Voltage issue with separate neutral from secondary panel

[Coastalguy1]

I had a recent issue with a project where a 20amp 120v circuit phase leg originated in one electrical panel but the neutral was connected from a second panel. The second panel was removed during a phase of demolition. As soon as the neutral in this panel was removed the 20amp 120v circuit became 240v and damaged several pieces of equipment. Can someone help explain how this 120v circuit became 240v? Did removing the neutral from the second panel (realize this is a code violation) cause 240v from the power co. transformer?

Thanks:?

 

[don_resqcapt19]

Are you sure there were not two circuits connected to that neutral? An open neurtal on a circuit with two ungrounded conductors sharing a neutral will do that.

 

[Coastalguy1]

Don,
There was actually (3) circuits tied to the neutral. There was a 12/3 NM cable run to a junction box from panel 1 and a neutral and a ground from panel 2 to the junction box.

 

[ActionDave]

Don,
There was actually (3) circuits tied to the neutral. There was a 12/3 NM cable run to a junction box from panel 1 and a neutral and a ground from panel 2 to the junction box.

Sounds like someone got the neutrals crossed before the old panel was removed or the neutral was lost on the 12-3 MWBC circuit but the over voltage was masked by the extra neutral.

 

[Coastalguy1]

Thank you for the replies.