Connecting transformer neutrals

[jlgreen]

I'm part of a team installing packaging equipment, which has several control transformers all sourced from the same branch circuit. The secondary neutrals of these are all tied. An additional Y-Y transformer is to be installed (for a new machine feature) and is sourced from a different branch circuit. This will power a controller/equipment which has a 24VDC input to a PLC. The PLC is sourced by one of the original transformers. The team is struggling with determining if the new transformer neutral should be tied with the other transformers. Any opinions?

Thanks in advance for your help

 

[Smart $]

The neutrals are not required to be tied together, but they are most likely required to be grounded. If all neutrals are grounded, they should effictively all be tied together as a result.

 

[jlgreen]

Thanks smart$....is there a NEC section I could refer to for this?

 

[Smart $]

Thanks smart$....is there a NEC section I could refer to for this?

250.20

I seem to recall there is/was an "exception" for smaller transformer (1000VA and less) secondaries to not be grounded... but I can't find it in the 2011 NEC (I'm not really searching that hard find it at present, though). Perhaps it is under grounding electrode system requirements.