I am having a debate on another site about ground wires. Can anyone give a code reference that requires all the ground wires one jbox from different circuits to be tied together. Or one that requires them not be tied together.

I don't think you'll find one. The only real requirement is that they all be electrically connected. So, you can tie them all together, or not tie them together, and it's all the same since they all tie back to the EGC.

Now... you *may* run into issues mixing high and low current circuits and ground paths- if you have a 20A and a 200A circuit going into a single metal box, the metal box is required to be grounded, and I'd argue that any metal in the box- including the bare #12 conductor- is "likely to become energized" and would be required to withstand the fault current from the 200A circuit ...which would require bonding the #12 and #6 ground conductors. So, in that case, 250.122 would apply. Although it *still* doesn't require them to be bonded, it's just the practical thing to do.

Might also come into play if you're mixing #12 and #14 in a box.

250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes.
Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductor(s) associated with those circuit conductors shall be connected within the box or to the box with devices suitable for the use in accordance with 250.148(A) through (E).

This is the article the other person is citing as requiring them to not be connected. He is saying the "associated with those circuit conductors" only refers to each individual circuit not all the separate circuits in the same box.

250.148. Only exception is isolated grounds

Let's remember that the OP is in Canada. I don't think that our article 250 holds much weight north of the border.

Dang it I fell for it again! I usually look for that. It was posted in the 2008 NEC discussion forum.

This is an NEC issue NOT a Canadian issue. It is a discusion I am having at a DIY site trying to convince them that all grounds from different circuits should be connected together or find out if they shouldn't be connected. I always thought they should be.

Regardless of the country, and whether you are an electrician or not, let's stop and think about this for a minute:

Say you have a two-gang metal box in a kitchen housing a switch for the light over the sink (on the lighting circuit) and a receptacle on one of the small appliance circuits. Using Romex (Loomex), how in the world could you possibly keep the grounds separated? Even if you didn't bond them together, there's no chance that those bare conductors aren't going to meet, either by touching the box directly or via the grounding connections to the device yokes. The separate grounds are going to meet at some point. I'd tend to think that an intentional bonding of EGCs would be better than those that may occur through unintentional contact.

I think that with this being said, the answer is obvious.

I think that any code that requires that such circuits be kept separate would be impossible to enforce unless separate device boxes were mandated for separate circuits. It would be even more difficult to comply with such a requirement. I think that pretty much sums up the answer to the original question.

The reason the code requires / permits the EGC's of different circuits to be connected together is due to the fact that EGC's serve as the primary effective fualt path for circuits.

With the EGC's of different circuits connectred together at junction boxes and other enclosures, a ground fault on the load side (downstream) of the box or at the utilization equipment will return all paths back to the source. With the fault current splitting among 2 or more EGC's, the total resistance of the effective fault path is reduced thus resulting in less stress on the insulated ungrounded conductor and reducing the trip time of the branch circuit overcurrent device.

The "other" persons argument makes no sense in that a metal junction box may contain several circuits that are brought to the box in metal raceways thus bonding all metal parts and EGC's together through mechanical connection. The same concept need not be changed for non-metallic wiring methods.

Be certain the person is refering to grounding conductors and not grounded conductors. Grounded conductors of separate circuits would NOT be permitted to be connected together.

Standing On My Soapbox!

< SOAPBOX MODE = 1 >
< PATH = SOAPBOX.EXE >
< MODULE: SOAPBOX = ENABLED >

I agree with Bryan (BPHgravity).

If there are Circuits from separate Systems, not bonding all the EGCs (Equipment Grounding Conductors) together + to a Metallic Enclosure / Box would result in an odd Ground Fault path, as described below:

One (1) 480Y/277V 4 Wire Multiwire Circuit (20 Amp) + One (1) 208Y/120V 4 Wire Multiwire Circuit (20 Amp) in same Box.

Branch Circuits run underground via PVC to stubs at finish slab level, EMT terminates to the PVC between the slab and Panelboard or Box, each raceway includes One (1) EGC, Outlet Box is 5s (Metallic).

Ground Fault path for an L-G 277V fault with only the EGC from the 208Y/120V "side" would have to flow back to the SDS Transformer, through the case to the Primary Circuit's EGC (bonded to the case), then back to "Some" Panelboard on the 480Y/277V System side.

Not necessarily the best fault path, and may have issues if the Transformer's Primary Circuit EGC is inadequately bonded, or not bonded at all.

For an opposite Ground fault (L-G 120V Fault, only bond is the EGC for the 480Y/277V "side"), the Fault Current would have to flow back to the 480Y/277 Panelboard, "find" the EGC which is included with the Transformer's Primary Feeder Circuit, which:
* Might be fed from another Panelboard,
* Might be fed from the Service Equipment,
* Might be fed from a Distribution Section ("Switchgear"), that is different than the one feeding the Panelboard, where the Transformer is derived from.
Then, flow through that EGC to the Transformer, through the Transformer case, and to the System Bonding Jumper between the case and "X0" Terminal.

Again, this fault path relies on solid and correct terminations for a low Impedance Circuit.
Being that the total loop length may be very long, there might be enough loop Impedance to keep the fault level down, thereby not tripping the OCPD on the Faulted Circuit.

If this occurs, the Metallic Equipment / Enclosures connected to the fault Path will have > 40 Volts (something between 1 Volt and 120 Volts) Potential to Ground (Earth), and a significant level of Current behind it!

