Bonding screw and a jumper in A secondary electrical panel

[Sam Morris]

Is this allowed in secondary (aka Sub-panel) Should the bonding screw be removed for a secondary panel and I cant figure out why this copper jumper at bottom left is linking the ground bus bar to the neutral bus bar (service wires were in metal conduit, if that makes a difference) ??



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[Jerry Peck]

First, that copper jumper is a factory piece which is installed to bond both sets of terminal bars to serve as neutral terminal bars instead of just the terminal bar with the neutral conductor in it.

Are you sure that is not "the" service equipment panel? (That there is a main service disconnect someplace else.)

Second, if you are sure that is not the service equipment panel, then not only does that screw need to be removed, but that bare ground conductor needs to be removed from the neutral terminal buss and connected to a grounding terminal attached to the panel enclosure.

And I would need to look at it on my computer, not just on my phone.

[Jerry Peck]

I suspect that whoever installed that panel "thought" it was service equipment.

Would be better if the overall photo was closer (but still shows the entire panel) and higher resolution/better focus (to see things better, even on the computer).

[Sam Morris]

I suspect that whoever installed that panel "thought" it was service equipment.

Would be better if the overall photo was closer (but still shows the entire panel) and higher resolution/better focus (to see things better, even on the computer).

Good stuff- Thanks
The neutrals and grounds are separated (2 neutral bars are bonded together with the factory strap -with 2 installed ground bars one at bottom left and one at top right), yes its a secondary panel. Service wires come out of meter base into a disconnect box, i couldn't get it open because it was rusted and had been painted over several times. I was talking about a copper jumper at the bottom left that connects the ground bus to the neutral bus , why are they connecting this (not talking about the factory bonding strap) What all the bonding to the metal conduit at bottom center ? (panel has no state inspector sticker) I may have to go back and try to open panel outside that was painted shut to be able to determine if panel is a Main or not)

[Don Hawley]

Looks like the installer went one step to far. Should be OK if the bonding screw and wire from neutral to separate grounding bar are removed. Should have a grounding bushing on the conduit with a #6 or larger bonding wire to the grounding strip.

[Jerry Peck]

"*I was talking about a copper jumper at the bottom left that connects the ground bus to the neutral bus"

That's what I was referring to with:
"but that bare ground conductor needs to be removed from the neutral terminal buss"

I couldn't tell if that was a jumper to the ground terminal bar, or if it was a conductor which went down and was hidden behind those other wires.

[Sam Morris]

"*I was talking about a copper jumper at the bottom left that connects the ground bus to the neutral bus"

That's what I was referring to with:
"but that bare ground conductor needs to be removed from the neutral terminal buss"

I couldn't tell if that was a jumper to the ground terminal bar, or if it was a conductor which went down and was hidden behind those other wires.

Thank You Sir, your the best

[Nicky Bharti]

Is this allowed in secondary (aka Sub-panel) Should the bonding screw be removed for a secondary panel and I cant figure out why this copper jumper at bottom left is linking the ground bus bar to the neutral bus bar (service wires were in metal conduit, if that makes a difference) ??

Hello, Sam Morris! It is normal that they must remove this metal bolt from the panel. In many cases, that causes fire because of these metal bolts. If you want to solve your problem, I suggest you buy plastic bolts with plastic adjustments to protect you from the inspector and other possible irregularities. Usually, I buy this kind of construction-related device at sites like https://www.scrooz.com.au/nuts-and-bolts/. They have good delivery options and offer good prices. If you are interested, let me know, I got some free delivery coupons from them. Have a great day, buddy!

[Jerry Peck]

It is normal that they must remove this metal bolt from the panel.

Depends on the type of panel (service equipment panel or non-service equipment panel) as service equipment panels require both the neutral and equipment grounding terminal bars be bonded to ground (and the enclosure, which is grounded); while non-service equipment panels require the neutral terminal bar to be isolated from ground and the equipment grounding terminal bar be bonded to ground (and the enclosure, which is grounded)

In many cases, that causes fire because of these metal bolts.

Please explain.

[david shapiro]

Is that bare copper heading off ot the lower left going into the wirenut with the smaller white wires, or is it heading out, behind that wirenut, heading perhaps for a grounding electrode?

[Jerry Peck]

Is that bare copper heading off ot the lower left going into the wirenut with the smaller white wires, or is it heading out, behind that wirenut, heading perhaps for a grounding electrode?

