I think my head is going to explode trying to figure this out.

Trying to go through and ensure the safety of my house's electrical system. It is a bit of a mess.

Currently working on grounding and bonding the system correctly.

I will start outside at the meter, this is what I am dealing with - 300 amp service going to x2 150-AMP "main/service" panels on opposite sides of the house. I have that 4-wire service cable running to both panels. There is no GEC at the meter. The bare ground wire and the neutral are bonded on the same bus here. enter image description here

Going inside...

This is one of the 150-AMP service panels. There is a ton of missing grounds that need to be landed on here but ignore that for now. You can see the 4-wires of the service cable entering here. Two hots, our neutral, and then the ground snakes back to the grounding bar. This panel is bonded (as is its brother on the other side of the house). You can also see our 4 AWG bare copper GEC on the left. This goes out to two grounding rods (correctly spaced and installed).

enter image description here

Finally, on the outside of the house we have a grounding bus that takes the GEC from both panels and connects it to the grounding rods. enter image description here

So my questions are...

  1. Is this an unsafe setup with multiple paths for current to return? I know we are supposed to only bond at one point. Should I remove the bonding screws in each panel to isolate the GEC? I am just unsure of how the two panels would interact with the grounds being "bonded" at the meter.

  2. Should I run a copper wire from my grounding bus (and therefore the rods) into the meter enclosure?

  3. Should both of the panels be bonded to water lines or just one?

If I am out of line on anything I have said here, I apologize. I have had several friends who are electricians work on my system and there never seemed to be a concern. Just wanted to see if anyone had a definitive opinion on this.

EDIT (additional information):

  • Non-metallic conduit between meter and service panels
  • Service entrance is (x2) 3-wire 4/0 aluminum cable with 2/0 bare conductor
  • Two "main" panels serving as service disconnects. 150 amps each. First panel is on other side of the meter and the second is about 20 feet straight line on other side of the basement. SE cable ran to both.
  • I am aware of missing grounds and incorrect range breaker. Both will be fixed ASAP.
  • Utility (First Energy) relevant information - "3.8 Grounding/Bonding The customer shall install the service entrance in such a manner to ensure that all the grounding/bonding requirements of the NEC are met or exceeded. The customer’s service entrance shall have a minimum of two driven ground rods (8 feet minimum length) separated at least six (6) feet apart. The grounding electrode conductor shall be continuous from the service entrance main disconnect to both driven ground rods..."
  • I grabbed an ammeter and checked both the bare 4AWG GEC from each panel and saw current on there (0.3-2 amps depending on location). I also checked the bare 2/0 aluminum wire and saw current on there as well (2-3 amps). I obviously have some parallel paths going on. Need to identify the correct fix.



2 Answers 2


Leave the bonding jumper screws in at both panels. NEC 250.24 provides the delineating line about where and how the required service bonding is done ahead of the service disconnect, and prohibiting after. The most relevant paragraphs to you are paragraphs:

(B) Load-Side Grounding Connections A grounded conductor shall not be connected to normally non-current-carrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article.

(D) Grounded Conductor Brought to Service Equipment If an ac system operating at 1000 volts or less is grounded at any point, the grounded conductor(s) shall be routed with the ungrounded conductors to each service disconnecting means and shall be connected to each disconnecting means grounded conductor(s) terminal or bus. A main bonding jumper shall connect the grounded conductor(s) to each service disconnecting means enclosure. The grounded conductor(s) shall be installed in accordance with 250.24(D)(1) through (D)(4). (Italics mine)

The bonding of the meter cabinet is line side of service, the grounded conductor is allowed/required to be bonded ahead of the service disconnecting means in paragraphs ahead of final bonding point above. The factory grounding of the grounded conductor in the meter cabinet assures that the required bonding ahead of the service disconnects is accomplished.

But I think your biggest problem is locations of the service disconnecting means, in comments you stated the panels were separated by at least 20 feet, the code says:

230.72 Grouping of Disconnects.(A) General. The two to six disconnects, if permitted in 230.71, shall be grouped. Each disconnect shall be marked to indicate the load served.

I don't see any way that is accomplished 20 feet apart.

Do not run an additional conductor between service panels and meter cabinet, it is already accomplished by the bare wire in the conduits between cabinets.

Your water line only needs to be connected to one panel.

I hope this is not yet energized, you need to get a lock nut on the conduit supplying the utility side of the meter cabinet.

  • 1
    Okay. Ideally we need two service disconnects outside with all bonding occurring there. This is likely cost prohibitive at the moment. Would like to make system as safe as possible for now. (I understand risks of unfused SE cable through basement). I think I understand but have some clarifying questions. 1. Should I remove that fourth 2/0 bare conductor to eliminate a parallel path for the neutral or leave it? Would leave 3 conductors L1-L2-N. 2. Should I removed GEC from both panels and just land that at the meter? This would effectively eliminate every parallel path for neutral. Thanks Commented Dec 24, 2023 at 6:18

Your bonding question doesn't need to matter, because so many other things need to be changed about this panel. This whole build was a clown show from stem to stern. I've never seen such wild misapplication. This is not the work of a licensed electrician, and my first reaction is "stop payment on the check!"

