Another sub panel question

[Ken Rowe]

We all know that the ground and neutral wires need to be on separate buss bars in the sub panel. How about this, grounding through the conduit to the main panel, hot wires run to the breakers in the sub panel, neutrals connected to the main panel buss bar?

I spoke with a master electrician who didn't think it was a problem, but stated it was not normal, hasn't seen it before and is not professional workmanship...so it got wrote up as such.

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[Jerry Peck]

How about this, grounding through the conduit ...

No problem with that - when done properly.

That is through eccentric knock outs and a reducing washer, that should have grounding bushings.

If that is a fairly old installation, before it was recognized that the knock outs, and especially the reducing washers, did not provide a good and reliable ground path, then it may have been okay at the time. Newer installation would have required grounding bushings, and just because poor grounding was not recognized at the time, that should also have grounding bushings.

[Ken Rowe]

I guess I should rephrased the question. Can the neutrals be connected to the main panel buss bar while the breakers are installed in a sub panel?

[Jerry Peck]

I guess I should rephrased the question. Can the neutrals be connected to the main panel buss bar while the breakers are installed in a sub panel?

No.

The neutrals need to run with the hot conductors. All circuit conductors need to be run together.

My apologies for not picking up on what you were asking.

[Gerry Bennett]

I would say it is OK. The ground and neutral are together in the main panel and separated in the sub panel. I don't think the neutrals need to be brought through, the one large neutral is sufficient. It is just like the gen-tran tranfer panels you may have seen. They bring one ground and one neutral and then the circuits, 6, 8, 10 even more. The gen-tran 301060 is basically a 60 amp sub panel, # 6 wire provided for the breaker and the neutral and a smaller ground wire.

[Jerry Peck]

I would say it is OK. The ground and neutral are together in the main panel and separated in the sub panel. I don't think the neutrals need to be brought through, the one large neutral is sufficient. It is just like the gen-tran tranfer panels you may have seen. They bring one ground and one neutral and then the circuits, 6, 8, 10 even more. The gen-tran 301060 is basically a 60 amp sub panel, # 6 wire provided for the breaker and the neutral and a smaller ground wire.

The neutrals are REQUIRED to be brought through with the hot conductors when run through ferrous metal fittings, raceways, and enclosures.

Negative effects will happen when all of the circuit conductors are not run together, especially through metal fittings and the sides of the metal cabinets. When the neutral and the hot conductors are run together, their magnetic fields cancel each other out. When run as shown, the magnetic fields created by the hot conductors will create eddy currents in the metal (ferrous metals) sides of the enclosure.

- 300.20 Induced Currents in Ferrous Metal Enclosures or Ferrous Metal Raceways.
- - (A) Conductors Grouped Together. Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.
- - - Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 250.130(C).
- - - Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with the provisions of 426.42 and 427.47.
- - (B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.
- - - Exception: In the case of circuits supplying vacuum or electric-discharge lighting systems or signs or X-ray apparatus, the currents carried by the conductors are so small that the inductive heating effect can be ignored where these conductors are placed in metal enclosures or pass through metal.
- - - - FPN: Because aluminum is not a magnetic metal, there will be no heating due to hysteresis; however, induced currents will be present. They will not be of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections.

Now, if those enclosures were aluminum or non-metallic, that is a different story.

[John Kogel]

I would say it is OK. The ground and neutral are together in the main panel and separated in the sub panel. I don't think the neutrals need to be brought through, the one large neutral is sufficient.

The large neutral has no branch connections to it, and the neutral bus is floating. Why have it there at all if the rest is all good?

What is not normal in this picture is the branch circuit hots returning to the main panel before continuing on. It is a kind of split bus arrangement.

There appears to be a shortage of branch circuit neutrals, or there are 240 volt circuits lacking tie-bars.

[Gerry Bennett]

The neutrals are REQUIRED to be brought through with the hot conductors when run through ferrous metal fittings, raceways, and enclosures.

Negative effects will happen when all of the circuit conductors are not run together, especially through metal fittings and the sides of the metal cabinets. When the neutral and the hot conductors are run together, their magnetic fields cancel each other out. When run as shown, the magnetic fields created by the hot conductors will create eddy currents in the metal (ferrous metals) sides of the enclosure.

