Open Neutral

[brian john]

When install a UPS with input out put transformers and dual source inputs it is IMPERAITIVE the EC understand grounding rules and proper wiring. It appears the contractor left out a neutral connection and the EGC was carrying current. The structure has metal wall coverings the UPS rear cover screw was tight against the wall and it appears the structure was the path for the neutral current. This is the rear cover, note burn marks, I did not take a picture of the wall as we were on OT late at night with a limited work window for UPS replacement.

 

[RUWired]

John, did he not run the grounded conductor or did he not make the bonding jumper.
Rick

 

[quogueelectric]

At hospital installs I have noticed the neutral to be switched in the ats's making some of the 480 v readings to ground unconnected at the ats. Dangerous for electricians extremely.

 

[brian john]

RU: They did not install the neutral for one of the transformers but did bond the XO/neutral connection.

 

[quogueelectric]

Should it have been corner grounded instead??

 

[benaround]

Should it have been corner grounded instead??

A transformer with XO would be a Y connection.

 

[brian john]

I think the confusion arise here as these are auto transformers and have XO and HO common. I found the existing installation confusing to follow.