEel so because it is not in a separate building, he does not need a grounding rod and just has to keep the ground and neutral separate in the sub-panel? also, what is considered a "separate" building? Is a garage "separate" from the house if it's connected only by a covered walkway and all the house wiring originates from a box in the garage and runs through the roofed walkway covering? – simpleuser Feb 5 '17 at 6:06

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