Shared/borrowed Neutrals

[JoeNorm]

Hello.
I have been doing a number of battery backup systems in residential homes that require creating a "backed-up" loads panel. One of the requirements of the system is that when both panels (the main and the backed up) are finished, there cannot be any neutrals shared between the two panels. If there are, it can kill the electronics in the backup inverter.

So far I have found continuity between both panels neutrals on every occasion. Usually one circuit being the culprit. Today we had a strange neutral to ground loop happening that we could not track down.

My question is why, typically in older or remodeled homes, is this so common? And also, what are the tests that can be performed to determine where in the house the neutrals may be connected?

thanks for your time

 

[texie]

First we need to be sure of the terms being used here. A MWBC is one thing. A circuit that is tied to neutrals that don't belong to that circuit are a violation. If you are encountering MWBSs there is no way to connect them in a compliant manner to separate panels with out redoing the whole circuit. Older homes that have been hacked on by DIYs,handyman and incompetent electricians are often full of all kinds of issues.

 

[growler]

Older homes that have been hacked on by DIYs,handyman and incompetent electricians are often full of all kinds of issues.

Sure you will find all kinds of hacked work in older and remodeled homes. A lot of the time they will just tie all of the white wires in a junction box together and it will work and no one will notice. I found one just the other day where they tied all the neutrals together and all the hots together but the hots were on different phases so they noticed but had no idea why the breakers were tripping.

 

[romex jockey]

The hackery continues , as we have found a number of new modular homes who's afci's trip due to factory noodlemania

I was under the impression the code mandated testing too.....hmy:

~RJ~

 

[JoeNorm]

Are there any good ways to find these problem locations? Or is it just looking around and finding them by chance?

 

[LarryFine]

It's probably due to connecting all EGCs in a box together, rather than neutrals. For example, kitchen counter switch/receptacle locations.