Section 250.30 Ground & Bonding Step-Down Xfrmr & Disconnect

Npstewart

Senior Member
I have a situation where an electrician made a field change that is out of the ordinary for me. The arrangement is a Step-down 480v transformer feeding a single phase 240v panel (Panel A for reference).

The issue is that he did not run an SSBJ or any type of ground at all between the transformer. The transformer is located inside the building.
  • The Main within Panel "A" is the disconnect for the transformer.
  • The GEC is located at the step-down transformer
  • The only conductors that run between the transformer and panel are the (2) phase conductors and the neutral.
  • He installed a bonding screw within panel "A".

After reviewing Section 250.30 (Specifically Exhibit 250.14 & 250.15 in the NEC 2014 Handbook) it would appear that an SSBJ is needed in both cases. It doesent appear as though any listed exception applies to the installation as described above.


Thank You all.
 

ActionDave

Moderator
Staff member
Is panel A on the secondary side of the transformer?

You can bond the neutral in the transformer or the first disconnect on the secondary but the GEC has to be in the same spot as the SSBJ.
 

Npstewart

Senior Member
Is panel A on the secondary side of the transformer?

You can bond the neutral in the transformer or the first disconnect on the secondary but the GEC has to be in the same spot as the SSBJ.
Yes, the Panel "A" is served from the secondary side of the Transformer.
 

ActionDave

Moderator
Staff member
Then the bonding jumper is allowed to be there but the GEC has to be there also and there has to be an equipment ground back to the transformer. The conduit that the secondary conductors can do that job if it qualifies.
 
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