Shared Neutrals

[Sierrasparky]

If it's a solid conductor, it can be fixed without having to disconnect it, without having to turn anything off.

With it still landed, go back to a spot that's not burnt and skin the insulation off with a knife, about an inch long. Then twist a pigtail into it with your Kleins and land that in the neutral bar. Then cut off the bad one and remove it from the neutral bar. Then wire nut your new splice

I know this sounds like a neat little trick, However much safer to de energize and fix. What is the boss going to say when you fried everything on three circuits when you lost the neutral?

 

[kwired]

I know this sounds like a neat little trick, However much safer to de energize and fix. What is the boss going to say when you fried everything on three circuits when you lost the neutral?

Chances are you don't fry everything on three circuits, but it is the lesser expensive items with resistance heating elements and relatively low resistance through those items which will see less then normal operating voltage during the event that will survive and the higher dollar items with electronic controls, processors, etc. and a high resistance through them that will see a higher then normal voltage during this event that will be damaged nearly every time:happyyes:

 

[Smart $]

.. The insulation will typically be rated 90C and many neutral bars will also be 90C (as a stand alone value anyway, as part of the panel assembly instructions may still call for 75C) ...

waiting to be shot down

Can't really shoot your assessment down save one fact that I'm uncertain of at present... and I underlined that in the quote above. Are neutral bus terminals rated 90°C? I've never checked, and the one thing that makes me question that is I've never seen a "set-screw" terminal rated higher than 75°C. If only rated 75°C, the potentially overloaded neutral conductor will not handle as much current as you suggest at the neutral bus termination... and exactly why it would show signs of insulation degradation there before elsewhere, at least within the panel enclosure.

 

[jaggedben]

New in 2014 edition. Previously not required.

Not entirely true. 210.4(D) predates the 2011. But it only applies to MWBCs.

 

[jaggedben]

I know this sounds like a neat little trick, However much safer to de energize and fix. What is the boss going to say when you fried everything on three circuits when you lost the neutral?

Seriously. I'd rather ask people a thousand times to shut down their computers for 3 mins than explain once why some has to replace their computer.

 

[Smart $]

Not entirely true. 210.4(D) predates the 2011. But it only applies to MWBCs.

And that actually got added in 2008.

(For iwire: I was wrong and I openly admit it. :happyyes

 

[1964element]

I mark the neutrals for the circuits it shares, I'm cool like that.

Sent from my E6782 using Tapatalk

 

[kwired]

Can't really shoot your assessment down save one fact that I'm uncertain of at present... and I underlined that in the quote above. Are neutral bus terminals rated 90°C? I've never checked, and the one thing that makes me question that is I've never seen a "set-screw" terminal rated higher than 75°C. If only rated 75°C, the potentially overloaded neutral conductor will not handle as much current as you suggest at the neutral bus termination... and exactly why it would show signs of insulation degradation there before elsewhere, at least within the panel enclosure.

There are many components with AL9CU marked on them, seems like many Square D equipment ground bars are marked with this as well (could be mistaken), many of their panels have same design bars used for neutral terminals. But that doesn't mean the entire assembly is recognized with 90 C terminations, though a neutral bar has a better chance then a circuit breaker, I think, unlike the breaker we are not trying to sink some heat from within the breaker into the conductor.

 

[mbrooke]

There are many components with AL9CU marked on them, seems like many Square D equipment ground bars are marked with this as well (could be mistaken), many of their panels have same design bars used for neutral terminals. But that doesn't mean the entire assembly is recognized with 90 C terminations, though a neutral bar has a better chance then a circuit breaker, I think, unlike the breaker we are not trying to sink some heat from within the breaker into the conductor.

When lugs are rated 90*C, is it because they expect the actual temperature to reach 90*C or is it something else like heat sink you mention?

 

[kwired]

When lugs are rated 90*C, is it because they expect the actual temperature to reach 90*C or is it something else like heat sink you mention?

IDK.
For a breaker lug marked AL90CU I think it is simply the lug itself is stand alone rated 90C, but the breaker assembly is only rated 75C, so no matter what lug is attached 75C is the limit.

 

[mbrooke]

IDK.
For a breaker lug marked AL90CU I think it is simply the lug itself is stand alone rated 90C, but the breaker assembly is only rated 75C, so no matter what lug is attached 75C is the limit.

So, if a breaker does reach 75*C will the breaker or lug fail? Or is 75*C just there so a larger wire is selected preventing a temp of over say 130*F?

I know you arent to sure but if anyone in this thread knows just hollar. ight?

 

[James L]

I know this sounds like a neat little trick, However much safer to de energize and fix. What is the boss going to say when you fried everything on three circuits when you lost the neutral?

I'm not saying this is an ideal method. I would also be at least a little cautious because the neutral could open during human contact.

But, if that neutral opens during contact, it's already such a horrible connection that it's on the verge anyway.

Live splice beats simply tightening a burnt connection. I've spliced this way without a hitch.

and damage is covered by proper insurance anyway
just kidding, don't throw rocks