Am I Missing Something

:mrgreen: :mrgreen: :mrgreen:

Newer panels tell you in the instructions not to install them together as well.

If the neutral was being disconnected in the panel, the breaker would be off. So regardless of where the ground wire is lugged, or if it is lugged at all the risk of shock would not be from this, but from touching something else in the panel. If there is a shock risk it would be because the breaker/circuit is still live, not because of the location of the ground.

So again I ask, what’s the big the deal of having them under the same lug? I’ve yet to hear a compelling reason why (above that it’s not allowed) for it being any big deal…

Okay, newer panels say don’t. Okay, NEC says not allowed. Still no answer as to why besides a smart *** “don’t you think a shock is a risk”.

I’m not arguing that it is allowed today. It clearly isn’t under code. My question is, why not?

Why on a 30 year panel that was installed this way correctly under the codes at that time, would anyone call this out as a defect? There has to be a reason beyond “it’s not allowed”.

If it is a shock risk, there needs to be an explanation as to what circumstances a shock would happen, and why it would be important to call out.

It was not installed correctly in the 30 year old panel either. The requirement was listed in the UL standard which is not as easy to access as the NEC. It was a violation of 110.3 before. Now it is specifically spelled out in the NEC to avoid the chance of someone not knowing. I don’t have access to a 30 year old panel label, but it might have been stated there and no one bothered to read it.

Here’s a pretty good explanation that was part of the required substantiation to put this directly into the 2002 NEC. This code change came from a representative of Square D. The CMP decided to make this a new code section and called it 408.21 in the 2002 NEC.

Thanks Bob for taking the time to post this…

This is the relivant info.

But we still come back to the question of why, and so what? If the neutral and ground for the circuit are under the same lug and the power it turned off there is no need for maintaining the equipment ground because there is no current.

Soooo… it’s not allowed by NEC because the equipment manufacturers say they should be under the same lug.

That’s not really a good explanation.

So let me ask again in a different way… Why does the manufacturer of the panel wish that the ground be connected if the neutral is disconnected? After all, if you are disconnecting the neutral, the power would be off anyway.

I know why you can’t have neutrals sharing luggs that’s obvious because they are different circuits.

The question is why not a ground and neutral that are in the same circuit. As far as I can tell it wouldn’t make any difference one way or the other…

PS… I’m not trying to be a jerk, or be argumentative. I am just trying to understand what the reason behind the rule, not just the rule itself.

The answer is there really is no answer if the lug is listed for more than one conductor and the condcutors are within the size range of the lug. You’re correct that no one has provided any real substantiation for this rule.

I think in this instance it simply boils back down to a “double tap” scenario and the associated hazard “potential” (similar to the hazard of a double tapped breaker)… as well as the intent of simply maintaining equipment ground at all times.

It is quite possible that if the device failed someone could pull it out to troubleshoot the problem. The power is not off so there is a very good chance of a shock hazard with no path back to the panel to clear the fault.

There is also the diferent coefficient of expansion from a current carrying conductor vs a non-current carrying conductor.

Thanks Michael . I got it . I always thought that arching was an increase in current . Now I now better . :D:D:D