Unprotected service wires force a meter-main

I will start outside at the meter, this is what I am dealing with - 300 amp service going to x2 150-AMP "main/service" panels on opposite sides of the house...

Problem #1: this does not work at all. The power at the meter is totally unfused. There isn't a "breaker in the meter" or anything like that. What happens if someone puts a nail through one of those two cables going clear across the house? Shorting current can be as much as 10,000 amps.

So classic NEC (that is, 230.70) required that the "service entrance wires" from the meter to the main breaker be as short as possible - e.g. the main breakers (and usually, for economic reasons, panels) need to be immediately on the other side of the wall from the meter, or right next to it for an outdoor-listed panel.

However under NEC 2020, there's now a requirement for a fireman's outdoor disconnect, which means, well, the fastest way to bring this into compliance is replace the pre-2020 "meter pan" with a NEC 2020 compliant meter-main. Such as this one, whose price isn't bonkers, and which gives you 8 breaker spaces right there at the meter - never know when they might come in handy (generator interlock, surge, solar, etc. - this panel would be fantastic for solar.) Or, you might shop for others which place the mains below the meter, and would play better with your existing wire lengths.

SMH the fool waste of materials installing a panel like it was 2002.

Anyway, now that you have main breakers at the meter-main, and they are grouped together satisfying NEC 230.72, they become your only choice for defining the grounding point. The now-subpanels cannot be, since they are not grouped.

Alien breakers

1" type breakers are not interchangeable, and when they are improperly mixed, we see a high incidents of burn-ups on the bus stabs from arcing. That makes sense, since the misfit is making edge or corner contact instead of surface contact.

See NEC 110.3(B) and the panel labeling, which lists legal breaker types. You cannot override that without a UL letter stating a new product is certified as compatible.

This is a brand new Siemens panel (design clues tip it off, as well as the label advising use of the SMK1 spacer kit). For some bizarre reason, every breaker in the panel is Eaton Type BR / Type C. That is not listed on the Siemens label.

Eaton has not received a "UL-Classified" status to allow the Type BR / Type C breakers in any other panel type, nor are the breakers marked "UL-Classified". I know that because Eaton does have a Type CL which is UL-Classified for this panel.

Every breaker needs to be changed to Siemens QP.

Numerous MWBCs, but no handle-ties.

It appears almost every circuit in the panel is wired as a MWBC (Multi-Wire Branch Circuit) aka shared neutral - two hots sharing the neutral. This is fine and safe if the two hot wires are phased carefully. For decades, an MWBC has required "handle-ties" between the two breakers. We don't see a single one. I don't see how any licensed electrician could not realize this.

No GFCI or AFCI breakers on a panel/wiring this new

That doesn't make any sense. Yes, GFCI can be at receptacles. AFCI needs to be at the breaker unless the wiring to the first receptacle is entirely metal jacketed or buried in 2" of concrete.

Regardless, AFCI and GFCI are both very tricky in MWBC circuits. Because of that, most people have stopped using MWBCs, which is why I'm gobsmacked to see so many in a panel this new.

It seems like this incompetent interpreted "A/GFCI is hard in MWBCs" as "therefore I am exempt". No you're not ROFL.

Here you catch a bit of luck. Siemens has developed a tandem AFCI which does play nicely with MWBCs. You can't put a MWBC on a tandem for a variety of reasons, but if you install 2 tandems (4 throws), you can handle-tie the inner throws and put an MWBC on the tied breakers. And then, you can add a third tandem to the stack and do it again, stacking the breakers as high as is needed. With Siemens' tandem AFCI, all legs will have AFCI protection. GFCI can then be done by receptacles.

Another option is add a bunch of neutrals to make each circuit not a MWBC anymore. However, you'd need to watch conduit fill, and enlarge wires as necessary, e.g. using #10 wire for 20A will allow up to ten 20A circuits in one conduit over 24 inches.

Is the wiring this connects to all 20A?

I half wonder if all this THHN wire is traveling to a central box somewhere, where it connects to older wiring in the house.

If that's the case, that could eliminate some of the A/GFCI requirements. But I can't help noticing every breaker in the panel is 20A. That may be fine for the #12 THHN wires leaving the panel, but if it connects to any old 14 AWG copper or 12 AWG aluminum wire, that breaker needs to be 15A.

Each circuit needs to be identified

For every circuit, including MWBCs, each circuit needs to be identified so you know which hot(s) go with which neutral(s). Now me, I own 10 colors of THHN wire, so I would have made MWBC #1 black-black-white, MWBC #2 brown-brown-white, etc. and put that same color tape on the shared neutral. But this wasn't done, so I'd just get tape of every color except white, red and black, and tape all 3 wires of a given partnership.

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