detached garage and 3 way switches

[iwire]

Re: detached garage and 3 way switches

Originally posted by georgestolz:
The purpose of 250.148 is to ensure the "Continuity and Attachment of Equipment Grounding Conductors to Boxes."

Correct 250.148 is about The Continuity of Equipment Grounding Conductors and the attachment of equipment grounding gonductors to boxes.

I think you are overlooked the "and"

Two issues, one section.

[ December 03, 2005, 11:40 AM: Message edited by: iwire ]

 

[George Stolz]

Re: detached garage and 3 way switches

Bob, with the two unassociated circuits kept seperate, but with their respective EGC's connected together, is the continuity compromised?

Edit: that statement was fuzzy. Let's try a different tack.

If the EGC's perform their job in a single gang box, then why would we have to connect them to another circuit's EGC's, or compromise continuity?

[ December 03, 2005, 12:27 PM: Message edited by: georgestolz ]

 

[George Stolz]

Re: detached garage and 3 way switches

The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire (fixture), or other device fed from the box will not interfere with or interrupt the grounding continuity.

It appears that the continuity that this section is concerned about is the continuity of downstream devices and boxes on the same circuit.

It is not concerned not the enhanced overall continuity brought about by connecting EGCs of seperate circuits. As a minimum, the continuity of a portion of the circuit shall not be dependent of a device upstream.

 

[iwire]

Re: detached garage and 3 way switches

Originally posted by georgestolz:
Isn't it odd that they used the phrase "equipment grounding conductors associated with those circuit conductors" instead of "any EGCs in a box" if they were trying to achieve what you interpret?

No it is not odd at all as this section does not apply to all EGCs in the box only the EGCs associated with the circuit conductors that are spliced or terminated.

I always failed English but I will give this a try.

Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box,

This first part singles out the conductor or group conductors that this second part presents a rule for.

any separate equipment grounding conductors associated with those circuit conductors shall be spliced or joined within the box or to the box

So the EGCs singled out in the first part are required to be joined together or to the box.

[ December 03, 2005, 01:24 PM: Message edited by: iwire ]

 

[iwire]

Re: detached garage and 3 way switches

Originally posted by georgestolz:

The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire (fixture), or other device fed from the box will not interfere with or interrupt the grounding continuity.

It appears that the continuity that this section is concerned about is the continuity of downstream devices and boxes on the same circuit.

Again this is another distinct and separate issue that section covers in addition to the EGCs being joined together.


[ December 03, 2005, 12:58 PM: Message edited by: iwire ]

 

[iwire]

Re: detached garage and 3 way switches

BTW in this weird set up we are discussing I think joining the EGCs might do more harm then good however IMO the NEC requires them to be joined.

 

[George Stolz]

Re: detached garage and 3 way switches

Originally posted by iwire:
I always failed English but I will give this a try.

So the EGCs singled out in the first part are required to be joined together or to the box.

Right. The EGCs associated with the spliced circuit. Where does it say that all the EGCs carried with circuits that are not associated with the first set be bonded together?

This changed a little in 2005, but the text remains largely the same. I see no language requiring the interconnection of different circuit's EGCs.

I'd imagine in raceway methods, it would be tempting to route neutral and grounding conductors through a box without a splice, for say a single pole switch in a mutligang box on the way to a load (Circuit #1). The hot could be interrupted with a switch and the others could cruise through unbroken. If other EGC's were in a box for Circuit #2, there would seem to be no requirement to break the EGC for that single pole switch, if it weren't for this section. At the time of installation, there would be a bonding path back to the source.

If Circuit #2 were removed upstream, then suddenly there would be no fault current path for Circuit #1's switch or box. That's not safe. It's safer that all equipment be bonded with the EGC's associated with it's own circuit.

An easy way to curb that practice is to state that if any of the circuit conductors are broken in a box, you'll need to break the EGC too and ensure that any devices that necessitated the circuit conductors to be broken are bonded by the appropriate EGC.

That's not to say that interconnecting the different circuits is bad, just that at the minimum, the EGC associated with a circuit should be bonding all exposed metallic paths on it's way to the outlets.

I wrote:
It appears that the continuity that this section is concerned about is the continuity of downstream devices and boxes on the same circuit.

Bob replied:
Again this is another distinct and separate issue that section covers in addition to the EGCs being joined together.

We have the heading, which states the overall purpose of the section, followed by the statement we're discussing. Now in the 2005, they've broken it up for ease in reading (I imagine). None of these subsections seem to indicate any straying from the heading:
Continuity of EGC connection to boxes, and
Attachment of the EGC connection to boxes.

Why such an unrelated requirement buried in the midst of that?

 

[iwire]

Re: detached garage and 3 way switches

Originally posted by georgestolz:
Right. The EGCs associated with the spliced circuit. Where does it say that all the EGCs carried with circuits that are not associated with the first set be bonded together?

any separate equipment grounding conductors associated with those circuit conductors shall be spliced

George IMO "any" and "those" are plural and mean they mean all of the circuit conductors.

 

[George Stolz]

Re: detached garage and 3 way switches

All of them must be addressed, but there is no reason they can't be addressed in groups. So circuit 1 must be joined together, and then circuit 2, and so on.

We could attach every "in" or "out" to a metal box itself, if we had a drill bit, a tap, a bunch of screws, some patience and way to much time on our hands.

A wise man once said that 250 gives us options, and options are a good thing.

 

[iwire]

Re: detached garage and 3 way switches

Originally posted by georgestolz:
All of them must be addressed, but there is no reason they can't be addressed in groups. So circuit 1 must be joined together, and then circuit 2, and so on.

I am sorry there are no options here, we will not see eye to eye on this one.

Hopefully others will be brave enough to step in and straighten you out.

 

[George Stolz]

Re: detached garage and 3 way switches

Naa, I know where you're coming from.

I just don't see the point of such a requirement. If it's fine alone, why does it need help from it's friends?

FWIW, I rarely do not interconnect the EGCs anyway.

 

[iwire]

Re: detached garage and 3 way switches

Originally posted by georgestolz:
I just don't see the point of such a requirement. If it's fine alone, why does it need help from it's friends?

I hear you.

Here is just a plain and simple guess.

It helps keep all grounded objects at the same potential under fault conditions.

Underground fault conditions the EGC carrying the fault will rise above the potential of the EGCs not under fault.

By tyeing them all together you will help keep this difference of potential as low as possible.

Kind of like the grounding grid at a pool.

 

[George Stolz]

Re: detached garage and 3 way switches

So we share the pain, instead of localizing it?

 

[iwire]

Re: detached garage and 3 way switches

Originally posted by georgestolz:
So we share the pain, instead of localizing it?

OK forget all that...it's just easer for inspection purposes to require all the EGCs together.

[ December 04, 2005, 10:11 AM: Message edited by: iwire ]