- 300.20 Induced Currents in Ferrous Metal Enclosures or Ferrous Metal Raceways.
- - (A) Conductors Grouped Together. Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.
- - - Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 250.130(C).
- - - Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with the provisions of 426.42 and 427.47.
- - (B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.
- - - Exception: In the case of circuits supplying vacuum or electric-discharge lighting systems or signs or X-ray apparatus, the currents carried by the conductors are so small that the inductive heating effect can be ignored where these conductors are placed in metal enclosures or pass through metal.
- - - - FPN: Because aluminum is not a magnetic metal, there will be no heating due to hysteresis; however, induced currents will be present. They will not be of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections.

Now, if those enclosures were aluminum or non-metallic, that is a different story.

Thanks Jerry, You answered a question I had. The Gen-tran panel I mentioned comes with 1" ENT to connect to the main panel, and the pre-wired panel comes with a greenfield sleeve, maybe aluminum. One other question. A while ago I had a job where the service had been relocated. When I removed the cover I was shocked to see no individual neutrals. They had run the circuits and one large neutral through conduit from the previous location. Someone on another site said it may have been code at one time with the"Superneutral", which I recall using on a job once in a large lighting dimmer panel. Any info on that? Thanks

[Jerry Peck]

Thanks Jerry, You answered a question I had. The Gen-tran panel I mentioned comes with 1" ENT to connect to the main panel, and the pre-wired panel comes with a greenfield sleeve, maybe aluminum. One other question. A while ago I had a job where the service had been relocated. When I removed the cover I was shocked to see no individual neutrals. They had run the circuits and one large neutral through conduit from the previous location. Someone on another site said it may have been code at one time with the"Superneutral", which I recall using on a job once in a large lighting dimmer panel. Any info on that? Thanks

It is *always best* to run the neutrals with the hot conductors, however, from what I can think of, it is not always 'required' to do so.

I had not heard of 'super neutrals', and on circuits with GFCI *breaker* protection that would cause the GFCIs to trip. Not sure exactly how an AFCI would react to that condition - but it is something to consider.

[Jim Port]

A superneutral would be one that is larger than the ungrounded circuit conductors. This is done in commercial work to avoid overheating from harmonics. I don't think you would see it too often in residential. It would also account for the greater loads on a neutral from two hots on the same leg.

[Jerry Peck]

A superneutral would be one that is larger than the ungrounded circuit conductors. This is done in commercial work to avoid overheating from harmonics. I don't think you would see it too often in residential. It would also account for the greater loads on a neutral from two hots on the same leg.

I've seen neutrals larger than the hot conductors, and, yes, it is usually to allow for the the higher current caused by harmonics, typically the 3rd harmonic as I recall, I had not heard the term 'superneutral' before. Interesting term for increasing the neutral a size or two, I would have thought a term like that would have applied for a neutral which is considerably larger than the hot conductors.

[Garry Blankenship]

The neutrals are REQUIRED to be brought through with the hot conductors when run through ferrous metal fittings, raceways, and enclosures.

Negative effects will happen when all of the circuit conductors are not run together, especially through metal fittings and the sides of the metal cabinets. When the neutral and the hot conductors are run together, their magnetic fields cancel each other out. When run as shown, the magnetic fields created by the hot conductors will create eddy currents in the metal (ferrous metals) sides of the enclosure.

- 300.20 Induced Currents in Ferrous Metal Enclosures or Ferrous Metal Raceways.
- - (A) Conductors Grouped Together. Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.
- - - Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 250.130(C).
- - - Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with the provisions of 426.42 and 427.47.
- - (B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.
- - - Exception: In the case of circuits supplying vacuum or electric-discharge lighting systems or signs or X-ray apparatus, the currents carried by the conductors are so small that the inductive heating effect can be ignored where these conductors are placed in metal enclosures or pass through metal.
- - - - FPN: Because aluminum is not a magnetic metal, there will be no heating due to hysteresis; however, induced currents will be present. They will not be of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections.

Now, if those enclosures were aluminum or non-metallic, that is a different story.

Right on-ski. Just wanted to add 300.5. I ~ All conductors of the same circuit and, where used, the grounded conductor and all grounding conductors shall be installed in the same raceway or cable.

[Jerry Peck]

Just wanted to add 300.5. I ~ All conductors of the same circuit and, where used, the grounded conductor and all grounding conductors shall be installed in the same raceway or cable.

Not exactly as stated.