David, it looks like it is a bonding jumper from the main grounding terminal bar to the grounding terminal bar which has been added over by the left side.

"Grounding terminal bar" ... which has the neutral conductor connected to the bottom lug. Which is okay if it is a service equipment panel ... not okay if it is not a service equipment panel.

[david shapiro]

Plausible, Jerry. Somewhat unusual for an installer to use a large bare solid conductor, but identifying the unusual is where we shine. I don't remember seeing a loadcenter that came from the manufacturer with a copper bonding jumper down to a separate ground bar. Only her hairdresser knows for sure. (That would be Sam.)

[Jerry Peck]

David, maybe it was the hair dresser, Sammie, who said 'you know, if you remove that bonding screw you are talking about, then you need to put a bonding jumper over to that other separate grounding terminal bar you mentioned, because that copper thingy you said going from neutral terminal bar to neutral/ground terminal bar was bonding the neutral terminal bar to ground at that bonding screw you said you took out.'

Followed by 'I don't really understand what I just said, I'm just repeating what my electrical contractor customer said on the phone to someone.'

[Gunnar Alquist]

I realize this is thread drift, but since we have people who know this stuff nearby...

I am having a bit of trouble with the terms Grounded conductor and Neutral conductor, at least in reference to reading the NEC (which I use to put myself to sleep at night when I'm suffering from insomnia). The NEC seems to use these two words interchangeably in many of the code articles.

I already understand the definitions of these two terms from the NEC (below) and that, in a residential, 240(ish) volt, single-phase electrical system, the neutral is bonded to the earth at the service equipment as well as at the transformer. Therefore, in this case, the terms are synonimous and the grounded conductor is the neutral conductor.

Is there a condition when the grounded conductor is not the neutral conductor?

How would I know? Would I be able to put one probe of my VOM on neutral and the other on the EGC and get some voltage difference? If so, what might it be?

From NEC Article 100:

Grounded Conductor. A system or circuit conductor that is intentionally grounded.

Neutral Conductor. The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.

[Jerry Peck]

I already understand the definitions of these two terms from the NEC (below) and that, in a residential, 240(ish) volt, single-phase electrical system, the neutral is bonded to the earth at the service equipment as well as at the transformer. Therefore, in this case, the terms are synonimous and the grounded conductor is the neutral conductor.

Is there a condition when the grounded conductor is not the neutral conductor?

On a 120 volt / 240 volt circuit, the 120 volts is created by grounding the the center point of the 240 volts, creating 120 volts to each side of that grounded point to each phase leg. So, to my knowledge and thinking, being that the conductor connected to that grounded point (i.e., the grounded conductor) is also the neutral conductor.

Would I be able to put one probe of my VOM on neutral and the other on the EGC and get some voltage difference? If so, what might it be?

As I recall, the Suretest measures the voltage between the ungrounded and grounded conductor, and between the grounded conductor and the grounding conductor. I haven't used, or seen, my Suretest since I moved (a year ago), and I just looked in my garages and didn't find it (hopefully I still have one somewhere, i had two and gave one away, hopefully I didn't give both away), so I can't verify that the Suretest measures that voltage.

There could be, and typically is, a very minor voltage (typically in mV as I recall) between the grounded conductor and the grounding conductor. Any difference in the resistance of connections, paths, etc., between the grounded conductor (which is basically always a wire conductor) and the grounding conductor (parts of metallic enclosures, metallic raceways, etc), and current passing through a resistance creates a voltage across that resistance.

I know the next question 'current on the grounding conductor'? Yes, nothing is ever "perfect".

Do you put a clamp on ammeter on the GEC? You'd be surprised what you will measure (yes, I know, that is different on that side of the grounded point (going back to the utility transformer) than on the other side of the grounded point (after the service equipment, but start doing that, and when you start reading "amps" versus "mA" ... start wondering why).

Reading mA is because the neutral path back to the utility transformer consists of a parallel circuit of the neutral conductor and "earth" (from ground rod at the service through "earth" back to ground rod at the transformer) as the other conductor in the parallel circuit.

[Gunnar Alquist]

Thank you Jerry, that coincides with my current (incomplete) knowledge.

I still wonder why the NEC seems to use grounded and neutral interchangeably. Is there a reason that they do that? I find it confusing and wonder if others do as well.