3 gang plastic box ground clarification

Status
Not open for further replies.
K

keepitsimplestupid

Member
A question came up where one has a 3 switches, 3 NM-B cables and a 3 gang plastic box. So far, so good.

If this were a metal box, one would connect all the ground conductors to the ground terminal on the switch, then bond to the box.

Now, I interpret 250.148d...

2008 NEC said:
(250.148d) Nonmetalic boxes: One or more equipment grounding conductors brought into a a nonmetalic box shall be arranged such that a connection CAN be made to any fitting or device in the box requiring grounding.
Click to expand...

To mean that it's permissable to connect the grounds from each NM-B cable to each switch without twisting them all together.

This, I believe, makes sense from an electronic standpoint.

Does this violate this rule

NEC said:
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 conductors(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) thru (E).
Click to expand...

So the question is:

When wiring 3 switches and 3 NM-B switch loops in a non-metalic box, do the

1) NB-B grounds have to be connected together and to each switch?
-or-
2) Each would have an NM-B ground from the NM-B cable of the corresponding switch loop and no connection to each other within the box?

Aside: A metal cover plate would inadvertantly connect these together.

Any takers?
 
My understanding is that all the grounds must be connected together. If the grounds where in conduit and loop to thru the box then it would not need to be spliced.
 
Dennis Alwon said:
My understanding is that all the grounds must be connected together. If the grounds where in conduit and loop to thru the box then it would not need to be spliced.
Click to expand...



If it's a switch loop,,,,,and grounded solidly where the loop recieves power, I see no reason for all 3 to come together with a greenie,,,,and then back out to each switch,,,,,I think they can go to each switch seperately, as long as they're grounded on the other end of each NM. IMO,,,,it's the same thing as having a 20 amp circuit switched in the same box as a 15 amp circuit,,,,,,they do not have to be landed together in the switch box,,,because they're grounded at the source. Together doesn't matter.
 
Last edited:
As with many Code items it may be in the eye of the reader. but from the section quoted (250.148)
Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductors(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) thru (E). (emphasis mine), it would seem to me that they have to be connected together if they attach to any equipment or are spliced.
 
augie47 said:
As with many Code items it may be in the eye of the reader. but from the section quoted (250.148)
Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductors(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) thru (E). (emphasis mine), it would seem to me that they have to be connected together if they attach to any equipment or are spliced.
Click to expand...


Every time I read this section I still fail to see where it says that they must all be connected together. :)

For a metal box you wouldn't need any jumpers to the screws on the switches.
 
Why would you not twist them together and then your choice have a greenie with a super long grounding wire looped between switches or 3 grounding pigtails. For safety the grounds need connected to each other even if mixed sizes and circuits. Very easy to comply with
 
Is this a hypothetical question because i see 3 switch loops in one box as a bad design plan in most instances? :confused:
 
Bobhook149 said:
Is this a hypothetical question because i see 3 switch loops in one box as a bad design plan in most instances? :confused:
Click to expand...
I see it very often. Two-three or more switch legs terminating in a box with each equipment ground going to the respective switch.
 
I witnessed the result of a lightning strike that struck the chimney of a house then tracked along the truss to an NM cable where the lightning blew a hole in the outer jacket. This cable fed a receptacle serving the kitchen counter top mounted in a two gang PVC box that also contained another circuit and a switch for lighting. Each equipment grounding conductor was connect to its respective device without twisting the two equipment grounds together. The lightning arced between the two equipment grounding conductors with enough energy that the receptacle and cover were blown away from the box and caused a small fire that self extinguished.

Would this have happened if the conductors were twisted together?
 
augie47 said:
As with many Code items it may be in the eye of the reader. but from the section quoted (250.148)
Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductors(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) thru (E). (emphasis mine), it would seem to me that they have to be connected together if they attach to any equipment or are spliced.
Click to expand...


Those are the key words that allow a 20 amp circuit and a 15 amp circuit to remain seperate.

They are also the key words that alow each loop,,,from the light box to the swich box, and back again, could be considered seperate circuits. Also, Keep in mind they're grounded at the source.
 
augie47 said:
As with many Code items it may be in the eye of the reader. but from the section quoted (250.148)
Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductors(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) thru (E). (emphasis mine), it would seem to me that they have to be connected together if they attach to any equipment or are spliced.
Click to expand...

After re-reading the ROP's referencing this section from the last two code cycles, I have to agree with augie47.
 
keepitsimplestupid said:
If this were a metal box, one would connect all the ground conductors to the ground terminal on the switch, then bond to the box.
Click to expand...
Actually, it's the metal box that must be connected to the EGC's, not the device. For example, with a self-grounding receptacle, the receptacle may be bonded via the screw. The box requires a direct connection regardless.
 
I feel the intent of 250.148 is to have all the equipment grounding conductors connected together. If that is not the intention why is the exception needed?

Exception: The equipment grounding conductor permitted in 250.146(D) shall not be required to be connected to the other equipment grounding conductors or to the box.
 
mcclary's electrical said:
Those are the key words that allow a 20 amp circuit and a 15 amp circuit to remain seperate.

They are also the key words that alow each loop,,,from the light box to the swich box, and back again, could be considered seperate circuits. Also, Keep in mind they're grounded at the source.
Click to expand...
In my opinion, the phase, "those circuit conductors" applies to all of the circuit conductors that are spliced or terminated within the box. I read this section as requiring all of the EGCs within the box to be connected to each other directly or to be connected to the box itself if it is a metal box.
 
don_resqcapt19 said:
In my opinion, the phase, "those circuit conductors" applies to all of the circuit conductors that are spliced or terminated within the box. I read this section as requiring all of the EGCs within the box to be connected to each other directly or to be connected to the box itself if it is a metal box.
Click to expand...

I agree. That's the way I have always done it. ALL the grounding conductors are connected together.
 
Status
Not open for further replies.
Top