With all the EGCs bonded together, the hazards from the above scenarios are greatly reduced (never say "completely removed"! - Poo-Poo does occur!!!).

Besides, why would anyone NOT want to bond all the EGCs together?

Is there some reason why separate terminations would be preferred (normal conditions only)?

Is there a benefit to separate bonding, or reduction in a Circuit's merit if all EGCs are bonded together (they eventually are bonded at the Transformer)?

Would someone prefer to identify ALL EGCs between separate systems, and apply additional labor for separate makeup?
(Project Manager's worst-case scenario: counter-productive labor!).

As mentioned by another Member, IG Conductors is an exception to this view, as these "Dedicated" EGCs are intended to be "Isolated" from raceways, boxes and enclosures, between the Outlet and the Panelboard of origin.

In this case, there is a merit for the circuit to separate the bonding conductors.

Lastly, Bryan's final statement is something that should be noted.

All GROUNDED CONDUCTORS (AKA "Neutrals") between two different systems (or even 2 different Panelboards of the same system) SHOULD NOT BE TERMINATED TOGETHER!!!

Also, none of them should be bonded to an outlet box, or other enclosure - unless:

* Bonded at the same point where the System is bonded to the Grounding Electrode System + Metallic Enclosures (Service or SDS Transformer / 1st Panelboard if bonded there),

* "Older" Multiwire Circuit, which does not include an EGC, instead the Grounded Conductor is bonded to the load equipment's Metallic Enclosures.

Bonding the Grounded Conductor to Metallic Equipment / Raceways / Outlet Boxes at multiple points results in "Unbalanced Current" flowing on both the Grounded Conductor(s) and the EGC / Metallic items.

This not only creates an L-G shock hazard, but also a Fire Hazard when loose or inadequate Conduit Terminations are encountered.

Leaving the Soapbox!!!

< SOAPBOX MODE = 0 >
< MODULE: SOAPBOX = DISABLED >

Scott35

By bonding all the grounding conductors will only increase the reliabiliy of the grounding system. If the electrical system is properly wired, then it should have no ill-effect on any of the systems. By tying each ground together in a sense gives you a larger ground wire between the connection and the breaker because you are paralleling them and it gives the fault an aternat path incase the shortest path is corrupted or open.

Let's break this up into separate issues.

If the box contains splices, and the box is metal (where the raceway or cable is not), then the ground needs to be tied to the box. Makes sense; if another splice comes loose, you want it to trip the breaker, not keep the box energized.

If you're using pipe, or AC, then you need not do that, as the raceway is the ground path. In this example, you're NOT tying all the ground paths together in the box.

If you're having another circuit pass through the box, without splices ... I see no need to tie that circuits' ground wire to the box. You've already got that box bonded. Whether you have transformers, generators, multiple service drops, whatever ... the grounds of all the systems are supposed to be tied together at the sources. If they're not ... I'm not sure you want to do that at some remote, unknown box, using tiny wire and a little wire nut.

Now, let's assume that you have two separate systems in the box, both with splices. One word comes to mind: PARTITION. Isn't that box supposed to be partitioned? Even when the one system is 277, and the other 120, it's possible for there to be more than 300v. difference between the two (phase differences). With the box partitioned, I can see where you would make separate bonds to the box.

Why have more than one wire nut tying the ground wires together? Well, wire nuts are limited in their capacity, and it can be a challenge making a good connection of five or six wires. You've got to start thinking about box fill at this point.

Scott's right to emphasize the distinction between groundingING (green) and groundED (white) wires. The white wires ought to be kept separate in the box, joining only at the panel. While the code might allow some wiggle room on this point, you're introducing an opportunity for all manner of bad things to happen.

Even if there is no splices in the box does not mean the wire will not short out downline from the box. Although the ground from the seperate system may not be comprimised, by tying them all together will only improve the grounding system, not hurt it.

I do believe that the intent of the partition is to insulate the exposed screws that are in close proximity to one another in the box. depending on the phase configuaration between the 120 and the 277 circuits, there is potential for the voltage to be over 300 volts that could in theory if the conditions are right to allow arcing between the two. It has nothing to do with the grounding.

I start thinking about wire fill when laying out the work. I use the 6 P's. Prior planning prevents piss poor performance. typically in new construction, the few wirenuts I have to use there are never more the four wires in them and my boxes only have the bare minimum wire count. Anything else is a waste especically with the cost of copper and plastic.

The neutrals from seperates services are rarely tided together even at the service. A building that have multi-voltages are typically fed with one voltage at the service. The lower voltages comes from transformers on-site that typically derive their own neutral at the transformer. Granted if the neutral from both the primary and secondary are tied together, then the neutrals is not seperate. I do not ever recall seeing the neutrals tide together both on the primary and secondary on power transformers. I have on buck and boosts, control, and auto transformers but that this is out of scope of the OP.

As for the neutrals on the seperate systems having a little wiggle room in the code, can you clearify what you mean on that?

The neutrals of different systems HAVE to remain separate. One might argue, however, that the code allows some different ways to run neutrals of the same systems.

While one might be able to find ways to combine neutrals in a junction box, and thus having only one big wire (rather than several small wires) go back to the panel, I advise against this practice. There's just too much potential for a loose wire to cause an over-voltage condition in some of the combined circuits.

I think I understand what you were saying now. Thanx