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.
#178061 - 05/22/0801:51 PMRe: ground wires from different circuits in same box
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.
#178111 - 05/23/0805:19 PMRe: ground wires from different circuits in same box
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.