300.5 addresses:
- 300.5 Underground Installations.
- - (I) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors shall be installed in the same raceway or cable or shall be installed in close proximity in the same trench.
- - - Exception No. 1: Conductors in parallel in raceways or cables shall be permitted, but each raceway or cable shall contain all conductors of the same circuit including equipment grounding conductors.
- - - Exception No. 2: Isolated phase, polarity, grounded conductor, and equipment grounding and bonding conductor installations shall be permitted in nonmetallic raceways or cables with a nonmetallic covering or nonmagnetic sheath in close proximity where conductors are paralleled as permitted in 310.4, and where the conditions of 300.20(B) are met.

Not only is that limited to "Underground Installations", that is further limited by the two exceptions.

[Dan Harris]

Dang, we're doing good. Two or three recent "sub panel " questions and JP didn't correct us

[H.G. Watson, Sr.]

None of the six individual branch circuit conductors (wires) originated from the subfeeder panel should be passing through that main (or upstream)panel, are neither grouped nor are any of the six L&ABP circuits in a common sheath (such as in a multi-conductor cable). None of the subfeeder panel branch circuit conductors (neither grounded nor grounding) should be landed in the main feeder panel. Two unidentified insulated conductors on the main panel neutral bus. Although you stated the fitting was the subfeeder grounding conductor, appears to be non-conductive bushing present and an undersized bare conductor for the 4-wire sub-feeder from the main's grounded bus to the subpanel grounding bus.

This is not a module panelboard system.

[Jim Port]

Two unidentified insulated conductors on the main panel neutral bus.

There is green tape on both of these "unidentified" conductors.

Although you stated the fitting was the subfeeder grounding conductor, appears to be non-conductive bushing present and an undersized bare conductor for the 4-wire sub-feeder from the main's grounded bus to the subpanel grounding bus.

That is just a plastic bushing on the end of the fitting to provide a smooth surface. There is a metal locknut under it.

The grounding conductor is not even needed since a metal offset nipple was used. Those look like #6s feeding the panel so you would only need a #10. Even if feed by up to a 100 amp breaker the EGC would only need to be a #8 by Table 250.122.

If the panel to the left is the service there are more than 6 throws to turn it off. If it is not a service panel the neutrals and grounds should be separated.

[John Kogel]

Thanks, Jim. I think the larger panel, which might be the service panel, is back fed thru that 100 amp breaker at the top, which, if so, provides the disconnect.

[Greg Weaver]

Okay, so here's a dumb question while we're discussing where and when the hot, neutral, and ground absolutely need to run together: 1950's home. Originally obviously ungrounded. Apparently, they later ran a ground to the panel, and ran insulated (green-colored) ~16ga stranded copper from the grounds to all the outlets in that section of the house. The home was later massively expanded on, and that main panel became a sub-panel. Neutral and ground were still bonded until the panel was replaced.

Upon replacing that panel, do they need to run new feeds for all the branch circuits fed by that panel?

[Jim Port]

I would say no Greg. A panel change rarely triggers the need to upgrade the branch circuit wiring. The few instances I have heard of have all been local amendments and not an NEC requirement.

The addition of a grounding conductor is one of the few exceptions to the rule that all conductors must be run together in the same cable or raceway.

[Jerry Peck]

The home was later massively expanded on,

Depends.

Depends on what "massively expanded" means. Here is an example:
- Let's say the house was a small house, selling for, say, $70,000, and let's say the lot value was $20,000, which means the house value was $50,000.

The easy way to get that value is to look at the property appraisers web site and look at the value given to the lot, the structure, and any other structures or values listed.

If the house was "massively expanded" and they put $35,000 into the house and now the house sells for $150,000 ... it does not matter what the house is worth *after* the work, what matters is the values *before* the work, and the value *before* the work was $50,000.

Significant Improvement kicks in when the value of the work is greater 50% of the value of the house *before* the work, in this example the value of the work is $35,000, which is greater than that 50% threshold. The same threshold is for Significant Damage, say from a flood, hurricane, snow blizzard, fire, etc.

Because the Significant Improvement threshold was crossed, the *entire* house is required to be brought up to current code. That's when you throw out the 'this was a legal structure and is allowed to remain as is with the new work meeting current code and the original work is allowed to remain' and replace it with 'break out the code books and the *entire structure* needs to be brought to current code'.

That $35,000 "massively expanded" work now becomes $75,000 to bring the entire structure to current code, including those ground wires - yes, the entire house would require re-wiring.

