Installing 240V Service To Your Shop - Price Breakdowns...

[MossRoad]

Sorry, again, not trying to be mean, but most of that is really not accurate....technically.... That was my point...

P
Please explain why its technically not accurate.

 

[aczlan]

Our provincial code book does not allow multiple cables through one connector.

Good thing Sodo is in WA and as such, those rules don't make him out of compliance.
It would appear that Thomas and Betts have a different interpretation than you do as several of their connectors are listed as ok for multiple cables to pass through:
2x 14/2: Thomas & Betts Canada
2x 12/2 or 14/2: Thomas & Betts Canada
It would also appear that they are allowed in Ontario IF the manufacturer has it listed as being ok (note the part in bold):

The OESC does not permit more than one non-metallic sheathed cable in one pry out using the internal
clamp. CSA Standard C22.2 No. 18 (Outlet Boxes, Conduit Boxes, and Fittings) tests for pullout and voltage
withstand after exposure to an elevated temperature are done with one cable per clamp. Use of more than
cable per clamp is a misapplication.
The standard does recognize box connectors that are approved to accommodate more than one cable and
such connectors can be used with more than one cable up to the limit stated by the manufacturer.

Aaron Z

 

[dstig1]

Sorry DB but Mossroad's statement is correct - if you bond together a neutral and a ground in a subpanel, then the ground wire will carry some portion of the unbalanced return to the main panel - i.e. which is 100% of the return of a solo 110v leg, or some fraction of a 3-wire 220V run such as a typical modern dryer or stove/range. The current will divide itself between the neutral and ground based on the relative resistance of both routes. The lower resistance route will caryy more current, but the old saying of "path of least resistance" is not really quite true. Path of least resistance carries more current, not all of it, unless the resistance difference is extremely dramatic.

When the ground is energized, then all equipment grounds are energized, which means the cabinet to your table saw, drill press, refrigerator etc is now hot to some degree. Touch that while standing in a puddle, and you could feel it bigtime, depending on conditions.

Not all code rules are as clear cut as this one. This one is truly dangerous. A lot of the newest rules seem more like trying to remove that last 0.0001% risk, but this one is a biggie.

 

[mikefromnh]

Sorry DB but Mossroad's statement is correct - if you bond together a neutral and a ground in a subpanel, then the ground wire will carry some portion of the unbalanced return to the main panel - i.e. which is 100% of the return of a solo 110v leg, or some fraction of a 3-wire 220V run such as a typical modern dryer or stove/range. The current will divide itself between the neutral and ground based on the relative resistance of both routes. The lower resistance route will caryy more current, but the old saying of "path of least resistance" is not really quite true. Path of least resistance carries more current, not all of it, unless the resistance difference is extremely dramatic.

When the ground is energized, then all equipment grounds are energized, which means the cabinet to your table saw, drill press, refrigerator etc is now hot to some degree. Touch that while standing in a puddle, and you could feel it bigtime, depending on conditions.

Not all code rules are as clear cut as this one. This one is truly dangerous. A lot of the newest rules seem more like trying to remove that last 0.0001% risk, but this one is a biggie.

Great explanation.

 

[Underdog57]

Question, what if the sub-panel has it's own ground wire to rod in ground????? Can neutral and common bars be tied together then????

 

[GPintheMitten]

Question, what if the sub-panel has it's own ground wire to rod in ground????? Can neutral and common bars be tied together then????

No.

...

 

[ThomasH]

Question, what if the sub-panel has it's own ground wire to rod in ground????? Can neutral and common bars be tied together then????

No, it is unsafe and will energize things with a grounded case. I don't understand why you would ever want to. The only safe thing to do is to install a compliant ground system which typically means two rods 10 feet apart with a single #6 wire which is attached to the gtround bus and NOT bonded to the neutral.

 

[Sodo]

Sorry for contributing to the off-topic,,,,but this is interesting, educational.

On my "main" panel (200A service house panel) the ground bar and neutral bar are bonded together, bare grounds and white neutrals are mixed on both bars. Inspected and passed. But on the subpanel, grounds and neutrals are separate, and the neutral bar isolated from the subpanel box.



It may be obvious to some but I'm having a hard time grasping why it should be any different on the subpanel. If I plug a drill press into a "house" outlet, the eqpt case will be grounded and connected to the neutral bar. And if plug the drill press in at a "garage outlet", then the same grounding condition occurs (at the house panel).

Neutral is "floating" in the subpanel but neutral is bonded to ground 30 feet away at the house panel.

I am puzzled and interested in the reasoning for this detail and will appreciate another attempt at explanation maybe it will become clear.

 

[buickanddeere]

Thank you dstig1 and ThomasH. Could not have said it better myself.

 

[ThomasH]

Sorry for contributing to the off-topic,,,,but this is interesting, educational.

On my "main" panel (200A service house panel) the ground bar and neutral bar are bonded together, bare grounds and white neutrals are mixed on both bars. Inspected and passed. But on the subpanel, grounds and neutrals must remain separate, and the neutral isolated from the subpanel box. ..snip...

I am puzzled and interested in this detail.

Normally the service entrance on the house is a somewhat small distance from the overhead drop or underground feed to the meter. And it is much larger typically than a feed to a sub-panel is. So the thinking was at the time that there wouldn't be much of a voltage difference if you did the bonding in the panel (which is no longer allowed - it is now at the meter along with the ground rod connection).

A barn or shop is often a hundred or more foot run with smaller wire, and has the potential of energizing the ground with enough voltage by the time it gets back to the main panel or meter, to be a hazard. So in order to not use the ground wires as a possible return leg and energizing the grounds that could be a long distance from the earth ground, they don't allow it any more.

And they are reviewing ground rods now and probably are going to require more and longer ground rods in the future. Don't assume that just because something was allowed at some point that it is really as safe as it should be to keep people from being shocked or killed. Grounds have always been an area that have been somewhat unsafe in the past. In our area, they considered water pipes as a valid ground rod in the past, so as long as you had a copper water service line, and your panel bonded to it, it was considered ok. That was just plain dangerous...