[Jim Port]

Seems like that could result in a hardship case given how involved that could get. Some states near me have a rehab code that would not require such an enormous task and even allow less than the current code would require.

I think a more prudent approach would be for just the new work to need to meet current codes.

[Greg Weaver]

Depends.

Depends on what "massively expanded" means.

Welp, there it is, then. A ~1700sqft home became a 6,908 sqft home. I think that's massive enough. However, the expansion was done in the 70s, though about 4,000 sq feet of that is internally unfinished. All the "new" part is properly wired...besides the now-replaced FPE breakers(hey, weren't they "top of the line" before it was learned that they'd pulled a fast one on UL?). Basically, an FPE main(in the "new" bomb shelter), an FPE sub in the internally-unfinished extension, and Bulldog Pushmatics in the old part and another in the (formerly detached) garage. All panels replaced with Homeline; new circuits in the unfinished extension(of which the old branch runs will probably mostly be replaced as well) of course will need to be AFCI/GFI since it's all living area.

Looks like there's a good bit of wire pulling in the future. As much of a PITA, that's probably for the best, anyway. The current wiring in that part is the now-disintegrating cloth-sheathed stuff. At least there's no aluminum branch wiring!

Thanks Jerry, I was hoping you'd provide your input. Jim, I don't know how PA handles these kinds of situations(or even this particular jurisdiction), but 14/2 is cheap (it's all 15 amp) and considering the overall amount of work to be done, the peace of mind is worth the additional work.

[Jim Port]

Greg,

The code now requires some circuits like bathrooms that used to be allowed on 15 amp circuits to now be 20 amps. The circuitry requirements can also be different.

[Jerry Peck]

Depends.

Depends on what "massively expanded" means. Here is an example:
- Let's say the house was a small house, selling for, say, $70,000, and let's say the lot value was $20,000, which means the house value was $50,000.

The easy way to get that value is to look at the property appraisers web site and look at the value given to the lot, the structure, and any other structures or values listed.

If the house was "massively expanded" and they put $35,000 into the house and now the house sells for $150,000 ... it does not matter what the house is worth *after* the work, what matters is the values *before* the work, and the value *before* the work was $50,000.

Significant Improvement kicks in when the value of the work is greater 50% of the value of the house *before* the work, in this example the value of the work is $35,000, which is greater than that 50% threshold. The same threshold is for Significant Damage, say from a flood, hurricane, snow blizzard, fire, etc.

Because the Significant Improvement threshold was crossed, the *entire* house is required to be brought up to current code. That's when you throw out the 'this was a legal structure and is allowed to remain as is with the new work meeting current code and the original work is allowed to remain' and replace it with 'break out the code books and the *entire structure* needs to be brought to current code'.

That $35,000 "massively expanded" work now becomes $75,000 to bring the entire structure to current code, including those ground wires - yes, the entire house would require re-wiring.

I went back and reviewed the code on this (I had not done so recently) and the term is "Substantial Improvement" and the work as been broken down into various sections. No longer is that applied to the structure overall, to various sections, some more than others, and some at a much lesser extent than the 50% rule (which was the old overall rule).

Now each section is addressed in the different levels of alterations. Guess I need to try to wipe XX years of overall substantial improvement out of my brain and replace it with all the individual items - that is the reason that the Existing Building Code is difficult to work through, and here I thought I had 'remembered' many of the changes - OOPS, I GUESS NOT! Sorry about that.

[Greg Weaver]

Sorry about that.

No worries Better safe than sorry, anyway--the place is a beautiful fixer-upper( & a helluva buy at $180K!), extremely well built(especially compared to the McMansions that sprouted up like crabgrass all over South-Central PA; the center beams of the garage and extension are 14" steel I-beams) but very dated.

Nothing appears to have been done out-of-code(at the time it was built) but with the sheer scope of work required to update and finish it, it'd be a shame to not do the relatively minor amount of work to bring the entire electrical system up to current code with the risk inherent to doing so. At least that part is single-story with a fully accessible attic, so fishing new wiring shouldn't be too much of a problem.

Apparently the owner, a civil engineer was stricken with cancer about halfway through his project, so it literally went unfinished for ~40 years. And I guess the it didn't help that the wife kept changing her mind about what she wanted. Hence the 1300 sqft bomb shelter with the 14" thick concrete & girder ceiling and ...fireplace.